e2e3 Technical

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Reading Material

Handout No-ALTMCUP106 02 Ver 3 28.02.2008

Technical Module

i

About this Handout This handout provides reading material on the technical topics included in the Syllabus of E2 to E3 Time scale promotion linked training of Officers belonging to Telecom wing of BSNL. The examination at the end of this one-week module will include discussions that take place in the class and general understanding of BSNL executives about the company’s telecom infrastructure. Mode of Examination The examinations will be conducted with break-up of 30% subjective & 70% objective pattern questions in each of the modules. Duration of Examination Examination duration will be 90 minutes Qualifying marks For the successful completion of the training, the executive undergoing the training ought to score a minimum of 50% of the total marks in each of the modules. Failure & Re-appearance The Executives who don’t qualify the examination would be given another chance to undertake/clear the examination in continuation of their training. This supplementary examination would be arranged within 3 days of the declaration of the results at the same venue. For still failing executives, a second / subsequent supplementary examination would be held on the date & place as finalized by ALTTC. However no TA/DA would be admissible to the executives appearing for the same. No repeat of training would be provided for the unsuccessful executives, unless specifically agreed by the CGM ALTTC in consultation with corresponding circle CGM. Reference:

1. Order No. 32-27/04/Trg dated 19th July 2007 of BSNL Corporate office

2. Order No. 32-27/04/Trg dated 12th April 2007 of BSNL Corporate office

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CONTENTS

TOPIC Chapter Page

SECTION-I Switching Digital Switching systems: Concepts 1 1-4

Signaling in Telecom Networks: CAS & CCS7 2 1-10

Switching systems in BSNL & introduction to NGN 3 1-15

Intelligent Network 4 1-9

Maintenance issues of battery and power plant 5 1-5

Air conditioning & Engine Alternator 6 1-10

Section-II Transmission OFC characteristics & laying 7 1-9

Testing & Measuring instruments 8 1-4

SDH Overview 9 1-9

Protection schemes in SDH 10 1-9

Synchronization 11 1-13

SECTION-III Mobile Overview of Mobile Communication & cellular concepts 12 1-6

GSM Architecture 13 1-5

GPRS/EDGE 14 1-6

GSM Services 15 1-9

Overview of CDMA Technology 16 1-14

SECTION-IV Data Communications Broadband Wire line Access Technologies 17 1-7

Broadband Wireless Technologies 18 1-5

Broadband Core Network 19 1-3

TCP/IP/Ethernet, IP Addressing 20 1-10

IP Routing, RIP, OSPF 21 1-3

MPLS-VPN 22 1-7

Multiplay 23 1-4

SECTION-V Information Technology BSNL Application Packages 24 1-12

Overview of NOS & RDMS Package 25 1-4

IT Security Policy 26 1-3

SECTION-VI Sample Questions 27 1-3

iii

Amendment Record

TOPIC Version Date

SECTION-I Switching Digital Switching systems: Concepts 2 28.02.2008

Signaling in Telecom Networks: CAS & CCS7 2 17.11.2007

Switching systems in BSNL & introduction to NGN 2 17.11.2007

Intelligent Network 2 17.11.2007

Maintenance issues of battery and power plant 1 24.08.2007

Air conditioning & Engine Alternator 1 24.08.2007

Section-II Transmission OFC characteristics & laying 2 17.11.2007

Testing & Measuring instruments 1 24.08.2007

SDH Overview 1 24.08.2007

Protection schemes in SDH 1 24.08.2007

Synchronization 1 24.08.2007

SECTION-III Mobile Overview of Mobile Communication & cellular concepts 2 28.02.2008

GSM Architecture 2 28.02.2008

GPRS/EDGE 2 28.02.2008

GSM Services 2 28.02.2008

Overview of CDMA Technology 1 24.08.2007

SECTION-IV Data Communications Broadband Wire line Access Technologies 2 28.02.2008

Broadband Wireless Technologies 2 28.02.2008

Broadband Core Network 3 28.02.2008

TCP/IP/Ethernet, IP Addressing 3 28.02.2008

IP Routing, RIP, OSPF 3 28.02.2008

MPLS-VPN 3 28.02.2008

Multiplay 2 28.02.2008

SECTION-V Information Technology BSNL Application Packages 1 24.08.2007

Overview of NOS & RDMS Package 1 24.08.2007

IT Security Policy 2 28.02.2008

SECTION-VI Sample Questions 1 28.02.2008

Section-I

Chapter-1

Digital Switching Systems

E2E3 Switching Concepts, Ver2 28.02.2008 1 of 4

1.0 DIGITAL SWITCHING CONCEPTS

Telephony was invented in 1876 and automatic telephone exchanges were developed in 1895. All these exchanges were analog. Now we have only digital exchanges in the network, which work on time switching or time and space switching. The digital exchanges are compatible to provide value added services and Intelligent services Communication can be defined as the transfer of information from one point to another point as per desire of the user under the control of some system. The key aspects of a communication network are :

1) Switching 2) Transmission 3) Call control or signaling 4) End terminals or network elements

2.0 SWITCHING

Switching is basically establishing a temporary path or connection between two points or it can also be defined as writing at one point of time and reading at another point of time.

There are two modes of switching employed in our network. 2.1 CIRCUIT SWITCHING

In normal telephone service , basically, a circuit between the calling party and called party is set up and this circuit is kept reserved till the call is completed. Here two speech time sots are involved one of calling subscriber other of called subscriber. It is called circuit switching Circuit switching is based on the principle of sampling theorem.

2.1.1 SAMPLING THEOREM Sampling Theorem States “If a band limited signal is sampled at regular intervals of time and at a rate equal to or more than twice the highest signal frequency in the band, then the sample contains all the information of the original signal. Mathematically , if fh is the highest frequency then sampling frequency Fs needs to be greater than or equal to 2 fh i .e. Fs >=2 fh Let us say our voice signals are band limited to 4 KHZ and let sampling frequency be 8KHZ. .


. . Time period of sampling Ts = 1 secs. 8000 . or Ts = 125 micro second If we have just one channel then this can be sampled every 125 microseconds and the resultant samples will represent the original signal. But if we are to sample N channels one by one at the rate specified by the sampling theorem, then the time available for sampling each channels would be equal to Ts/N microseconds The time available per channel would be Ts=125�s N=32 for 32 chl PCM 125/32=3.9 microseconds per chl Thus in a 30 channel PCM system, time slot is 3.9 microsecond and time period of sampling i.e. interval between 2 consecutive samples of a channels is 125 microsecond. This duration i.e. 125 microsecond is called time Frame. A signal band is limited to max freq of say fm if sampled at the rate of 2fm then this signal can be reconstructed at the receiving end. This theorem was given by Nyquist. 2.2 PACKET SWITCHING

The information (speech, data etc) is divided into packets each packet containing piece of information also bears source and destination address. These packets are sent independently through the network with the destination address embedded in them. Each packet may follow different path depending upon the network.

3.0 SWITCHING CONCEPT

To connect any two subscribers, it is necessary to interconnect the time-slots of the two speech samples which may be on same or different PCM hightways. The digitalised speech samples are switched in two modes. Viz. Time Switching and space Switching . This time Division Multiplex Digital Switching System is popularly known as Digital Switching System

3.1 Digital Time Switch

Principle

A Digital Time Switch consists of two memories, viz., a speech or buffer memory to store the samples till destination time-slots arrive, and a control or connection or adddress memory to control the writing and reading of the samples in the buffer memory and directing them on to the appropriate time-slots.


Speech memory has as many storage locations as the number of time-slots in input PCM,e.g.,32 location for 32 channel PCM system.

The writing / reading operations in the speech memory are controlled by the control Memory It has same number of memory locations as for speech memory, i.e.,32 locations for 32 channel PCM system. Each location contains the address of one of the speech memory locations where the channel sample is either written or read during a time-slot. These address are written in the control memory of the CC of the exchange

depending upon the connection objective.

A Time –Slot Counter which usually is a synchronous binary counter. is used to count the time – slots from 0 to 31 as they occur. At the end of each frame, it gets reset and the counting starts again. It is used to control the timing for writing/reading of the samples in the speech memory.

Buffer/speech memory

Incoming PCM 01 Outgoing PCM 02 04

TS4 TS6 31

Read address 00 01 06 31

Control /Connection/Address Memory

Fig. output Associated Control Switch 3.2 SPACE SWITCH:

A space switch is used to simple change the PCM of a incoming time slot keeping the time slot number same in the outgoing PCM.

The memory location requirement rapidly go up as a Time Switch is expanded making it uneconomical. Hence, it becomes necessary to employs both types of switches, viz.., space switch and time switch, and therefore is known as two dimensional network. These network can have various combinations of the two types of switches and are denoted as TS, STS TSST, etc.

4 ( four)

Time slot counter


4.0 Telecom network structure The telecom network consists of –

Local exchanges (LE) Which has only subscribers connected to it. TAX Exchanges (TAX) Trunk automatic exchanges contains only outgoing and incoming circuits and no subscriber is connected to it. It is used only for routing calls. Tandem exchanges Out going and incoming tandem exchanges are basically exchanges between TAX and local exchanges for better management of traffic. These exchanges do not connect subscribers. Network elements (like telephone, fax, modem etc.)

The telephone network is also referred as PUBLIC SWITCHED TELEPHONE NETWORK (PSTN) .The offered voice service is referred as PLAIN OLD TELEPHONE SERVICE (POTS) The PSTN network is organized in a hierarchical manner with Lev-1/Lev-2 TAX

exchanges and then tandem and Local exchanges. Trunk Automatic Exchange

Lev-I TAX -------In 21 places Lev-II TAX-------In 301 Places

Types of call

• Local call: Call originated and terminated in the same exchange is called local call

• Outgoing call: Call originated from local exchange and terminated in other exchange after picking up outgoing circuit.

• Incoming call: Call received from other exchange and terminated in local exchange.

• Transit call: Call received from other exchange and terminated in other exchange. When a new call is set up, it needs to be routed from calling party to the called party through the switch network. The routing is based on the called party number. Normally in PSTN the switching is ‘static’ type. In case of link failure alternate paths are available and routing is done through the alternate paths.

Section-I

Chapter-2

Signaling: CAS & CCS7

E2E3 Signaling: CAS & CCS7, Ver2 17.11.2007 1 of 10

Signaling in Telecom Networks

Channel Associated Signaling 1.0: Introduction

The exchange communicates with other equipment in the telephone network according to the committed signaling system(s). A signaling system defines the meaning and physical characteristics of the signals or messages and the applicable signaling procedures.

A signaling system is called a channel associated signaling system when the location of the signaling information is related directly to the user voice/data. The

location of the signaling information always identifies the related user voice/data.

Fig.1 Channel Associated Signalling

Examples are signaling systems which use the same circuit for signaling and

user voice/data, and signaling systems which transport the signaling information in timeslot 16 of a PCM link.

The 30 channel PCM link (also called 2Mb link) consists of 32 timeslots. Of the 32

timeslots, 30 channels are used to transport user voice/data, one channel (timeslot 0) is used for timing, status and synchronization. One channel (timeslot 16) is used to transport signaling information related to the 30 voice/data channels. Figure 2 shows the structure of a PCM link. The traffic on the PCM link consists of consecutive multiframes, which are transmitted at 8000 Hz. These multiframes consist of 16 frames. Every frame consists of 32 timeslots onto which the 30 channels are mapped. Every timeslot consists of 8 bits. In timeslot 16, frame 1, signaling information related to the user voice/data in timeslots 1 and 17 is located. In timeslot 16, frame 2, signaling information related to the user voice/data in timeslots 2 and 18 is located, etc. Timeslot 1 to 15 and 17 to 31 are used for user voice/data (channels). After one multiframe has been sent, signaling information related to all 30 channels in a PCM link has been sent.


Fig.2 30 chl PCM Link Subscriber Signaling Signaling systems used between the exchange and subscriber equipment, such as terminals and PBX (Private Branch eXchanges), are called subscriber signaling systems. Subscriber signaling must not be confused with line signaling. Subscriber signaling can be transported over lines and subscriber trunks. Trunk Signaling Trunk signaling are signals used between public exchanges. They are used to connect exchanges in order to build up a circuit. The signals can be divided in supervision and address signaling. Supervision Signaling Supervision signaling (also called line signaling) is used to control and monitor the status of the transmission circuits. Examples of supervision signals are the seizure signal and idle state signal. Supervision signals do not contain any specific subscriber information such as the directory number. Address Signaling Address signaling (also called build-up or register signaling) is a protocol which is used to transfer the specific subscriber information necessary to connect the calling party to the called party. Address signaling is related to a certain call. Examples of address signaling information are the called party's directory number and the calling party's category. Compelled Signaling A signaling protocol is called compelled if a forward signal is transmitted until it is acknowledged with a backward signal. The backward signal is transmitted until a forward signal is received. Non-Compelled Signaling In a non-compelled signaling protocol, the signals are pulsed out for a specified duration. All signals are sent as a block, without any acknowledgement from receiving side. Inband Signaling A signaling system is called inband when the frequencies of the signals are inside the band of frequencies used for voice transmission(300-3400Hz ).


Out-of-band Signaling A signaling system is called out-of-band when the frequencies of the signals are outside the band of frequencies used for voice transmission. Link-by-Link Signaling A signaling system is called link-by-link when the total signaling information is sent from one exchange to the other. The receiving exchange uses a part of the information for routing. When all digits are received, the exchange takes over control of the originating exchange and sends the total signaling information to the next exchange. End-to-End Signaling A signaling system is called end-to-end if the originating exchange remains the originating exchange for the entire signaling procedure. The originating exchange sends the specific signaling information needed by the subsequent exchange to establish the signaling path. As soon as the next exchange has received enough digits to determine the routing, the exchange switches through his voice path and becomes transparent for the originating exchange. 2.0 Supervision Signaling Systems Supervision systems are used to control and monitor the status of lines and trunks. These signaling systems are link-by-link. 2.1: Signal Definitions Answer Signal Signal sent to the outgoing exchange to indicate that the called party has answered the call. On metering trunks the first metering pulse is considered as the answer signal. Blocking Signal A signal sent for maintenance purposes to the exchange at the other end of a circuit. It causes engaged conditions on that circuit for subsequent calls outgoing from that exchange. Clear-Back Signal Signal sent in the backward direction to indicate that the called party has cleared. Clear-Forward Signal A signal sent in the forward direction to terminate the call or call attempt and to release all switching units held on the call in the incoming exchange and beyond it. Metering Signal A signal sent in the backward direction to charge the call to the A-party. The metering signal consist of metering pulses, which are sent periodically. One metering pulse normally corresponds with a certain monetary value. Reanswer Signal A signal sent in the backward direction indicating that the called party, after having cleared, again lifts his receiver or in some way reproduces the answer condition.


Release-Guard Signal A signal sent in the backward direction in response to a clear-forward signal to indicate that the circuit concerned has been brought into the idle condition. The "Release-Guard" signal is also called "Return to Idle" signal. Seizure-Acknowledgement Signal A signal sent in backward direction to indicate the transition of the equipment at the incoming end from the idle state to seized state. The "Seizure Acknowledgement" signal is also called "Seizure Control" signal. Seizure Signal A signal sent in the forward direction at the beginning of the call to initiate transition of the circuit at the incoming end from the idle state to seized state. Unblocking-Acknowledgement Signal A signal sent in response to an unblocking signal indicating that the speech circuit has been unblocked. Some of the supervision signals for operator functions are as follows: Force Release Signal A forward operator-originated line signal that requests a terminating exchange to connect a busy terminating subscriber line to the incoming toll operator, and disconnect the third subscriber who is in conversation with the operator-called subscriber. Forward-Transfer Signal A signal sent in the forward direction on semi-automatic calls when the outgoing international exchange operator wants the help of an operator at the incoming international exchange. Intrusion Signal A forward operator-originated line signal used for requesting that the terminating exchange connect the incoming toll operator with an established speech path. Operator Ring-Back Signal A backward line signal initiated by an operator terminating subscriber to request that an originating toll operator be re-connected into the conversation. Re-ring Signal A forward operator-originated line signal sent to the terminating exchange (after answer and clear back) to request re-ringing of a now on-hook terminating subscriber line.


2.1: MFC Address Signaling Signaling Procedure There are 6 forward frequency combinations i.e. 1380,1500,1620,1740,1860 and 1980 Hz each having spacing of 129 Hz. In backward direction MFC freq are 1140,1020,900,780,660 and 540 Hz. For a particular signal we need combination of two frequencies. MFC (Multi Frequency Code) signaling is an in-band address signaling system. The signals consist of a combination of two of a set of six frequencies between 300 and 3400 Hz. This implies that fifteen different combinations can be made. Since more than fifteen signals are needed, signal groups are implemented. There are two forward groups, I and II, and three backward groups called A, B and C.

Common Channel Signaling System No. 7

A signaling system is called a common channel signaling system when the signaling information related to a group of circuits is transported over a separate common signaling link. 3.0 Basic Concepts CCS No. 7 is a CCS (Common Channel Signaling) system which may be used in an associated and non-associated mode of operation. CCS7 being a common channel signaling system, has following features –

• Based on separation of speech circuit from the signaling link. • Speech ckt has no signaling function except when a continuity check is done. • Results in faster call setup • Efficient utilisation of speech ckts.

The overall objective of CCS No. 7 is to provide an internationally standardized general purpose CCS system:

• optimized for operation in digital telecommunications networks in conjunction with stored program controlled exchanges.

• that can meet present and future requirements of information transfer for inter-processor transactions within telecommunications networks for call control, remote control and management and maintenance signaling

• that provides a reliable means of transfer of information in correct sequence and without loss or duplication.

The signaling system is optimized for operation over 64-Kbit/s digital channels. It is also suitable for operation over analog channels and at lower speeds. The system is suitable for use on point-to-point terrestrial and satellite links.


3.1: Functional Blocks in CCS No. 7 The CCS No. 7 consists of the following functional blocks:

• MTP (Message Transfer Part) • TUP (Telephone User Part) • ISUP (ISDN User Part) • SCCP (Signaling Connection Control Part) • TC (Transaction Capabilities)

Fig.3 Architecture of CCS no7

Level Structure of CCS No. 7 The CCS No. 7 protocol has a layered structure consisting of four levels (fig 4):

• Level 1 defines the physical, electrical and functional characteristics of the signal link.

• Level 2 defines functions relevant to individual signaling links, including error control and link monitoring. This level is responsible for reliable transfer of signaling information between two directly connected signaling points.

• Level 3 defines network functions such as message routing and network management.

• Level 4 defines application and user functions. User parts are defined to control the establishment and release of traffic circuits.

The first three levels together form the Message Transfer Part (MTP). The functions of each of the CCS No. 7 layers are transparent to one another because of well-defined interfaces between them. A mechanism has been provided to deliver CCS messages of up to 272 octets between the MTP and the user part, and within the user part.


Fig .4

Signalling Associations A CCS7 network can have following types of associations between speech and signaling path –

• Associated -Signaling path same as speech path • Non-associated - Signaling path different from speech path and the signaling

path to be used not specifically determined. • Quasi-associated - Non-associated with a predetermined signaling path.

Fig. 5 – Associated and Quasi-associated mode of signalling 3.3: CCS No. 7 Network Elements The signaling network consists of several network elements: · SEP (Signaling End Point) · STP (Signaling Transfer Point) · STEP (Signaling Transfer and End Point)

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

CCS link

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

SWITCHING

SIGNALING

CCS link


- - - - - Voice ckt Signalling link

Fig.6 Network Elements An SEP provides high speed, Common Channel Signaling connections for the speech circuits which terminate at its exchange. Signaling messages arriving at an SEP are used to set up the necessary speech circuits to complete a telephone call to the end user. The STP transfers signaling messages that arrive on one signaling link to a second signaling link where the message will then be routed toward the destination. An STP does not contain voice circuits, but it does provide the important function of transferring messages (either to another STP or to an SEP) towards their ultimate destination. The STEP performs both the SEP and STP functions. The STEP can transfer signaling messages that are destined for another exchange, and it can analyze signaling messages used to set up speech circuits in its exchange. 3.2 Signal Unit Composition ITU-T Signaling System No. 7 signals are sent in packets known as signal units. The signal units vary in length according to the type of information transferred. There are three types of signal units:

• MSU (Message Signal Unit): This is used for transferring signaling information supplied by the MTP itself or by the user part or SCCP.

• LSSU (Link Status Signal Unit: This is used for transferring signaling information used to indicate and monitor the status of the signaling link.

• FISU (Fill-In Signal Unit): This is used when there is no signaling traffic to maintain link alignment.


Point Codes Every SP (Signaling Point) and STP (Signaling Transfer Point) when integrated in a network will be allocated its own unique point code. This is used by the MTP routing function to direct outgoing messages towards their destination in the network as indicated by the inclusion of the appropriate point code in the routing label. This point code is known as the DPC (Destination Point Code). The routing label also contains the point code of the SP originating the message known as the OPC (Originating Point Code). The combination of the OPC and the DPC will determine the signaling relation. If two or more signaling links are required then the message handling function performs load sharing over the links. In this case the SLS (Signaling Link Selection) field is used to identify the chosen link. 3.3 User Part The CCS No. 7 functional Level 4, known as the MTP User functions, defines the functions of the signaling system that are particular to users. The ITU-T has defined several user functions of CCS No. 7, important are:

TUP - Telephone User Part ISUP - ISDN User Part SCCP - Signaling Connection Control Part TCAP - Transaction Capabilities Application Part

Telephone User Part The TUP defines the telephone signaling functions necessary for CCS No. 7 to control national and international telephone calls. ISDN User Part The ISUP defines the signaling functions needed for basic and supplementary services for ISDN voice and non voice applications. Signaling Connection Control Part The SCCP is used by call control for non-circuit related message transfer. Intelligent network features requiring database access, such as credit card verification, virtual private network services, and 800 services use connectionless SCCP in conjunction with TCAP to query these databases. ISDN supplementary services use TCAP and connectionless SCCP for sending information end-to-end. OMAP (Operations, Maintenance, and Administration Part) uses TCAP and the SCCP connectionless service in MTP and SCCP routing verification tests, and in circuit validation tests. Connection-oriented SCCP can be used for the ISUP user-to-user service 3 for data transfer, and is used for reliable data transfer on the interface between a base station and MSC (Message Switch Controller) in the GSM network.


Transaction Capabilities Application Part (TCAP) The TCAP provides services for interactive applications distributed over exchanges and specialized centers in an CCS No. 7 telecommunication network. The TCAP provides the means to establish non-circuit related communication between two nodes in the signaling network. Some examples of interactive applications that use the services of TCAP are as follows:

• MAP (Mobile Application Part) used by GSM (Global Systems of Mobile communications)

• INAP (Intelligent Network Application Part) • OMAP (Operations and Maintenance Application Part)

5.0 CCS7 Normal Call Processing Messages

• IAM (Initial Address Message): The IAM contains the dialed digits, voice/data trunk identity, and other related info. IAM/SAM contains all necessary information to set the path from one switch to the other.

• Check tone (optional): For speech path continuity check After completion the COT (Continuity Signal) message is sent. If the check tone fails, the CCF(Continuity Check Failure) message is sent .

• ACM (Address Complete Message) • Audible ringing tone • ANC (Answer, Charge): On receipt of the answer signal, charging is started. • CLF (Clear Forward): If called subscriber hangs up first, the CLB (Clear-

back) signal is sent in the other direction, followed by the CLF. • RLG (Release Guard): When the incoming equipment is released, a release-

guard signal is sent back. Advantages of CCS7 signaling:

1. Faster call setup. 2. No interference between signalling tones by network and frequency of human

speech pattern. 3. Greater trunking efficiency due to the quicker set up and clear down, thereby

reducing traffic on the network. 4. No security issues related to the use of in-band signalling with CAS. 5. CCS allows the transfer of additional information along with the signalling

traffic providing features such as caller ID. 6. New services like IN services are possible because of CCS7 signaling. 7. Efficient utilisation of speech ckts.

http://en.wikipedia.org/wiki/Caller_ID

http://en.wikipedia.org/wiki/In-band_signalling

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E2E3 Switching systems & NGN, Ver2 17.11.2007 1 of 15

EWSD - System Overview

1.0 System Features :

EWSD Digital switching system has been designed and manufactured by M/s Siemens, Germany. The name is the abbreviated form of German equivalent of Electronic Switching System Digital (Electronische Wheler Systeme Digitale). EWSD switch can support maximum 2,50,000 subscribers or 60,000 incoming, outgoing or both way trunks, when working as a pure tandem exchange. It can carry 25,200 Erlang traffic and can withstand 1.4 million BHCA. It is claimed that with the latest hardware and software version (Ver. 16), the system can withstand a BHCA of 16 million , can connect 6,50,000 subscribers or 2,40,000 trunks and handle 1,00,800 Erlang traffic. It can work as local cum transit exchange and supports CCS No.7, ISDN and IN and V5.X features.

3.0 System Architecture :

The main hardware units of an EWSD switch are as under:- (1) Digital line unit (DLU) - functional unit on which subscriber lines are

terminated. (2) Line/Trunk Group (LTG) - Digital Trunks and DLUs are connected to

LTGs. The access function determined by the network environment are handled by DLUs and LTGs .

CCNC

MDD MTD

MB

CCG SYP CP

LTG(B)

LTG(C)

SN

TTRRUUNNKKSS

OMT PRINTER

DLU SSUUBBSS


(3) Switching Network (SN) - All the LTGs are connected to the SN which inter connects the line and trunks connected to the exchange in accordance with the call requirement of the subscribers. CCNC and CP are also connected to SN.

(4) Coordination Processor (CP) - It is used for system-wide coordination

functions, such as, routing, zoning, etc. However each subsystem in EWSD carryout practically all the tasks arising in their area independently.

(5) Common Channel Signaling Network Control (CCNC) Unit or Signaling

System Network Control (SSNC)- This unit functions as the Message Transfer Part (MTP) of CCS#7. The User Part (UP) is incorporated in the respective LTGs.

2.1 Digital Line Unit (DLU)

Analog or Digital (ISDN-BA) subscribers, PBX lines are terminated on DLU . DLUA, DLUB, DLUD & DLUG are the existing types in hardware configuration of the DLU. DLUs can be used locally within the exchange or remotely as remote DLUs are connected to EWSD sub-systems via a uniform interface standardized by CCITT, i.e., Primary Digital Carrier (PDC) to facilitate Local or Remote installation. A subset of CCS# 7 is used for CCS on the PDCs. One DLU is connected to two different LTGs for the reasons of security. A local DLU is connected to two LTGs via two 4 Mbps (64 TSs) links, each towards a different LTG. In case of remote DLUs, maximum 4 PDCs of 2 Mbps (32 TSs) are used per DLU, two towards each LTG. Signaling information is carried in TS16 of PDC0 and PDC2. In case of a local DLU interface, TS32 carries the signaling information. Within the DLU, the analog subscribers are terminated on SLMA (Subscriber Line Module Analog) cards (module). Similarly Digital (ISDN) subscribers are terminated on the SLMD modules. Each module can support 16 subscribers (in case of DLUB or DLUD), and one processor SLMCP. One DLU can carry traffic of 100 Erlangs. A standard rack of local DLU (in case of DLUD) can accommodate two DLUs of 992 subscribers each. In case the link between a remote DLU and the main exchange is broken, the subscribers connected to the remote DLU can still dial each other but metering will not be possible in this case. For emergency service DLU-controller (DLUC) always contain up-to-date subscribers data. Stand Alone Service Controller card (SASCE) is provided in each R-DLU for switching calls in such cases for analog and ISDN subscribers and enables DTMF dialing for push-button subscribers. This card is also used for interconnecting a number of remotely situated DLUs (maximum 6), in a cluster, called a Remote Control Unit (RCU), so that subscribers connected to these remote


DLUs can also talk to each other in case the link of more than one DLU to the main exchange is broken. DLUG : The latest type of DLU is DLUG which can accommodates upto 1984 analogue subscribers with 32 ports per SLMA but the SLMD still accommodates 16 subscribers. A standard rack of DLU can accommodate two such DLUGs . The DLUG can be connected to four LTGs with 16 PDCs with a provision of one signalling channel (CCS) per LTG. It can handle up to 390 Erlangs of traffic. 2.2 Line/Trunk Groups The line/trunk groups (LTG) forms the interface between the digital environment of an EWSD exchange & SN. MMaaxxiimmuumm ttrraaffffiicc hhaannddlliinngg ccaappaacciittyy ppeerr LLTTGG iiss 110000 EErrllang as it is able to connect four PDCs either from lines or trunks. Hardware-wise LTGG, LTGM, LTGN and LTGP are existing in our country. The LTGs are connected in any of the following ways : (i) Via 2/4 Mb/s PDCs with remote/local DLUs to which subscribers are

connected (ii) Via 2 Mbps digital access lines to other digital exchanges in the network ((

MMFF RR22 TTrruunnkkss,, CCCCSS##77 TTrruunnkkss)) (iii) Via Primary rate Access lines to ISDN PBXs (ISDN subscribers with

PA) ((iivv)) VV55..22 IIFF,, AAnnnnoouunncceemmeennttss TTrruunnkkss,, OOCCAANNEEQQ,, IIPP ((IInntteelllliiggeenntt PPeerriipphhrraall))

((SSSSPP))

Function–wise LTGs are of two types:

(i) B Function LTG is used to connect lines e.g. DLU, PA, V5.2 IF etc.

(ii) C Function LTG is used to connect trunks on CAS and CCS#7

The bit rate on all highways linking the LTGs and the switching network is 8192 kbps ( 8 Mbps ). Each 8 Mbps highway contains 128 channels at 64kbps each ,

2.3 Switching Network

Different peripheral units of EWSD, i.e., LTGs, CCNC, MB are connected to the Switching Network (SN) via 8192 kbps highways called SDCs (Secondary Digital Carriers), which have 128 channels each. The SN consists of several duplicated Time Stage Groups (TSG) and Space Stage Groups (SSG) housed in separate racks. Connection paths through the TSGs and SSGs are switched by the Switch Group Controls (SGC) provided in each TSG and SSG, in accordance with the switching information from the


coordination processor (CP). The SGCs also independently generate the setting data and set the message channels for exchange of data between the distributed controls. The switching network is always duplicated (planes 0 and 1). Each connection is switched simultaneously through both planes, so that a standby connection is always immediately available in the event of a failure.

SN(B) has only 5 types of modules and each TSG and SSG is accommodated in only two shelves of the respective racks. Here one shelf can either accommodate one TSG or two SSGs thus requiring maximum 10 racks for 504 LTGs. Remaining four shelves normally accommodate LTGs. The latest, SN (D) can connect 2016 LTGs and thus handle traffic of 1,00,800 erlangs

Main Functions:

*Speech Path Switching *Message Path Switching

*CCS#7 signaling channels connection (NUC) 2.4 Coordination Area

2.4.1 Coordination Processor The coordination processor (CP) handles the data base as well as

configuration and coordination functions, e.g.:

- Storage and administration of all programs, exchange and subscriber data,

- Processing of received information for routing, path selection, zoning, charges,

- Supervision of all subsystems, receipt of error messages, analysis of supervisory result messages, alarm treatment, error detection, error location and error neutralization and configuration functions.

- Handling of the man-machine interface. The Basic functional units of CP 113C are as follows:

- Base Processor (BAP) for operation & maintenance and call processing,

- Call Processors (CAP) for sharing call processing load if the exchange BHCA cannot be handled by BAPs. Maximum 10 CAPs can be provided.

- Common Memory (CMY)- 64 to 1024 MB mainly for resident programs & database.

- Bus to Common Memory (BCMY)- For giving a time shared access to processors to read CMY whenever a number of processors give such a request.


- Input / Output Controller (IOC) - 2 to 4 IOCs coordinate and supervise accessing of CMY by IOPs.

- ATM Bridge Processor (AMP) – If a SSNC (EWSD powernode) is connected, the AMP is used (usually instead of the second IOC pair). It represents the interface between the ATM equipment in the SSNC and the CP. Its task is to convert the ATM oriented data streams from SSNC to the internal EWSD format.

- Input/output processors (IOP) - Various types of IOPs are used to connect the CP113C to the other subsystems and functional units of the exchange as well as to the external mass storage devices (EM i.e., MDD, MTD, MOD), the two O&M terminals (OMT/ BCT), to OMC via data lines etc. Maximum 12 IOPs can be connected to one IOC. The figure is shown on next page.

2.4.2 Other units assigned to CP are:

• Message Buffer (MB) for coordinating internal message traffic between

the CP- SN, CP-LTG, LTG-LTG, LTG- CCNC/SSNC in the exchange. • Central Clock Generator (CCG) for the synchronization of the exchange

and, where necessary, the network. The CCG is extremely accurate with error rate (10-9). It can, however, be synchronized even more accurately by an external master clock (10-11).

• System Panel Display (SYPD) to display system internal alarms & the CP

load It thus provides a continuous overview of the state of the system. The SYP can also displays external alarms such as fire & air-conditioning system failure .

• Operation and Maintenance Terminals/ Basic Craft Terminal for

Input/output. Two OMTs/ BCTs are provided for O&M functions.

2.5 Units for Message transfer part (MTP) of CCS#7 e.g. CCNC/SSNC

The common MTP functions in an EWSD exchange are handled by the common channel signaling network control (CCNC) or Signaling System Network Control (SSNC). The UP is incorporated in the software of the relevant LTG.


OCB – 283 SWITCHING SYSTEM

M/s Alcatel France has developed OCB_283 switching system. It has single ‘T “ Stage switching.

OCB-283 Exchange has got 3 basic subsystems :- 1. Subscriber Access subsystem 2. Connection & Control subsystem 3. Operation & Maintenance Subsystem

Fig. 1 (OCB 283 Functional Architecture)

The various connection and control functions in OCB-283 system are distributed with appropriate redundancy as indicated in the diagram.

n=7

STS 1X3

1 to 4 MAS

LR LR

LR MCX

SMX (1 to 8) x 2

SMT (1 to 64) x 2

SMA

CSDN

CSED

Circuits +MP

SMC 2 to 32

1 MIS

MAL

SMM

TMN AL

CSNL


2. Brief description of the functional components :- 2.1 STS ( BT Time base) : Time pulses are generated in triplicate and

distributed to LRs at Switching unit. The time base is usually synchronised with the network by a synch. interface. Synchronisation interface gets the clock from PCMs which carry traffic also and synchronises the local clock with the PCM clock and thus network synchronisation is achieved.

2.2 SMX Host switching Matrix (MCX)/Switch Control Function

“COM” This is a pure time switch of maximum 2048 LRs connectivity

capability. The switching of LR time shots are controlled by the function COM which in turn obtains the connection particulars from call handler known as Multiregister.

LRs are 2 Mbps binary coded PCM links with 32 time slots. 2.3 SMA Auxiliaries : Following auxiliary functions are available

- Auxiliary Equipment Manager (ETA) :

The ETA supports the following function: - Tone generation (GT) e.g. dial tone, busy tone etc. - Frequency generation & reception (RGF) for R2 MF signal, tone

dial reception etc. - Conference call facility (CCF). - Exchange clock.

2.3.2 CCS # 7 Protocol Manager (PU/PE) 64 kbps signalling channels are connected to this by semipermanent

link and carries out level 2 and level 3 of the signalling message transfer.

The defence and signalling link resource allocation is done by a control function PC.

2.3.3 V 5.2 Protocol Handler : The signalling protocol between an

access network an d local exchange is processed and managed by this function.

2.4 SMC Call Handler “MR” This obtains necessary data from subs and circuits and process for

connection and disconnection of call with the help of a database manager TR. In addition this helps in carrying out circuit tests and some observations. Besides MR function there is one CC (Call Contorl) function which again contains register to handle CCS # 7 calls in conjunction with MR registers.


2.4.2 Data Manager TR: This function is responsible for managing and storing various

subscriber and trunks related data base. The data is returned by the call handler “MR” as and when required during call processing.

2.4.3 Charging function (TX):

This function is responsible for charge computation on the basis of certain charging parameters supplied by the translator during analysis of digits received from a source (Subs or Circuit). This also prepares detailed billing messages and forwarding the same to the operation & maintenance function for further processing. Besides the charge related function the TX also is responsible for carrying out some traffic observation on subscriber and trunks.

2.4.4 Matrix handler (GX)

This function is responsible for processing and for defence of connections on receipt of :-

(a) request for connection and disconnection from MR or MQ

(marker). (b) fault in connection signalled by the switching controller function

(COM). GX also carrier out monitoring of connections and checks data links

periodically.. 2.4.5 Message Distribution function (MQ) marker:

Its function is to format if required and distribute messages - It also supervises semi permanent links . - Interchange of messages between different communication

multiplexes.

2.5 SMT PCM controller (URM) : PCM interface receives PCM from other exchanges remote subs access units, access networks and digital recorded announcement systems and the URM function carrier out the following:

• HDB3/Binary code conversion • Injection / extraction of TS 16 for CAS.

2.6 SMM OM Function:

This function enables to create all data required for subs/circuits and their testing. This also enables spontaneously issuing fault and alarm messages in case of indications coming from OCB units. OM function further provides features for saving detail billing/ bulk billing messages on mag tape (cartridge) . The OM function possess a two way communication path with the exchange system.


2.7 TOKEN RINGS There are 1 MIS and 4 MAS token rings for control message

communication between different stations.

2.8 CSNL/CSND Subscriber access function :

This functional component is implemented in CSNL/CSND or CSED and is responsible to forward new call connection & disconnection requests to control functions.

SUBSCRIBER DIGITAL ACCESS UNIT (CSN)

• The digital satellite exchange (CSN) is an entity for connection of

subscriber, which is capable of serving analogue subscribers and digital subscribers simultaneously.

• The CSN is a connection unit designed to adapt to a wide variety of geographical situations. It can either be local (CSNL) or remote (CSND) in relation to the connecting exchange.


INTRODUCTION TO THE 5ESS SWITCH

The 5ESS switching system has been designed M/s AT & T and supplied by M/s Lucent Technologies Ltd.The 5ESS-2000 Switch has 3 major types of equipment modules:

1. SM/SM-2000 (Switching Module),

2. CM (Communication Module)

3. AM (Administrative Module).

1.0 BASIC CHARACTERISTICS OF THE 5ESS SWITCH The 5ESS-2000 Switch is a digital exchange that can serve as a local (lines), toll (trunks), tandem (lines and trunks), OSPS (Operator Service Position System) or international gateway exchange, depending on the type of switch. It can serve a small community with fewer than 100 subscribers or a large metropolitan area serving more than 200,000 subscribers.

Modular Distributed Design

AM

CMSM SM

DSCH

NCT Links NCT Link

SM

Fig. 1– Different Modules of 5-ESS Switch

The SM connects all lines and trunks . It performs most of the call processing functions. There can be many SMs per 5ESS-2000 Switch.

The CM provides communication between the SMs and the AM. There is one CM per 5ESS-2000 Switch.

AM provides O& M functions for the switch.

2.0 SWITCHING MODULE All external lines, trunks, and special services circuits like tones, announcements , testing and conferencing circuits are terminated at the switching module. The analog and digital signals are converted to the digital format used inside the 5ESS-2000 Switch. The SM performs almost 95% of the call processing and maintenance functions including:


- Line and trunk scanning

- Tone and cadence generation

- Digit analysis

- Call routing

- Circuit switching

- Packet switching

- Announcements

- Call progress supervision

- Routine maintenance and self-maintenance

One 5ESS-2000 Switch can support as many as 192 SMs (SM Classic type). Each SM can handle as many as 5120 lines or 500 trunks, or a combination of the two. The SM-2000 can handle more than 65,000 lines or about 18,000 trunks. 2.1 Types Of Switching Modules A 5ESS-2000 Switch can be equipped with the following types of SMs.

- LSM (Local Switching Module) :This type of SM serves local lines, and ISDN (Integrated Services Digital Network) users. The LSM is usually referred to as the SM.

- HSM (Host Switching Module) : This type of SM provides the normal LSM subscriber interfaces and also interfaces one or more RSMs (Remote Switching Modules).

- RSM (Remote Switching Module) : This is done by having the RSM connected to an HSM. This RSM can be as far away as 242 kilometers from the host. UP to 4 RSMs (called a MMRSM (Multi-Mod RSM) can be interconnected to serve 16,000 lines, 2,000 trunks, or a combination of line and trunks. The RSM provides full stand-alone capabilities, including direct trunks to other exchanges, and can be used singularly or grouped in clusters

- PSM (Position Switching Module) : This type of SM supports OSPS (Operator Services Position System ) features.

3.0 COMMUNICATION MODULE 3.1 The CM provides communication between the SMs and the AM and

between different SMs. Major Components of The CM

All versions of the CM are divided into two functional units : The MSGS (Message Switch), and the ONTC, (Office Network and Timing Complex). The following description is based on the most common type of CM in the field, the CM2.

The MSGS and ONTC are each made up of subunits. The four major functions of the CM are performed by these hardware subunits :


MSGS

- MSCU (Message Switch Control Unit): It controls MSPU unit

- MSPU (Message Switch Peripheral Unit):It stores control information of different SMs

ONTC

- CMCU (Communications Module Control Unit):It controls TMSU and clock generator is available.

- TMSU (Time Multiplexed Switch Unit) Where NCT links are terminated

CM3: is the latest hardware version of CM. In this type of CM there is a single rack/shelf.

4.0 ADMINISTRATIVE MODULE In the 5ESS-2000 Switch, the AM (Administrative Module) is a switch equipment module which has the overall control of the entire 5ESS-2000 Switch. The AM controls the CM and communicates with all the SMs (through the CM).

Administrative Module Functions The AM has a minimum of one cabinet and can have a maximum of three cabinets. The AM performs resource allocation and processing functions that are done more efficiently on a centralized basis such as:

Call routing for inter module and intra module calls

Administrative data processing/billing data

• Traffic measurement reports/system performance reports

• Memory management

• System maintenance

• Maintaining file records of changes to the system Software Release.

• Personnel interface/system monitoring

• Allocating trunks for call processing.

4.1 Administrative Module Components

There are three main units located within the AM :

• CU (Control Unit)

• IOP (Input/ Output Processor)

• DFC (Disk File Controller)

The CU monitors overall system operation. The IOP interfaces with the MCC (Master Control Center), ROP (Receive Only Printer) and other peripheral devices. The DFC controls the TD (Tape Drive) and (DD) Disk Drive.


- Manages data transfer - controls memory transfer between its own memory, its hard disk, and the microprocessors that serve the peripheral units in the IOP.

- The MM stores program instructions and data. The MM stores the instructions and other data needed by the processor to process calls, collect administrative information, and perform system maintenance.

CU

CC

MM

DFC

IOP

TD

DD

MCC

ROP Fig. 2– Administrative Module Components

4.3 AM Peripheral Component Functions Disk File Controller

The DFC is responsible for interfacing with the SCSI (Small Computer System Interface) Peripheral Devices, such as the disk and tape drives.

Tape Drive

The tape drive is a backup for information stored on disk.

Input/ Output Processor

The IOP is the interface for other peripheral devices used by the switch, such as maintenance interfaces (MCC and ROP), datalinks and alarm signaling.

Master Control Center

The primary functions of the MCC are to provide the following

- Visual displays of system status and alarm information

- The means to control, test and reconfigure the system

- The means to manually recover the system

- Access to exchange data

The ROP (Receive-Only Printer) provides a printed copy of reports from the MCC.


NGN: CONCEPT AND ARCHITECTURE

The current generation network of BSNL, popularly known as PSTN is mainly circuit switching based network and it is organized into an hierarchical architecture viz. Level –I TAX exchanges, then Level-II exchanges and then tandem/local exchanges. The PSTN network is mainly optimized for voice calls and not much suited for data services. We have a separate network for data services. Today the world over trend is for a single converged network used for all type of services viz. voice, data, video which is called Next Generation Network and is a packet switching based network. To change over from current generation network to next generation network we have to move in a step-by-step manner to safeguard our existing network infrastructure and investment and therefore we have to follow an evolutionary path. 2.0 Why NGN? The NGN concept takes into consideration new realities in the telecommunication industry characterised by factors such as: the need to converge and optimise the operating networks and the extraordinary expansion of digital traffic (i.e., increasing demand for new multimedia services, increasing demand for mobility, etc.). The other reasons why we should evolve our existing network to NGN are that the existing circuit switched networks have following problems:

• Slow to develop new features and capabilities. • Expensive upgrades and operating expenses. • Proprietary vendor troubles • Large power and cooling requirements. • Limited migration strategy to New tech. • Model obsolescence.

3.0 What is NGN? 3.1 ITU-T’s Definition of NGN A Next Generation Network (NGN) is a packet-based network able to provide Telecommunication Services to users and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent of the underlying transport-related technologies. It enables unfettered access for users to networks and to competing service providers and services of their choice. It supports generalised mobility which will allow consistent and ubiquitous provision of services to users. 3.2 ETSI’s Definition of NGN As per ETSI NGN is a concept for defining and deploying networks, which due to their formal separation into different layers and planes and use of open interfaces, offers service providers and operators a platform, which can evolve in a step-by-step manner to create, deploy and manage innovative services. The following diagram depicts the concept of NGN.


Current Gen networks NGN

In NGN basically the call control (i.e. signaling) and the switching is separated out in different layers and between these layers open interfaces are used. The call control functionality is realized by the component which is called call server or softswitch or media gateway controller and the interfaces to the existing PSTN switches is done with the help of media gateways for voice transport and by signaling gateways for signaling transport. For switching and transport of the packets existing IP/MPLS backbone is used. With NGN architecture the new and innovative services can be given very fast and cost effectively. Also the capital expenditure and operational expenditure come down drastically.

The NGN is characterized by the following fundamental aspects:

• Packet-based transfer • Separation of control functions among bearer capabilities,

call/session, and application/service • Decoupling of service provision from transport, and provision of

open interfaces • Support for a wide range of services, applications and mechanisms

based on service building blocks (including real time/streaming/non-real time services and multi-media)

• Broadband capabilities with end-to-end QoS and transparency • Interworking with legacy networks via open interfaces • Generalised mobility • Unfettered access by users to different service providers

Interfaces

Switching

Call Control

Call Server

IP/MPLS

Gateways

SDH Transport with Overlay packets for data

Common IP MPLS Transpo

��

��

��

E2E3 IN Ver2 17.11.2007 1 of 9

INTELLIGENT NETWORK Over the last thirty years one of the major changes in the implementation of Public Switched Telephone Networks (PSTN) has been the migration from analogue to digital switches. Coupled with this change has been the growth of intelligence in the switching nodes. From a customer’s and network provider’s point of view this has meant that new features could be offered and used. Since the feature handling functionality was resident in the switches, the way in which new features were introduced into the network was by introducing changes in all the switches. This was time consuming and fraught with risk of malfunction because of proprietary feature handling in the individual switches. To overcome these constraints the Intelligent Network architecture was evolved both as a network and service architecture. In the IN architecture, the service logic and service control functions are taken out of the individual switches and centralized in a special purpose computer. The interface between the switches and the central computer is standardised. The switches utilize the services of the specialized computer whenever a call involving a service feature is to be handled. The call is switched according to the advice received by the requesting switch from the computer. For normal call handling, the switches do not have to communicate with the central computer. 1.1. Objectives of the Intelligent Network The main objectives of the IN are the introduction and modification of new services in a manner which leads to substantial reduction in lead times and hence development costs, and to introduce more complex network functions. An objective of IN is also to allow the inclusion of the additional capabilities and flexibility to facilitate the provisioning of services independent of the underlying network's details. Service independence allows the service providers to define their own services independent of the basic call handling implementation of the network owner. The key needs that are driving the implementation of IN are: Rapid Service Deployment Most businesses today require faster response from their suppliers, including telecommunication operators. By separating the service logic from the underlying switch call processing software, IN enables operator to provide new services much more rapidly. Reduced Deployment Risk Prior to IN, the risk associated with the deployment of new services was substantial. Major investments had to be made in developing the software for the services and then deploying them in all of the switches. With the service creation environment available, the IN services can be prototyped, tested and accessed by multiple switches simultaneously. The validated services can then be rolled out to other networks as well.

E2E3 IN Ver2 17.11.2007 2 of 9

Cost Reduction Because the IN services were designed from the beginning to be reusable, many new services can be implemented by building on or modifying an existing service. Reusability reduces the overall cost of developing services. Also, IN is an architecture independent concept, i.e. it allows a network operator to choose suitable development hardware without having to redevelop a service in the event that the network configuration changes. Customization Prior to IN, due to complexity of switch based feature handling software, the considerable time frame required for service development prevented the provider from easily going back to refine the service after the customer started to use it. With IN, the process of modifying the service or customization of service for a specific customer is much less expensive and time consuming. The customization of services is further facilitated by the integration of advanced peripherals in the IN through standard interfaces. Facilities such as voice response system, customized announcements and text to speech converters lead to better call completion rate and user friendliness of the services. 1.2. IN Architecture Building upon the discussion in the previous section, one can envisage that an IN would consist of the following nodes: ��Specialized computer system for - holding services logic, feature control, service

creation, customer data, and service management. �� Switching nodes for basic call handling �� Specialized resources node

The service logic is concentrated in a central node called the Service Control Point

(SCP). The switch with basic call handling capability and modified call processing model for

querying the SCP is referred to as the Service Switching Point(SSP). Intelligent Peripheral (IP) is also a central node and contains specialized resources

required for IN service call handling. It connects the requested resource towards a SSP upon the advice of the SCP.

Service Management Point (SMP) is the management node, which manages services

logic, customers data and traffic and billing data. The concept of SMP was introduced in order to prevent possible SCP malfunction due to on-the-fly service logic or customer data modification. These are first validated at the SMP and then updated at the SCP during lean traffic hours. The user interface to the SCP is thus via the SMP.

E2E3 IN Ver2 17.11.2007 3 of 9

Physical Plane Service Switching Point (SSP)

The SSP serves as an access point for IN services. All IN service calls must first be routed through the PSTN to the "nearest" SSP. The SSP identifies the incoming call as an IN service call by analysing the initial digits (comprising the "Service Key") dialled by the calling subscriber and launches a Transaction Capabilities Application Part (TCAP) query to the SCP after suspending further call processing. When a TCAP response is obtained from the SCP containing advice for further call processing, SSP resumes call processing. The interface between the SCP and the SSP is G.703 digital trunk. The MTP, SCCP, TCAP and INAP protocols of the CCS7 protocol stack are defined at this interface Service Control Point (SCP)

The SCP is a fault-tolerant online computer system. It communicates with the SSP's and the IP for providing guidelines on handling IN service calls. The physical interface to the SSP's is G.703 digital trunk. It communicates with the IP via the requesting SSP for connecting specialized resources. SCP stores large amounts of data concerning the network, service logic, and the IN customers. For this, secondary storage and I/O devices are supported. As has been commented before, the service programs and the data at the SCP are updated from the SMP. Service Management Point (SMP)

The SMP, which is a computer system, is the front-end to the SCP and provides the user interface. It is sometimes referred to as the Service Management System (SMS). It updates the SCP with new data and programs(service logic) and collects statistics from it. The SMP also enables the service subscriber to control his own service parameters via a remote terminal connected through dial-up connection or X.25 PSPDN. This modification is filtered or validated by the network operator before replicating it on the SCP. The SMP may contain the service creation environment as well. In that case the new services are created and validated first on the SMP before downloading to the SCP. One SMP may be used to manage more than one SCP's. Intelligent Peripheral (IP)

The IP provides enhanced services to all the SSP's in an IN under the control of the SCP. It is centralized since it is more economical for several users to share the specialized resources available in the IP which may be too expensive to replicate in all the SSPs. The following are examples of resources that may be provided by an IP: �� Voice response system �� Announcements �� Voice mail boxes ��Speech recognition system �� Text-to-speech converters

E2E3 IN Ver2 17.11.2007 4 of 9

The IN architecture is depicted in below given Figure:

Data Base

CCS7 Network

IP SSP

USER USER USER USER

Communication Interface

Data Base

Communication Interface

Program Interface Communication Interface

Legend SMP: Service Management Point SCP: Service Control Point Service switching Point IP: Intelligent peripheral

SMP

SCP

E2E3 IN Ver2 17.11.2007 5 of 9

1.3. DESCRIPTION OF IN SERVICE FEATURES An IN service comprises mandatory (providing core functionality) and optional features. A brief description of the various features that constitute the IN services offered as part of IN solution is given in the following paragraphs. Call Forwarding on Busy/No Answer (CFC): This service feature allows the called user to forward calls if the called user is busy or doesn't answer within a specified number of rings. Customer Profile Management (CPM): This feature allows the user to perform online modification of the password (authorization Code). Mass Calling (MAS): This service feature allows processing of large numbers of incoming calls in a given time span, generated by call-in broadcasts, advertisements or games, etc. Origin Dependent Routing (ODR): This service feature allows the subscriber to have calls routed according to the calling party's area of origination. Based on the area of origination the subscriber can also accept or reject the call. Origination Call Screening (OCS): This service feature allows the subscriber to bar the calls originating from certain areas identified by their area codes. Off-net Access (OFA): This service feature allows a VPN user to access his or her VPN from any non-VPN station by using a personal identification number. Off-net Calling (ONC): This service feature allows the VPN user to call any external public number from a VPN location. Authorization is required for accessing this feature. Premium Charging (PRMC): This service feature allows for the pay back of the part of the cost of a call to the called party, when he is considered a value added service provider. The call is charged at a premium over normal call charge. Private Numbering Plan (PNP): This service feature allows the subscriber to maintain a numbering plan within his private network, which is separate from the public numbering plan. Reverse Charging (REVC): This service feature allows the service subscriber to receive calls at his own expense and be charged for the entire cost of the call. Time Dependent Routing (TDR): This service feature enables the subscriber to route calls based on time of day, day of week and day of year. The precedence when more than one type of parameters are specified for determining routing shall be 1. Day of year 2. Day of week 3. Time of day Call Distribution (CD) This service feature allows the subscriber to have the calls routed to more than one directory number. Based on the values defined, only a percentage of calls are routed to a directory number.

E2E3 IN Ver2 17.11.2007 6 of 9

IN Services and access codes

Existing New Codes Service Access 1600 1800 Free Phone 1601 1801 VPN 1602 1802 VCC(ITC) 1603 1803 Tele voting (no charge) 1604 1804 ACC 1901 1860 UAN(Local) 1902 1861 Tele voting(Charge) 0900 1867 PRM 0901 1860 UAN(LD) 1868 UPN 1907 1807 UAN Mgmt 1808 UPN Mgmt 1809 VPN Mgmt FLPP

IN platforms in BSNL and its SCP Codes: Kolkata (East Zone)

345 General purpose (GPIN)

Bihar, Jharkhand, West Bengal,Orissa,Assam, North East-I & II, CTD and A&N Islands

Bangalore (South Zone)


TamilNadu, Kerala, Karnataka, Chennai T.D.

Lucknow (North Zone)


UP (E), UP (W), Uttaranchal, Punjab, Haryana, H.P., J&K and Rajasthan

Ahmedabad (West Zone)


Gujarat, Maharashtra, Madhya Pradesh, Chattisgarh, AP

Hyderabad (Central)

424 Mass Calling IN (MCIN)

All India(Mass Calling)

Virtual Card Calling Service (ITC) Also known as Indian Telephone Card. Meant for customers who want to make STD/ISD calls from any Bfone (may not be his own) and limit the usage. No metering will be there on the Calling Telephone Number. Metering will be there against the VCC account.

• Access code : 1602-SCP Code- PIN – Destination No. (1802 by 30-04-2009)

E2E3 IN Ver2 17.11.2007 7 of 9

Account Card Calling Service (ACC) • To place calls from any PSTN phone to any destination no and have the

cost of these calls charged to the account specified by the account card calling (ACC) number.

• Personal identification number(PIN) is required for o Balance enquiry o Making call o Change of PIN

• Subscriber can renew the account by depositing a fresh amount of money after expiry of existing deposit with in the validity period of the Account.

• Detailed record for all the ACC calls will be sent to the subscriber for his information.

Free Phone Service (FPH) or Toll Free No. Meant for customer oriented organizations who want that their customers should feel free to contact without worrying about call charges.

• Here the concept of reverse charging is applied with additional features. • The service subscriber will have one logical number against more than

one PSTN no. distributed all over the network. He can have his own routing plan using Time Dependent Routing, Origin Dependent Routing facilities.

Premium Rate Services

• Concept of charging on higher pulse rate for the Services rendered by the subscriber.

• The pulse rate will be decided by the subscriber. Caller is charged. • The revenue will be shared by the Subscriber and BSNL • He can have his own routing plan using TDR, ODR on local access basis. • A typical PRM no. would look like 1867 XYZ ABCD Where Service Access Code : 1867 XYZ : 3 digit SCP code ABCD : Last 4 digits are PRM no

Universal Access Number Service

• Publish one number(unique IN number) and have the incoming call routed destination based on origin of call or time/day on which the call is made.

• The caller will be charged as per the normal charge of PSTN call. • One logical number against more than one PSTN no. distributed all over

the network.

E2E3 IN Ver2 17.11.2007 8 of 9

Universal Personal Number Service Outgoing facility also available in UPN service. It introduces the concept of Personal mobility rather than terminal mobility.

• A subscriber to this service can receive or make calls using his Universal Personal Number from any BSNL phone.

• The subscriber will be given some management codes and password. Using that he can convert/reconvert any BSNL phone into his Universal Personal Number.

• All the calls made by subscriber using his UPN will be billed at his UPN by the IN platform.

• The subscriber will be able to get all his calls incoming on the UPN number anywhere in India.

This is a service newly introduced through Alcatel IN Platform. Virtual Private Network

• Enables the subscriber to establish a private network using existing public network resources.

• Virtual PABX and it can be nation wide. • Individual members can have privileges-ON net. • Calling possible from outside VPN-Off net • Billing will be against the Group id

VPN Features

• Multi site Organization • Short Group Numbers • Abbreviated Dialing • Date & Time Screening • Exception List • Call Duration Control

• Multiple Account Codes • Dual Invoicing • Call Forwarding • Hunting List • Substitution

Tele-Voting Service

• To conduct telephonic public opinion polls and surveys. Thus provides easiest way to conduct poll/survey.

• Opinion by dialing the advertised Tele-voting number. The calling user can be charged (Unit) or charge free.

• The service can be available based on origin or time basis. Tele Vote Features

• Validity Period • Counters • Global Vote Counter • Local Tele voting Counter per

VOT number • Winner Counter

• Black List • Origin Dependent Handling • Day Type/Time Dependent

Handling • Pre Filtering at SSP

E2E3 IN Ver2 17.11.2007 9 of 9

Fixed Line Pre-paid Service

Types of FLPP Services in BSNL 1. PCO FLPP Account - offering only Prepaid Services (for Local +STD+ISD) 2. General FLPP Account - offering both Prepaid & Postpaid services 3. General FLPP Account offering only Prepaid services

FLPP PCO and FLPP General Pure pre paid - can be given to subscribers from AXE-10, 5ESS, EWSD, E-10B, OCB-283 and not from CDOT. Dialing Plan: Only Destination Number needs to be dialed. Internal Routing Plan:

• As on date only OCB-283 exchanges can act as SSP and trigger the FLPP Calls to the SCP.

• Rest of the new Technology exchange shall only prefix the FLPP Call with 1805- 345/ 233 and then the call shall be routed to nearest OCB –283 exchange which will further trigger the FLPP Calls to the SCP.

• If the FLPP Call is originated from E-10B Exchange then the exchange shall simply route to any of the new technology exchange. Further routing shall be as explained above.

FLPP General ‘Pre paid over post paid’ - can be given to subscribers from AXE-10, 5ESS, EWSD, OCB-283 and not from E-10B, CDOT. Dialing Plan: a. Post paid by default : Only Destination Number needs to be dialed(this shall not be FLPP Call). b. To Make prepaid call: 1805 345/233 + destination number Internal Routing Plan:

• As on date only OCB-283 exchanges can act as SSP and trigger the FLPP Calls to the SCP.

• Rest of the new Technology exchange shall simply route the FLPP Calls to nearest OCB -283 exchange which will further trigger the FLPP Calls to the SCP.

(Not available from CCB PCOs) Note:

• FLPP ‘Prepaid over Post paid’ can not be provided from E-10B and C-DoT exchanges because of its inability to send more than 16 digits on trunks.

• FLPP ‘Pure Prepaid’ can not be provided from C-DoT exchanges because of it routes the local without treating it as IN Call and ISD calls can also be not made because of its inability to send more than 16 digits on trunks.

Section-I

Chapter-1

Maintenance issues: Battery and Power plant

E2E3 Battery Power plant, Ver1 24.08.2007 1 of 5

GENERAL INTRODUCTION The power plant of any telecommunication system is usually referred as the ‘heart’ of the installation since the communication system can function only as long as power supply is available. Failure of power supply system in any installation renders the communication facilities offered by it to be instantly paralyzed. Requirement of Power Supply: Any power supply arrangement for a communication system must have two basic characteristics.

i. Reliability of the components of the power plant and continuity of the power supply.

ii. The power fed to the exchange equipment should be free from noise or hum

and to telegraph equipment from large ripple harmonics.

Maintenance – Free Secondary Cells

Maintenance free, valve-regulated lead-acid (VRLA) batteries ensure a reliable effective and user friendly source of power. It is spill proof and explosion resistant and there is no need to add water or to clean terminals. It has low self-discharge rate which eliminates the need for equalizing charges. The container is made of polypropylene. Each plate is individually wrapped by a highly absorbent, microporous glass separate developed specially for VRLA batteries. The chemically inert glass ensures life long service. The absorbed electrolyte ensures that there is no spillage even in the unlikely event of puncture of the cell. Gas evolution under float conditions is negligible. The water loss throughout life due to gassing is roughly 0.1% of the total electrolyte present in the cell. This will in no way affect performance and also eliminate the need for specially ventilated battery room and acid resisting flooring. As the batteries can be installed in stacks, there will be considerable space saving also. Various capabilities of Batteries are 120 AH, 400 AH, 600 AH, 1000AH, 1500 AH, 2000 AH, 2500 AH, 3000 AH, 4000 AH & 5000 AH. VRLA Technology – A brief review of Chemical Reaction The electrode in all lead acid batteries, including VRLA battery is basically identical. As the battery is discharged the lead dioxide positive active material and the spongy lead negative active material react with the sulphuric acid electrolyte to form lead sulphated and water. During charge, this process is reversed. The Coulombic efficiency of the charging process is less than 100% on reaching final stage of charging or under over charge conditions, the charging energy is consumed for electrolyte decomposition of


water and the positive plates generate oxygen gas and the negative plates generate hydrogen gas. Under typical charging conditions, oxygen at the positive plate occurs before hydrogen evolution at the negative. This feature is utilized in the design of VRLA batteries. In flooded cells, the oxygen gas evolved at the positive plate bubbles upwards through the electrolyte and is released through the vents. In MF-VRLA batteries the oxygen gas evolved, at the positive plate, instead of bubbling upwards in transported in the gas phase through the separator medium to the negative plate. The separator is a highly absorbent glass matrix type with very high porosity, designed to have pore volume in excess of the electrolyte volume (starved electrolyte design), due to which the oxygen gas finds an unimpeded path to the negative plate. the oxygen gas gets reduced by reaction with the spongy lead at the negative plate, turning a part of it into a partially discharged condition, there by effectively suppressing the hydrogen gas evolution at the negative plate. This is what is known as the oxygen recombination principle. The part of negative plate which was partially discharged is then reverted to the original spongy lead by subsequent charging. Thus a negative plate keeping equilibrium between the amount which turns into spongy lead by charging and the amount of spongy lead which turns into lead sulphated by absorbing the oxygen gas generated at the positive plate. The oxygen recombination principle can be shown by the following reaction: 1. Reaction at positive plate : H2O = 1/2 O2 + 2e ………(1) 2. Reaction at negative plate : Pb + 1/2 O2 = PbO ……….(2) PbO + H2SO4 = PbSO4 + H2O ……….(3) To reaction (1) PbSO4 + 2H + 2e = Pb + H2SO4 ………(4) To reaction (3) To reaction (2) 3. The total reaction at negative plate 1/2 O2 + 2H = H2O Thus, the recombination technology makes the battery virtually Maintenance Free.


♦ Battery capacity :The energy that can be taken out of a battery before the cell voltage collapses is called the battery capacity. It is defined as Discharge current (A ) × Discharge Duration time (hours).

MONITORING OF VRLA BATTERIES

Following steps are required for monitoring of the VRLA Batteries: (a) Periodic physical inspection of each cell of the battery for cracks and leaking etc. (b) Discharge of battery for a short duration and recording the voltages of each cell

in the string. (c) Measurement of a mark deviation (>30%) in the impedance or conductance of

the cell as compared to the one recorded at the time of commissioning. (d) Measurement & recording of cell temp. periodically. (e) Float Voltage of cells & its comparison with the mid point voltage. (f) Float current in fully charged battery.

Periodic Physical Inspection: Check for any crack or leakage every month. If not every month, at least once in two months. Battery Partial Discharge Test: Put battery to a test discharge for 30 minutes by shutting power plant so that 20% of the battery is discharged. This can be decided by the table supplied by the manufacturer. Record the Voltage of each cell. Any cell showing more than 5% variation compared to voltage of other cell can be potential weak cell. Impedance Measurement:Take impedance measurement when the charger is on and the battery is on float. Any change in impedance/conductance of the cell more than 40% shows imminent failure of the battery/cell. A change of <30% shows a healthy battery/ cell. Temperature: Every 10 degree rise in battery temperature doubles the chemical reaction in the battery. The SMPS power plant takes care of the temperature by reducing the charging voltage but still it is important to measure individual cell temp. periodically and keep record for study and analysis. Float Voltage: Float voltage is another important parameter on which life and performance of the battery depends. The float voltage should be set to 2.25 V per cell and charge voltage to 2.3 V per cell taking the adjustment factor of 3 mV/cell per degree centigrade. Mid-point Voltage Measurement: Some battery monitors measure the midpoint voltage of each battery string. In this method the monitor will raise an alarm if there is a sufficient imbalance in the two half string voltages. Individual Cell Monitoring: In this technique, the voltage of each is measured and deviation in any of cell can be detected quickly.


Effect of Temperature on the battery: With rise in temperature the battery life decreases. For every 10 degree rise in temperature, the capacity of battery becomes half. There is a temperature compensation in SMPS Power Plants and it is 3 milli-volt per degree rise in temp. Life of battery:

• Batteries upto 200AH: 4 Years • Batteries more than 200 AH: 6 years

SMPS(Switched Mode Power Supply) Power plant: The salient features of SMPS power plant are:

1) The power system is intended primarily to provide uninterrupted DC power to telecom exchange and current for charging the batteries.

2) The system works from commercial AC mains which is rectified and regulated to -54 V DC and is fed to the equipment (exchange).

3) The modules switching frequency for SMPS is 107.5 kHz. Therefore size of the module is very compact.

4) The system has provision to connect three sets of VRLA batteries and facility to charge them simultaneously to ensure that uninterrupted DC power is always available to the exchange.

5) The power systems is suitable for VRLA batteries. Life of Power Plant:

• Static P/P : 15 years • SMPS P/P: 15 years


Earthing

Purposes of Earthing Apart from protection from hazardous stray currents in electrical equipment in

Telecommunication circuits and equipments, earthing is provided for the following purposes:

(a) Reduction of Crosstalk and Noise :

One pole of the battery (+ve pole) is earthed in the telephone exchange so that cross talk between the various circuits due to the speech currents of one circuit finding path through the other via common battery feed points of the transmission bridge and poor NSN via earthed terminal of the battery is reduced.

(b) Protection of buildings and equipments from lighting strikes. (c) Used as return path for the conductors in some telegraph and voice circuits. (d) Protection of costly apparatus and persons against foreign voltages and

leakage currents from power wirings to the metallic frame of the equipment. (e) Earth is used to afford convenience &” reliability, in the operate path of the

circuits involved in the switching apparatus of telecom circuits. (f) Earthing power supply systems is used to effect reliability of power as it

helps to provide stability of voltage conditions preventing excess fluctuations and providing a measure of protection against lighting.

Earth Electrodes :

Three types of earth electrodes are commonly used for earthing systems. 1) Rod electrodes 2) Plate electrodes 3) Strip electrodes

Instruction for monitoring of Earth resistance were issued from Corporate office. As per the instruction:

• E/R is to be measured every six months. • Earth resistance should be less than 0.5 � for electronic • One dry season must be included in these two occasions. • For lightning prone area, it should be measured every month. • Wherever, it is beyond limits, it should be immediately brought within limits. • Procedure for laying earth resistance may be followed as prescribed in the latest

issue of EI on Protection Earthing I-001. • Reduction in card failure has been observed by improving the earth resistance.

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E2E3 AC and EA, Ver1 24.08.2007 6 of 10

ENGINE & ALTERNATOR

The standby power supply commonly used in T.E buildings is from Diesel Engine Alternator Set .In the Engine Alternator Set, the Diesel engine is the prime mover which rotates the alternator of the engine Alternator set and alternator in turn produces Electrical energy. In the first stage of energy conversion, the chemical energy of fuel is converted in to the mechanical energy at the common shaft of Engine & Alternator. This mechanical energy is then converted into electrical energy at alternator in the second stage of energy conversion.

PRINCIPLE OF OPERATION OF ENGINE When the fuel ignites in the combustion chamber, energy in the form of heat and gases is generated. The rapid expansion of hot gases creates pressure in the combustion chamber which pushes the piston away. The reciprocating motion of the piston is converted in to the circular motion by the engine crankshaft, which is connected to the piston by the connecting rod.

FOUR –STROKE PRINCIPLE OF DIESEL ENGINES The four stroke working principle of Diesel Engine is as under:

(i) ADMISSION STROKE

The piston draws fresh air into the cylinder on its downward travel through the open admission valve. With turbo charged engines the air is first compressed by a blower and admitted to the cylinder under increased pressure.

(ii) COMPRESSION STROKE

On its upward travel the piston compress the fresh air in the cylinder with the valves closed. The temperature of the fresh air is thus increased to exceed the ignition temperature of the fuel. Shortly

E2E3 AC and EA, Ver1 24.08.2007 7 of 10

before the piston reaches the top dead centre, fuel is injected into the combustion space.

(iii) POWER STROKE

The fuel injected ignites in the hot air and burns. The combustion causes a high pressure which forces the piston down. Resulting into reciprocating movement of the shaft.

(iv) EXHAUST STROKE

The piston moving upward forces the exhaust gas through the open exhaust valve into the exhaust pipe. When the exhaust stroke is terminated the exhaust valve close and the admission valve opens for a new operation cycle.

SYSTEMS OF A DIESEL ENGINE Various systems of diesel engine constituting the working system are as below:

E2E3 AC and EA, Ver1 24.08.2007 8 of 10

(1) LUBRICATION SYSTEM The moving parts of the diesel engine are lubricated for their optimum operation by this lubrication system. A dipstick in the oil sump serves to check the oil level. The lub oil level and the lubrication oil pressure have to be checked for satisfactory performance and long life of the engine. (2) FUEL SYSTEM

Depending on the position of the fuel, the fuel is supplied to the distributing pipe through fuel filter either by natural head from an elevated tank or by a fuel pump. Fuel is supplied inside the cylinder by injection nozzles.

(3) AIR EXHAUST SYSTEM For the combustion of fuel sufficient quantity of the filtered air is taken in the combustion chamber. After the combustion the exhaust gases are taken away from the engine through suitable ducting or piping. This is known as air exhaust system.

(4) COOLING SYSTEM

Cooling System is essential for cooling the engine body, and to act as a heat exchanger for lubricating oil. This can be either water-cooled or air –cooled.

(5) STARTING SYSTEM

The Diesel Engine can be equipped with the starting system i.e. with an electric starter with a pinion, which engages with the fly wheel of the engine. The power to the electric starter is provided by means of a battery which is kept in charged condition by means of a dynamo or electric rectifier.

ALTERNATOR

Alternator works on Faraday’s law of Electromagnetic induction. There are two requirements for the functioning of Alternator– (1) Magnetic field & (2) Rotation. Magnetic field is produced by passing direct current through the field winding of the Alternator and rotation is achieved by means of coupling the alternator from engine. The Automatic Voltage regulator (AVR) is provided in the alternator for maintaining the terminal voltage within the close limits over wide operating condition.

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INDICATIONS OF A HEALTHY ENGINE

An engine is said to be healthy if it has:

1. Good Compression: The temperature of the induced air when entrapped and compressed in the combustion chamber is about 540 deg C to 560 deg C.

2. Good Combustion:

Fuel is sprayed in atomized form to ensure proper ignition of the fuel. Burning temperature is about 1425 deg C.

3. Clean exhaust:

The exhaust system is clean and back pressure is with in permissible limits. The general condition of the Engine can be determined by the type of smoke it emits. This can be said as “The pulse of the engine”. Smoke should be of brown colour (Barely visible haze). Any other colour of smoke indicates some problem in the engine.

IMPORTANT MAINTENANCE CHECKS FOR ENGINE ALTERNATOR SET

Daily

1. Check Engine oil level and leakage if any. 2. Check Radiator for water level and leakage if any. 3. Check fuel level. 4. Check that battery charger is in trickle charging position. 5. Check whether insulation of the Exhaust pipe is proper. 6. Check that ventilation of the EA Room is proper. 7. Check oil pressure. 8. Check if lights and exhaust fan are working properly. 9. Check physically before start for loose connection/nut bolt.

Weekly

1. Check Air line connection and filter. 2. Check fan belt, and its tension.

E2E3 AC and EA, Ver1 24.08.2007 10 of 10

Fortnightly

1. Check Battery voltage, Terminals, Electrolyte level (Top up if necessary) . 2. Check Specific Gravity of Electrolyte.

(After the above checks, start the Engine for No Load/Connected Load and test for 10 minutes the following) 1. Check for any abnormal noise. Shut down the E/A immediately and cause

be examined. 2. Check frequency and out put voltage. 3. Check the colour of Exhaust gas 4. Check working of the Indication Lamps. 5. Check working of the Dynamo and Auto Cut off of the Battery charger. 6. Check for any Exhaust gas restriction. 7. Check manual/ auto-changeover from commercial supply on connected

load. 8. Record various readings in the logbook.

Monthly

1. Check for tightness of connections in Engine and Control Panel. 2. Watering of earth pits and tightening of connections. 3. Check functioning of safety devices. 4. Check belt tensions. 5. Check battery charger. 6. Check for leakage of fuel line. 7. Check for leakage in exhaust pipes. 8. Inspect the manufacturer’s chart for due date of maintenance.

Half Yearly

1. Cleaning of bus bars & chambers and tightening of nut bolts. 2. Checking of ACB/MCCB tripping mechanism. 3. Earth testing and Meggering. 4. Relays and other protection devices are working properly.

Yearly

1. Tighten all mounting, nut and bolt. 2. Check crankshaft and float. 3. Clean injector inlet screen. 4. Clean and calibrate all injectors. 5. Check fuel pump calibration. 6. Replace fuel pump filter screen and magnet.

Section-II

Chapter-7

OFC Characteristics & Laying

E2E3 OFC Ver2 17.11.2007 1 of 9

Fiber Characteristics

The main job of optical fibers is to guide light waves with a minimum of attenuation (loss

of signal). Optical fibers are composed of fine threads of glass in layers, called the core

and cladding, that can transmit light at about two-thirds the speed of light in a vacuum.

Though admittedly an over simplification, the transmission of light in optical fiber is

commonly explained using the principle of total internal reflection. With this

phenomenon, 100 percent of light that strikes a surface is reflected. By contrast, a mirror

reflects about 90 percent of the light that strikes it.

Light is either reflected (it bounces back) or refracted (its angle is altered while passing

through a different medium) depending upon the angle of incidence (the angle at which

light strikes the interface between an optically denser and optically thinner material).

Total internal reflection happens when the following conditions are met :

• Beams pass from a more dense to a less dense material. The difference between the

optical density of a given material and a vacuum is the material’s refractive index.

• The incident angle is more than the critical angle. The critical angle is the maximum

angle of incidence at which light stops being refracted and is instead totally reflected.

The principle of total internal reflection within a fiber core is illustrated in Figure 2-6.

The core has a higher refractive index than the cladding, allowing the beam that strikes

that surface at less than the critical angle to be reflected. The second beam does not meet

the critical angle requirement and is refracted.

E2E3 OFC Ver2 17.11.2007 2 of 9

An optical fiber consists of two different types of highly pure, solid glass (silica)—the

core and the cladding—that are mixed with specific elements, called dopants, to adjust

their refractive indices. The difference between the refractive indices of the two materials

causes most of the transmitted light to bounce off the cladding and stay within the core.

The critical angle requirement is met by controlling the angle at which the light is

injected into the fiber. Two or more layers of protective coating around the cladding

ensure that the glass can be handled without damage.

Multimode and Single-Mode Fiber

There are two general categories of optical fiber in use today, multimode fiber and single-

mode fiber.

Multimode, the first type of fiber to be commercialized, has a larger core than single-

mode fiber. It gets its name from the fact that numerous modes, or light rays, can be

carried simultaneously through the waveguide. Figure 2-7 shows an example of light

transmitted in the first type of multimode fiber, called step-index. Step-index refers to the

fact that there is a uniform index of refraction throughout the core; thus there is a step in

the refractive index where the core and cladding interface. Notice that the two modes

must travel different distances to arrive at their destinations. This disparity between the

times that the light rays arrive is called modal dispersion. This phenomenon results in

poor signal quality at the receiving end and ultimately limits the transmission distance.

This is why multimode fiber is not used in wide-area applications.

To compensate for the dispersion drawback of step-index multimode fiber, graded-index

fiber was invented. Graded-index refers to the fact that the refractive index of the core is

graded—it gradually decreases from the center of the core outward. The higher refraction

at the center of the core slows the speed of some light rays, allowing all the rays to reach

E2E3 OFC Ver2 17.11.2007 3 of 9

their destination at about the same time and reducing modal dispersion. The second

general type of fiber, single-mode, has a much smaller core that allows only one mode of

light at a time through the core (see Figure 2-8). As a result, the fidelity of the signal is

better retained over longer distances, and modal dispersion is greatly reduced. These

factors attribute to a higher bandwidth capacity than multimode fibers are capable of. For

its large information carrying capacity and low intrinsic loss, single-mode fibers are

preferred for longer distance and higher bandwidth application including DWDM.

Single-Mode Fiber Designs

Designs of single-mode fiber have evolved over several decades. The three principle

types and their ITU-T specifications are:

• Non-dispersion-shifted fiber (NDSF), G.652

• Dispersion-shifted fiber (DSF), G.653

• Non-zero dispersion-shifted fiber (NZ-DSF), G.655

As discussed earlier, and shown in Figure 2-1, there are four windows within the infrared

spectrum that have been exploited for fiber transmission. The first window, near 850 nm,

was used almost exclusively for short-range, multimode applications. Non-dispersion-

shifted fibers, commonly called standard single-mode (SM) fibers, were designed for use

in the second window, near 1310 nm. To optimize the fiber’s performance in this

window, the fiber was designed so that chromatic dispersion would be close to zero near

the 1310-nm wavelength As optical fiber use became more common and the needs for

greater bandwidth and distance increased, a third window, near 1550 nm, was exploited

for single-mode transmission. The third window, or C band, offered two advantages: it

had much lower attenuation, and its operating frequency was the same as that of the new

erbium-doped fiber amplifiers (EDFAs). However, its dispersion characteristics were

severely limiting. This was overcome to a certain extent by using narrower linewidth and

higher power lasers. But because the third window had lower attenuation than the 1310-

nm window, manufacturers came up with the dispersion-shifted fiber design, which

E2E3 OFC Ver2 17.11.2007 4 of 9

moved the zero-dispersion point to the 1550-nm region. Although this solution now

meant that the lowest optical attenuation and the zero-dispersion points coincided in the

1550-nm window, it turned out that there are destructive nonlinearities in optical fiber

near the zero-dispersion point for which there is no effective compensation. Because of

this limitation, these fibers are not suitable for DWDM applications. The third type, non-

zero dispersion-shifted fiber, is designed specifically to meet the needs of DWDM

applications. The aim of this design is to make the dispersion low in the 1550-nm region,

but not zero. This strategy effectively introduces a controlled amount of dispersion,

which counters nonlinear effects such as four-wave mixing (see the “Other Nonlinear

Effects” section on page 2-11) that can hinder the performance of DWDM systems.

Transmission Challenges

Transmission of light in optical fiber presents several challenges that must be dealt with.

These fall into the following three broad categories:

• Attenuation—decay of signal strength, or loss of light power, as the signal

propagates through the fiber

• Chromatic dispersion—spreading of light pulses as they travel down the fiber

• Nonlinearities—cumulative effects from the interaction of light with the material

through which it travels, resulting in changes in the lightwave and interactions

between lightwaves

Attenuation

Attenuation in optical fiber is caused by intrinsic factors, primarily scattering and

absorption, and by extrinsic factors, including stress from the manufacturing process, the

environment, and physical bending. The most common form of scattering, Rayleigh

scattering, is caused by small variations in the density of glass as it cools. These

variations are smaller than the wavelengths used and therefore act as scattering objects

(see Figure 2-9). Scattering affects short wavelengths more than long wavelengths and

limits the use of wavelengths below 800 nm.

Attenuation due to absorption is caused by the intrinsic properties of the material itself,

the impurities in the glass, and any atomic defects in the glass. These impurities absorb

the optical energy, causing the light to become dimmer (see Figure 2-10). While Rayleigh

scattering is important at shorter wavelengths, intrinsic absorption is an issue at longer

E2E3 OFC Ver2 17.11.2007 5 of 9

wavelengths and increases dramatically above 1700 nm. However, absorption due to

water peaks introduced in the fiber manufacturing process are being eliminated in some

new fiber types.

The primary factors affecting attenuation in optical fibers are the length of the fiber and

the wavelength of the light. Figure 2-11 shows the loss in decibels per kilometer (dB/km)

by wavelength from Rayleigh scattering, intrinsic absorption, and total attenuation.

Dispersion

Dispersion is the spreading of light pulses as they travel down optical fiber. Dispersion

results in distortion of the signal (see Figure 2-12), which limits the bandwidth of the

fiber.

Two general types of dispersion affect DWDM systems. One of these effects, chromatic

dispersion, is linear while the other, polarization mode dispersion (PMD), is nonlinear.

E2E3 OFC Ver2 17.11.2007 6 of 9

Chromatic Dispersion

Chromatic dispersion occurs because different wavelengths propagate at different speeds.

The effect of chromatic dispersion increases as the square of the bit rate. In single-mode

fiber, chromatic dispersion has two components, material dispersion and waveguide

dispersion. Material dispersion occurs when wavelengths travel at different speeds

through the material. A light source, no matter how narrow, emits several wavelengths

within a range. Thus, when this range of wavelengths travels through a medium, each

individual wavelength arrives at a different time. The second component of chromatic

dispersion, waveguide dispersion, occurs because of the different refractive indices of the

core and the cladding of fiber. The effective refractive index varies with wavelength as

follows:

• At short wavelengths, the light is confined within the core. Thus the effective

refractive index is close to the refractive index of the core.

• At medium wavelengths, the light spreads slightly into the cladding. This

decreases the effective refractive index.

• At long wavelengths, much of the light spreads into the cladding, bringing

effective refractive index very close to that of the cladding.

This result of the phenomenon of waveguide dispersion is a propagation delay in one or

more of the wavelengths relative to others. Total chromatic dispersion, along with its

components, is plotted by wavelength in Figure 2-13 for dispersion-shifted fiber. For

non-dispersion-shifted fiber, the zero dispersion wavelength is 1310 nm.

Though chromatic dispersion is generally not an issue at speeds below STM-16, it does

increase with higher bit rates due to the spectral width required. New types of zero-

dispersion-shifted fibers greatly reduce these effects. The phenomenon can also be

mitigated with dispersion compensators.

E2E3 OFC Ver2 17.11.2007 7 of 9

Polarization Mode Dispersion

Most single-mode fibers support two perpendicular polarization modes, a vertical one and

a horizontal one. Because these polarization states are not maintained, there occurs an

interaction between the pulses that results is a smearing of the signal. Polarization mode

dispersion (PMD) is caused by ovality of the fiber shape as a result of the manufacturing

process or from external stressors. Because stress can vary over time, PMD, unlike

chromatic dispersion, is subject to change over time. PMD is generally not a problem at

speeds below STM-64.

Other Nonlinear Effects

In addition to PMD, there are other nonlinear effects. Because nonlinear effects tend to

manifest themselves when optical power is very high, they become important in DWDM.

Linear effects such as attenuation and dispersion can be compensated, but nonlinear

effects accumulate. They are the fundamental limiting mechanisms to the amount of data

that can be transmitted in optical fiber. The most important types of nonlinear effects are

stimulated Brillouin scattering, stimulated Raman scattering, self-phase modulation, and

four-wave mixing.

In DWDM, four-wave mixing is most critical of these types. Four-wave mixing is caused

by the nonlinear nature of the refractive index of the optical fiber. Nonlinear interactions

among different DWDM channels creates sidebands that can cause interchannel

interference. In Figure 2-14 three frequencies interact to product a fourth frequency

resulting in cross-talk and signal-to-noise degradation.

The effect of four-wave mixing is to limit the channel capacity of a DWDM system.

Four-wave mixing cannot be filtered out, either optically or electrically, and increases

with the length of the fiber. Due to its propensity for four-wave-mixing, DSF is

unsuitable for WDM applications. This prompted the invention of NZ-DSF, which takes

advantage of the fact that a small amount of chromatic dispersion can

be used to mitigate four-wave mixing.

E2E3 OFC Ver2 17.11.2007 8 of 9

Summary

In the long-distance network, the majority of embedded fiber is standard single-mode

(G.652) with high dispersion in the 1550-nm window, which limits the distance for STM-

64 transmission. Dispersion can be mitigated to some extent, and at some cost, using

dispersion compensators. Non-zero dispersion-shifted fiber can be deployed for STM-64

transport, but higher optical power introduces nonlinear effects. In the short-haul

network, PMD and nonlinear effects are not so critical as they are in long-haul systems,

where higher speeds (STM-64 and higher) are more common. DWDM systems using

optical signals of 2.5 Gbps or less are not subject to these nonlinear effects at short

distances.

The major types of single-mode fibers and their application can be summarized as

follows:

• Non-dispersion-shifted fiber (standard SM fiber)—accounts for greater than 95

percent of deployed plant; suitable for TDM (single-channel) use in the 1310-nm

region or DWDM use in the 1550-nm region (with dispersion compensators). This

type of fiber can also support 10 Gigabit Ethernet standard at distances over 300

meters.

• Dispersion-shifted fiber—suitable for TDM use in the 1550-nm region, but

unsuitable for DWDM in this region.

• Non-zero dispersion-shifted fiber—good for both TDM and DWDM use in the

1550-nm region.

• Newer generation fibers—includes types that allow the energy to travel further

into the cladding, creating a small amount of dispersion to counter four-wave

mixing, and dispersion-flattened fibers, which permit use of wavelengths farther

from the optimum wavelength without pulse spreading.

Note As bit rates increase to 40 Gbps and beyond, the interdependence between system

design and fiber design will become increasingly important for strategic planning.

Laying of cable

It is as per letter no DOT. 352/91 TPL(OP) dated at ND- 08-04-1992 1) soil categorization : ( for depth of trench ) (A) Rocky : Cable trench, where can not be dug without blasting

and/or chiseling. (B) Non Rocky : Other than ‘A’ above including murram and soil mixed with stone and soft rock.

E2E3 OFC Ver2 17.11.2007 9 of 9

2) Pipes for cable laying and protection (1) HDPE pipe 75 mm (diameter) length 5m. (approx 18 to 20’ ) phase I (2) HDPE pipe 50 mm (diameter) length 5m. (approx 18 to 20’ ) phaseII (3) PLB pipe (40 mm. outer diameter ) length 1km/200m ( town limets with rope) phase III (4) GI pipe for PLP 50 mm dia length 6 meter 3) Measurement of cable depth (all depth should be measured from the top of pipe. However it is acceptable if it is less by more then eight cms. from the specified. (A) Cross country rout (normal soil)

• above HDPE pipe 1.5 meter

• trench depth 1.65 meter

• in rocky area minimum depth 0.9 m ( where dug is not possible more then 1 meter above pipe due to any obstruction should be consider) and all cables having depth less then 1.2 meter should be protected by RCC/GI pipes

(B) In built up area (city/town/urban area)

1. OF cable should be laid through exiting duct. 2. GI pipe or RCC pipe at the entry of duct. 3. In non duct area it should be laid through HDPE pipe/PLP pipe at dept 1.5

meter using RCC/GI pipe for protection. 4. Depth in rocky soil may be consider as 0.9 to 1.0 meter

(C) On culvert/bridge over river and nallah.

(1) At the depth of 1.5 meter below the bed throw HDPE/RCC Pipe. Pipe length should be 2 meter extended at both ends. (2) This should be fixed along the parapet wall/bridge wall when the river or nalla full of water through out year, through fixed GI pipe on wall at suitable height above the water level.

(D) Along rail bridge or crossing Through HDPE pipe/PLP pipe protected by RCC or iron pipe as per the prescribed by railway authority.

(E) On road crossing

At a depth of 1.5 meter through HDP pipe enclosed in RCC pipe extended by 3.0 meter to the side end of the read.

4) Indicators along route (A) Route indicator

At every 200 m route length of showing name of route & no of indicators. (B) Joint indicator At every joint (Splice) generally it is placed at every 2/4 Km(Drum length) (C) Branch (Root diversion) indicator Provided at route diversion or branching from the main root.

Section-II

Chapter-8

OFC Test Measuring Instruments

E2E3 OFC testing instruments Ver1 24.08.2007 1 of 4

OFC Test Measuring Instruments

1.0 Main Tests on OFC • Cable Loss. • Splice Loss. • Connector Loss. • Fibre Length. • Continuity of Fiber. • Fault Localizations/Break Fault

2.0 Main Instruments Required

• Calibrated Light Source. • Optical Power Meter. • Optical Attenuator. • Optical Time Domain Reflectometer (OTDR).

2.1 Calibrated Light Source

• Generates Light signals of known power and wavelength (LED or LASER). • Wavelength variations to match Fiber's Wavelength.

2.2 Calibrated Power Source

• Measures Optical Power over wide range (Typically 1 nW to 2mW/-60dBm to + 3dBm)

• It is never measured directly, but measured through Electrical conversion using Photo Electric conversion. It is known as OPTICAL SENSOR of known Wavelength.

• The accuracy of the Optical Power meter depends upon the stability of the Detector’s power to current conversion which changes with Ageing.

2.3 Power Attenuator

TYPES:- • Fixed Attenuators. • Variable Attenuators.

APPLICATIONS:-

• To Simulate the Regenerator Loss at the FDF. • To Provide Local Loop Back for Testing. • To measure the Bit Error Rate by varying the Optical Signal at the

Receiver Input. (RECEIVER SENSITIVITY)


2.3.1 Requirements of Attenuators

• Attenuation Range. • Lowest Insertion Loss. • Independent of Wavelength. • Type of Connectors at the Input and Output

2.4 OPTICAL TIME DOMAIN REFLECTOMETER is used for measuring

• Fiber Loss. • Splice Loss. • Connector Loss. • Fiber Length. • Continuity of Fiber. • Fault Localization.

OPERAING PRINCIPLES

• One Port Operation. • Works on the Principle of Back Scattering (Raleigh Scattering).

o Scattering is the main cause of Fiber Loss o Scattering Coefficient=1/l4 o An Optical Pulse is launched into one End of Fiber and Back

Scattered Signals are detected. o These Signals are approximately 50 dB below the Transmitted

level. • Measuring conditions and Results are displayed.



Section-II

Chapter-9

SDH Overview

E2E3 SDH Overview, Ver1 24.08.2007 1 of 9

SDH Introduction SDH (Synchronous Digital Hierarchy) is a standard for telecommunications transport formulated by the International Telecommunication Union (ITU), previously called the International Telegraph and Telephone Consultative Committee (CCITT). SDH was first introduced into the telecommunications network in 1992 and has been deployed at rapid rates since then. It’s deployed at all levels of the network infrastructure, including the access network and the long-distance trunk network. It’s based on overlaying a synchronous multiplexed signal onto a light stream transmitted over fiber-optic cable. SDH is also defined for use on radio relay links, satellite links, and at electrical interfaces between equipment. The comprehensive SDH standard is expected to provide the transport infrastructure for worldwide telecommunications for at least the next two or three decades. The increased configuration flexibility and bandwidth availability of SDH provides significant advantages over the older telecommunications system. These advantages include:

• A reduction in the amount of equipment and an increase in network reliability.

• The provision of overhead and payload bytes – the overhead bytes permitting management of the payload bytes on an individual basis and facilitating centralized fault sectionalisation.

• The definition of a synchronous multiplexing format for carrying lower-level digital signals (such as 2 Mbit/s, 34 Mbit/s, 140 Mbit/s) which greatly simplifies the interface to digital switches, digital cross-connects, and add drop multiplexers.

• The availability of a set of generic standards, which enable multi-vendor interoperability.

• The definition of a flexible architecture capable of accommodating future applications, with a variety of transmission rates.

In brief, SDH defines synchronous transport modules (STMs) for the fiber-optic based transmission hierarchy.

Background Before SDH, the first generations of fiber-optic systems in the public telephone network used proprietary architectures, equipment line codes, multiplexing formats, and maintenance procedures. The users of this equipment wanted standards so they could mix and match equipment from different suppliers. The task of creating such a standard was taken up in 1984 by the Exchange Carriers Standards Association (ECSA) in the U.S. to establish a standard for connecting one fiber system to another. In the late stages of the development, the CCITT became involved so that a single international standard might be developed for fiber interconnect between telephone networks of different countries. The resulting international standard is known as Synchronous Digital Hierarchy (SDH).


Synchronization of Digital Signals To understand correctly the concepts and details of SDH, it’s important to be clear about the meaning of Synchronous, Plesiochronous, and Asynchronous. In a set of Synchronous signals, the digital transitions in the signals occur at exactly the same rate. There may however be a phase difference between the transitions of the two signals, and this would lie within specified limits. These phase differences may be due to propagation time delays, or low-frequency wander introduced in the transmission network. In a synchronous network, all the clocks are traceable to one Primary Reference Clock (PRC). The accuracy of the PRC is better than ±1 in 1011 and is derived from a cesium atomic standard. If two digital signals are Plesiochronous, their transitions occur at “almost” the same rate, with any variation being constrained within tight limits. These limits are set down in ITU-T recommendation G.811. For example, if two networks need to interwork, their clocks may be derived from two different PRCs. Although these clocks are extremely accurate, there’s a small frequency difference between one clock and the other. This is known as a plesiochronous difference. In the case of Asynchronous signals, the transitions of the signals don’t necessarily occur at the same nominal rate. Asynchronous, in this case, means that the difference between two clocks is much greater than a plesiochronous difference. For example, if two clocks are derived from free-running quartz oscillators, they could be described as asynchronous.

SDH Advantages The primary reason for the creation of SDH was to provide a long-term solution for an optical mid-span meet between operators; that is, to allow equipment from different vendors to communicate with each other. This ability is referred to as multi-vendor inter working and allows one SDH-compatible network element to communicate with another, and to replace several network elements, which may have previously existed solely for interface purposes. The second major advantage of SDH is the fact that it’s synchronous. Currently, most fiber and multiplex systems are plesiochronous. This means that the timing may vary from equipment to equipment because they are synchronized from different network clocks. In order to multiplex this type of signal, a process known as bit stuffing is used. Bit stuffing adds extra bits to bring all input signals up to some common bit-rate, thereby requiring multi-stage multiplexing and demultiplexing. Because SDH is synchronous, it allows single- stage multiplexing and demultiplexing. This single stage multiplexing eliminates hardware complexity, thus decreasing the cost of equipment while improving signal quality. In plesiochronous networks, an entire signal had to be demultiplexed in order to access a particular channel; then the non-accessed channels had to be re-multiplexed back together in order to be sent further along the network to their proper destination. In SDH format, only those channels that are required at a particular point are demultiplexed, thereby eliminating the need for back to-back multiplexing. In other words, SDH makes individual channels “visible” and they can easily be added and dropped.


Plesiochronous Digital Hierarchy (PDH) Traditionally, digital transmission systems and hierarchies have been based on multiplexing signals, which are plesiochronous (running at almost the same speed). Also, various parts of the world use different hierarchies which lead to problems of international inter working; for example, between those countries using 1.544 Mbit/s systems (U.S.A. and Japan) and those using the 2.048 Mbit/s system. To recover a 64 kbit/s channel from a 140 Mbit/s PDH signal, it’s necessary to demultiplex the signal all the way down to the 2 Mbit/s level before the location of the 64 kbit/s channel can be identified. PDH requires “steps” (140-34, 34-8, 8-2 demultiplex; 2-8, 8-34, 34- 140 multiplex) to drop out or add an individual speech or data channel (see Figure 1). This is due to the bit stuffing used at each level.

Demultiplex

Demultiplex

Multiplex

Multiplex

MultiplexElectric/

optical

A D M

2Mbit/s (Electric signal)

SDH

Optical/

electric

155Mbit/s 155Mbit/s

140/34Mbit/s

Optical

interface

2Mbit/s (Electric signal)

34/8Mbit/s8/34Mbit/s

34/140Mbit/s

8/2Mbit/s 2/8Mbit/s

PDHOptical/

electric

DemultiplexDemultiplex

Optical

interface

Figure 1. Comparison between the adding/dropping signals of SDH and those of PDH

Limitations of PDH Network The main limitations of PDH are: • Inability to identify individual channels in a higher order bit stream. • Insufficient capacity for network management; • Most PDH network management is proprietary. • There’s no standardized definition of PDH bit rates greater than 140 Mbit/s. • There are different hierarchies in use around the world. Specialized interface equipment is required to interwork the two hierarchies.


Basic SDH Signal The basic format of an SDH signal allows it to carry many different services in its Virtual Container (VC) because it is bandwidth-flexible. This capability allows for such things as the transmission of high-speed packet-switched services, ATM, contribution video, and distribution video. However, SDH still permits transport and networking at the 2 Mbit/s, 34 Mbit/s, and 140 Mbit/s levels, accommodating the existing digital hierarchy signals. In addition, SDH supports the transport of signals based on the 1.5 Mbit/s hierarchy.

SDH Frame Structure SDH transmission is in the unit of byte and its frame structure is a rectangular massive

one based on the byte structure, including 270 × N columns and 9-row bytes, each of which has 8 bits. The rectangular frames of SDH are transmitted row by row on optical fibers after parallel/serial conversion at the optical transmitting end and are recovered into rectangular massive ones for processing after serial/parallel conversion at the optical receiving end. The bytes in an SDH frame are transmitted row by row from left to right, beginning with the first byte at the left top of the figure. This transmission row

by row continues until 9 × 270 × N bytes are all transmitted. Then it is time for the next frame to be transmitted. Thus, one frame after another is transmitted. 8,000 frames with the constant frame length being 125µs can be transmitted. The frame frequency of SDH is 8,000 frames/second. That is, a specific byte in a signal frame is transmitted

8,000 times per second and the bit rate of this byte is 8,000 × 8bit=64kbit/s, namely, the transmission rate of 1-channel digital telephone. Take for example the STM-1

level, whose rate is 270 (270 columns/frame) × 9 (altogether 9 rows) × 64kbit/s (64kbits for each byte) =155520kbit/s =155. 520Mbit/s. It can be seen in Fig.2 that the frame structure of STM-N is made up of three parts: section overhead, including Regenerator Section Overhead (RSOH) and Multiplex Section Overhead (MSOH), Information Payload (Payload) and Administrative Unit Pointer (AU-PTR).

1. Section Overhead (SOH) area SOH means the additional bytes in the STM-N frame structure needed for normal and flexible transmission of information payload and these bytes are mainly used for the

running, management and maintenance of the network. In the 1~ 9 × N columns of the SDH frame, 1~3 rows and 5~9 rows are allocated to the SOH. SOH can be further categorized as RSOH and MSOH}. 1~3 rows are allocated to RSOH and 5~9 rows to MSOH. RSOH can be accessed either at the regenerator to at the terminal equipment. However, MSOH passes a regenerator transparently and is terminated at the terminal equipment.

2. Payload (Payload) area Information payload area is the place where information about various services is

stored in the SDH frame structure. Horizontal columns 10 × N~270 × N, and vertical rows 1~9 belong to the information payload area. In it, there are still some Path Overhead (POH) bytes transmitted as part of the payload in a network and these


bytes are mainly used for the monitor, management and control of the path performance.

3. Administrative Unit Pointer (AU-PTR) area AU PTR is a kind of indicator, mainly used to indicate the accurate position of the first byte of information payload in the STM-N frame, so that the information can be

correctly decomposed at the receiving end. It is located at the fourth row of 1~9 × N columns in the STM-N frame structure. The adoption of the pointer mode is an innovation of SDH. It can perform multiplex synchronization and STM-N signal frame locating in the quasi-synchronization environment.

Regenerator

section overhead

(RSOH)

Administrative unit

pointer

(AU-PTR)

M ultiplex section

overhead

(M SOH)

STM-1 Payload (Payload)

9 x N Column (Byte)261 x N Column (Byte)

270 x N Column

9 Row

Transmission

direction

125¦ s

1

3

5

9

4

Figure 2. SDH frame structure

Logic composition of SDH equipment

SDH transmission network is made up of different types of NEs connected via optical cable lines and performs the transmission function of an SDH network via different NEs. These functions are add/drop services, cross-connection services, network fault self-healing, etc. Among the commonly seen NEs in an SDH network are Terminal Multiplexer (TM), Add-drop Multiplexer (ADM), Regenerator (REG) and Digital Cross-connection System (DXC). Terminal Multiplexer (TM)

A TM is used at a network terminal node, as shown in Fig. 3

TM

2M

bit/s

34

Mb

it/s

ST

M-M

14

0M

bit/s

STM-N

Fig. 3 Schematic diagram of model of a TM


The function of a TM is to multiplex the low-speed signals of a tributary port to high-speed signal STM-N of a line port or to de-multiplex low-speed tributary signals from STM-N signals. 1-channel STM-N signals are input/output to its line port while multi-channel low-speed tributary signals can be output/input at a tributary port. When low-speed tributary signals are multiplexed into the STM-N frame of line signals, the locations of tributary signals in the line signals STM-N can be specified arbitrarily.

Add-Drop Multiplexer (ADM)

ADM is used at the transfer site of an SDH transmission network, such as the middle node of a link or a node in a ring, and is the most important NE used most frequently in an SDH network, as shown in Fig. 4

ADM

2M

bit/s

34

Mb

it/s

ST

M-M

14

0M

bit/s

STM-N STM-N

Fig. 4. Schematic diagram of model of an ADM

ADM has two line ports and one tributary port. The two line ports are connected with optical cables on their respective sides (two trans-receiving optical fibers on each side). For the sake of description, we specify them as the West (W) line port and East (E) line port. The function of ADM is to multiplex low-speed tributary signals to lines (line singles) in cross-connection mode or de-multiplex low-speed tributary signals from the line signals received from line ports. In addition, cross-connection of the STM-N signals on Eastward/ westward line sides can be implemented. ADM is the most important NE in an SDH network and can be equivalent to other NEs, i.e., it can perform the functions of other NEs. For example, ADM may be equivalent to two TMs.

Regenerator

There are two kinds of regenerators in an optical transmission network. One is the pure optical regenerator, mainly used to amplify optical power so as to extend the optical transmission distance. The other is an electric regenerator used for pulse regeneration shaping and it can achieve the goal of accumulating no line noise and ensuring complete waveforms of transmission signals by means of Optical/electric (O/E) conversion, sampling of electric signals, decision, regeneration shaping, Electric/optical and other processing. Described here is the latter one, which has only two line ports, as shown in Fig. 5.

REGSTM-NSTM-N

Fig 5. Schematic diagram of model of a regenerator


The function of REG is to send the received optical signals from the offside after O/E, sampling, decision, regeneration shaping and E/O. An REG in a real sense only needs to process RSOH in the STM-N frame and needs no cross-connection function. However, ADM and TM need to process both RSOH and MSOH because they are to insert low-speed tributary signals into STM-N. In addition, both ADM and TM have the cross-connection function.

Digital Cross-connection System (DXC)

The DXC is mainly responsible for the cross-connection of STM-N signals and is actually equivalent to a cross-connect matrix, which implements the cross-connection of various signals, as shown in Fig. 6.

DXCM

channel

N

channel

Fig. 6. Schematic diagram of model of DXC

DXC can implement cross-connection of the input M-channel STM-N signals to the output N-channel STM-N signals. The core of DXC is a cross-connect matrix and the powerful DXC can implement the low priority cross-connection of high-speed signals in a cross-connect matrix. Usually, DXC m/n is used to represent the type and

performance of a DXC (m≥n). m represents the maximum rate level which can be accessed to DXC and n does the minimum rate level of a cross-connection which can be implemented in a cross-connect matrix. The greater m is, the higher bearer capacity a DXC has. The smaller n is, the more flexible cross-connection DXC has. The meanings of corresponding values of m and n are shown in Table 1. Table 1. DXC m/n value rate correspondence table

m or n 0 1 2 3 4 5 6

Correspond

ent rate 64 kbit/s 2Mbit/s; 2Mbit/s; 2Mbit/s;

2Mbit/s;

2Mbit/s; 2Mbit/s; 2. 5Gbit/s

Physical topology of an SDH transmission network Network physical topology generally refers to the shape of a network, namely, geometric arrangement of network nodes and transmission lines, and reflects physical connectivity of network nodes. The effectiveness, reliability and economy of a network depend to a great extent on the specific network architecture. There are 5 simple kinds of network physical topology structures, as shown in Fig. 7.


(a) Line topology

If all nodes in a communication network are cascaded with the first and last nodes open, a line topology is formed. In this topology structure, all nodes between two non-adjacent nodes should be connected so as to implement the connection between non-adjacent nodes. Line topology is an economical form of network topology used in an early SDH.

(b) Star topology (junction)

If a special node is connected with all the other nodes, and there is no direct connection between them, a star topology is formed. In this topology structure, any two nodes except the junction nodes are connected with each other via a junction node, which implements the routing and connection function for passing information stream. In this network topology, the nodes at a junction center station can connect multiple optical fiber terminals to form a unified network, which implements integrated bandwidth management.

(c) Tree topology

If the ending node of a point-to-point topology unit is connected with several special nodes, a tree topology is formed. Tree topology can be considered as the combination of line topology and star topology. This topology structure is applicable to broadcast services, but not to bi-directional communication services because there exist such problems as bottleneck and restriction on optical power budget.

(d) Ring topology

If all the nodes in a communication network are cascaded with no node open, a ring network is formed. If the first and last open nodes of a line network are connected, a ring network is formed. In a ring network, To connect two nodes, all the nodes between them should be connected. The best advantage of this network topology is its strong survivability, which is of vital importance to a modern high-capacity optical fiber network. Therefore, special importance is attached to a ring network in an SDH network.

(e) Mesh topology

If many nodes in a communication network are directly interconnected, a mesh topology is formed. If all the nodes are directly interconnected, such mesh topology is called an ideal one. In a non-ideal mesh topology, any two nodes not connected directly with each other can be connected via the connection function of other nodes. The mesh structure is not influenced by the problems of node bottleneck and failure and there are multiple optional routes between two nodes. It has a high reliability, but a complex structure and high costs. Therefore, it is applicable to a backbone network with heavy traffic.


In a word, all these topology structures have their own features and can be applied in a network to different degrees. What network topology to be selected depends on many factors. For instance, a network should be of high survivability and easy to configure, and the net architecture should be suitable for the introducing of new services. The different parts of an actual network are applicable to different topology structures. For instance, ring topology and star topology structures are very applicable to a local network (namely, an access network or user network), with a line topology structure sometimes used. Ring topology and line topology are very applicable to a local interchange relay network while a toll network may demand mesh topology.

(a) Line

topology

(b) Startopology

(c) Treetopology

(d) Ring

topology

(e) Mesh

topology

TM

TM

TM

TM

TM TM TM

TM

TM

TM

ADM

ADM

ADM

ADM

ADM

ADM

ADM

ADM

DXC/ADM

DXC/ADM

DXC/ADM

DXC/ADM

DXC/ADM

DXC/ADM

TM

Fig. 7. Physical topology of an SDH network

Section-II

Chapter-10

SDH Protection Schemes

E2E3 SDH Protection, Ver1 24.08.2007 1 of 9

SDH Network Survivability Network survivability

Modern society relies more and more on communication and the survivability of a communication network has become a design index of vital importance. The so-called self-healing network means that a network can automatically recover the carried services from a failure fault in a very short period of time without making users be aware of any network fault. Its basic principles are to enable a network to find faults and reestablish communication. A self-healing network involves no repairing and replacement of a specific faulty component or part but the reestablishment of communication. The former case still demands manual interference. Different Protection scheme applicable in network 1.Linear Protection

There are three different protection scheme in Linear Protection

a. 1+1 protection scheme ( 1+1 configuration )

The simplest from of Protection is known as 1+1 APS. Here, each working line is

protected by one protection line. The same signal is transmitted on both lines. If a

failure or degradation occur, the network elements switch the connection over to the

Protection line at the receive end

b. 1:1 Protection scheme (1:1 configuration )

. A protection line is used to directly replace the working line when it fails.

The protection path can only be used if a switchover takes place at both the transmitting end

and the receiving end. Switching at the far end is initiated by a return message in the backward

channel.

W

P

W

P


c. 1:N Protection scheme A 1:N configuration represents a more cost- effective solution than the other two

mechanisms describe above. N working channels are protected by one protection channel. If

there are no defects in the network, this protection channel can be used to transport low-

priority traffic

Sub Network Connection (SNC) Protection:

Sub network connection protection is a dedicated protection mechanism that can be

used on any physically structure (i.e. meshed ring, or mixed). It may be applied in any path in a

layered network.. it can be used to protect a portion of a path ( e.g. that where two separate

path segments are available), or the full end to end path. It switches on server failures (using

inherent monitoring) or it switch using client layer information (using non intrusive

monitoring). It need not be used on all VCs within al multiplex section. SNC protection

operates in a single- ended manner.

SDH Rings

Ring: A collection of nodes forming al-closed loop whereby each node is connected to two

adjacent nodes via a duplex communication facility. A ring provides redundant bandwidth or

redundant network equipment, or both; so distributed services can be automatically restored

following a failure or degradation in the network. Thus a ring can be self-healing.

SDH is normally configured as ring architecture. This is done to create loop diversity

for uninterrupted service protection purposes in case of link or equipment failures. The SDH

ring are commonly called self-healing ring, since the traffic flowing along a certain path can

automatically be switched to an alternate or standby path following failure or degradation or

link failure.

The important features SDH rings,

• There can be either two or four fibers running between the nodes on a ring.

• The operating signals can travel either clockwise only (unidirectional ring) or in

both directions around the ring (bi-directional ring)

• Protection switching can be performed either via a line- switching or a path-

switching scheme.

Upon link failure or degradation, line switching moves all single channels of an entire STM-N

channel to al protection fiber. Conversely, path switching can move individual payload

channels within an STM-N channel to another path.

the following two ring architectures have become popular for SDH network

• Two fiber unidirectional, self healing ring (USHR)

W W

P


• Two-fiber or four-fiber, bi-directional, line- switching ring (two-fiber or four-fiber

BSHR)

They are also referred to as unidirectional or bi-directional self_ healing ring

(USHR or BSHR) respectively.

Figure show below a two-fiber unidirectional self-healing ring network By convention, in a

unidirectional ring the normal working traffic travels clockwise around the ring, on the primary

path. For example, the connection from node 1 to node 3 uses links 1 and 2, whereas the traffic

from node 3 to node 1 traverses link 3 and 4. Thus two communicating nodes use a specific

bandwidth capacity around the entire perimeter of the ring. If nodes 1 and 3 exchange

information at an STM-1 rate in an STM-4 ring then they use one -quarter of the capacity

around the ring on all the primary rings. In a unidirectional ring the counter-clockwise path is

used as an alternate route for protection against link or node failures. This protection path

(links 5-8) is indicated by dashed lines. To achieve protection, the signal from a transmitting

node is dual-fed into both the primary and protection fibers. The receiver normally selects the

signal from the primary path. However, it continuously compares the fidelity of each signal

and chooses the alternate signal in case of severe degradation or loss of primary signal.

Primary path

1

4 5 7 2

6

3

Figure (a)

FEATURES OF USHR:

This scheme offers less information regarding operating system. In normal condition

the traffic flows in clockwise directions in one fiber. In failure condition the traffic in counter

clockwise directions path is used as alternate path for protection against ring or node failure.

The USHR mechanism is itself does not aware which fiber is carrying traffic. In case traffic is

switched over alternate path, the traffic returned on normal path after restoration. But it protect

positively. It offers cost effective solution for low level of capacity network.

Two-fiber or four-fiber, bi-directional, line- switching ring (two-fiber or four-fiber

BSHR):

Node 1

Node 3

Node 2

Node 4

8

Protection path


FEATURE OF BSHR:

The scheme requires a APS protocol to make operative. The traffic flows from node 1

to node 3 in clockwise direction along links 1p and 3p. but in return path the the traffic flows

from node 1 to node 3 in counter clockwise direction along links 7p and 8p Thus the

information exchange between nodes 1 and 3 does not tie up any of the primary channel

bandwidth in the other half of the ring

1p

8p

4p 5p 7p 2p

6p

3p

MS shared protection rings

MS shared protection ring can be categorized into types: two fiber and four fiber. The ring APS protocol accommodates both types.

For MS shared protection rings, the working channels carry service to be protected while the protection channels are reserved for protection of this service. Working traffic is transported bi-directional over spans: an incoming tributary travels in one direction the working channels while its associated outgoing tributary travels in the opposite direction but over the same spans. Depending upon the tributary pattern, the maximum load that can be placed on a (bi-directional) MS shared protection ring can exceed the maximum load that can be placed on the equivalent type of unidirectional ring (e.g. MS dedicated a capacity advantage over unidirectional ring, except whenever the tributaries are all destined for only one node on the ring, in which case they are equivalent. One advantage of MS shared protection ring is that service can be routed on the ring in either one of the two different directions, the long way around the ring or the short way. All through the short way will usually be preferred, occasionally routing service over the long way permits some load balancing capabilities. When the protection channels are not being used to restore the working channels, they can be used to carry extra traffic. In the event of a protection switch, the working traffic on the working channels will access the protection channels causing any extra traffic to be removed form the protection channels.

Node 1

Node 3

Node 2

Node 4


During a ring switch, working channels transmitted toward the failed span are switched at one

switching node to the protection channels transmitted in the opposite direction ( away from the

failure). This bridged traffic travels the long way around the ring on the protection channels to

the other switching node where the protection channels are switched back onto the working

channels. In the other direction, the working channels are bridged and switched in the same

manner. Figure 6-2 illustrates a ring switch in response to a cable cut.

During a ring switch, the fails span is effectively “replaced” with the protection channels

between the switching nodes, traveling the ling way around the ring. Since the protection

channels along each soon (except the failed span) are used for recovery, the protection capacity

is effectively shared by all spans.

The pair of tributaries (incoming and outgoing) only uses capacity along the spans between the

nodes where the pair is added and dropped. Thus, as shown in following figure the pattern that

these pairs of tributaries are placed on the ring impacts the maximum load that can be placed

on MS shared protection rings. The sum of the tributaries that traverse a span cannot exceed

the maximum capacity of that particular span.

The switching protocol shall be able to accommodate up to 16 node on a ring excluding regenerators

TX - 1 Facu lty

A LT T C, G haziabad

N ode A

N ode D

N ode B

N ode C

T w o-fib re ST M -16 ring

2 A U -4s

8 AU -4s

6 AU -4s 16 AU -4s total

Spare betw een

N odes A & B and

N odes A & D are

at capacity

C entralized T raffic Pattern 8 A U -4s

6 A U -4s

2 A U -4s

T w o fiber ST M -16 ring

Note- since all the traffic is destined for Node A, and the span between Node A and B

is full, traffic form Node C routes through Node D, leaving the span between Node B and Node

C vacant.

(a) All traffic destined for one node, Node A


Node A

Node D

Node B

Node C

Two-fibre STM-16 ring

8 AU-4s

8 AU-4s

8 AU-4s 8 AU-4s32 AU-4s

total

All spare are

at capacity

Purely Distributed Traffic Pattern 8 AU- 4s

8 AU-4s

8 AU-4s

(a) All traffic destined for adjacent nodes only.

Node A

Node D Node C

Two-fibre STM-16 ring

4 AU-4s

2 AU-4s

8 AU-4s 5 AU-4s22 AU-4s

total

All spare are

at capacity

Node B

4 AU-4s

3 AU-4s 3 AU-4s

T1516760-94d11

Mixed Traffic Pattern 3 AU_4s

3 AU-4s

2 AU-4s

1 AU-4s

4 AU-4s

4 AU-4s

(c) Mixed traffic pattern

Effect of demand pattern on capacity of bi-directional MS shared protection ring .

Application architecture:

(a) Two – fiber MS shared protection rings

Two – fiber MS switched ring require only tow fibers for each span of the ring. Each fiber

carries both working channels and protection channels. On each fiber, half the channels are

defined as working channels and half are defined as protection channels. The working channels

in one fiber are protected by the protect on channels traveling in the opposite direction around


the ring. This permits the bi-directional transport of working traffic. Only one set of overhead

channels is used on each fiber.

Fiber (arrow indicates transmission direction)

Note – Each fiber carries both working and protection traffic, as shown in the exploded view.

(b) Four- fiber MS shared protection rings.

Four – fiber MS shared protection ring require four fiber for each span of the ring. Working

and protection channels are carried over different fiber: two multiplex section transmitting in

opposite directions carry the working channels while two multiplex sections also transmitting

in opposite directions, carry the protection channels. This permits the bi-directional transport of

working traffic. The multiplex section overhead is dedicated to either working or protection

channels since working and protection channels are not transported over the same fibers.

Fiber carrying working traffic (arrow indicates transmission direction)

Fiber carrying protection traffic (arrow indicates transmission direction)

Node 1

Node 3

Node 2

Node 4

Node 1

Node 3

Node 2

Node 4


Algorithm of Application architecture:

The AU groups that traverse the span between any two adjacent nodes are divided into working

channels and protection channels. In the vase of the two fiver ring, the STM-N can be viewed

as a multiplex of N AU-4s, where the AU-4 are numbered from 1 to N according to the order

that they appear in the multiplex. AU-4s numbered from 1 to N/2 shall be assigned as working

channels, and AU-4s numbered from (N/2)+1 to N shall be assigned as protection channels

further more working channels m is protected by protection channels (N/2) +m. for example,

an STM-16 can be considered a multiplex of sixteen channels and multiplex of sixteen AU-4s.

One to eight would be assigned as working channels and nine to sixteen would be assigned as

protection channels. This assignment applies to both direction of transmission and to all spans.

The ring APS protocol shall be carried on bytes K1 and K2 in the multiplex section overhead.

In the case of the four-fiber ring, the APS protocol is only active on the fiber carrying

protection channels. Functions that are required in real time and required to make al protection

switch are defined in the ring APS Protocol using bytes K1 and K2 Other operations channels,

including the regenerator section and multiplex section Data communication Channels, may

also provide protection switching function that are not tome critical (for example, function that

need not be completed within 50 milliseconds).

Each node on the ring shall be assigned an ID that is a number from zero to fifteen, allowing a

maximum of sixteen nodes on the ring. Each node has a ring map that is maintained by local

craft or by an OS and contains information abut the assignment of channels that the node

handles.

Procedure of loading MS-spring.

RX TX

TX RXRX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RXRX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

RX TX

TX RX

Master Station

01 2

3

4

5

67

89

10

11

12

13

1415

S6 S1S6 S1

S6

S6

S6

S6

S1

S6 S1

S1

S1

S1

S1

S6

S6S1

S6S1

S6

S1

S6

S1

S6

S1

S6

S1

S6

S1S6

S1


Preparation of MS – Spring Node

Map Editor

14015

131514

121413

111312

101211

91110

8109

798

687

576

465

354

243

132

021

1510

Slot No. 06Slot No. 06Slot No. 1Slot No. 1Node ID Node ID

Example of circuit routing in failure state for a ring switch

Node A

Circuit Q

Node B Node C

Node F Node E Node D

Working

Protection

Circuit Transporting Service

Normal Traffic In MS-Spring Node a

Node b Node c

Node dNode e

Node f

working

protection

Ckt transporting service

Normal state

`

Node A

Circuit Q

Node B Node C

Node F Node E Node D

Working

Protection

Circuit Transporting Service

Protected Traffic In MS-Spring

workingprotection

Ckt transporting service

Node a Node b Node c

Node dNode e

Node f

Failed state

Section-II

Chapter-11

Synchronization

E2E3 Synchronization, Ver1 24.08.2007 1 of 13

Introduction to Synchronization

Network synchronization is one important part in network planning, especially so for an

SDH network on the basis of synchronous transmission. Only when network synchronization is

reasonably planned can the optimal synchronization effects be achieved between NEs. Different

equipment provides the synchronization plane based on SSM information. Synchronization Status

Messaging (SSM) can be used to ensure that an NE selects an effective timing source of the best

synchronization quality, prevent timing from forming loop and guarantee the timing

synchronization performance of a network.

Synchronization

Traditionally, transmission systems have been asynchronous, with each terminal in the

network running on its own recovered clock timing. In digital transmission, “timing” is one of the

most fundamental operations. Since these clocks are not Synchronized, large variations can occur

in the clock rate and thus the signal bit rate.

For example, an E3 signal specified at 34 Mbit/s ±20 ppm (parts per million) can produce a

timing difference of up to 1789 bit/s between one incoming E3 signal and another. Asynchronous

multiplexing uses multiple stages. Signals such as asynchronous E1s (2 Mbit/s) are multiplexed

(bit-interleaving), extra bits are added (bit-stuffing) to account for the timing variations of each

individual stream and are combined with other bits (framing bits) to form an E2 (8 Mbit/s) stream.

Bit-interleaving and bit-stuffing is used again to multiplex up to E3 (34 Mbit/s). The E1s are

neither visible nor accessible within an E3 frame. E3s are multiplexed up to higher rates in the

same manner. At the higher synchronous rate, they cannot be accessed without de-multiplexing. In

a synchronous system, such as SDH, the average frequency of all clocks in the system is the same.

Every slave clock can be traced back to a highly stable reference clock. Thus, the STM-1 rate

remains at a nominal 155.52 Mbit/s, allowing many synchronous STM-1 signals to be multiplexed

without any bit stuffing. Thus, the STM-1s are easily accessed at a higher STM-N rate.

Low-speed synchronous virtual container (VC) signals are also simple to interleave and

transport at higher rates. At low speeds, 2.048 Mbit/s E1 signals are transported within

synchronous VC-12 signals, which run at a constant rate of 2.304 Mbit/s. Single-step multiplexing

up to STM-1 requires no bit stuffing and VCs are easily accessed. A mechanism known as

“pointers”, operating in conjunction with buffers, accommodates differences in the reference

source frequencies and phase wander, and so prevents data loss during synchronization failures.

Synchronization Hierarchy Digital switches and digital cross-connect systems are commonly employed in the digital

network synchronization hierarchy. The network is organized with a master slave relationship with

clocks of the higher-level nodes feeding timing signals to clocks of the lower-level nodes. All

nodes can be traced up to a Primary Reference Clock (PRC).

Synchronizing SDH

The internal clock of an SDH terminal may derive its timing signal from a Synchronization

Supply Unit (SSU) used by switching systems and other equipment. Thus, this terminal can serve

as a master for other SDH nodes, providing timing on its outgoing STM-N signal. Other SDH

nodes will operate in a slave mode with their internal clocks timed by the incoming STM-N signal.

Present standards specify that an SDH network must ultimately be able to derive its timing from a

PRC.


SSM function of an SDH interface

The service add/drop and rerouting capabilities of an SDH network enable a network to be

applied with unprecedented flexibility and high survivability and makes selection of network

synchronization timing more complex. In an SDH network, the timing reference allocation

between nodes is made by means of a great number of low-level SDH network clocks, therefore

the quality of the timing reference must be labeled by some means. SSM is right used to display

the information of the timing reference quality. SSM is transferred by the 5th

~8th

bits of S1 byte in

an SDH multiplex section overhead, as shown in Fig. 1

b1 b2 b3 b4 b5 b6 b7 b8

SSM

Fig. 1. Contents of S1 byte

These four bits have 16 different kinds of codes representing 16 different synchronization quality

grades, as shown in table.1

Table 1. SSM Code

S1 (b5~b8) Descriptions of SDH synchronization quality grades

0000 Unknown synchronization quality (existing synchronization network)

0001 Reserved

0010 G. 811 clock signal 0011 Reserved 0100 G. 812 transit exchange clock

signal 0101 Reserved

0110 Reserved 0111 Reserved 1000 G. 812 local exchange clock signal 1001 Reserved 1010 Reserved 1011 Synchronous Equipment Timing

Source (SETS)

1100 Reserved 1101 Reserved 1110 Reserved 1111 Not to be used as synchronization

In an SDH network, the timing reference allocation between nodes is made by means of a

great number of low-level SDH network clocks. With the increase in NEs on the synchronization

links, the quality of timing reference signals degrade gradually. Therefore, when there are multiple

optional synchronization paths of the same quality grade in an NE, selection of the synchronization

path passing the smallest number of NEs helps improve the timing performance of an SDH


network. In an SDH network, the selection of clock source of SDH NE is made mainly based on

S1 byte and the following principle should be followed:

When there are multiple optional effective clock sources in an NE, the NE first selects the

clock of the highest quality grade based on the quality grade information of clock source. If the

clock sources are of the same quality grade, the NE will select the one passing the smallest number

of NEs based on the number of NEs a clock source transmission path passes.

Evolution of Timing and Synchronization

This is a time of great change for Timing and Synchronization in the network and there are

many challenges for operators and suppliers – and many issues to resolve:

• Synchronization networks are changing with the introduction of SDH; the historical PDH-based

sync network will be replaced by an SDH-based architecture.

• New equipment, network timing, and sync standards have been developed.

• Transport networks are evolving and hybrid SDH/PDH has specific problems due to the

quantisation of network phase variation as pointer justifications.

• New services such as video and ATM depend on excellent timing and network

Sync to deliver good Quality of Service.

• Jitter/Wander measurement technology is changing from analogue to digital,

Leading to dramatically new instrument capabilities.

• New test equipment standards are being developed.

Proposed BSNL Draft Synchronization Plan Introduction:

Whether in a fixed telephone network or in the field of mobile telephony (with the new 3G

systems), traffic in the network is constantly increasing. More and more information is being

transported at higher and higher data speeds. Synchronization of the traffic in the networks is

becoming increasingly important. Telecommunications’ reliability is based on the data signals

being synchronized and clocked using the same clock everywhere in the network.

The basic clock in the SDH networks is called E1, and it must be exactly 2.048 MHz. In a

Synchronous Digital Hierarchy (SDH) network, there is a cesium clock (2.048 MHz) that functions

as a "master clock" or primary reference clock (PRC). The PRC is distributed throughout the

network using the transmission backbone comprising of DWDM and SDH transport network. The

clock is regenerated in the network’s nodes in “slave clocks” called as synchronization supply

units (SSUs). The SSUs regenerate and distribute the signal recieved after a chain of SECs (SDH

equipment clocks). The SSUs can also temporarily be used as a PRCs if the input connection from

the master clock is interrupted. The SECs are the clocks in the network elements (see Figure 1).

This clock regeneration is never completely perfect; rather, each regenerated clock will

have variations in frequency and phase. The more nodes passed "en route", the less stable the clock

will be. The same is shown as given below.


Figure-I

Standards:

The following is the ITU-T specification for the timing resources.

SPEC AREA DESCRIPTION

G.811 PRS Timing Characteristics of Primary Reference Source

G.812 SSU Timing Requirements for Slave Clocks for use as Node

Clocks in Synchronized Networks

G.813 Sync Timing Characteristics of SDH Equipment Slave Clocks

G.810 Sync Definitions and Terminology for Synchronized Networks

Current Sync status:

At present, the master clock for BSNL transmission network is drawn from VSNL at

Mumbai. The backup PRC clock is drawn from MTNL, Delhi. BSNL network does not have its

own Primary Reference Clock ( PRC ). Approximately, 50 number of Synchronous Supply Units

are installed in the BSNL network. The installation plan for these 50 SSUs is issued on 25.10.2002

by the TX branch and the same is implemented.


The total number of telephones have increased to 4 crores in the BSNL network. The

transmission network has also grown very big. Large number of STM-16/STM-4 rings are working

in the backbone network connecting all the SSA head quarters. Huge number of STM-1 systems

are also working in the network providing connectivity in the Access area. The connectivity is

provided to 37,000 number of exchanges/TAX stations. Many RSUs, RLCs DLCs and WLL sites

are connected by the SDH network. More than 7000 number of BSNL GSM sites are connected by

the SDH/PDH systems. Large number of data customers are also connected on the SDH network.

In 2005-06, TX cell had rolled out large number of SDH systems into the network. 770

number of STM-16 equipment, 2279 no of STM-4 equipment and 7200 no of STM-1 systems into

the network. Much larger quantity of the equipment is planned on 2006-07.

The quality of service is directly related to the synchronization of this huge SDH

infrastructure. The current fifty number of SSUs, functioning as Stratum 2 clocks, are not capable

of catering to the needs of this SDH network. Some circles have reported that the ports of the SSUs

are exhausted already and more cards are required for carrying out the synchronization of the

network elements. There is an immediate need for having the master clocks and good number of

SSUs delivering the synchronized clock to the SDH network elements, the switch elements and the

access elements.

The synchronization committee constituted by BSNL CO vide 27-3/2003-ML/754 dated

23.10.2003 submitted its report. Committee has suggested both long term and short term measures.

As part of long term measures the committee has suggested for four PRCs to be owned by BSNL.

The committee has requested to urgently review the synchronization strategy and implement the

same urgently.

The committee has also suggested that three SSUs are required in each of the metros Delhi,

Mumbai, Kolkata and Chennai.

PRCs and the SSUs

With reference to the above observations, the following proposal is made.

It is proposed have Primary Reference Clocks with G.811 standard at the locations shown

in the map. All these geographically spread out clocks shall provide uniform high precision clock

to the respective regions.

For the Primary Reference Clock and the Synchronous Supply clock, there are two

technological choices. The first and the most reliable technology is based on the cesium atomic

clock. The energy difference is specific to a particular quantum transition in the cesium-133 atom,

whose unperturbed frequency has been defined as 9,192,631,770 Hz. When the defined number of

cycles transpire for the electromagnetic signal associated with the photon either being given off or

absorbed by this quantum transition, we have one official “second”.

The second technology is the derivative of the first technology deployed thorough the

satellites system and also called as the Global Positioning System ( GPS ). The atomic clock in the

satellites is transmitted to the GPS receivers on earth. Even though is available everywhere and

also reliable, but the entire system is controlled by the United States of America. In case of the first

technology, BSNL shall be owning the PRC clock. Hence the Cesium atomic clock technology is

preferable to the GPS receiver technology.


Figure - II

The sync committee has suggested that four PRCs may be planned at NewDelhi, Mumbai,

Kolkata and Chennai. As per the TEC GR (old GR) a PRC is supposed to have four Cesium clocks

inside. TEC has been requested to revise the GR by removing the engineering details in the GR. It

is now proposed to have one Cesium clock in a PRC as Cesium tube, which is guaranteed for 12

years at least. Hence keeping four Cesium at one place shall result in excessive redundancy. This

shall also add to the cost of the equipment. The PRC GR is revised by TEC recently incorporating

the suggestion of TX cell for geographically distributed Cesium.

Apart from the above, by using only four PRCs, the remotest element in the network may

not be reached within the ITU-T norm of 60 nodes. Please refer the figure –II. After every 20

nodes one SSU is required as the MTIE and TDEV parameters cross the ITU-T standard mask. A

lesser no of nodes (less than 20) may be preferable in BSNL network as the geographical distance

which cause higher phase deviations are more.

This method requires that every SSU in the network needs to have GPS as the backup

solution. This not only adds to the cost of the synchronization equipment but also increases the

dependency on the US controlled GPS network. In order to reduce such dependence and to have a

strategic reliance on own resources, it is preferable to have more number of Cesium located

throughout the network, instead of concentrating them in a few cities.

Apart from this keeping all the Cesium at one place shall be catastrophic in case of any

disaster and natural calamity. Hence it is preferred to have robust redundancy through

geographical diversity. As per the NM cell suggestion two Cesiums tubes are proposed in one PRC.

SSU

K=1

PRS

SSU

SSU

Rule 1 K < 10 SSUs N < 60 SECs

SEC (NE with SONET/SDH Equipment Clock)

Rule 2 N < 20 SECs

K=2

K=3

SSU

Co-located PRS & TSG

SSU K=1

PRS

1

201 2

0 PRS

1

20

SSU K=1

1

20

1

20

201

20

1

1

20

SSU K=2


Core Synchronisation Plan

Considering all the problems above, a Core Synchronization plan has been made as under,

for synchronizing the core transmission and switching elements. It is proposed 21 number of

PRCs with two cesium tubes are suggested at the following places for geographical diversity and

for ensuring the minimum nodes compliance. It is proposed to have the PRCs at all the Level 1

TAXs. However, in view of the requirement for the orderly distribution of the PRC clock

throughout the transmission network, it is proposed to locate the SSUs at the convergent nodes of

the existing backbone DWDM rings. Overlapping with DWDM network enables us to transport

the clock on a number of SDH rings to as many district head quarters, where SSUs are proposed to

be located. Most of these nodes are collocated with the Level –I TAX stations. A total of no of L-

I TAXs are covered. are proposed to overlap with the existing DWDM terminal stations in most of

the cases. Thus these 21 PRCs are expected to supply clock for all the Transmission. Switching

and Access elements in the transmission geographic area, also called as the PRC timing Island.

1. NewDelhi

2. Jammu

3. Jaipur

4. Lucknow

5. Ahmadabad

6. Mumbai

7. Nagpur

8. Bhopal

9. Hyderabad

10. Belgaum

11. Bangalore

12. Chennai

13. Ernakulam

14. Visakhapatnam

15. Sambalpur

16. Ranchi

17. Kolkata

18. Patna

19. Guwahati

20. Agartala

21. Portblair

Thus there will be 21 PRC timing islands in the network. Sample timing islands for PRCs

located at a few places is shown below in figure -III.

The synchronization plan for the network is suggested now as under.

One Synchronous Supply Unit ( SSU ) with G.812 standard, which are primarily the

Stratum 2 clocks, are proposed at all the 21 Level-I TAX stations. These SSUs are proposed with

transit node clock standard are only proposed and the SSUs with local node clock standard are not

proposed to be deployed. Please ref Figure-I. The primary difference between the Transit node

clock standard and the local node clock standard is that the clock hold over capability of the former

is much higher and is almost 15 days while that of the later is only one day. The SSUs with transit

node clock standard having the Rubidium oscillator are only proposed to be deployed.

Since there are two Level-I TAXs in each L-I locations, to ensure the clock distribution

redundancy in line with the TAX policy, one SSU each is planned in each L-I TAX. One SSU is


planned in the Maintenance region’s transmission room, where the PRC is also proposed. This

enables the distribution of the clock to the L1 TAXs and also to long distance transmission links

over which the clock shall be distributed throughout the PRC timing island. Most of these L1 cities

have large number of DELs. Hence it is in line with the proposed policy to have three SSU in very

big cities. Thus 63 no of SSU are required. However at places such as Chennai there are three L-I

TAXs in same city. Accordingly, additional SSUs may be planned in all the L-I TAXs. At all the

Level-II TAX stations one SSU each is proposed.

Of the 301 level II TAX stations. already 50 no of SSUs are working in the network. The

actual number of SSUs existing and their locations may be ascertained during the preparation of

the final sync plan. The proposed place for shifting these SSUs may also be planned. Additional

cards may be required in all the existing SSUs. The balance SSUs required shall be 272 no.

Similarly at every GSM MSC and CDMA MSC, which is not collocated with a L-I TAX or L-II

TAX or the transmission centres ( where already one SSU is installed) one additional SSU is

proposed. These SSUs shall draw the primary clock from the nearest PRC.

Figure-III


The DWDM network is as shown below in Figure IV.

Figure-IV

The proposed PRC locations are shown as given below in Figure-V.


Figure-V

An SSU at a PRC location is fed with the master clock from the co located PRC. This SSU

is also supplied with three of the surrounding PRC clocks as stand by for the Co located PRC.

Thus minimum four inputs are required for an SSU. Apart from these four clock inputs, an in built

GPS in the SSU shall be the final standby. Only an SSU, which is collocated with the PRC shall

have the inbuilt GPS module. All other SSUs located throughout the network shall not have any

other GPS module. Thus the GPS timing island coincides with the PRC timing island for the

respective PRC. Due to the geographical limitation Agartala has only one standby PRC input from

Guwahati apart from the GPS. However alternate inputs from Kolkata and Patna can also be

extended in alternate paths. In case of Portblair, GPS shall be the standby clock input.

With this kind of synchronization network, not only the quality of service improves

immensely, but also BSNL shall become the nation wide sync provider for all other agencies also.

This kind of networking enable BSNL to assume the role of carrier of carriers.

Portblair


Figure-VI

The SSU at the PRC location depends on the PRC itself for the first master clock input. In

case of failure or deterioration of the PRC, the SSU depends on the other three PRC clock inputs

received from the nearest three PRCs. In the event of complete failure of the PRC inputs or in the

event of the deterioration of clock quality all the PRCs below the GPS standard, the SSU draws the

clock from the GPS clock, which shall be in-built in SSU.

The clock generated by the PRC shall be fed to an SSU co-located in PRC location.

It is proposed to place atleast one SSU at each of the SSA Headquarter. Thus atleast 322 SSUs

shall be required for distributing the clock. In all the cities, where more than 3 lakh DELs are

available atleast 3 SSUs are proposed in the same city for distributing the clock across the city

network. Similarly in all the cities with more than one Lakh DELs but less than 3 Lakh DELs two

SSUs are proposed in the same city for distributing the clock.

In general, the number of equipment rings/linear systems in region transmission room shall

be of the order of 30no in a bigger city. I.e. all the equipment needs to be fed with the clock

directly. At present due to lack of port outputs, the clock output of one equipment is fed to another

equipment, which shall not result in desired clock quality in the daisy chained equipment.

Apart from the transmission equipment in the region transmission room, equal number or

more equipment needs to be supplied with clock for the transmission equipment of the circle in the

same city. The SSU needs to supply clock to all the SDCAs and all the telephone exchanges,

MSCs, BSCs, in the same district. Hence more output ports are required. Hence the project circles

may also requested to assess the average requirement of ports in the SSU. In some equipment 2

MHz clock input is required while 2 Mb/s is required in other equipment. It is proposed to use

existing SSUs in smaller districts for distributing the traffic.

outputs

outputs

outputs

Remote PRC-1

PRCC

SSU with 4 inputs

360 outputs

Remote PRC-2

SSU with 360

outputs

SSU with 360

outputs

SSU with 360

outputs

Remote PRC-3


Disaster management:

The proposed redundancy clocks for the SSU at every PRC is mentioned as given below.

Sl

No

First input

Choice

Of SSU in

PRC Location

Second

Input

Third

Input

Fourth

Input

Fifth input

1 New Delhi Jaipur Lucknow Bhopal GPS Delhi

2 Jammu NewDelhi Jaipur Lucknow GPS Jammu

3 Jaipur New Delhi Ahmadabad Bhopal GPSJaipur

4 Lucknow Patna Bhopal NewDelhi GPS Lucknow

5 Ahmadabad Jaipur Mumbai Bhopal GPS

Ahmadabad

6 Mumbai Ahmadabad Belgaum Nagpur GPS Mumbai

7 Nagpur Bhopal Hyderabad Sambalpur GPS Nagpur

8 Bhopal Nagpur Ahmadabad Jaipur GPS Bhopal

9 Hyderabad Belgaum Visakhapatnam Nagpur GPS Hyderabad

10 Belgaum Bangalore Hyderabad Mumbai GPS Belgaum

11 Bangalore Hyderabad Belgaum Chennai GPS Bangalore

12 Chennai Bangalore Visakhapatnam Hyderabad GPS Chennai

13 Ernakulam Chennai Bangalore Belgaum GPS Ernakulam

14 Visakhapatnam Hyderabad Chennai Sambalpur GPS

Visakhapatnam

15 Sambalpur Visakhaptnam Ranchi Nagpur GPS Sambalpur

16 Ranchi Sambalpur Patna Kolkata GPS Ranchi

17 Kolkata Ranchi Patna Visakhapatnam GPS Kolkata

18 Patna Kolkata Lucknow Ranchi GPS Patna

19 Guwahati Kolkata Patna Agrtala GPS Guwahati

20 Agartala Guwahati GPS Agartala

21 Portblair GPS Portblair

Table-I

In the event of the disaster such as complete clock deterioration at the SSU in the PRC

location, and other input failures due to the failure of transmission links and also with the GPS

failure, atleast three field SSUs of this PRC timing Island located nearer to the Remote PRCs,

surrounding this timing island may be allowed to have a direct clock input from these three remote

PRCs which are backing the timing island in question. Thus these three SSUs shall start supplying

the master clock to the current PRC timing island and three smaller islands are formed.


Timing Loops:

The primary problem in the synchronisation networking is the formation of timing loops.

The timing loops are generally formed when an ADM supplying the master clock, received from

the PRC directly at the external input, to the ring in the east direction, also receives the same clock

input from the west direction on the Line aggregate.

Since the West line aggregate is synchronised with PRC clock, the clock quality of the

aggregate shall be comparable to that of the PRC. Accordingly, the ADM receiving the external

PRC input and the line aggregate shall start flipping among these clocks and thus the timing loops

are formed. This situation can happen in every ADM which is in the Sync chain or the Main trail

of the clock and passing the clock upto the last node. Thus clock trail for every station in the Sync

map must be drawn individually and analysed to avoid these timing loops.

ADM ADM

ADM ADM

ADM PRC

East West

Section-III

Chapter-12

Overview of

Mobile Communication & Cellular Concepts

E2E3 Mobile concepts, Ver2 28.02.2008 1 of 6

Mobile communications: Basic concepts

From ancient to modern times, mankind has been looking for means of long distance

communications. For centuries, letters proofed to be the most reliable way to transmit

information. Fire, flags, horns, etc. were used to transmit information faster. Technical

improvements in the 19th

century simplified long distance communications: Telegraphy,

and later on telephony. Both techniques were wireline. In 1873, J. C. Maxwell laid the

foundation of the electro-magnetic theory by summarising empirical results in four

equations, which are still valid today. It would however be several decades before

Marconi made economic use of this theory by developing devices for wireless

transmission of Morse signals (about 1895). Already 6 years later, the first transatlantic

wireless transmission of Morse signals took place. Voice was transmitted the first time in

1906 (R. Fesseden), and one of the first radio broadcast transmission 1909 in New York.

The economically most successful wireless application in the first half of the 20th

century was radio broadcast. There is one transmitter, the so-called radio station.

Information, such as news, music, etc. is transmitted from the radio station to the

receiver equipment, the radio device. This type of one-way transmission is called

simplex transmission. The transmission takes place only in one direction, from

the transmitter to the receiver.


The first commercial wireless car phone telephony service started in the late 1940

in St. Louise, Missouri (USA). It was a car phone service, because at that time,

the mobile phone equipment was bulky and heavy. Actually, in the start-up, it

filled the whole back of the car. But it was a real full duplex transmission

solution. In the 50ies, several vehicle radio systems were also installed in Europe.

These systems are nowadays called single cell systems. The user data

transmission takes place between the mobile phone and the base station (BS). A

base station transmits and receives user data. While a mobile phone is only

responsible for its user’s data transmission and reception, a base station is capable

to handle the calls of several subscribers simultaneously. The transmission of user

data from the base station to the mobile phone is called downlink (DL), the

transmission from the mobile phone to the base station uplink (UL) direction.

The area, where the wireless transmission between mobile phones and the base

station can take place, is the base stations supply area, called cell. For

conversation, a technical solution is required, where the information flow can take

place in two directions. This type of transmission is called duplex transmission.

Walky-talky was already available the early 30ies. This system already allowed a

transmission of user data in two directions, but there was a limitation: The users

were not allowed to transmit at the same time. In other words, you could only

receive or transmit user information. This type of transmission is therefore often

called semi-duplex transmission. For telephony services, a technical solutions is

required, where subscribers have the impression, that they can speak (transmit)

and hear (receive) simultaneously. This type of transmission solution is regarded

as full duplex transmission.


Single cell systems are quite limited. The more and more distant the subscriber is from

the base station, the lower the quality of the radio link. If the subscriber is leaving the

supply area of the cell, no communication is possible any more. In other words, the

mobile communication service was only available within the cell. In order to overcome

this limitation, cellular systems were introduced. A cellular mobile communication

system consists of several cells, which can overlap. By doing so, a whole geographical

area can be supported with the mobile communication service.

But what happens, when a subscriber moves during a call from one cell to another cell? It

would be very annoying, if the call is dropped. If the subscriber is leaving a cell, and in

parallel is entering a new cell, then the system makes new radio resources available in the


neighbouring cell, and then the call is handed over from on cell to the next one. By doing

so, service continuation is guaranteed, even when the subscriber is moving. The process

is called handover (HO).

A handover takes place during a call, i.e. when the mobile phone is in active (dedicated)

mode. A mobile phone can also be in idle mode. In this case, the mobile phone is

switched on, but no resources are allocated to it to allow user data transmission. In this

mode, the mobile phone is still listening to information, broadcasted by the base station.

Why? Imagine, there is a mobile terminated call. The mobile phone is then paged in the

cell. This means the phone receives information that there is a mobile terminated call. A

cellular system may consist of hundreds of cells. If the mobile network does not know, in

which cell the mobile phone is located, it must be paged in all of them. To reduce load on

networks, paging in is done in small parts of a mobile an operators network. Mobile

network operators group cells in administrative units called location areas (LA). A

mobile phone is paged in only one location area.

But how does the cellular system know, in which location area the mobile phone is

located? And how does the mobile phone know? In every cell, system information is

continuously transmitted. The system information includes the location area information.

In the idle mode, the mobile phone is listening to this system information. If the

subscriber moves hereby from one cell to the next cell, and the new cell belongs to the

same location area, the mobile stays idle. If the new cell belongs to a new location area,

then the mobile phone has to become active. It starts a communication with the network,

informing it about it new location. This is stored in databases within the mobile network,

and if there is a mobile terminated call, the network knows where to page the subscriber.


The process, where the mobile phone informs the network about its new location is called

Location Update Procedure (LUP).

With the introduction of cellular mobile communication systems, we

refer to generations. First generation prominent mobile communication systems were

• TACS (Total Access Communications System)

• NMT (Nordic Mobile Telephony)

• AMPS (Advanced Mobile Phone Service)

• C450

All of them were commercially launched in the 80s of the last century. The 1st

generation

mobile communication systems often offered national wide coverage. But there were

limitations: Most of them did not support roaming. Roaming is the ability to use an other

operator’s network infrastructure. International roaming is the ability to go even to

another country and use the local operator’s infrastructure.

Most 1st

generation mobile communication systems only supported

speech transmission, but not data transmission, such as fax. Supplementary services, such

as number indication and call forwarding, when busy. The transmission takes place

unprotected via the radio interface – as a consequence, eavesdropping is possible. Also

the radio interface was the main bottleneck in terms of capacity. Improved solutions were

urgently required. This led to the inauguration of the 2nd

generation mobile

communication systems, one of which is GSM.


GSM Frequency Bands

• GSM-900 uses 890–915 MHz to send information from the mobile station to the base station (uplink) and 935–960 MHz for the other direction (downlink), providing 124 RF channels (channel numbers 1 to 124) spaced at 200 kHz. Duplex spacing of 45 MHz is used.

In some countries the GSM-900 band has been extended to cover a larger frequency range. This 'extended GSM', E-GSM, uses 880–915 MHz (uplink) and 925–960 MHz (downlink), adding 50 channels to the original GSM-900 band. The GSM specifications also describe 'railways GSM', GSM-R, which uses 876–915 MHz (uplink) and 921–960 MHz (downlink). GSM-R provides additional channels and specialized services for use by railway personnel. All these variants are included in the GSM-900 specification.

• GSM-1800 uses 1710–1785 MHz to send information from the mobile station to the base tranceiver station (uplink) and 1805–1880 MHz for the other direction (downlink), Duplex spacing is 95 MHz.

• GSM-850 uses 824–849 MHz to send information from the mobile station to the base station (uplink) and 869–894 MHz for the other direction (downlink).

• GSM-1900 uses 1850–1910 MHz to send information from the mobile station to the base station (uplink) and 1930–1990 MHz for the other direction (downlink).

GSM Handsets

Today, most telephones support multiple bands as used in different countries. These are typically referred to as multi-band phones. Dual-band phones can cover GSM networks in pairs such as 900 and 1800 MHz frequencies or 850 and 1900. European tri-band phones typically cover the 900, 1800 and 1900 bands giving good coverage in Europe and allowing limited use in North America, while North American tri-band phones utilize 850, 1800 and 1900 for wide-spread North American service but limited world-wide use. A new addition has been the quad-band phone, supporting all four major GSM bands, allowing for global use.

Section-III

Chapter-13

��

E2E3 GSM Architecture, Ver2 28.02.2008 1 of 5

GSM Introduction GSM (Global System for Mobile communications) is a 2nd Generation (2G), an open, digital cellular technology used for transmitting mobile voice and data services. GSM differs from first generation wireless systems in that it uses digital technology and time division multiple access transmission methods. GSM is a circuit-switched system that divides each 200kHz channel into eight 25kHz time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US. The 850MHz band is also used for GSM and 3GSM in Australia, Canada and many South American countries. GSM supports data transfer speeds of up to 9.6 kbit/s, allowing the transmission of basic data services such as SMS (Short Message Service). Another major benefit is its international roaming capability, allowing users to access the same services when travelling abroad as at home. This gives consumers seamless and same number connectivity in more than 210 countries. GSM satellite roaming has also extended service access to areas where terrestrial coverage is not available. GSM Architecture

Above figure shows the functional blocks at macro level. These are briefly explained in this handout.

MS


1.0 Mobile Station (MS) In GSM, the mobile phone is called Mobile Station (MS). The MS is a combination of terminal equipment and subscriber data. The terminal equipment as such is called ME (Mobile Equipment) and the subscriber's data is stored in a separate module called SIM (Subscriber Identity Module). Therefore, ME + SIM = MS. From the user’s point of view, the SIM is certainly the best-known database used in a GSM network. The SIM is a small memory device mounted on a card and contains user-specific identification. The SIM card can be taken out of one mobile equipment and inserted into another. In the GSM network, the SIM card identifies the user − just like a traveller uses a passport to identify himself. The SIM card contains the identification numbers of the user and a list of available networks. The SIM card also contains tools needed for authentication and ciphering. Depending on the type of the card, there is also storage space for messages, such as phone numbers. A home operator issues a SIM card when the user joins the network by making a service subscription. The home operator of the subscriber can be anywhere in the world, but for practical reasons the subscriber chooses one of the operators in the country where he/she spends most of the time. 2.0 Network Switching Subsystem (NSS) The Network Switching Subsystem (NSS) contains the network elements MSC, GMSC, VLR, HLR, AC and EIR.

The Network Switching Subsystem (NSS)


The main functions of NSS are: • Call control: This identifies the subscriber, establishes a call, and clears the

connection after the conversation is over. • Charging: This collects the charging information about a call (the numbers of the

caller and the called subscriber, the time and type of the transaction, etc.) and transfers it to the Billing Centre.

• Mobility management: This maintains information about the subscriber's location.

• Signalling: This applies to interfaces with the BSS and PSTN. • Subscriber data handling: This is the permanent data storage in the HLR and

temporary storage of relevant data in the VLR. 2.1 Mobile services Switching Centre (MSC): The MSC is responsible for

controlling calls in the mobile network. It identifies the origin and destination of a call (mobile station or fixed telephone), as well as the type of a call. The MSC is responsible for several important tasks, such as the following.

• Call control: MSC identifies the type of call, the destination, and the origin of a call. It also sets up, supervises, and clears connections.

• Initiation of paging: Paging is the process of locating a particular mobile station in case of a mobile terminated call (a call to a mobile station).

2.2 Gateway Mobile services Switching Centre (GMSC): The GMSC is

responsible for the same tasks as the MSC, except for paging. It is needed in case of mobile terminated calls. In fixed networks, a call is established to the local exchange, to which the telephone is connected to. But in GSM, the MSC, which is serving the MS, changes with the subscriber’s mobility. Therefore, in a mobile terminated call, the call is set up to a well defined exchange in the subscriber’s home PLMN. This exchange is called GMSC. The GMSC than interacts with a database called Home Location Register, which holds the information about the MSC, which is currently serving the MS. The process of requesting location information from the HLR is called HLR Interrogation. Given the information about the serving MSC, the GMSC then continues the call establishment process. In many real life implementations, the MSC functionality and the GMSC functionality are implemented in the same equipment, which is then just called MSC. Many operators use GMSCs for breakout to external networks such as PSTNs.

2.3 Visitor Location Register (VLR): VLR is a database, which contains

information about subscribers currently being in the service area of the MSC/VLR, such as: • Identification numbers of the subscribers • Security information for authentication of the SIM card and for

ciphering


The VLR carries out location registrations and updates. When a mobile station comes to a new MSC/VLR serving area, it must register itself in the VLR, in other words perform a location update. Please note that a mobile subscriber must always be registered in a VLR in order to use the services of the network. Also the mobile stations located in the own network is always registered in a VLR. The VLR database is temporary, in the sense that the data is held as long as the subscriber is within its service area. It also contains the address to every subscriber's Home Location Register, which is the next network element to be discussed.

2.4 Home Location Register (HLR): HLR maintains a permanent register of

the subscribers. For instance the subscriber identity numbers and the subscribed services can be found here. In addition to the fixed data, the HLR also keeps track of the current location of its customers. As you will see later, the GMSC asks for routing information from the HLR if a call is to be set up to a mobile station (mobile terminated call).

2.5 Authentication Centre (AC): The Authentication Centre provides security

information to the network, so that we can verify the SIM cards (authentication between the mobile station and the VLR, and cipher the information transmitted in the air interface (between the MS and the Base Transceiver Station)). The Authentication Centre supports the VLR's work by issuing so-called authentication triplets upon request.

2.6 Equipment Identity Register (EIR): As for AC, the Equipment Identity

Register is used for security reasons. But while the AC provides information for verifying the SIM cards, the EIR is responsible for IMEI checking (checking the validity of the mobile equipment). When this optional network element is in use, the mobile station is requested to provide the International Mobile Equipment Identity (IMEI) number. The EIR contains three lists: • A mobile equipment in the white list is allowed to operate normally. • If we suspect that a mobile equipment is faulty, we can monitor the use

of it. It is then placed in the grey list. • If the mobile equipment is reported stolen, or it is otherwise not allowed

to operate in the network, it is placed in the black list.


3.0 Base Station Subsystem (BSS): The Base Station Subsystem is

responsible for managing the radio network, and it is controlled by an MSC. Typically, one MSC contains several BSSs. A BSS itself may cover a considerably large geographical area consisting of many cells (a cell refers to an area covered by one or more frequency resources). The BSS consists of the following elements:

• BSC Base Station Controller • BTS Base Transceiver Station • TRAU Transcoder and Rate Adaptation Unit (often referred to as TC

(Transcoder))

Radio path control: In the GSM network, the Base Station Subsystem (BSS) is the part of the network taking care of radio resources, that is, radio channel allocation and quality of the radio connection. Synchronisation: The BSS uses hierarchical synchronisation, which means that the MSC synchronises the BSC, and the BSC further synchronises the BTSs associated with that particular BSC. Inside the BSS, synchronisation is controlled by the BSC. Synchronisation is a critical issue in the GSM network due to the nature of the information transferred. If the synchronisation chain is not working correctly, calls may be cut or the call quality may not be the best possible. Ultimately, it may even be impossible to establish a call. Air- and A-interface signalling: In order to establish a call, the MS must have a connection through the BSS. The BSS is located between two interfaces, the air- and the A-interface. The MS must have a connection through these two interfaces before a call can be established. Generally speaking, this connection may be either a signalling connection or a traffic (speech, data) connection. Mobility management and speech transcoding: BSS mobility management mainly covers the different cases of handovers.

Section-III

Chapter-14

Overview of GPRS & EDGE

E2E3 GPRS & Edge, Ver2 28.02.2008 1 of 6

Overview of GPRS GPRS (General Packet Radio Service) is the world's most ubiquitous wireless data service, available now with almost every GSM network. GSM system (2G) with GPRS capability is sometimes also known as 2.5G. GPRS is a connectivity solution based on Internet Protocols that supports a wide range of enterprise and consumer applications. Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about three times as fast as the data transmission speeds possible over today's fixed telecommunications networks and ten times as fast as current Circuit Switched Data services on GSM networks. Practically with throughput rates of up to 40 kbit/s, users have a similar access speed to a dial-up modem, but with the convenience of being able to connect from anywhere. GPRS customers enjoy advanced, feature-rich data services such as colour Internet browsing, e-mail on the move, powerful visual communications such as video streaming, multimedia messages and location-based services. �

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GPRS standardization The ETSI (European Telecommunications Standardization Institute) does the standardisation work for GPRS.


Key points GPRS uses a packet-based switching technique, which will enhance GSM data services significantly, especially for bursty Internet/intranet traffic. Some application examples:

• Bus, train, airline real-time information • Locating restaurants and other entertainment venues based on current

Location • Lottery • E-commerce • Banking • E-mail • Web browsing

The main advantages of GPRS for users: • Instant access to data as if connected to an office LAN • Charging based on amount of data transferred (not the time connected) • Higher transmission speeds

The main advantages for operators: • Fast network roll-out with minimum investment • Excess voice capacity used for GPRS data • Smooth path to 3G services

In circuit switching, each time a connection is required between two points, a link between the two points is established and the needed resources are reserved for the use of that single call for the complete duration of the call. In packet switching, the data to be transferred is divided up into packets, which are then sent through the network and re-assembled at the receiving end.


The GPRS network acts in parallel with the GSM network, providing packet switched connections to the external networks. The requirements of a GPRS network are the following:

• The GPRS network must use as much of the existing GSM infrastructure with the smallest number of modifications to it.

• Since a GPRS user may be on more than one data session, GPRS should be able to support one or more packet switched connections.

• To support the budgets of various GPRS users, it must be able to support different Quality of Service (QoS) subscriptions of the user.

• The GPRS network architecture has to be compatible with future 3rd and 4th generation mobile communication systems.

• It should be able to support both point-to-point and point-to-multipoint data connections.

• It should provide secure access to external networks.

Figure shows the architecture of a GPRS network. The GPRS system brings some new network elements to an existing GSM network. These elements are:

• Packet Control Unit (PCU) • Serving GPRS Support Node (SGSN): the MSC of the GPRS network • Gateway GPRS Support Node (GGSN): gateway to external networks • Border Gateway (BG): a gateway to other PLMN • Intra-PLMN backbone: an IP based network inter-connecting all the

GPRS elements • Charging Gateway (CG) • Legal Interception Gateway (LIG) • Domain Name System (DNS)


Firewalls: used wherever a connection to an external network is required. Not all of the network elements are compulsory for every GPRS network. Packet Control Unit (PCU) The PCU separates the circuit switched and packet switched traffic from the user and sends them to the GSM and GPRS networks respectively. It also performs most of the radio resource management functions of the GPRS network. The PCU can be either located in the BTS, BSC, or some other point between the MS and the MSC. There will be at least one PCU that serves a cell in which GPRS services will be available. Frame Relay technology is being used at present to interconnect the PCU to the GPRS core. Channel Codec Unit (CCU) The CCU is realised in the BTS to perform the Channel Coding (including the coding scheme algorithms), power control and timing advance procedures. Serving GPRS Support Node (SGSN) The SGSN is the most important element of the GPRS network. The SGSN of the GPRS network is equivalent to the MSC of the GSM network. There must at least one SGSN in a GPRS network. There is a coverage area associated with a SGSN. As the network expands and the number of subscribers increases, there may be more than one SGSN in a network. The SGSN has the following functions:

• Protocol conversion (for example IP to FR) • Ciphering of GPRS data between the MS and SGSN • Data compression is used to minimise the size of transmitted data units • Authentication of GPRS users • Mobility management as the subscriber moves from one area to another,

and possibly one SGSN to another • Routing of data to the relevant GGSN when a connection to an external

network is required • Interaction with the NSS (that is, MSC/VLR, HLR, EIR) via the SS7

network in order to retrieve subscription information • Collection of charging data pertaining to the use of GPRS users • Traffic statistics collections for network management purposes.

Gateway GPRS Support Node (GGSN) The GGSN is the gateway to external networks. Every connection to a fixed external data etwork has to go through a GGSN. The GGSN acts as the anchor point in a GPRS data connection even when the subscriber moves to another SGSN during roaming. The GGSN may accept connection request from SGSN that is in another PLMN. Hence, the concept of coverage area does not apply to


GGSN. There are usually two or more GGSNs in a network for redundancy purposes, and they back up each other up in case of failure. The functions of a GGSN are given below:

• Routing mobile-destined packets coming from external networks to the relevant SGSN

• Routing packets originating from a mobile to the correct external network • Interfaces to external IP networks and deals with security issues • Collects charging data and traffic statistics • Allocates dynamic or static IP addresses to mobiles either by itself or with

the help of a DHCP or a RADIUS server • Involved in the establishment of tunnels with the SGSN and with other

external networks and VPN. From the external network's point of view, the GGSN is simply a router to an IP sub-network. This is shown below. When the GGSN receives data addressed to a specific user in the mobile network, it first checks if the address is active. If it is, the GGSN forwards the data to the SGSN serving the mobile. If the address is inactive, the data is discarded. The GGSN also routes mobile originated packets to the correct external network. GPRS MS (Mobile Station/Handset) Different GPRS MS classes were introduced to cope with the different needs of future subscribers. The mobiles differ in their capabilities.


��

Further enhancements to GSM networks are provided by Enhanced Data rates for GSM Evolution (EDGE) technology. EDGE provides up to three times the data capacity of GPRS. Using EDGE, operators can handle three times more subscribers than GPRS; triple their data rate per subscriber, or add extra capacity to their voice communications. EDGE uses the same TDMA (Time Division Multiple Access) frame structure, logic channel and 200kHz carrier bandwidth as today's GSM networks, which allows it to be overlaid directly onto an existing GSM network. Some people classify the GSM network with EDGE capability as 2.75G. EDGE allows the delivery of advanced mobile services such as the downloading of video and music clips, full multimedia messaging, high-speed colour Internet access and e-mail on the move. Although EDGE requires no hardware or software changes to be made in GSM core networks, base stations must be modified. EDGE compatible transceiver units must be installed and the base station subsystem (BSS) needs to be upgraded to support EDGE. New mobile terminal hardware and software is also required to decode/encode the new modulation and coding schemes and carry the higher user data rates to implement new services. Due to the very small incremental cost of including EDGE capability in GSM network deployment, virtually all new GSM infrastructure deployments are also EDGE capable and nearly all new mid- to high-level GSM devices also include EDGE radio technology. The Global mobile Suppliers Association (GSA) states that, as of May 2007, there were 223 commercial GSM/EDGE networks in 113 countries, from a total of 287 mobile network operator commitments in 142 countries (source: www.gsacom.com).

http://www.gsacom.com/

Section-III

Chapter-15

��

E2E3 GSM services Ver2 28.02.2008 1 of 9

INTRODUCTION The primary objective of a mobile telephony system is to allow mobile subscribers to communicate effectively. GSM systems provide this by offering a number of different basic telecommunications services.

The service functionality of GSM system improves with each system release. Technical specifications are continuously being developed in order to incorporate new and improved functions into the system.

SERVICE CATEGORIES

There are two main types of telecommunications services:

• Basic services: These are available to all subscribers to a mobile network.

For example, the ability to make voice telephone calls is a basic service. Basic telecommunication services can be divided into two main categories:

�� Teleservices: A teleservice allows the subscriber to communicate

(usually via voice, fax, data or SMS) with another subscriber. It is a complete system including necessary terminal equipment.

�� Bearer services: A bearer service transports speech and data as digital information within the network between user interfaces. A bearer service is the capability to transfer information and does not include the end-user equipment. Every teleservice is associated with a bearer service. For example, a bearer service associated with the speech telephony teleservice is the timeslot assigned to a call on a TDMA frame over the air interface.

• Supplementary services: These are additional services that are available by

subscription only. Call forwarding is an example of a supplementary service.

GSM systems are also designed to enable operators to differentiate their services from their competitor’s services using a technique based on Mobile Intelligent Network (MIN) solutions.

BASIC TELECOMMUNICATIONS SERVICES 1.0 BEARER SERVICES

GSM systems offer a wide range of bearer services. The DTI supports data services offered by the system. Rates up to 48 kbits/s are possible.

1.1 Traffic to PSTN: for data traffic external to PLMN such as internetworking

with ISDN or directly to PSTN, the system selects a suitable modem in the DTI.


1.2 Traffic to ISDN: an entire set of data communication services with ISDN terminals is available. Unrestricted digital information is transferred and no modem is necessary.

1.3 Traffic to Packet Switched Public Data Network (PSPDN): Packet service

supports synchronous data transfers with the PSPDN with rates from 1.2 to 48 kbits/s. With synchronous data transfers a packet mode terminal can be directly connected to the MS. Synchronous data communication between an MS and a packet switched network is possible via the packet Assembler-Disassembler (PAD) facility. Rates between 300 and 9600 bits/s are supported.

Figure 1 Data call in GSM to PSPDN

1.4 Traffic to Circuit Switched Public Data Network (CSPDN): Data communications with a CSPDN is possible via the PSTN or ISDN, depending on the CSPDN-transit network interface.

1.5 Traffic to Internet: traditionally, an MSC accessed Internet nodes via existing

networks such as the PSTN. However, the direct access function enables an MSC to communicate directly with Internet nodes, thus reducing call set-up time.

1.6 ISDN Primary Rate Access (PRA): this function enables an MSC to provide

PRA services to subscribers. For example, a network operator can offer PABX connection services through the PLMN. In this way the operator can compete directly with PSTN operators for ISDN business subscribers. PRA provides a data rate of up to 2 Mbits/s.

MSC/VLR

PAD PSTN

PAD

PSTN

BSC IPNetwork PSPDN


2.0 TELESERVICES

This section describes the major teleservices supported by GSM systems.

2.1 Speech: This is normal telephony (two-way voice communication) with the ability to make and receive calls to/from fixed and mobile subscribers worldwide. This is the most fundamental service offered.

2.2 Emergency calls: The emergency call function enables a subscriber to make an

emergency call by pressing a predefined button or by using the emergency number. With an emergency area origin identifier, the call is automatically routed to the emergency center nearest to the subscriber. Emergency calls can be made with the phone itself, without a valid SIM-card, overriding locked phone and pin codes.

2.3 Facsimile group 3: GSM supports International

Telecommunications Union (ITU) group 3 facsimile. Standard fax machines are designed to be connected to a telephone using analog signals, a special fax converter is connected to the exchange. This enables a connected fax to communicate with any analog fax in the fixed network.

2.4 Dual Tone Multi Frequency (DTMF): This is a tone signaling facility which

is often used for various control purposes, such as remote control of answering machines and interacting with automated telephone services.

2.5 Alternative Speech/Fax: This service allows the subscriber to alternate

between speech and fax within one call setup. The subscriber can start the call either with speech or fax and then alternate between the two call types. The subscriber can switch several times within the same call.

2.6 Short Message Services (SMS): This service allows simple text messages

consisting of a maximum of 160 alphanumeric characters to be sent to or from an MS.

If the MS is switched off, or has left the coverage area, the message is stored in a Short Message Service Center (SMS-C). When the mobile is switched on again or has re-entered the network coverage area, the subscriber is informed that there is a message. This function guarantees that messages are delivered.

2.7 SMS Cell Broadcast (SMSCB): The cell broadcast facility is a variation of the short message service. A text message with a maximum length of 93 characters can be broadcast to all mobiles within a certain geographic area. Typical applications are traffic congestion warnings and accident reports, and in the future, possibly advertisements.


2.8 Voice mail: This service is an answering machine within the network that is controlled by the subscriber. Calls can be forwarded to the subscriber’s voice mailbox. The subscriber accesses the mailbox using a personal security code.

2.9 Fax mail: This service allows the subscriber to receive fax messages at any fax

machine via the MS. Fax messages are stored in a network service center. The subscriber accesses the fax mail via a personal security code and the fax is then sent to the desired fax number.

3.0 SUPPLEMENTARY SERVICES

This section describes the main supplementary services supported by GSM systems.

3.1 Call forwarding: This service provides the subscriber with the ability to

forward incoming calls to another telephone number in the following situations: • Call forwarding on MS not reachable • Call forwarding on MS busy • Call forwarding on no reply • Call forwarding, unconditional

3.2 Barring of outgoing calls: The subscriber can activate or deactivate this service from the MS with a variety of options for barring outgoing calls. For example, the subscriber can:

• Bar all outgoing calls • Bar all outgoing international calls • Bar all outgoing international calls except those directed to

the home PLMN

3.3 Barring of incoming calls: With this function, the subscriber can prevent incoming calls. This is desirable because in some cases the called mobile subscriber is charged for parts of an incoming call (e.g. during international roaming).

There are two incoming call barring options:

• Barring of all incoming calls • Barring of incoming calls when outside home PLMN

3.4 Advice of Charge: The advice of Charge (AoC) service provides the MS with information needed to calculate the charge of a call. This information is provided at call set-up.

Charges are indicated for the call in progress when mobile originated. For a mobile terminated call, AoC only offers information on the roaming leg.


3.5 Account Codes: This service enables a subscriber, e.g. a business, to identify

an account number, which is to be charged for particular call components. Account codes can be identified on a per call basis.

3.6 Call waiting: This service notifies the mobile subscriber, usually by an audible

tone, for incoming call. The call can then be answered, rejected or ignored. The incoming call can be any type of basic service including speech, data or fax. There is no notification in the case of an emergency call or SMS.

3.7 Call hold: This supplementary service enables the subscriber to put the basic

normal telephony service on hold in order to set up a new call or accept a waiting call. Communication with the original call can then be re-established.

3.8 Multiparty service: The multiparty service enables a mobile subscriber to

establish a multiparty conversation, that is, a simultaneous conversation between up to six subscribers. This service can only be used with basic speech telephony.

3.9 Calling line identification services:

These supplementary services cover both the presentation and restriction of the calling line identity. The presentation part of the service supplies the called party with the ISDN or MSISDN number of the calling party. The restriction service enables calling parties to restrict the presentation of their numbers on the MSs of called parties. Restriction overrides presentation

3.10 Connected line identification presentation/restriction:

These supplementary services supply the calling party with the ISDN number of the connected (called) party. The restriction enables the connected party to restrict the presentation. Restriction overrides presentation. This service is useful when the call is forwarded or when it is connected via a switchboard.

3.11 Closed User Group (CUG):

The CUG service enables subscribers connected to the PLMN/ISDN and possibl0y other networks, to form groups in which access is restricted. For example, members of a specific CUG can communicate with each other, but generally not with users outside the group.


4.0 INNOVATIVE SERVICES

Innovative features offer a level of service beyond the basic network standards. New features are developed on an ongoing basic as customer demands and competition increase. Some features are described in this section.

Single personal number: The single personal number service allows a subscriber to arrange call forwarding to other networks when the mobile is not reached in the subscriber’s primary network. With this feature, one directory number can reach the subscriber even though the subscriber may have subscriptions in several different networks.

Dual numbering: This feature allows the subscriber to have two different directory numbers connected to the same subscription and the same mobile equipment. In this way different accounts can be connected to the different directory numbers. For example, the subscriber may want one business account and one private account connected to the same subscription. Support for this feature is required in the MS.

Immediate call itemization: This feature is also called ‘Hot billing’. It is used when it is necessary to have immediate call charging data output (e.g. to bill a third party for use of a telephone, which is rented).

Regional call itemization: These features allow subscribers to subscribe to a service in a specified geographical area. Requests for service outside the area are rejected with the exception of emergency calls and SMS. For local subscriptions, the geographical area consists of a number of cells, and for regional subscriptions, the area consists of LAs. The cells or LAs do not need to be adjacent but can be spread out over the PLMN. For regional subscriptions, LAs in other PLMNs in other countries may be included. Handovers are not influenced.

Geographically differentiated charging: This feature enables the GSM PLMN area to be divided into different tariff regions. A tariff region is defined as a set of cells. A subscriber may be offered cheaper calls within certain areas. This feature can be combined with the service regional subscription.


5.0 LOCATION BASED SERVICES A location Based service (LBS) can be described as an application that is dependent on a certain location. Two broad categories of LBS can be defined as triggered and user requested. In a user requested scenario, the user is retrieving the position once and uses it on subsequent requests for location dependent information. This type of service usually involves either personal location (i.e. finding where you are) or service location (i.e. where is the nearest). Examples of this type of LBS are navigation (usually involving a map) and direction (routing information). A triggered LBS by contrast relies on a condition set up in advance that, once fulfilled, retrieves the position of a given device. An example is when the user passes across the boundaries of the cells in a mobile network. Another example is in emergency center triggers an automatic location request from the mobile network.

5.1 GSM Cellular Locations

Due to the cellular nature of the GSM mobile telephone network, it is possible to determine the location of a regular GSM mobile telephone. The basic system of cell ID, described below, is somewhat crude but techniques are available to provide increased accuracy. This section describes one method of increasing the accuracy of cell ID but others also exit. The advantage of cellular positioning over GPS is that the signal is much stronger and therefore will operate indoors; it is also unaffected by the urban canyon effect (subject to GSM coverage).

5.1.1 Cell lD

Cell ID is the most basic form of cellular location and works simply by detection the Base Transceiver Station (BTS) with which the telephone is registered. At any moment in time, the mobile telephone/Station (MS) is registered to a BTS. This is usually the nearest BTS but may occasionally be the BTS of a neighbouring cell due to terrain, cell overlap or if the nearest BTS is congested. Cells vary in size depending on terrain and the anticipated number of users; hence in city centers cells are much smaller than in rural location. This difference in cell size greatly affects the accuracy of a position fix since the location reported is in fact the location of the BTS and the MS may be anywhere within the boundary of the cell. Typically the extent of error in urban locations may be around 500 metres but in rural locations this can increase up to about 15 kms. Each base-station will have multiple antennae, each covering a sector of the cell. So a BTS with there antennae will produce a cell with there 1200 sectors. By detecting the antenna with which the MS is registered, the location of the MS can be narrowed down to somewhere within a sector of the cell with the BTS at its apex.


5.2 Applications

Service providers hope that location services will stimulate demand for wireless data services. Location information may be used by an application provider to personalize the service, or to improve the user interface by reducing the need to interact with a small device while on the move. This section aims to give a brief insight into a range of likely applications of location based services.

5.2.1 Communication

Some LBS applications with self-contained user device obtain a position using one of the methods described above, perform some processing and then present the resulting data back to the user. Many other applications will require the position to be sent to a server either for display to other parties, processing or referencing against additional content. Consumer applications will often use SMS text messaging because it is simple to use and familiar to most mobile users. The disadvantage of SMS is that it is limited to text-based data (although the impending Multimedia Messaging Service (MMS) will allow still images, audio and video to be transmitted). WAP may be considered as an alternative communications channel that provides more data capacity and reduces the end-to-end delay. SMS is also rather expensive as a data carrier and so may not be cost effective for some applications where position reports need to be transmitted at 5 minutes intervals though out the day, for example. GPRS may be a more appropriate bearer for some applications as only the data transmitted will be charged for and the high data rates would allow for large position and telemetry logs to be downloaded at the end of the day if required. All of the communications channels discussed so far have relied on the GSM network but for safety critical applications or for tracking of devices in remote areas GSM may not be appropriate. A satellite network, such as Inmarsat C or D+ may be preferable if global coverage is required, although there will be an obvious trade off with cost per position report and the hardware is likely to be more bulky and demand more power.

5.2.2 Fleet Management The purpose of a fleet management application is to allow a company to keep track of its mobile assets in near real time and to be able to use that information not only to increase performance and utilization but also decrease operating costs. As an example, consider the case of a delivery company. By having its fleet of delivery vans reporting their position at regular intervals throughout the day, if an urgent collection is required the company knows which is the nearest van and can calculate the travel time required, therefore optimizing the distribution of tasks. If the vehicle is also reporting telemetry data about engine performance and driving habits (acceleration, breaking etc.) the company can also detect mechanical problems before they cause damage and encourage their drivers to adopt a more fuel efficient driving behavior. Geographic boundaries, known as geofences, could be configured that trigger alerts when the object


being traced crosses the geofences perimeter. These could be defined so that when the lorry arrives within 5 miles of the depot an alert is triggered to forewarn the loading day crew of the van’s arrival. Location data could also be viewed by customers to get information about the location of their deliveries and expected delivery time.

5.2.3 Routing Navigation is another increasingly common implantation of location based services and the benefits in terms of optimized routing, avoidance of traffic congestion and early warning of diversions, accidents and road works are easy to recognize. Apart from detailed turn-by-turn directions, there is growing demand for ‘Where’s my nearest…? Type applications where an end user requests the nearest business of a particular type relative to their current location. For example, “Where’s my nearest Italian restaurant?” .To date, there applications have relied on self positioning by the user where the user has to define their location manually either by entering a street name, town name, postcode or some other reference. This is because until now it has not been possible for a third party application provider to determine roll-out of APls to the network’s Cell ID data will provide a significant boost to these services.

5.2.4 Safety and Security

An emerging application of location-based services is in the area of workforce safety. By equipping their workforce with a small electronic device that enables location determination and transmission into a service center, a company can monitor the condition of lone workers and those in high-risk areas. Status updates may be requested at regular intervals and the device may have a ‘panic button’ to allow the user to request for assistance to be dispatched to their precise location in the event of an emergency. Vehicles can now be equipped with covertly installed tracking devices to allow their safe recovery in the event of theft. Many of these systems are so successful that motor insurance companies now offer discounts to the insurance premiums of those that choose to have the relevant devices installed.

5.2.5 Entertainment

The limited availability of low-cost, mass market positioning devices has so far been a barrier to location based services entering the entertainment arena because they require specialized GPS hardware. However, the combination of the ever-decreasing price of GPS technology and the imminent availability of GSM Cell ID, positing has contributed to the appearance of some innovative entertainment applications. Location-based directory services are using either a WAP or SMS interfaces. Examples for this type of applications are DJ requests, voting, competitions are dating services. Many applications within the entertainment sector will be enhanced by the MMS application.

Section-III

Chapter-16

��

E2E3 CDMA Overview, Ver1 24.08.2007 1 of 14

OVERVIEW OF CDMA

1. INTRODUCTION Access Network, the network between local exchange and subscriber, in the Telecom Network accounts for a major portion of resources both in terms of capital and manpower. So far, the subscriber loop has remained in the domain of the copper cable providing cost effective solution in the past. Quick deployment of subscriber loop, coverage of inaccessible and remote locations coupled with modern technology have led to the emergence of new Access Technologies. The various technological options available are as follows:

1. Multi Access Radio Relay 2. Wireless In Local Loop 3. Fibre In the Local Loop

2. WIRELESS IN LOCAL LOOP (WILL). Fixed Wireless telephony in the subscriber access network also known as Wireless in Local Loop (WILL) is one of the hottest emerging market segments in global telecommunications today. WILL is generally used as “the last mile solution” to deliver basic phone service expeditiously where none has existed before. Flexibility and expediency are becoming the key driving factors behind the deployment of WILL. Different technologies have been developed by the different countries, like, CT2 from France, PHS from Japan, DECT from Europe, and DAMPS & CDMA from USA. Let us discuss CDMA technology in WILL application as it has a potential ability to tolerate a fair amount of interference as compared to other conventional radios. This leads to a considerable advantage from a system point of view.

3. SPREAD SPECTRUM PRINCIPLE Originally Spread spectrum radio technology was developed for military use to counter the interference by hostile jamming. The broad spectrum of the transmitted signal gives rise to “Spread Spectrum”. A Spread Spectrum signal is generated by modulating the radio frequency (RF) signal with a code consisting of different pseudo random binary sequences, which is inherently resistant to noisy signal environment. A number of Spread spectrum RF signals thus generated share the same frequency spectrum and thus the entire bandwidth available in the band is used by each of the users using same frequency at the same time. On the receive side only the signal energy with the selected binary sequence code is accepted and original information content (data) is recovered. The other users signals, whose codes do not match contribute only to the noise and are not “de-spread” back in bandwidth (Figure-I).This transmission and reception of signals differentiated by “codes” using the same frequency simultaneously by a number of users is known as Code Division Multiple Access (CDMA) Technique as opposed to conventional method of Frequency Division Multiple Access and Time Division Multiple Access.


1.25MHz 1.25MHz

10KHz

CDMA ACCESS -A CONCEPT

Wideband Spectrum Transmitted

• Other CELL Interference

•Other Users Noise

10KHz

DATA(9.6Kbp)

ENCODING

CARRIER

PNSOURCE

DATADECODER

CARRIER

FILTER

1.25MHz 1.25MHz

PNSOURCE

•Background Noise

Wideband Spectrum Received

“Despread” original data&other noiseDATA to be transmitted

•Externalinterference

Figure-1 In figure -1 it has been tried to explain that how the base band signal of 9.6 Kbps is spread using a Pseudo-random Noise(PN) source to occupy entire bandwidth of 1.25 Mhz. At the receiving end this signal will have interference from signals of other users of the same cell, users of different cells and interference from other noise sources. All these signals get combined with the desired signal but using a correct PN code the original data can be reproduced back. CDMA channel in the trans and receive direction is a FDD (Frequency Division Duplexing) channel. The salient features of a typical CDMA system are as follows: • Frequency of operation: 824-849 Mhz and 869-894 Mhz • Duplexing Method: Frequency Division Duplexing (FDD) • Access Channel per carrier: Maximum 61Channels • RF Spacing: 1.25 Mhz • Coverage: 5 Km with hand held telephones and approx. 20 Km

with fixed units. The different types of codes used for identification of traffic channels and users identification etc. are as follows: 4. DIFFERENT CODES 4.1. Walsh Code: In CDMA the forward traffic channels are separated by unique “Walsh” code. All such codes are orthogonal to each other. The individual subscriber can start communication using one of these codes. These codes are traffic channel codes and are used for orthogonal spreading of the information in the entire bandwidth. Orthogonality provides nearly perfect isolation between the multiple signals transmitted by the base station


The basic concept behind creation of the code is as follows: (a) Repeat the function right (b) Repeat the function below (c) Invert the function diagonally

Seed 0 0 0 0 0 0 0 0 1 0 1 0 1 0 0 1 1 0 1 1 0 4.2. Long Code: The long pseudo random noise (PN) sequence is based on 242characteristic polynomial. Reverse traffic channels (Mobile to Base) are separated by this long code and the data in the forward direction (Base to Mobile) is scrambled. The PN codes are generated using linear shift registers. The long code is unique for the subscribers and is known as users address mask. It repeats every 41 days (at a clock rate of 1.2288 Mcps) PN offset (Masking)

- Masking will cause the generator to produce the same sequence but offset in time. - Masking provides the shift in time for PN codes. - Different masks correspond to different time shifts. - ESN are used as masks for users on the traffic channels.

4.3. Short Code: The short pseudo random noise (PN) sequence is based on 215 characteristic polynomial. This short code differentiates the cells & the sectors in a cell. It also consists of codes for I & Q channel feeding the modulator. Each cell uses different PN offsets. It repeats every 26.67 msec (at a clock rate of 1.2288 Mcps) 5.0 CDMA Channels Forward Link Channels Pilot Channel Sync Channel Paging Channels Traffic Channels Reverse Link Channels Access Channels Traffic Channels Pilot channel (W0) The pilot is used by the subs unit to obtain initial system synchronization and to distinguish cell

sites. Every sector of every cell site has a unique pilot channel. • Transmitted constantly. • Allows the mobile to acquire the system. • Provides mobile with signal strength comparison. • Approximately 20% of the radiated power is in the pilot. • Has unique PN Offset for each cell or sector.


Sync channel (W32) Used during system Acquisition stage. Sync channel provides the subscriber unit with network

information related to cell site identification, pilot transmit power & cell site PN offset. • Used by mobile to synchronize with the system • Transmits sync message with

- Pilot PN offset - System time - Long PN code - System ID - Network ID - Paging channel data rate

• Tx at 1200 bps PAGING CHLS (W1-W7) On this channel base station can page the subs unit and it can send call set-up and traffic

channel assignment information. • Means of communication between base to mobile station. • Paging CHL data Rates can be 2.4,4.8 or 9.6 Kbps. • CDMA assignment has 7 paging channel. • Each paging CHL supports 180 pages per second. • Total pages/ CDMA RF channel = 1260 • Provides mobile with • - System Parameter message - Neighbour list • - Access Parameter list - CDMA Channel list • Used by base station to : • - Page mobile - Transmit overhead information • - Assign mobile to traffic channel Traffic Channels (W8-W31 & W33-W63) The traffic channel carries the actual call. That is, the voice and control information between the subs unit & base station. TX up to 9.6kbps on rate set 1 and up to 14.4kbps on rate set 2.

Access Channel. (a) Provides communication from Mobile to base station when mobile is not using traffic

Channel. The access channel is used for call origination & for response to pages, orders & registration requests. It is paired with corresponding paging channel.

(b) Each Access CHL use long PN code. (c) Base station responds to transmission on a particular Access Channel. (d) Mobile responds to base station message by emitting on Access Channel. (e) Transmits at 4800bps.


It is clear from the figure that in the forward direction both the rate sets are supported and the data rate after convolution encoding will be 19.2 Ksps. Then using the PN code the signal is scrambled. In which each symbol coming out of block interleaver is exclusively-ORed with one symbol of scrambling sequence. Power control bits are then punctured at appropriate places. Then this signal is orthogonally spread using one of the walsh codes. At this place the data rate increases to 1.2288 Mcps, which is sent on I & Q channel. All the information is sent on both the quadrature channels and the each quadrature is spread using short PN code. These short PN codes are second layer of coding used to isolate one sector from another. Now this signal is transmitted which will be received and demodulated at the mobile end. Rake receiver CDMA mobiles use rake receivers. The rake receiver essentially a set of four or more receivers (or fingers). One of the receivers constantly searches for different multipaths and helps to direct the other three fingers to lock onto strong multipath signals.

• Allows combined reception of up to three different paths. • Provides searcher receiver to identify changes in path characteristics/new cells. • Provides both path diversity and frequency diversity.

Forward Traffic Channel Generation

9600 bps 4800 bps 2400 bps 1200 bps Rate set 1

I PN

Convolutional Encoder & Repetition

Block interleaver

Long Code PN

decimator decimator

User Address Mask (ESN)

O PN

Power Control bit

19.2 ksps

1.2288

19.2 ksps

R=1/2

Mcps 800bps

Rate set 2 14400 bps 7200 bps 3600 bps 1800 bps

R=3/4

Wt

1.2288 Mcps

64:1 24:1


In this process also both the rate sets are supported. After convolutional encoding the rates will be 28.8 Ksps. In this case orthogonal modulation is followed by a data burst randomizer that determines when to turn off the mobile transmitter to reduce average transmit power. In order to

Reverse Traffic Channel Generation

9600 bps 4800 bps 2400 bps 1200 bps Rate set 1

I PN

Convolutional Encoder &

Block interleav

Long Code PN

User Address Mask (ESN)

O PN

28.8 ksps

1.2288

19.2 ksps

R=1/3

Mcps

Rate set 2 14400 bps 7200 bps 3600 bps 1800 bps

R=1/2

1.2288 Mcps Data

Burst Rand.

Orthogonal Modulation

307.2 KHz

Correlator 1

Correlator 2

Correlator 3

Searcher Correlator

C O M B I N E R

CDMA mobile rake receiver


take advantage of reduced speech activity the vocoder reduces its data rate allowing the transmission of the signal at a lower average level of power. The mobile uses full rates when it transmits, but when redundant information is produced by symbol repetition scheme the data burst randomizer turns off the transmitter pseudo randomly reducing the average transmission power. Then the signal is direct sequence spread using long code and occupies the entire bandwidth. The signal is then sent on I and Q channels and short PN codes are used for spreading the signal, the quadrature branch is delayed by ½ bit to produce OQPSK modulation.Which is sent to base station for reception and demodulation. 5. ADVANTAGES : CDMA wireless access provides the following unique advantages: 5.1. Larger Capacity: Let us discuss this issue with the help of Shannon’s Theorem. It states that the channel capacity is related to product of available band width and S/N ratio. C = W log2 (1+S/N) Where C = channel capacity W = Band width available S/N = Signal to noise ratio It is clear that even if we improve S/N to a great extent the advantage that we are expected to get in terms of channel capacity will not be proportionally increased. But instead if we increase the bandwidth (W), we can achieve more channel capacity even at a lower S/N. That forms the basis of CDMA approach, wherein increased channel capacity is obtained by increasing both W & S/N. The S/N can be increased by devising proper power control methods. 5.1.1 Vocoder and variable data rates: As the telephone quality speech is band limited to 4 Khz, when it is digitized with PCM its bit rate rises to 64 Kb/s. Vocoding compress it to a lower bit rate to reduce bandwidth. The transmitting vocoder takes voice samples and generates an encoded speech/packet for transmission to the receiving vocoder. The receiving vocoder decodes the received speech packet into voice samples. One of the important features of the variable rate vocoder is the use of adaptive threshold to determine the required data rate. Vocoders are variable rate vocoders. By operating the vocoder at half rate on some of the frames the capacity of the system can be enhanced without noticeable degradation in the quality of the speech. This phenomenon helps to absorb the occasional heavy requirement of traffic apart from suppression of background noise. Thus the capacity advantage makes spread spectrum an ideal choice for use in areas where the frequency spectrum is congested. 5.2. Less (Optimum) Power per cell: Power Control Methods: As we have already seen that in CDMA the entire bandwidth of 1.25 MHz, is used by all the subscribers served in that area. Hence they all will be transmitting on the same frequency using the entire bandwidth but separated by different codes. At the receiving end the noise contributed by all the subscribers is added up. To minimize the level of interfering signals in CDMA, very powerful power control methods have been devised and are listed below:


1. Reverse link open loop power control 2. Reverse link closed loop power control 3. Forward link power control

The objective of open loop power control in the reverse link (Mobile to Base) is that the mobile station should adjust its transmit power according to the changes in its received power from the base. Open loop power control attempts to ensure that the received signal strength at the base station from different mobile stations, irrespective of their distances from the base station, should be same. In Closed loop power control in reverse link, the base station provides rapid corrections to the mobile stations’ open loop estimates to maintain optimum transmit power by the mobile stations. The base station measures the received signal strength from the mobile connected to it and compares it with a threshold value and a decision is taken by the base every 1.25ms to either increase or decrease the power of the mobile. In forward link power control (Base to Mobile) the cell(base) adjusts its power in the forward link for each subscriber, in response to measurements provided by the mobile station so as to provide more power to the mobile who is relatively far away from the base or is in a location experiencing more difficult environment. These power control methods attempt to have an environment which permits high quality communication (good S/N) and at the same time the interference to other mobile stations sharing the same CDMA channel is minimum. Thus more numbers of mobile stations are able to use the system without degradation in the performance. Apart from the capacity advantage thus gained, power control extends the life of the battery used in portables and minimizes the concern of ill effects of RF radiation on the human body. 5.3. Seamless Hand-off: CDMA provides soft hand-off feature for the mobile crossing from one cell to another cell by combining the signals from both the cells in the transition areas. This improves the performance of the network at the boundaries of the cells, virtually eliminating the dropped calls. 5.4. No Frequency Planning: A CDMA system requires no frequency planning as the adjacent cells use the same common frequency. A typical cellular system with a repetition rate of 7 and a CDMA system is shown in the following figures which clearly indicates that in a CDMA network no frequency planning is required.


FFFF

FFFF

FFFF

FFFF

FFFF

FFFF

FFFF

C D M A Frequency Reuse

F 7F 6

F 2F 1F 5

F 3 AF 4 F 1

F r e q u e n c e y R e u s e o f 7

5.5. High Tolerance to Interference: The primary advantage of spread spectrum is its ability to tolerate a fair amount of interfering signals as compared to other conventional systems. This factor provides a considerable advantage from a system point of view. 5.6. Multiple Diversity: Diversity techniques are often employed to counter the effect of fading. The greater the number of diversity techniques employed, the better the performance of the system in a difficult propagation environment. CDMA has a vastly improved performance as it employs all the three diversity techniques in the form of the following: A. Frequency Diversity: A wide band RF signal of 1.25 Mhz being used. B. Space Diversity: Employed by way of multipath rake receiver. C. Time Diversity: Employed by way of symbol interleaving, error detection and correction coding.

6. CAPACITY CONSIDERATIONS Let us discuss a typical CDMA wireless in local loop system consisting of a single base station located at the telephone exchange itself, serving a single “cell”. In order to increase the


number of subscribers served the cell is further divided into “sectors”. These sectors are served by directional antennas.

CDMA Capacity

W/R 1 1 N= -------*-----*--------*n *g Eb/Io d 1+f Where N= calls per sector W= Spread spectrum Bandwidth (1.25 MHz) R= data rate (9.6 kbps or 14.4 kbps) Eb/Io= Bit energy/ other user interference density (7dB) d= Voice activity factor (0.4) f= other interference/ same interference (0.6) n= loading factor (0.8) g= reduction for variable power (0.85) N= 27 users per sector for R=9.6Kbps 18 users per sector for R=14.4Kbps

Evolution of CDMA Networks First deployment of CDMA in commercial cellular systems was in 1994-95 only with IS-95 A as air-interface standard and IS-41 in core network; the complete network known as cdmaOne. Next evolutionary step was use of IS-95B air interface standard which supported maximum data rate up-to 64 kbps to a user. Further in CDMA 2000 1x version many of the limitations of earlier IS-

Data only 2.4 Mbps RF backward compatible

Voice, 14.4k Voice, 64k

Voice, 9.6k Data only 10-60k

Voice, 128k/384k

GSM (Europe)

CDMA CDMA2000 1x IS-95A

GPRS

EDGE

WCDMA

CDMA2000 1xEV-DO

IS-95B


95 standard were overcome and new features were added. As a result CDMA 2000 1x has a higher voice capacity and better handling of packet data services.

Salient Features of CDMA 2000 1x

• Backward Compatibility with IS-95A & IS-95B • Support for High data rates on same 1x Carrier • Support for Simple IP and Mobile IP functionality for seamless mobility for data services. • Higher capacity for voice communication • Increased battery life • Faster forward Power control (relative to IS-95) • New Radio Configuration to support high data rates and more voice capacity.

Architecture of CDMA 2000 1x Network: CDMA 2000 1x Network Architecture is divided in to three parts.

• CS-CN (Circuit Switched Core Network) • PS-CN (Packet Switched Core Network) • RAN (Radio Access Network)


Circuit Switched Core Network: This section is dedicated for voice communication and also for wireless authentication. This section includes four parts MSC (Mobile Switching Center) HLR (Home Location Register) VLR (Visitor Location Register) AUC (Authentication Center) MSC (Mobile Switching Center): It is responsible for setting up, managing and clearing connections as well as routing the calls to the proper user & provides the network interfaces, the charging function and the function of processing the signaling. MSC get data for call handling from 3 databases: VLR/HLR/AUC. HLR (Home Location Register): It is a static database. When a user applies for mobile service, all data about this subscriber will be stored in HLR. It have information of a subscriber like ESN, MDN, IMSI, MIN, service information and valid term. It also stores the mobile subscriber location (MSC/VLR address), to set up the call. VLR (Visitor Location Register): VLR is a dynamic database used by MSC for information index. It stores all related information of mobile subscribers that enter its coverage area, which enables MSC to set up incoming and outgoing calls. It stores the subscriber parameters which includes subscriber number, location area identity (LAI), user’s status, services which subscriber can use and so on. When the subscriber leaves this area, it should register in another VLR, and the previous VLR will delete all the data about this subscriber. VLR can be built together with the MSC or set separately. AUC (Authentication Center): It is an entity to prevent illegal subscribers from accessing CDMA network. It can generate the parameter to confirm the subscriber’s identity. At the same time it can encrypt user’s data according to user’s request. AUC can be built separately or together with HLR Packet Switched Core Network: To provide better connectivity to the internet a new core network i.e. PS-CN is introduced to the CDMA 2000 1x network. This section includes four parts PDSN (Packet Data Serving Node) AAA Server Home Agent/ Foreign Agent Server PDSN (Packet Data Serving Node): Packet Data Serving Node (PDSN) provides the function of routing of data between Radio Access Network (RAN) and internet. AAA Server: PS-CN also has the responsibility to authenticate, authorise and account for the CDMA 2000 subscribers wishing to obtain packet data services & to fulfil these task PDSN requires support of AAA server.

Authenticate: verifying that the user is valid & allowed to use packet data services.


Authorization: subscription to the service being offered is valid. Accounting: Accounting for the service used. Home Agent/ Foreign Agent Server: HA & FA server is used when mobile IP services are supported by CDMA 2000 PDSN. HA can be considered analogous to HLR and FA with VLR. RAN (Radio Access Network): As in IS-95 RAN is composed of number of BSCs & BTSs The CDMA 2000 1x RAN is enhanced to support a higher no. of users on air interface or in other words it has a better spectral efficiency relative to IS-95. It is also modified to support the new packet data services on same 1.25 Mhz channel. This is achieved by software up-gradation at BTS and BSC and addition of a new hardware unit called Packet Control Function (PCF) at BSC. The CDMA 2000 1x air interface is very different from IS-95 but still maintains the backward compatibility with IS-95. CDMA 2000 1x EV-DO: Although IS-2000 is already capable of meeting the 3G data rate requirement of 2 Mbps (By using 3x option) Qualcomm proposed a new standard 1xEV-DO (1x Evolution for Data Optimized) in March of 2000 as another option that supports high-rate data services. EVDO is optimized for delivering high speed IP wireless data to many mobile and stationary terminals running multiple applications. EVDO is designed for an always on user experience. In a classical CDMA 2000 system base station controls its power by using the power control algorithms to provide the mobile a constant data rate and a quality of service for voice applications Power Data Rate But in EV-DO networks the base station transmits at a fixed power at all the times and controls the rate of data transmission given a constant transmit power. Power Data Rate

Distance from the Base Station

Mobile Received Power Power

Distance from the Base Station


Since EV-DO is specially designed for packet data services therefore EV-DO designs its air interface to takes advantage of the characteristics of some data services, which are Data rates are mostly asymmetrical: Data rate requirements downstream (on the forward link) are usually higher than those upstream (on the reverse link). Latency can be tolerated: Data services, unlike voice services, can withstand delays of up to seconds. Transmissions are bursty in nature: A burst of data transmission is often followed by a period of inactivity. Salient features of EV-DO

• EV-DO uses both CDMA and TDMA. • Uses its own dedicated 1.25 Mhz carrier. • It can support a maximum data rate of 2.4 Mbps in forward link. • It can support a maximum data rate of 153.6 Mbps in reverse link. • No power control on forward link is required. • RF system components may be shared with 1xRTT.

Section-4

Chapter-17

Broadband Wire line Access Technologies

E2E3 Broadband Wireline, Ver2 28.02.2008 1 of 7

Broadband Wire line Access Technologies

Introduction:

There is always increasing demand for higher capacity systems and more bandwidth for new generation, hence new various types of access technologies for broadband have to be found for this exponential growth. Broadband service commonly is high-speed Internet related services more than 256 kbps to several mbps. There are many different broadband technologies both wired and wireless. This article describes various types of broadband access technologies and BSNL’s access network of broadband.

High-speed Internet access (sometimes loosely referred to as “broadband internet access” or simply “broadband”) allows users to access the Internet and internet-related services at significantly higher speeds than traditional modems. High-speed Internet access makes the data processing capabilities necessary to use the Internet available via several devices or high-speed transmission technologies.

Learning Objective:

At the end of this topic you will be able to know- . a) What is broadband? Type of Internet services. b) Advantages of Broadband. Multiple Broadband Technologies. c) How Does Broadband Work. d) Digital Subscriber Line (DSL), DSLAM, Symmetrical Digital Subscriber Line

(SDSL), Asymmetrical Digital Subscriber Line (ADSL), ISDN Digital Subscriber Line (IDSL). DSL compared to ISDN.

e) BSNL’S Broadband Access Technology and Objectives. f) Differences between DSL and CM Service. g) Getting DSL or CM service and Installation at the premises of customer.

1.0 Narrowband Service category:

• Dial up Internet Service (PSTN + ISDN)

• Direct Internet Access Service (DIAS)

• CLI based Account less Internet Service

• Internet Leased Line Service

1.1 What is Broadband? As per TRAI: Broadband is an “An always-on data connection that is able to support interactive services and has the capability of minimum download speed of 256 kbps” Note: This definition for throughput may undergo upward changes in the future.


1.2 Advantages of Broadband • Always on (Not on shared media)

• Fast (speed ranging from 256 kbps to 2 Mbps)

• No disconnection

• No additional access charge

• Telephone and Data simultaneously

• Fat pipe has to be continuously supplemented with value added applications to enjoy the advantage.

1.3 Multiple Broadband Technologies There are many different types of broadband access technologies, such as cable, DSL, power line, satellite and wireless. Each of these technologies can compete to provide similar services to consumers and businesses.

• Digital Subscriber Line (DSL)

• Cable Modem (CM)

• Wireless Access WIMAX and WIFI

• Satellite Access

• Fiber technology

• Power Line Broadband There are many advantages of high-speed Internet access:

• The connection is always on, which means users can access the Internet without the need to dial up Internet service provider over a telephone line.

• Information can be download into your computer at significantly higher speeds than traditional modem.

• Users can go online without tying up their telephone lines.

• Business can use broadband networks for videoconferencing, and to let employees telecommute.

• Users can tap into an expand number of entertainment resources.

• An ‘ always-on’ data connection that is able to support interactive services including Internet access and has the capability of the minimum download speed of 256 kbps to an individual subscriber from the Point of presence (POP) of the service provider intending to provide Broadband service where multiple such individual Broadband connections are aggregated and the subscriber is able to access these interactive services including the internet through this POP. The interactive services will exclude any services for which a separate license is specifically required, for example, real-time voice transmission, except to the extent that it is presently permitted under ISP license with Internet Telephony.

1.4 How Does Broadband Work? High speed Internet access makes the data processing capabilities necessary to use the Internet available via one of several high-speed transmission technologies. These data processing capabilities are “digital” in nature, meaning that they compress vast amounts of voice, video and data information that are broken down into what are called “bts”. These bits become words, pictures, etc. on our computer screens. The transmission technologies that make high speed Internet access possible move these bits much more quickly than do traditional telephone or wireless connections.


2.0 Digital Subscriber Line (DSL) • Digital Subscriber line (DSL) is a wireline transmission technology that brings

data and information faster over copper telephone lines already installed in homes and business. Traditional phone service connects your home or business to a telephone company office via copper wires. A DSL modem accesses the local telephone company’s central office where a DSL Access DSLAM then transmits the signal from the copper telephone line onto a network backbone, and eventually to the Internet. With high-speed Internet access that uses DSL transmission technology, there is no need to “dial in” to a traditional modem. This service allows consumers and business to have an “always-on” dedicated connection to the Internet.

2.1 DSLAM

• DSLAM is the equipment located at a phone company’s central office (CO) that links many customer DSL connections over exiting copper telephone lines to a single high-speed ATM line. When the phone company receives a DSL signal, an ADSL modem with a POTS splitter detects voice calls and data. The DSLAM intermixes voice-frequency signals and high-speed DSL data traffic into a customer’s DSL line. It also separates incoming phone and data signals and directs them onto the appropriate carrier’s network. Voice calls are sent to the PSTN, and data are sent to the DSLAM, where it passes through the ATM to the Internet, then back through the DSLAM and ADSL modem before returning to the customer’s PC. More DSLAM channels a phone company has the more customers it can support. The DSLAM is the cornerstone of the DSL system and routes traffic to and from the customer via a business or home telephone line to provide high-speed DSL access to multimedia services such a Internet, fast data transfer, video conferencing, pay –per-view TV or video-on-demand and broadcast video. There are more than 40 million copper loops in the country available with BSNL and MTNL out of which 14 millions loops are in rural areas. Copper cable network of these operators is a combination of old and new cables and this makes provisioning of Broadband on the entire available copper loop technically unfit. Therefore around 25 to 30% of the remaining 26 million loops i.e. approximately 7 million loops can be leveraged for broadband service by BSNL and MNTL taking into account the condition/ life of copper cable and demand potential. Management of BSNL and MTNL has decided to provide 1.5 million connections by the end of 2005. The estimated growth for Broadband and internet subscribers in the country envisaged through various technologies is as follows. Year Ending Internet Subscribers Broadband Subscribers 2005 6 million 3 million 2007 18 million 9 million 2010 40 million 20 million


The following are types of DSL transmission technologies that may be used to provide high-speed Internet access:

• Symmetrical Digital Subscriber Line (SDSL): It is used typically for business applications such as video conferencing. The traffic from the user to the network is upstream traffic, and from the network to the user is downstream traffic. When the data rate in both directions is equal, it is called a symmetric service.

• Asymmetrical Digital Subscriber Line (ADSL): It is used primarily by residential users who receive a lot do data but do not send much, such as Internet surfers. ADSL provides faster speed in a downstream direction (from the telephone central office to the customer’s premises) than upstream (from customer’s premise to the telephone central office). When the upstream data rate is lower than the downstream rate, it is called an asymmetric service.

• Isdn Digital Subscriber Line (IDSL): It provides symmetrical connection with Integrated Services Digital Network (ISDN), and is designed to extend DSL to locations with a long distance to a telephone central office.

• High-data-rate Digital Subscriber Line (HDSL): it provides fixed symmetrical high-speed access at T1 rate (1.5 mbps), and is designed for business purposes.

• Very high-data-rate Digital Subscriber Line (VDSL): it provides both symmetrical and asymmetrical access with very high bit rate over the copper line. Deployment is very limited at this time.

2.2 DSL Compared to ISDN ISDN is an affordable way to have rapid access to the Internet. It is digital technology that is widely available and is an option for business located in areas not yet served by DSL. DSL and ISDN are different transmission technologies, yet both offer many of the same higher speed benefits to consumers. DSL offers potentially higher transmission speeds as well as a choice of connection speeds. ISDN is presently more widely available than DSL. DSL is an always-on service while ISDN requires dialing into a service provider’s network. If DSL transmission technology is not available in your area, ISDN may serve as an acceptable substitute for use in providing high-speed Internet access.

3.0 BSNL’S Broadband Access Technology BSNL has commissioned broadband, a world class, multi-gigabit, multi-protocol,

convergent IP infrastructure through National Internet Backbone II (NIB-II), that will provide convergent services through the same backbone and broadband access network. The Broadband service will be available on DSL technology (on the same copper cable that is used for connecting telephone). On a countrywide basis spanning 198 cities.

With the NIB-II project, BSNL has planned to roll Broadband services in a big way across the country. However, with the current plans under the NIB-II project, BSNL will still be in a position to become the number one player in the segment in the country with its nation-wide rollout. Broadband Services proposed to be rolled out include the following:


High Speed Internet Access 1. 1 mbps Upstream 2. 8 mbps Downstream 3. Video Streaming 4. Video-on-Demand 5. Video Conferencing 6. Interactive Gaming 7. Point-to-Point Data Network on IP

3.1 BSNL’s Objectives BSNL has undertaken this project with the following objectives:

• To utilize to the maximum BSNL’s exiting infrastructure � 40 million BSNL customers on CU � Large scale deployed Fibres in Access & core network � Deployed DLC system on Fibre.

• To increase the footprint across the country to provide Access Country-wide.

• To provide Value Added Services (Video, Broadband Data in addition to Voice) to accelerate development and growth. BSNL has envisioned that the Broadband services rolled as part of the ambitions NIB-II project will be used for high speed Internet connectivity and shall be the primary source of Internet bandwidth and used for connecting broadband customers to the MPLS/VPN through the BRAS. Also will be used for connecting dial VPN customers to the MPLS VPN through the Narrowband RAS. The BSNL’s broadband network cosisits of core routers located at Mumbai, New Delhi, Kolkata, Chennai and Bangalore connected in mesh topology with STM 16 links, with cities in India classified as A1, A2, A3, A4 and other cities.. The network connectivity consists of DSLAM, TIER 2 Switch, Tier 1 Switch, Bras, Core Router and CPE (Customer Premises equipment) consists of Splitter and ADSL modem.

4.0 Cable Modem (CM)

Cable TV connection as last mile infrastructure reaches more people than even the telephone copper infrastructure and can be leveraged in providing cable operators a new business model while giving a stimulus to Broadband penetration. Therefore cable TV network can be used as franchisee network of the service provider for provisioning Broadband services. However all responsibilities for ensuring compliance of terms & conditions of the licensee shall vest with the Licensee. The terms of franchise agreement between Licensee and his franchise shall be settled mutually by negotiation between the two parties involved. Cable Modem (CM) is a device that enables cable operators to provide high-speed Internet access using the coaxial cables used for cable TV. Today, most CMs are external devices that connect to the computer. They will typically have two connections, one to the cable wall outlet and the other to a computer. CMs are attached to the same Cable TV company lines that deliver pictures and sound to yout TV set. High-speed Internet access using CM offers both always-on capability and speed. With this service, users never have to dial up using telephone lines and their cable viewing is not hampered while on line. Speeds for this service vary


depending on the type of cable modem, cable network and traffic load, but are generally faster than those offered by traditional dial-up Internet access.

4.1 Differences between DSL and CM Service High-speed Internet access that uses CM offers shared bandwidth or speed among neighbours on the same cable system. Speed is asymmetric and will vary depending on the number of people on the network. With high-speed Internet access that uses DSL service, you have a dedicated connection to your home. In most cases, however, the performance of DSL based service depends on the distance between end user and phone company central office. Today, high-speed Internet access provided using either DSL or CM typically is offered with a pricing plan that allows without incurring additional usage charges. Many phone and cable companies are offering bundled packages of various services (such as telephone, cable and high-speed Internet access) to lower costs to consumers. High-speed Internet access using CM is targeted towards residential use while DSL-based service is targeted towards residential and business uses.

4.2 Advantages and Disadvantages of having DSL or CM High-speed Internet access provided using DSL and cable modems is much

faster than dial-up modems, however their speeds differ. The distance between the user’s premises and the phone company’s central office is a primary factor in deciding if DSL-based Internet access service is available and its speeds. In contrast, the speed of CM-based Internet access service does not depend on the distance from Cable Company to end-user. Because DSL transmission technology office, competitive providers using DSL technology must coordinate with local phone companies to provide service. Because both versions of high-speed Internet access (DSL and CM) are always on, you may want to check with the provider about security precautions. DSL and CM equipments are generally based on standard specifications and required certification, however, the best advice is to check with the service provider prior to purchase of such equipment. Different varieties of DSL transmission technology provide different maximum speeds, from twice as fast as analog modems to higher than 100 times faster.

4.3 Getting DSL or CM service Contact a provider in your geographical area. For booking of Broadband service

of BSNL there is online register form available on website www.bsnl.co.in, otherwise contact directly to value added services section or nearest customer service center. The provider may be your local telephone service provider or one of its competitors (for DSL-based Internet access), or your local cable company (for CM-based Internet access). There are different high-speed Internet access service available, and the equipment of one provider may not be interoperable in another area or with another provider. Check with your service provider for technical compatibility. Compatible modem may be purchased otherwise service may be affected.


Customer Premises Installation

Section-4

Chapter-18

Broadband Wire less Access Technologies

E2E3 Broadband Wireless Ver2 28.02.2008 1 of 5

Broadband Wireless Access Technologies Introduction: Broadband wireless access technologies offer effective, economic & secure high-

speed wireless communications solutions to telecom service providers, internet

service providers, governments, institutes , healthcare & enterprises. It eliminates the

need for costly wire line infrastructure, bringing voice & high-speed data services to

every user within the range of base station. It offers huge benefits in terms of fast,

easy & cost effective, unsurpassed flexibility & reduced cost of ownership. The

solutions are scalable & offers broadband capacity in city & in remote rural locations.

Learning objective : After going through this topic, the participants will be able to understand:

1) Wireless internet access. 2) Hotspots. 3) Wireless access technologies like Wi-Fi (for LAN) & WiMAX (for MAN). 4) Blue tooth technologies used in PAN. 5) Internet access via satellite.

1.0 Wireless internet access

Wireless access providers connect homes and businesses to the Internet using

wireless or radio connection technology, rather than using technologies such as

coaxial cable (CM) or twisted copper paired telephone lines (DSL). Wireless providers

can use mobile or fixed wireless technologies.

Generally, with fixed wireless technology, a computer, or network of computers,

employ a radio link from the customer’s location to the service provider. This radio link

is usually established between rooftop antennae in direct line of sight. These rooftop

antennae are usually dish shaped with a very narrow beam of connectivity to prevent

interference. The antenna at the customer’s location is connected by a cable to the

local transmitting and receiving radio equipment. This terminal base station equipment

is then connected to the local computer network.


1.1 Features of wireless access Fixed wireless access customers can be located between 2 and 35 miles from the

wireless provider’s network base station. Fixed wireless provides Internet-access at speeds ranging from one up to 155 mbps. Of course the fixed wireless radio access is dependent on the radio connection and the quality of the radio connection will determine the ultimate quality of service to the customer. 3G technologies provide internet access up to 2 mbps on appropriate digital / cellular phones. Multimedia types of services are available on 3G mobile phones

1.2 Hotspots There are thousands of commercial locations across the country, such as restaurants,

hotels, airports, bookstores, convention centers, city parks and squares, where customers can use laptop computers, handheld devices and other portable computing devices with special “wireless modem cards” to connect to the Internet wirelessly. These locations are called hotspots. Inside the hotspots they can get Internet access on their devices at speed of up to 11 mbps. Also, some wireless providers offer customers packages where they can get wireless Internet access at a collection of different hotspots. The technology that enables the wireless access in hotspots is called “Wi-Fi”. This technology was originally developed as a home networking technology to network home computers wirelessly. There are currently efforts in the industry to develop solutions to extend this technology for longer distances where Wi-Fi can be used as the last-mile solution for Internet access.

Internal Access Point with hub

Ethernet

Radio Link

Customer Premise (Home, business or hotspot)

Subscriber Station With High-Gain Antenna

Internet

Base station /Access Point

Wireless Internet Access


1.3 Wi-Fi Short name for Wireless Fidelity and is meant to be used generically when referring to

any type of 802.11 network, whether 802.11a, 802.11b, 802.11g, etc. The term is promulgated by the Wi-Fi Alliance.

Any products tested and approved as “Wi-Fi Certified” (a registered trademark) by the Wi-Fi Alliance are certified as interoperable with each other, even if they are from different manufactures. A user with “Wi-Fi Certified” product can use any brand of access point with any other brand of client hardware that also is certified. Typically, however, any WiFi product using the same radio frequency (for example, 2.4 GHz for 802.11b or 802.11g, 5 GHz for 802.11a) will work with any other, even if not “WiFi Certified”.

1.4 Wireless IEEE / Ethernet Standards IEEE 802.11 is the initial release of the standard capable of transmissions of 1 to

2 Mbps and operates in 2.4 Ghz band. It was introduced by IEEE in June 1997. IEEE 802.11a is capable of transmission up to 54 mbps and operates in 5 Ghz band. IEEE 802.11b is capable of transmission up to 11 mbps and operates in 2.4 Ghz band. IEEE 802.11g is capable of transmission up to 54 mbps and operates in 2.4 Ghz band.

1.5 Wi-Fi in outdoor access Network operators have developed two approaches for using Wi-Fi in outdoor:

1) Wi-Fi with directional antenna or Wi-Fi single hop & 2) Wi-Fi with a mesh-network topology. or Wi-Fi multihop. In this approach the access

points also called nodes are omni direction broadcaster. Each AP acts as a simple router. Meshing allows wireless connectivity between access points. Coverage is over 10 km.

1.6 WiMAX

WiMax (World-wide Interoperability for Microwave Access) is the IEEE 802.16 standards-based wireless technology that provides MAN (Metropolitan Area Network) broadband connectivity. WiMax is an Air Interface for Fixed Broadband Wireless Access Systems, also known as the IEEE Wireless-MAN air interface. WiMax-based systems can be used to transmit signals to as far as 30 miles. So far, WiMax can offer a solution to what is normally called the “last-mile” problem by connecting individual homes and business offices communications.

WiMax covers a couple of different frequency ranges. Basically, the IEEE 802.16 standard addresses frequencies from 10 GHz to 66 GHz. The 802.16a specification, which is an extension of IEEE 802.16, covers bands in the 2 GHz to 11 GHz range. WiMax has a range of up to 30 miles with typical cell radius of 6 to 4 miles.

WiMax supports ATM, Ipv4, Ipv6, Ethernet and VLAN services. So it can provide a rich choice of service possibilities to voice and data network service providers. WiMAX uses orthogonal frequency division multiplexing (OFDM). OFDM is a spread-spectrum technology that bundles data over narrowband carriers transmitted in parallel at different frequencies.


In addition, WiMax provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial hotspots with the Internet.

The WiMax-based solution is set up and deployed like cellular systems using base stations that service a radius of several miles / kilometers. The most typical WiMax-based architecture includes a base station mounted on a building and is responsible for communicating on a point to multi-point basis with subscriber stations located in business offices and homes. The customer Premise Equipment (CPE) will connect the base station to a customer as well; the signal of voice and data is then routed through standard Ethernet cable either directly to a single computer, or to an 802.11 hot spot or a wired Ethernet LAN.

1.7 WiMax Connectivity and Solutions WiMax allows equipment vendors to create many different types of IEEE 802.16

based products, including various configurations of base stations and customer premise Equipment (CPE). WiMax also allows the services provider to deliver many types of wireless access services. WiMax can be used on a variety of wireless broadband connections and solutions:

• “Last Mile” Broadband Access Solution-Metropolitan-Area Network (MAN) connections to home and business office, especially in those areas that were not served by cable or DSL or in areas where the local telephone company may need a long time to deploy broadband service. The WiMax-based wireless solution makes it possible for the service levels in short times with client request.

• Backhaul network for cellular base stations, bypassing the public Switched Telephone Network (PSTN); the cellular service providers can look to wireless backhaul as a more cost-effective alternative. The robust WiMax technology makes it a nice choice for backhaul for hotspots as well as point-to-point backhaul solutions.

• Backhaul enterprise connections to the Internet for WiFi hotspots. It will allow users to connect to a wireless Internet service provider even when they roam outside their home or business office.

• A variety of new business services by wireless Internet service provider. Unlike WiFi, WiMax’s range is typically measured in miles rather than feet. The main

distinction of the difference between the two standards means that WiFi is focused on a local Area Network (LAN) technology and that WiMax is a MAN technology.

WiMax-based solutions include many other advantages, such as robust security features, good QoS (Quality of Service), and mesh and smart antenna technology that will allow better utilization of the spectrum resources. Also, the WiMax-based voice service can work on either traditional Time Division Multiplexed (TDM) voice or IP-based Voice, also known as Voice over IP (VoIP).

The WiMAX standard enables system vendors to create many different types of WiMAX-based products, including various configurations of base stations and Customer Premise Equipment (CPE). WiMAX supports a variety of wireless broadband connections such as:

� High-bandwidth Metropolitan-Area Networks (MANs) to home and small-

business users, replacing DSL and cable modems.


� Backhaul networks for cellular base stations, bypassing the public switched telephone network.

� Backhaul connections to the Internet for WiFi hotspots. 1.8 Blue tooth, WPAN, IEEE 802.15

Blue tooth is a short range (PAN) wireless technology. It is an IEEE 802.15 standard technology. It is designed for:

- Interconnecting computer and peripherals. - Interconnecting various handhelds. 1.9 WWAN IEEE 802.20 is the wireless standard for wide area network. 2.0 Internet access via satellite Very Small Aperture Terminal (VSAT) & Direct-To-Home (DTH) provide broadband

& internet services via satellite. The customer premises equipment / devices required are (1) two to three feet dish antenna often called base station.(2) a satellite internet modem with the condition that the line of sight is clear between the base station & provider’s satellite.

2.1 Advantage & disadvantages Advantage: It can serve remote & inaccessible areas. Disadvantages: - It is based on line of sight technology. - It is affected by weather. - It is costly.

-Transmission delay is higher than other alternatives. Summary

Wireless in the last / first mile is suitable in areas not served by cable or DSL & where deployment of wired line needs a long time. Wi-Fi (IEEE 802.11) is the wireless standard for LAN. Bluetooth (IEEE 802.15) is the wireless standard for PAN. WiMAX (IEEE 802.16) is the wireless standard for MAN. Hotspots uses Wi-Fi technology. Any product tested & approved by Wi-Fi alliance is termed as Wi-Fi certified. VSAT & DTH provide internet access via satellite.

Reference: 1. Wi-Max and Wi-Fi wireless mobility online document www.wifi-org and

www.wimax.org 2. www.broadband.org 3. Broadband policy 2004 online document www.dotindia.com 4. http://www.thestandard.com/movabletype/datadigest/archives/003203.php 5. http://standards:ieee.org.

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Section-4

Chapter-19

��

E2E3 Broadband core network, Ver3 28.02.2008 1 of 3

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Core of BSNL’s Broadband service is National Internet Backbone (NIB). NIB is a mission to build world-class infrastructure to help accelerate the Internet revolution in India. It has following features:

1. It provides a diversified range of Internet access services including support for VPN (Layer-2, Layer-3 and Dialup and Broadband services)

2. It also offers SLA Reports including security, QoS (quality of service) and any to any connectivity.

3. Offers fully managed services to customers. 4. It offers services like bandwidth on demand etc. over the same network. 5. The network is capable of on-line measurement and monitoring of network parameters

such as latency, packet loss, jitter and availability so as to support SLAs with customers 6. The routers support value added services such as VPNs, Web and content hosting,

Voice over IP, Multicast etc. 7. Value Added Services

a. Encryption Services b. Firewall Services c. Multicast Services d. Network Address Translation (NAT) Service that will enable private users to

access public networks 8. Messaging Services 9. Internet Data Centre Services at Bangalore, Delhi and Mumbai. 10. Broad Band Services

a. Broadcast TV using IP Multicasting service b. Multicast video streaming services c. Interactive Distant learning using IP multicasting Services d. Video on demand e. Interactive gaming service

NIB-II has been implemented in four projects ��

�� MPLS based IP Infrastructure (The backbone consisting of Core & Edge Routers)

�� Narrowband Access (Dialup Remote Access) �� Broadband Access (DSL Access) �� Messaging, Storage, Provisioning, Billing, Security, Order Management,

Enterprise Management, AAA, Help Desk and Inventory Management. Network Architecture The cities in India have been classified in six types namely A1, A2, A3, A4, B1, B2. Important aspects are given below:

1. A1 – 5 Core cities a. Bangalore, Chennai, Mumbai, Delhi, Kolkatta

2. A2/A3 – 9 next level core cities a. Pune, Hyderabad, Ahmedabad, Ernakulam, Lucknow, Jaipur, Indore, Jullundur,

Patna


3. A4 – 10 Major cities 4. B1, B2 – 47 other cities 5. A1 city core routers are fully meshed between locations on STM-16 6. IGW – International Gateway Router – Connectivity to Internet is through this router 7. IXP – Internet Exchange Point – ISP’s connect each other through this router 8. IDC – Internet Data Center – for connecting to BSNL Data Centers 9. B1 and B2 cities have only EDGE routers. 10. All Core locations also have edge routers 11. Primary Network Operating center at Bangalore and Disaster Recovery is at Pune

NIB2 Expansion and Year 2 Order Overview 1. 29 locations added which makes the total to 100 2. Core backbone is getting aligned to BSNL Transmission (DWDM) network 3. 24 City core network increased to 29 4. All 29 city core network links are STM-16 (ie STM1 connectivity of A4 cities will be

upgraded to STM16) 5. New 5 Cities are Belgaum, Dehradun, Rajkot, Jodhpur, Jabalpur

Components of Broad Band Access Network 1. Broad band Remote Access Server (BBRAS) 2. Gigabit and Fast Ethernet Aggregation Switches (LAN Switches). 3. Digital Subscriber Line Access Multiplexers (DSLAMs) 4. SSSS/SSSC (Subscriber Service Selection System/ Centre) 5. Servers for AAA, LDAP at NOC. 6. Provisioning and configuration management at NOC. 7. DSL CPEs (MODEM) 8. The DSLAMs will in general be collocated with existing PSTN exchanges, which

provide last mile access to customers over copper wire up to average span lengths of 3 kms.

9. All DSLAMs will be aggregated through a FE interface except 480 port DSLAM, which will be aggregated through Gigabit Ethernet Interface.

10. The 240 ports DSLAM will have two number of FE interface. 11. The FX or GBIC module in DSLAM and LAN switch capable of driving upto 10km on

a single mode fibre. 12. The SX or GBIC module in LAN Switch used for connecting Tier2 to Tier1. In bigger

cities like A1, A2, A3 and A4, one BBRAS per city will be deployed initially. 14. There will be no BBRAS at B1 and B2 cities. 15. The DSLAMs in B1.B2 and other lower hierarchical cities will be aggregated through

Layer 2 switches, and will be connected to the nearest BBRAS of A cities on Ethernet over SDH.

16. The BRAS shall terminate the PPP sessions initiated by the customer and extend the connection further to MPLS VPN/ Internet as desired by the customer.

BBRAS: A Broadband Remote Access Server (BBRAS) routes traffic to and from the digital subscriber line access multiplexers (DSLAM) on an Internet service. DSLAM: Digital Subscriber Line Access Multiplexer. Specifically, a device that takes a number of ADSL subscriber line and concentrates these to a single ATM line. CPE: Customer Premises Equipment - Any equipment provided by the customer at their premises. GBIC: Gigabit Interface Converter; a Fiber Channel optical or copper transceiver that is easily swapped to offer a flexible choice of copper or fiber optic media.


Starting NIB connectivity diagram. Expansion is a continuous process hence many new sites keep getting added.

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IP routing, RIP and OSPF

E2E3 IP, RIP,OSPF Ver3 28.02.2008 1 of 3

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� � �� When several networks are joined together by hosts that are connected to more than one network, hosts on one network may want to communicate with hosts on another network. To do so, the messages between them must pass through several (i.e. more than one) networks on the way. This is accomplished by turning some hosts with connections to more than one network into routers, which forward messages to the networks they can reach (to which they are connected). Each router has a routing table, which specifies where that router should send a message it receives. In IP routing, the routing table will usually consist of a network address (and a subnet mask) and the address of the "next hop", which is the target to which the message should be forwarded if the destination's IP address matches the subnet mask of the network address. The next hop can be a local network to which the router is connected physically, or the IP address of another router on the network, which will then continue forwarding that message according to its own routing table. If the routers are set up correctly and the network is healthy, eventually the message will reach its destination. �

��In relatively small networks, or in networks where the network topology rarely changes, setting up the routing tables can be done manually. This means that in the event of a malfunction in one of the routers or of a network, the other routers will not know about the problem and will not circumvent it until someone, usually the network administrator, will reconfigure each and every one of them with the new settings. While this might turn out to be an impossible task for most networks, static routing is still a viable solution in some cases. �

� �� Things get complicated when the conditions aren't ideal, and they rarely are. Networks tend to grow, evolve and change, hardware usually isn't impregnable, and errors tend to occur on computer networks, especially large ones, in such high frequencies that manually reconfiguring everything every time can be quite impossible. This is where dynamic routing comes into play. In dynamic routing, the routers themselves, by communicating with one another, learn the topology of the network by themselves. By running the same dynamic routing protocol they can get that information and build their routing tables automatically, and respond to changes in the network much faster than a manual update ever could. In dynamic routing protocols, routers communicate with neighboring routers, i.e. routers that are connected to the same networks that they are. The protocol dictates what information they exchange and when, how the information will be saved on each router, and how the routing table can be constructed from it. These are of two types:

1. Distance Vector Routing Protocols Example: RIP; IGRP

2. Link State Routing Protocols Example: OSPF; IS-IS

Routing Information Protocol

• Designed for smaller networks • Uses Hop Count as metric • RIP has an administrative distance of 120


�� Neighbors

• Routers sharing a common data link. • Periodically send routing updates to all neighbors by broadcasting their entire routing

tables. Periodic Updates

• A period of time after which entire routing table updates will be transmitted (30 seconds) • Neighbors receiving these updates glean the information they need and discard

everything else Routes are advertised as vectors of distance and direction:

• Distance is defined in terms of a metric • Direction is defined in terms of the next hop router • Each router learns routes from its neighbor router’s perspective • Each router then advertises the routes from its own perspective

This routing is also referred to as Routing by Rumor as each router depends on its neighbors for information which the neighbor in turn might have learned from their neighbor and so on � �� The Open Shortest Path First (OSPF) protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy. The current version, Version 3, defined in RFC 2740 (OSPFv3 1999), supports IPv6 as well as IPv4, has various internal enhancements, and is backwards compatible with the earlier version, (OSPFv2 1998). OSPF Operation

• A link state database (LSDB) is constructed as a tree-image of the network topology, and identical copies of the LSDB are periodically updated on all routers in each OSPF-aware area (region of the network included in an OSPF area type - see "Area types" below).

• An OSPF router, when switched on, maintains an interface data structure for each OSPF enabled interface

• OSPF-speaking routers send Hello packets out OSPF-enabled interfaces • Two routers sharing a common link, if agreed on certain parameters specified in their

respective Hello packets, become neighbors • Adjacencies are formed between some neighboring routers and depends upon:

o Type of routers exchanging hellos o Type of network

• Link State Advertisements (LSAs) i.e. router’s links and their state, are exchanged between adjacent routers

• Each router receiving an LSA from a neighbor records the LSA in Link State Database and sends a copy of the LSA to all of its other neighbors.

• LSAs are exchanged, until all the routers build identical Link State Databases i.e. the link state databases have been synchronized

• In contrast to the Routing Information Protocol (RIP) or the Border Gateway Protocol (BGP), OSPF does not use TCP or UDP but uses IP directly, via IP protocol 89. OSPF handles its own error detection and correction, therefore negating the need for TCP or UDP functions.

� ��OSPF uses path cost as its basic routing metric, which was defined by the standard not to equate to any standard value such as speed, so the network designer could pick a metric important to the design. In practice, it is determined by the speed (bandwidth) of the interface addressing the given route, although that tends to need network-specific scaling factors now that links faster than 100


Mbit/s are common. Metrics, however, are only directly comparable when of the same type. There are four types of metrics, with the most preferred type listed in order below. An intra-area route is always preferred to an inter-area route regardless of metric, and so on for the other types.

��Intra-area ��Inter-area ��External Type 1, which includes both the external path cost and the sum of

internal path costs to the ASBR that advertises the route, ��External Type 2, the value of which is solely that of the external path cost

� � �� OSPF-TE is an extension to OSPF extending the idea of route preference to include traffic engineering. The Traffic Engineering extensions to OSPF add dynamic properties to the route calculation algorithm. The properties are:

��Maximum Reservable bandwidth ��Unreserved bandwidth ��Available bandwidth

� � ��!��OSPF defines the following router types:

��Area border router (ABR) ��Autonomous system border router (ASBR) ��Internal router (IR) ��Backbone router (BR)

The router types are attributes of an OSPF process. A given physical router may have one or more OSPF processes. " �� #��$�An ABR is a router that connects one or more OSPF areas to the main backbone network. It is considered a member of all areas it is connected to. An ABR keeps multiple copies of the link-state database in memory, one for each area to which that router is connected. " ��% ��!��% �#��&" � '�(�$�An ASBR is a router that is connected to more than one AS and that exchanges routing information with routers in other ASs. ASBRs typically also run a non-IGP routing protocol (e.g., BGP), or use static routes, or both. An ASBR is used to distribute routes received from other ASs throughout its own AS. �� )��An IR is a router that has only OSPF neighbor relationships with routers in the same area. ' �*#��Backbone Routers: These are routers that are part of the OSPF backbone. By definition, this includes all area border routers, since those routers pass routing information between areas. However, a backbone router may also be a router that connects only to other backbone (or area border) routers, and is therefore not part of any area (other than Area 0). To summarize: an area border router is always also a backbone router, but a backbone router is not necessarily an area border router. + �� ,��,�A designated router (DR) is the router interface elected among all routers on a particular multi-access network segment, generally assumed to be broadcast multi-access. Do not confuse the DR with an OSPF router type. A given physical router can have some interfaces that are designated, others that are backup designated (BDR), and others that are non-designated. ' �*�� A backup designated router (BDR) is a router that becomes the designated router if the current designated router has a problem or fails. The BDR is the OSPF router with second highest priority at the time of the last election.

��

��

MPLS- VPN

E2E3 MPLS VPN Ver3 28.02.2008 1 of 7

Multi-Protocol Label Switching (MPLS) What is MPLS? Multi Protocol Label Switching (MPLS) is a data-carrying mechanism in packet-switched networks and it operates at a TCP/IP layer that is generally considered to lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer or IP Layer), and thus is often referred to as a "Layer 2.5" protocol. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients, which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. The Internet has emerged as the network for providing converged, differentiated classed of services to user with optimal use of resources and also to address the issues related to Class of service (CoS) and Quality of Service (QoS). MPLS is the technology that addresses all the issues in the most efficient manner. MPLS is a packet-forwarding technology that uses labels to make data forwarding decisions. With MPLS, the Layer 3 header analysis (IP header) is done just once (when the packet enters the MPLS domain). What is a MPLS header? MPLS works by prefixing packets with an MPLS header, containing one or more 'labels'. This is called a label stack. Each label stack entry contains four fields:

- 20-bit label value (This is MPLS Label) - 3-bit Experimental field used normally for providing for QoS (Quality of Service) - 1-bit bottom of stack flag. If this is 1, signifies that the current label is the last in the

stack. - 8-bit TTL (time to live) field.

Various functions & Routers in MPLS Label A label identifies the path a packet should traverse and is carried or encapsulated in a Layer-2 header along with the packet. The receiving router examines the packet for its label content to determine the next hop. Once a packet has been labelled, the rest of the journey of the packet through the backbone is based on label switching. Label Creation Every entry in routing table (build by the IGP) is assigned a unique 20-bit label either per platform basis or per interface basis. SWAP: The Incoming label is replaced by a new Outgoing label and the packet is forwarded along the path associated with the new label. PUSH A new label is pushed on top of the packet, effectively "encapsulating" the packet in a layer of MPLS. POP The label is removed from the packet effectively "de-encapsulating". If the popped label was the last on the label stack, the packet "leaves" the MPLS tunnel. LER A router that operates at the edge of the access network and MPLS network LER performs the PUSH and POP functions and is also the interface between access and MPLS network, commonly know as Edge router. LSR An LSR is a high-speed router device in the core of an MPLS network, normally called Core routers. These routers perform swapping functions and participate in the establishment of LSP. Ingress / Egress Routers: The routers receiving the incoming traffic or performing the first PUSH function are ingress routers and routers receiving the terminating traffic or performing the POP function are Egress routers. The same router performs both functionality i.e. Ingress and Egress. The routers performing these functions are LER. FEC The forward equivalence class (FEC) is a representation of a group of packets that share the same requirements for their transport. All packets in such a group are provided the

http://en.wikipedia.org/wiki/Packet_%28information_technology%29

http://en.wikipedia.org/wiki/Datagram

http://en.wikipedia.org/wiki/Packet-switching

http://en.wikipedia.org/wiki/Telecommunication_circuit

E2E3 MPLS VPN Ver3 28.02.2008 2 of 7

same treatment en route to the destination. As opposed to conventional IP forwarding, in MPLS, the assignment of a particular packet to a particular FEC is done just once, as the packet enters the network at the edge router. MPLS performs the following functions: 1. Specifies mechanisms to manage traffic flow of various granularities, such as flows

between different hardware, machines, or even flows between different applications. 2. Remains independent of the Layer-2 & layer-3 protocols. 3. Provides a means to map IP addresses to simple, fixed-length labels used by different

packet-forwarding and packet-switching technologies 4. Interfaces to existing routing protocols such as resource reservation protocol (RSVP)

and open shortest path first (OSPF). 5. Supports the IP, ATM, and frame- relay Layer-2 protocols. Label Distribution Protocol (LDP): The LDP is a protocol for the distribution of label information to LSRs in a MPLS networks. It is used to map FECs to labels, which, in turn, create LSP. LDP sessions are established between LDP peers in the MPLS network (not necessarily adjacent). The peers exchange the following types of LDP messages: Discovery messages – announce and maintain the presence of an LSR in a network Session messages – establish, maintain, and terminate sessions between LDP peers Advertisement messages – create, change, and delete label mappings for FECs. Notification messages – provide advisory information and signal error information Traffic Engineering Traffic engineering is a process that enhances overall network utilization by attempting to create a uniform or differentiated distribution of traffic throughout the network. An important result of this process is the avoidance of congestion on any one path. It is important to note that traffic engineering does not necessarily select the shortest path between two devices. It is possible that, for two packet data flows, the packets may traverse completely different paths even though their exposed or less used network segments can be used and differentiated services can be provided. MPLS Operation : The following steps must be taken for a data packet to travel through an MPLS domain. Label creation and distribution, Table creation at each router, Label-switched path creation, Label insertion/table lookup and Packet forwarding. The source sends its data to the destination. In an MPLS domain, not all of the source traffic is necessarily transported through the same path. Depending on the traffic characteristics, different LSPs could be created for packets with different CoS requirements.

In Figure 1, LER1 is the ingress and LER4 is the egress router. ��

Destination

LER2

LSR1 LER1

LER3

LSR3

LSR2 LER4

Label request

Label distribution

Data flow

E2E3 MPLS VPN Ver3 28.02.2008 3 of 7

Tunnelling in MPLS A unique feature of MPLS is that it can control the entire path of a packet without explicitly specifying the intermediate routers. It does this by creating tunnels through the intermediary routers that can span multiple segments. This concept is used for provisioning MPLS – based VPNs. MPLS Applications MPLS addresses today’s network backbone requirements effectively by providing a standards-based solution that accomplishes the following:

1. Improves packet-forwarding performance in the network 2. MPLS enhances and simplifies packet forwarding through routers using Layer-2 switching

paradigms. 3. MPLS is simple which allows for easy implementation. 4. MPLS increases network performance because it enables routing by switching at wireline

speeds. 5. Supports QoS and CoS for service differentiation 6. MPLS uses traffic-engineered path setup and helps achieve service-level guarantees. 7. MPLS incorporates provisions for constraint-based and explicit path setup. 8. Supports network scalability 9. MPLS can be used to avoid the N2 overlay problem associated with meshed IP – ATM

networks. 10. Integrates IP and ATM in the network 11. MPLS provides a bridge between access IP and core ATM. 12. MPLS can reuse existing router/ATM switch hardware, effectively joining the two disparate

networks. 13. Builds interoperable networks 14. MPLS is a standards-based solution that achieves synergy between IP and ATM networks. 15. MPLS facilitates IP – over –synchronous optical network (SONET) integration in optical

switching. 16. MPLS helps build scalable VPNs with traffic-engineering capability.

MPLS VPN MPLS technology is being widely adopted by service providers worldwide to implement VPNs to connect geographically separated customer sites. VPNs were originally introduced to enable service providers to use common physical infrastructure to implement emulated point-to-point links between customer sites. A customer network implemented with any VPN technology would contain distinct regions under the customer's control called the customer sites connected to each other via the service provider (SP) network. In traditional router-based networks, different sites belonging to the same customer were connected to each other using dedicated point-to-point links. The cost of implementation depended on the number of customer sites to be connected with these dedicated links. A full mesh of connected sites would consequently imply an exponential increase in the cost associated. Frame Relay and ATM were the first technologies widely adopted to implement VPNs. These networks consisted of various devices, belonging to either the customer or the service provider, that were components of the VPN solution. Generically, the VPN realm would consist of the following regions: Customer network— Consisted of the routers at the various customer sites. The routers connecting individual customers' sites to the service provider network were called customer edge (CE) routers.

E2E3 MPLS VPN Ver3 28.02.2008 4 of 7

Provider network— Used by the service provider to offer dedicated point-to-point links over infrastructure owned by the service provider. Service provider devices to which the CE routers were directly attached were called provider edge (PE) routers. In addition, the service provider network might consist of devices used for forwarding data in the SP backbone called provider (P) routers. Depending on the service provider's participation in customer routing, the VPN implementations can be classified broadly into one of the following:

Overlay model Peer-to-peer model

Overlay model

1. Service provider doesn’t participate in customers routing, only provides transport to customer data using virtual point-to-point links. As a result, the service provider would only provide customers with virtual circuit connectivity at Layer 2.

2. If the virtual circuit was permanent or available for use by the customer at all times, it was called a permanent virtual circuit (PVC).

3. If the circuit was established by the provider on-demand, it was called a switched virtual circuit (SVC).

4. The primary drawback of an Overlay model was the full mesh of virtual circuits between all customer sites for optimal connectivity.

Overlay VPNs were initially implemented by the SP by providing either Layer 1 (physical layer) connectivity or a Layer 2 transport circuit between customer sites. In the Layer 1 implementation, the SP would provide physical layer connectivity between customer sites, and the customer was responsible for all other layers. In the Layer 2 implementation, the SP was responsible for transportation of Layer 2 frames (or cells) between customer sites, which was traditionally implemented using either Frame Relay or ATM switches as PE devices. Therefore, the service provider was not aware of customer routing or routes. Later, overlay VPNs were also implemented using VPN services over IP (Layer 3) with tunneling protocols like L2TP, GRE, and IPSec to interconnect customer sites. In all cases, the SP network was transparent to the customer, and the routing protocols were run directly between customer routers. Peer-to-peer model The peer-to-peer model was developed to overcome the drawbacks of the Overlay model and provide customers with optimal data transport via the SP backbone. Hence, the service provider would actively participate in customer routing. In the peer-to-peer model, routing information is exchanged between the customer routers and the service provider routers, and customer data is transported across the service provider's core, optimally. Customer routing information is carried between routers in the provider network (P and PE routers) and customer network (CE routers). The peer-to-peer model, consequently, does not require the creation of virtual circuits. The CE routers exchange routes with the connected PE routers in the SP domain. Customer routing information is propagated across the SP backbone between PE and P routers and identifies the optimal path from one customer site to another. Dial VPN Service Mobile users of a corporate customer need to access their Corporate Network from remote sites. Dial VPN service enables to provide secure remote access to the mobile users of the Corporate. Dial VPN service, eliminates the burden of owning and maintaining remote access servers, modems, and phone lines at the Corporate Customer side. Currently accessible from PSTN (127233) & ISDN (27225) also from Broadband.�

E2E3 MPLS VPN Ver3 28.02.2008 5 of 7

MPLS VPN Architecture and Terminology In the MPLS VPN architecture, the edge routers carry customer routing information, providing optimal routing for traffic belonging to the customer for inter-site traffic. The MPLS-based VPN model also accommodates customers using overlapping address spaces, unlike the traditional peer-to-peer model in which optimal routing of customer traffic required the provider to assign IP addresses to each of its customers (or the customer to implement NAT) to avoid overlapping address spaces. MPLS VPN is an implementation of the peer-to-peer model; the MPLS VPN backbone and customer sites exchange Layer 3 customer routing information, and data is forwarded between customer sites using the MPLS-enabled SP IP backbone. The MPLS VPN domain, like the traditional VPN, consists of the customer network and the provider network. The MPLS VPN model is very similar to the dedicated PE router model in a peer-to-peer VPN implementation. However, instead of deploying a dedicated PE router per customer, customer traffic is isolated on the same PE router that provides connectivity into the service provider's network for multiple customers. The components of an MPLS VPN shown in Figure are highlighted next.

Figure MPLS VPN Network Architecture The main components of MPLS VPN architecture are: Customer network, which is usually a customer-controlled domain consisting of devices or routers spanning multiple sites belonging to the customer. In Figure, the customer network for Customer A consists of the routers CE1-A and CE2-A along with devices in the Customer A sites 1 and 2. CE routers, which are routers in the customer network that interface with the service provider network. In Figure , the CE routers for Customer A are CE1-A and CE2-A, and the CE routers for Customer B are CE1-B and CE2-B. Provider network, which is the provider-controlled domain consisting of provider edge and provider core routers that connect sites belonging to the customer on a shared infrastructure. The provider network controls the traffic routing between sites belonging to a customer along with customer traffic isolation. In Figure, the provider network consists of the routers PE1, PE2, P1, P2, P3, and P4. PE routers, which are routers in the provider network that interface or connect to the customer edge routers in the customer network. PE1 and PE2 are the provider edge routers in the MPLS VPN domain for customers A and B. P routers, which are routers in the core of the provider network that interface with either other provider core routers or provider edge routers. Routers P1, P2, P3, and P4 are the provider routers.

E2E3 MPLS VPN Ver3 28.02.2008 6 of 7

Advantages of MPLS over other technologies BSNL's primary objectives in setting up the BGP/MPLS VPN network are: 1. Provide a diversified range of services (Layer 2, Layer 3 and Dial up VPNs) to meet the

requirements of the entire spectrum of customers from Small and Medium to Large business enterprises and financial institutions.

2. Make the service very simple for customers to use even if they lack experience in IP routing.

3. Make the service very scalable and flexible to facilitate large-scale deployment. 4. Provide a reliable and amenable service, offering SLA to customers. 5. Capable of meeting a wide range of customer requirements, including security, quality

of Service (QOS) and any-to-any connectivity. 6. Capable of offering fully managed services to customers. 7. Allow BSNL to introduce additional services such as bandwidth on demand etc over the

same network. Tariff

Service 64 Kbps

128 Kbps

192 Kbps

256 Kbps

384 Kbps

512 Kbps

768 Kbps

1 Mbps

2 Mbps 8 Mbps 34

Mbps 45

Mbps Gold 63000 105000 138000 178000 221000 301000 368000 423000 610000 2134000 3902000 4389000 Silver 52000 88000 116000 149000 185000 249000 306000 353000 487000 1706000 3119000 3509000 Bronze 43000 72000 95000 122000 162000 219000 267000 305000 355000 1242000 2272000 2556000 IP VPN 35000 60000 79000 102000 137000 186000 229000 263000 294000 1028000 1880000 2115000 ��

1. Committed Data Rate in Bronze category - The bandwidth of Bronze category would be restricted to 50% of bandwidth. However, the minimum B/W of 25% B/W will be committed to Bronze customers

2. Discount on MPLS VPN ports - It has been decided to give multiple port discounts on the total number of ports hired across the country as given below. It may be noted that multiple ports are not required to be located in a city for offering this discount:

3. Discount Rates

No. of Ports Existed discount on VPN Ports on Graded basis

Revised discount on VPN Ports on Non-graded basis

1 to 4 ports 0% 0% 5 to 25 ports 10% 5% 26 to 50 ports 15% 10% 51 to 100 ports 20% 10% 101 to 150 ports 20% 15% More than 150 ports 20% 20%

4. Volume based discount on MPLS VPN Service - Annual volume based discount on

graded basis may be given to all customers as under:

Annual Revenue( in Rs.) on MPLS VPN Service per annum Volume based Discount on Graded basis

Upto Rs.50 lakhs No discount Rs.50 lakhs to 1 Crore 5% Rs.1 Crore to 2 Crore 7.5% Rs.2 Crore to 5 Crore 10% More than Rs.5 Crore 15%

E2E3 MPLS VPN Ver3 28.02.2008 7 of 7

5. Shifting charges of MPLS VPN & IP VPN Port - Rs.2000/- per port. 6. Minimum hiring period for MPLS VPN and IP VPN ports - One year. 7. Upgradation of port to higher Bandwidth � No charges to be levied for up-gradation

to higher bandwidth. The rent for the lower BW port to be adjusted on pro-rata basis.

8. Provision of last mile on R&G/ Special construction basis - The charges to be levied as per prevalent R&G/ Special construction terms.

9. Local Lead charges: Included in Port Charges, if these are within Local Area of Telephone system of a City/Town (Virtual Nodes).

10. All charges are exclusive of Service Tax. Virtual Nodes VPN Service based on MPLS technology was launched on 24th May 2003. The VPN infrastructure consists of ten physical Point of Presence (POP) at Delhi, Kolkatta, Chennai, Mumbai, Bangalore, Pune, Hyderabad, Ahemdabad, Lucknow and Ernakulem. These ten POPs cater for the VPN requirement throughout India. In view of competitive scenario, the cities where MLLN VMUX are existing were declared as Virtual Nodes (For calculation of Local Lead Charges). There are currently 290 cities declared as virtual nodes and also BSNL felt that flexibility towards dynamic expansion of Virtual Nodes of MPLS VPN will help boost the customer base of MPLS VPN segment hence the power to declare a city as a virtual node (condition MLLN VMUX should exist) has been delegated to CGM vide letter no: No.112-3/2006-Comml Dated: 2nd April, 2007. The charges (in addition to port charges) are to be calculated as below:

While Calculating the Leased Line charges for Connecting the VPN site to the MPLS Node, the distance from the VPN site to the nearest MPLS Virtual Node or MPLS Node, which ever is less, is only to be taken into account. This will be in addition to the local Lead charges.

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Section-4

Chapter-23

��

E2E3 Multiplay, Ver2 28.02.2008 1 of 4

��

1. What is broadband Triple Play / Multiplay 2. Service offered in Broadband Triple play 3. Components of broadband triple play 4. What is IPTV 5. What is VoIP

�

� �� The triple play service means providing the following service to the customer: -

1. Data (Internet) 2. Voice (VoIP and not the PSTN which is already provided on broadband also) 3. Video (IPTV, VoD or in general live broadcast and stored broadcasting using video

streaming protocols) If the above services are offered on mobile or wireless access network, the same services are termed as broadband Multiplay services. �! ��"��

� � � �� The BSNL’s Broadband multiplay network consists of the following components: -

a. L3PE (MCR / PE Router of NIB-2 Project 1 – Supplied by HCL) b. BNG – Broadband Network Gateway

i. Connects Multiplay Network to NIB2 Backbone (Project 1) through L3PE c. RPR Tier-1 Switch

i. Provides connectivity from BNG to Tier –2 network d. RPR Tier-2 Switch e. OC LAN Tier-2 Switch f. DSLAM g. ADSL CPE h. DSL Tester


��#�� $ %&�&$ %��1. T1 & T2 changed from star topology to RPR ring topology – High reliability 2. IP-DSLAM connected on GE interface as compared to FE interface. 3. BNG behaves as customer edge router whereas BRAS was a PE Router. 4. BRAS were present at 23 “A” locations only whereas BNG is present upto “B” type cities. ' ��$ (��)�* ��

�� ! �� ! ��

�

�1. IPTV or TVoIP delivers television programming to households via broadband

connection using Internet protocols. 2. It requires a subscription and IPTV set-top box (STB), this box will connect to the

home DSL line and is responsible for reassembling the packets into a video stream and then decoding the contents

3. IPTV is typically bundled with other services like Video on Demand (VOD), Voice Over IP (VOIP) or digital Phone, and Web access.

4. IPTV viewers will have full control over functionality such as rewind, fast-forward, pause, and so on.

5. If you've ever watched a video clip on your computer, you've used an IPTV system in its broadest sense.

6. The video stream is broken up into IP packets and dumped into the core network, which is a massive IP network that handles all sorts of other traffic (data, voice, etc.)

�� * � � �+* �� ! ��"�

Video on Demand service allows the user the luxury of watching the movie of his / her choice at his / her convenience.

�

� ""��(��, ��* � � �� - �+�.#.�� * �� /�0�In DTH, as it is broadcasting and not communication so the request for VOD has to be

registered through some other mean than the Set top Box say can be through phone call, SMS or Internet and the same four to five movies are broadcasted and the viewers have to choose among them only and at predefined timings.

In true VOD, as offered by BSNL, the set-top box behaves just like a DVD player and viewer can select a movie from the boutique, view it at his / her desired time and day, pause it,


rewind it, forward it or can have the exactly same experience has viewing from a personalized DVD player. This is only possible because of the two-way communication between the set-top box and the server. In BSNL one has a choice of selecting from hundreds of movies while VOD offered by DTH providers may have only few movies to offer. �

' ��&��1��The set-top box is a smart solid-state device that acts as the gateway to a host of

services offered on the BSNL Multiplay network. On one side the set-top box interfaces with the television using the 3-RCA or the S-Video ports, and on the other side it is connected to broadband ADSL modem via the Ethernet port. BSNL franchisee in Pune has named the set-top box as WICE Box (Window for Information, Communication and Entertainment) and supports all sorts of inputs like audio, video, tablet data, text data, pointer devices etc. it has a USB port and a microphone and headphone jack in addition to essential ports. In future, it will be possible to connect keyboard, mouse, web cams, pen-drives and other such devices for various applications that will be provided on the box. The WICE box is fully upgradeable through the network. This means, any new application launched will be directly uploaded into WICE box without getting the box to service center. All software upgrade will be handled this way.

# �$%��&�� '��(� �� )�"�

S/No. Item Charges 1. Installation and Activation Charges (Non-Refundable) Rs. 600 2. WICE. Box sale Rs. 3950

# �$%��&�� '��(*�� "�1. Installation and Activation Charges (Non-Refundable) Rs. 600 2. Security Deposit for WICE. Box (Refundable) Rs. 1500 3. Fixed Monthly Charge for WICE. Box Rs. 99 Service and other taxes will be charged separately as applicable + ��$��)�S/No. Service Name Scheme Charges Remarks

1. Digital TV Rs. 150* All major TV channels Any two movies free from a list of movies

2. Plan 2 Rs. 325* All major TV channels Movies worth Rs 220/- free

* �

' ��$ (��)�&�* � (��

! ��(!��"�1. The technology used to transmit voice conversations over a data network using the Internet

Protocol. 2. A category of hardware and software that enables people to use the Internet as the transmission

medium for telephone calls. 3. VoIP works through sending voice information in digital form in packets, 4. VoIP also is referred to as Internet telephony, IP telephony, or Voice over the Internet (VOI)


�

�� )��!��1. Cost reduction

a. Toll by-pass b. WAN Cost Reduction

2. Operational Improvement a. Common network infrastructure b. Simplification of Routing Administration

3. Business Tool Integration a. Voice mail, email and fax mail integration b. Web + Call c. Mobility using IP

�

�' � ��: BSNL has planned to roll out this service in 898 cities progressively. The service is being provided at Pune, Chennai, Bangalore, Kolkatta, Hyderabad and Ahemdabad. This service is being provided through franchisees. Many cities already have franchisees for broadband content and they can offer this service. A pool of private IP addresses will be allotted by BSNL to the said franchisee, which will be used for allotting IP address to the IPTV customer.

Section-V

Chapter-24

BSNL Application Packages

E2E3 BSNL Application Packages, Ver1 24.08.2007 1 of 12

DOTSOFT

1.0 DOTSOFT is an Integrated Telecom Database System comprising of :-

• Commercial

• TRA (Billing & Accounting)

• Directory Enquiry

• Fault Repair Service

• Running on a Wide Area Network

2.0 INTRODUCTION

• DOTSOFT is an integrated telecom database system comprising commercial,

billing, accounting, fault repair service and directory enquiry services

• It can run not only on a wide area network (WAN) spanning an entire district

but also on a local LAN in the offline mode.

• DOTSOFT is based on the latest software technologies running on a WAN

and is the first of its kind in BSNL in the field of information technology.

• It has been conceptualised, designed and developed entirely by the core group

of the Software Development Centre of the Andhra Pradesh Telecom Circle,

Hyderabad.

• It has been successfully implemented in all the districts in AP Circle. It has

been also successfully implemented in many circles in BSNL.

2.1 Concise description of DOTSOFT

• DOTSOFT is an enterprise wide telecom database system that revolutionizes

the operation and supervision of customer services by enabling all the

personnel to work online.

• The central server contains the complete database to which all the nodes

anywhere in the district log in. The database is accessed using application

software residing in the nodes which have GUI interface.

• The nodes in the customer service centre service all the subscriber requests

which flow to the commercial and accounts sections as the case may be.

• After validation and approval from the the concerned sections the work orders

flow to the different field units depending on the activity

• After the completion of the work orders the commercial and billing data of the

subscriber gets updated.

• Bill generation is absolutely easy and totally secure.

• Payments are faster and completely hassle free for the customer and the

counter personnel because of the use of bill scanners.

• Revenue accounting and ledger reports are available immediately at the end of

the month.

• The system can generate any kind of detailed as well as statistical reports.

• Online enquiry is available for supervision and queries


2.2 IMPORTANT FEATURES OF DOTSOFT

• Every subscriber is identified by an identification number which shall be

unique all over the country (CCCSSAYYYYMMXXXXX).

• All-India shift and closure cases are processed immediately.

• Database security is implemented through database grants and dynamically

changing menus.

• System is highly scalable and can run on a wide variety of operating system

platforms.

• The system can run on both client-server or host based systems or web based

intranet without any change in the software.

• All the parameters of the system are table driven.

• State of the art technology used in the designing of the wide area network.

• Central control of the WAN using a robust network management software

2.3 UTILITY OF DOTSOFT

• DOTSOFT is one of the first steps towards the bold and ultimate goal of E-

Governance and paperless offices.

• All the work is done online which results in excellent customer service, non

duplication of work, total supervision, complete transparency, better planning

and with a facility of instant reports.

• Single window concept introduced for the first time.

• Concept of request registration number introduced through which the status of

the request can be tracked and inquired.

• Signature warehousing to be included for online verification purpose.

• Instant electronic flow of data between the offices and field units with facility

to print wherever required.

• Various intimation letters to subscribers automatically generated.

• Priority execution of advice notes.

• Messaging system between CO and Field units.

• DOTSOFT mail system between all users.

• Complete history of subscriber’s activities available online.

• Details of subscriber records & requests, bills, demand notes,

wait list, payments and work orders available online.

• Variable billing cycle, ISDN billing.

• Centrex and WLL billing U/D.

• NPC advice notes once completed online are billed in the next schedule.

• Un-addressed bills are generated when a DEL is working but the NPC advice

note has not been completed in the system.

• Finalization of closed connections are settled immediately and a summary of

outstanding OR refund order is generated.

• Uncollected deposits can be billed in the regular bills and the accounting is

taken care of automatically.


• Supplementary bills can be issued for any uncovered amount.

• Outstanding details can be taken for any month on any given date.

• Debit charges and credits generated by the system and hence remove any

requirement of manual entry.

• Voluntary deposits incorporated.

• Outstanding surcharge if any, will be transferred to the next bill, which

reduces the number of outstanding bills.

• Automatic generation of ringing/disconnection list, which can be ported to an

interactive voice response system to alert the subscriber.

• Directory Enquiry shows the status at the moment of enquiry. It can query on

any of the subscriber’s details in part or in full.

• Complete managerial supervision is possible about the activities happening

anywhere in the district.

• Statistical data is generated to find out activity, usage and payment patterns to

facilitate better customer service.

• Online help facility covering all rules and regulations is provided.

• User manual is provided in the .html format.

2.4 Security features in DOTSOFT

• Blocking of User access to DOTSOFT menu if user password violating

password rules.

• Allotment of Dynamic Roles at the time of login through DOTSOFT Menu as

a security measure (Blocking of SQL ACCESS to DOTSOFT MENU users

and all DOTSOFT Modules will work only through DOTSOFT Menu.)

• Blocking of user access from unauthorized IP address.

• Restricting SQL access with product user profile.

• Provision for profile creation/allotment.

• Enabling log in triggers to block unauthorized module Developers other than

DBA.

• Designed security policy for oracle DBMS and placed on DOTSOFT site.





BSNL HR Package

1.0 About HR Package

It is an in-house package developed by the employees of BSNL for usage by

BSNL. The design and development of the package started initially at Telecom

Factory as a part of their effort of internal computerization, and the Employee

master was developed. Since the HR requirements of all the employees of BSNL

are more or less same, the same package was adopted for entire BSNL and the

development was taken over by IT Project Circle. The initial development was

done in Forms and was launched for a trial run at Maharashtra circle, Kolhapur

SSA and Telecom Factory Mumbai.

Since the Forms are heavy for deployment over a network, the development at

ITPC was continued in PHP/JAVA, and even the initial development was

converted and was launched on All-India Level on 16th

Aug 2005.

The further development is continuing at ITPC, to cover all other areas of HR,

like transfers, promotions, training, quarter allotment, leaves, attendance, medical

schemes, nominations and Pay Roll.

2.0 Platforms used

OS --- Linux

Data Base --- Oracle 9i/10g

Application Server --- 9iAS/ 10g AS

Front end --- JAVA/ PHP

3.0 Who can access the package?

All the employees are envisaged to be the users of the package ultimately as all

the leaves, all the advances and other personal claims are proposed to be applied

on-line by the employee for sanction and payment on line. A provision is made

for the supervisor of the employee to make all these applications on behalf of the

illiterate sub ordinate employees.

The transactions on the package are to be done only by the authorized users.An

employee with a system generated staff number, generated by the system on

entering certain mandatory data of an employee, only can be made an authorized

user. Go through the instructions on links below to know more about this.

After the staff number is generated, the employee can be made as a user by the

concerned SA (System Administrator). The employee will be given as the user


name( the employees’ staff no.) and a pass word initially. But on first log on the,

system will force the change of pass word by the user. The user name can not be

changed. Please note that the changed pass word is case sensitive.

4.0 How to access the package?

The authorized user has to log into intranet site, and click the HR Package link

available there in. This activity opens a page asking options for the type of

network connection used, ie. either MPLS VPN or an internet connection. This

page also has one other link for getting the details about HR Package, and

another link for sending a request for issue of user name and pass words or any

other clarification.

Choosing and clicking the appropriate option will open the log in page of the HR

Package. The user name and password for HR package will allow the bonafide

user to access the HR package.

Creating the system administrators and Use of One – Time User Name and Pass

Word by the System Administrator

1. The SA has to be created for each of the main offices ie the corporate office,

circles and SSAs.

A One Time user name and password for the SA will be mailed to mail address of

the SA or to the address from which the request is received.

Using this One Time details, the HR package can be accessed. The system will open

the employee master page to the SA.

The SA will have to enter his details in the staff master and submit the page. The

system will generate a new staff no. for the SA. The system will also make the SA as

a user automatically with the newly generated staff no. as the username and

password.

Only on the generation of the new staff no., the one time user name and pass word

will become invalid. If the staff no. is not generated for any reason, the one time UN

& PW will continue to be valid.

The SA can log in with his new staff no. as the user name and pass word and will be

forced by the system to change the PW on first log in.

There after the SA can enter the details of any no. of employees and generate new

staff nos. for them. He can also make them the USERS for data entry purpose. The

initial user name and pass word for the employee will be will be the staff no. of the

employee generated by the system and the pass word will have to be changed by the

user on first log in.


5.0 Concept of the Location (Based on organizational structure, address and the type

of service provided by the office concerned)

Through the LOCATION we are trying to define the organizational structure of

BSNL. Organization helps in governance at each level by way of decentralization.

Organisational structure is the most important part of the BSNL, in fact, for any

organization. Generally organizations are defined in different layers depending on

the functions to be carried out. The reporting/relational structure between the

layers also is well defined. The layers can one below the other, one parallel to the

other, or any other way as the organization defines.

Each layer of the organization is manned by certain number of employees. The

reporting structure among the employees in a layer also well defined by way of

grades in which the employee is placed. Hence organizational structure has no

relation with the grades and the number of the employees in that layer of the

organization. The number of employees and the grades of those employees in

each layer depends on the functionality, responsibility and other parameters

assigned to the layer by the organization.

As many posts, in different grades, as may be required are created in each

location for discharging the assigned work.

Traditionally BSNL (DOT) was having the following structure.

a). DOT(Ministry) ---- analogous to the Corporate Office of BSNL (Ministry

remains today also but as far as the BSNL is concerned , Ministry is not a part of

its’ structure).

This was/ is the top most layer. (Headed by DG/ CMD )

b). Circles ---- There are many Circles and are discharging different functions

like, Territorial and Metro Districts for telecom operations , Project Crcles,

Maintenance Regions, Production, QA, T&D, Training, Civil Wing, Electrical

Wing, Architectural Wings etc.

Names of all the circles are already entered in the system.

This is the second layer. (Headed by CGM). They normally report to the

Corporate Office

c). SSA ---- This layer came into the being in 1980s. Earlier there were Divisions

, Sub- Divisions.( They still exist).

Names of all the SSAs for the relevant circles are already entered in the system.


This is the third layer. ( It is headed by officer in an appropriate grade).

We had, in the past, a defined structure at next levels called Divisions and Sub-

Divisions under the Circles before SSAs came into being. But after SSAs came

into being, the structure under each SSA has been different to suit its’ needs.

There is a general similarity in all the structures below the SSA, but it is not the

same for all the SSAs.

The corporate office, the circles, the SSAs are referred to as main offices – only

for the purpose of understanding the location concept.

d). Units ----

Units are to be created by the Sys. Admn. of the relevant main office. Before

creating the units in the system it is highly recommended that the structure is

made on the paper and after confirming the correctness, the same may be entered

in the system.

Unit is defined based on the following.

a) Name the unit

b) Address of the unit --- postal address

c) Service rendered by the unit --- operation, civil, electrical, production etc.

5.1 Each of the main offices i.e. Corporate office, Circle, SSA can have units under

them based on the above criterion. For eg.

a) BSNL corporate office has its office at Statesman building.— If some of the

employees in the corporate office are located at Sanchar Bhavan and at other

addresses like Jan path hotel, then Sanchar Bhavan will be one of the units of the

Corporate office and Jan path hotel will be another unit of the corporate office.

Here name of the office is same but the address is different.

b) Maharashtra Circle has its’ office at Fountain building, and another office at Juhu

in Mumbai. Juhu office will be a unit under Maharashtra circle.

c) There are number of circles which do not have SSAs under them like QA, T&D,

TFs etc. Each office under their direct control will be a separate unit and one unit

can be reporting to the parent office or to another unit of the parent unit. For eg.

i) QA circle has its main office at Bangalore. There are many offices in

India which are directly reporting to QA office at Bangalore. Each will

be a unit, say unit 1 at Mumbai, unit 2 at Kolkatta with reporting office

as Circle office.

ii) There are many other offices of QA like QA of TF Mumbai ,QA of

Pune say unit 3, unit 4 respectively which report to unit 1 of QA

iii) This process will continue till all the offices of QA are covered.


iv) Same procedure will be followed in all the main offices.

v) In case of civil wing, electrical wing, etc. the reporting structure has to

be defined. If the civil wing is reporting to the circle office/SSA then it

will be treated as a unit of the circle/SSA. If the civil wing is a treated

as a separate circle, then a separate civil circle has to be created and all

the offices reporting to the civil circle will be treated as units of this

civil structure with service type as civil. Same logic is applicable to

electrical wing with electrical as the service type and to Telecom

Factories with service type as production.

d) Service type is defined as Operation for all telecom circles including CMTS, QA,

T&D etc.; training for training institutes; production for Telecom Factories etc.

PLEASE NOTE THAT THE LEVEL OFFICER HEADING THE LOCATION IS NOT AT

ALL MENTIONED IN THE ABOVE DISCUSSION

.

Each of the main offices and each of the units is known as a location and the existing

BSNL structure is mapped into the package.

Every employee is assigned to a location in the structure. By doing so the details of the

employee relating to the office in which he/she is working, the address of the office and

the service he/she is rendering to BSNL are identified. For eg.

-if we ask an employee where he/she is working – the reply would be that I am

working in the Juhu office of Maharashtra circle, rendering the service of Telecom

operations to BSNL.

Whenever a new office is created, say for eg. a new circle is created like UP(E), then a

new location has to be created and employees have to be reallocated to the new

office/unit. Even if a new building is to be used, a new location in the form of a new unit

has to be created and employees have to reallocated to it.

The reallocation can be done through the transfer module, which will be taking some

time to be introduced till such a time the changes have to be done manually.

SA for the UNITS created by the respective SA of the main office.

As and when a new unit is created, the system, by default creates and inserts a ONE –

TIME user name and PW for that unit. The format for both of them is “Short Description

of the unit _ TRG”. For eg if a unit of QA is created in Pune with short description as

“QA_PUNE” then both the one time UN & PW for this unit will be

“QA_PUNE_TRG”.

This can be given to any employee of QA Pune for following the above instructions.

While creating a SA of a unit, the level of the officers have to be kept in view, as

prescribed in BSNL instructions.


Using this one time user name and password, the same procedure as above for creating

the SA will have to be followed for creating users in the units.

The data entry into the employee master will be only in capitals. System automatically

does it. So the one time PW & UN are in capitals only. But the changed PW by the

user on first log in is case sensitive.

System requirements at the users’ end

The package can be best operated on any computer with the following configuration..

1. Pentium P-III or above version.

2. Widows 98, XP, 2000, but not the server versions

3. Minimum 128 MB RAM

4. Best viewed in Internet explorer-6 or above.

5. Network connectivity.

6. Pop ups should not be blocked.

Section-V

Chapter-25

NOS & RDBMS

E2E3 NOS & RDBMS, Ver1 24.08.2007 1 of 4

Network Operating System

Operating System

An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes raw system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. At the foundation of all system software, an operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides a user interface for managing the operating system, such as a command line interpreter or graphical user interface. The operating system forms a platform for other system software and for application software. Mac OS, Windows, and Linux are some of the most popular OSes.

Network Operating System

Network Operating System (NOS) is an operating system that includes special functions for connecting computers and devices into a local-area network (LAN) or Inter-networking. Some popular NOSs for DOS and Windows systems include Novell Netware, Windows NT, 2000, 2003, RHEL, IBM AIX and Sun Solaris etc.. The Cisco IOS (Internet Operating System) is also a Network Operating System with a focus on the Internetworking capabilities of network devices. A NOS controls a network and its message (e.g. packet) traffic and queues, controls access by multiple users to network resources such as files, and provides for certain administrative functions, including security. A network operating system is most frequently used with local area networks and wide area networks, but could also have application to larger network systems. The upper 5 layers of the OSI Reference Model provide the foundation upon which many network operating systems are based.

Features of NOS Some of the features of Network Operating System are:

• Provide basic operating system features such as support for processors, protocols, automatic hardware detection and support multi-processing of applications.

• Security features such as authentication, authorization, logon restrictions and access control

• Provide name and directory services • Provide file, print, web services, back-up and replication services • Support Internetworking such as routing and WAN ports • User management and support for logon and logoff, remote access; system management,

administration and auditing tools with graphic interfaces Services offered by NOS Network services are the foundation of a networked computing environment. Generally network services are installed on one or more servers to provide shared resources to client computers. Network services are configured on corporate LAN’s to ensure security and user friendly operation. They help the LAN run smoothly and efficiently.


Authentication Service Authentication service provides authentication service to users or other systems. Users and other servers authenticate to such a server, and receive cryptographic tickets. These tickets are then exchanged with one another to verify identity. Authentication is used as the basis for authorization, privacy, and non-repudiation. The major authentication algorithms utilized are passwords, Kerberos, and public key encryption. Directory Service A directory service (DS) is a software application that stores and organizes information about a computer network's users and network resources, and that allows network administrators to manage users' access to the resources. Additionally, directory services act as an abstraction layer between users and shared resources. DHCP Service

The Dynamic Host Configuration Protocol (DHCP) is a set of rules used by communications devices such as a computer, router or network adapter to allow the device to request and obtain an IP address from a server which has a list of addresses available for assignment. DHCP is a protocol used by networked computers (clients) to obtain IP addresses and other parameters such as the default gateway, subnet mask, and IP addresses of DNS servers from a DHCP server. The DHCP server ensures that all IP addresses are unique, Thus IP address pool management is done by the server. DNS Domain Name System is used for transalating human readable names for machines (Servers, Domains, Clients) to IP addresses and vice versa. It also stores other information such as the list of mail exchange servers that accept email for a given domain. In providing a worldwide keyword-based redirection service, the Domain Name System is an essential component of contemporary Internet use. e-Mail Service Electronic mail is a store and forward method of composing, sending, storing, and receiving messages over electronic communication systems. The term "e-mail" applies both to the Internet e-mail system based on the Simple Mail Transfer Protocol (SMTP) and to intranet systems allowing users within one organization to e-mail each other. Often these workgroup collaboration organizations may use the Internet protocols for internal e-mail service. Network Print Service Print service is a facility that is extended to the users so that printer service is available to all users through the network and no individual printer is required on the client machine. Network File Service network file system is any computer file system that supports sharing of files, printers and other resources as persistent storage over a computer network. The Network File System (NFS) which became the first widely used distributed file system. Other notable distributed file systems are Andrew File System (AFS) and Server Message Block SMB, also known as CIFS


RDBMS

Short for relational database management system and pronounced as separate letters, a type of database management system (DBMS) that stores data in the form of related tables. Relational databases are powerful because they require few assumptions about how data is related or how it will be extracted from the database. As a result, the same database can be viewed in many different ways. An important feature of relational systems is that a single database can be spread across several tables. This differs from flat-file databases, in which each database is self-contained in a single table. Almost all full-scale database systems are RDBMS's. Small database systems, however, use other designs that provide less flexibility in posing queries. Database

�� A group of ‘tables’ with related data in them is called a Database �� Coherent collection of data with some inherent meaning, designed, built and populated

for a specific purpose. DBMS and RDBMS

�� Software designed to manage data in database is DBMS. �� In relational databases, data is organised into tables and tables are closely related.

Designing Relational Database

�� Analyze the situation to gather information about the purpose. �� Decide on columns, data types and the lengths of data. �� Create the database and tables. �� Populate the tables

Normalizing the Data

�� Normalizing is the process of organizing data into related tables. �� Purpose - Eliminate Redundant Data

Rules for Normalizing

�� FNF ��Columns can’t contain multiple values �� SNF ��Every non-key column must depend upon the entire key and not just a part of primary

key. �� TNF ��All non-key elements must not depend upon any other non-key columns

Relational Database Objects

�� Tables �� Columns �� Data types �� Stored Procedures �� Functions �� Triggers �� Views �� Indexes

http://www.webopedia.com/TERM/R/query.html

http://www.webopedia.com/TERM/R/system.html

http://www.webopedia.com/TERM/R/RDBMS.html

http://www.webopedia.com/TERM/R/table.html

http://www.webopedia.com/TERM/R/data.html

http://www.webopedia.com/TERM/R/store.html

http://www.webopedia.com/TERM/R/database_management_system_DBMS.html


Concept of Keys �� Primary Keys – to enforce uniqueness and Not-NULL among the rows �� Foreign Keys – are one or more columns that reference the primary keys or unique

constraints of other table. �� Constraints are server-based system implemented data integrity enforcement

mechanism. �� Rules/checks

Managing Data Integrity Data integrity means data in a database adheres to business rules

�� Application Code �� Database triggers �� Declarative Integrity constraints

Database triggers: Programs that are executed when an event, such as insert or update on a column, occurs in a table. Types of Constraints

�� NOT NULL �� UNIQUE �� PRIMARY KEY �� FOREIGN KEY �� CHECK

Concept of Schema A schema is a logical grouping of database objects based on the user who owns them SQL

�� IBM invented SEQUEL(structured English query language) for data queries �� Over the data it has been added now it can not only query but fully build and manage

databases �� SQL sentences are ��DDL (data definition language) ��DML (data manipulation language) ��DCL (data control language)

Processing of SQL statement �� SQL statement is received as strings and broken into – Oracle verbs and oracle objects �� Oracle verbs are then compared with verbs available in Pursing Tree (appropriate and

correct position check) �� Then check for availability of Database objects(refers data dictionary) �� Check for permissions to the user who has fired the statement (refers data dictionary) �� Opening of Cursor(area where data is to stored)

Steps of SQL statement Processing 1.Open the area in memory and maintain a pointer to that location 2.Parse the SQL statement 3.Bind the select list columns to the cursor columns 4.Define variables to fetch the data from the cursor variables 5.Execute the query 6.Fetch data one row at a time 7.Perform required processing 8.Close the opened cursor

Section-V

Chapter-26

IT Security

E2E3 IT Security, Ver2 28.02.2008 1 of 3

“Information Security ABSTRACT In the age of Information Revolution, the management of information and its security is the key concern for all organisations and nations. For sharing of information among the intended users, the systems have to be networked. With this networking the risk of unauthorized use and attacks have taken major attention of Managers. Networks and Information are subject to various types of attacks and various products are available in the market for securing the systems. But it needs the thorough understanding of the various issues involved and proper implementation. Need of Securing Information Information is most important asset for any organization especially for a telecom operator. All our revenue comes from some information only. Besides revenue if there is loss of information all our processes can come to a stand still and it will result in interruptions. It takes lot of efforts to build up information, but the small negligence at any level can result in loss of information. The good aspect of information is that now it is easy to move and easy to alter and this aspect has added insecurity dimension to information during security incidents besides revenue, the image of the company is also at stake. So it a high time that we have a security policy endorsed by the higher management and get it implemented. Implementation of security policy is just not putting up data security devices and having a tight access control mechanism, it is an on going process. The security mechanism is to be continued reviewed against the failures and new threats and risks. The risks are to be analyzed and managed accordingly. The management of risk involves its acceptance, mitigation or transfer. The most important aspect is to have a security organizational set up which will do all these activities. Information Security ensures

• Availability, • Integrity and • Confidentially of information��

The information security set-up of any organisation has to think of security of individuals and file-level data objects and to protect the network from being launching pad of attacks by hackers. The general solution to security design problems lies in ‘authentication’ and ‘authorisation’ model, which is collectively known as access control. However access control does not provide enough security because it ignores the potential threat from insiders. Accountability steps in where access control leaves off. A lot can be observed by just watching. Pay attention to what you can see and measure. How is it to be done? Answer lies in intercepting all transactions that involve files. Think of it as event detection. The event records are filtered and correlated at the time of


capture to distinguish between OS and application activities from user-initiated data use. The audit trail is to be compressed and made temper proof and archived. Because this capture occurs in real time, the reaction can be in real time. The reaction should be risk-appropriate and may range from issuing an alarm to change in authorisation policy. The point is that you should have the event log and monitor it. Various Types of Attacks and their Counter Measures Security Incidents are mainly due to:

• Malicious Code Attacks • Known Vulnerabilities • Configuration Errors

Indications of Infection A system infected with malicious codes will have following symptom(s):

1. Poor System Performance 2. Abnormal System Behavior 3. Unknown Services are running 4. Crashing of Applications 5. Change in file extension or contents 6. Hard Disk is Busy

There can be various types of malicious codes like Virus, Worms, Trojan Horses, Bots, Key Loggers, Spyware, Adware etc. The solution against these is to have good anti-virus software. The anti-virus software should be updated in routine so that it is effective against new malicious codes. The Configurations of the systems are Vulnerable because of

1. Default Accounts 2. Default Passwords 3. Un-necessary Services 4. Remote Access 5. Logging and Audit Disabled 6. Access Controls on Files

�

Monitoring Security of Network

��Monitor for any changes in Configuration of ‘High risk’ Devices ��Monitor Failed Login Attempts, Unusual Traffic, Changes to the Firewall, Access

Grants tom Firewall, Connection setups through Firewalls ��Monitor Server Logs

Security has to implemented at all levels i.e. Network, NOS, Application and RDBMS. Security of Network Firewalls are used for Perimeter Defence of Networks. Using Firewall Access Control Policy is implemented. It controls all internal and external traffic.


Security of OS/NOS

Keep up-to-date Security Patches and update releases for OS Install up-to-date Antivirus Software Harden OS by turning off unnecessary clients, Services and features Security of Application Keep up-to-date Security Patches and update releases for Application Package Don’t Install Programs of unknown origin Precautions with Emails Protection from Phishing attacks Securing Web Browsers Security of RDBMS For securing data the following are needed:

1. User Management 2. Password Management 3. Managing Allocation of Resources to Users 4. Backup and Recovery 5. Auditing

Summary of Action Items 1. Secure Physical Access 2. Remove Unnecessary Services 3. Secure Perimeter 4. Properly Administer Network 5. Apply Patches in Time 6. Install Antivirus Software 7. Backup Data 8. Encrypt Sensitive Data 9. Install IDS 10. Proper Monitoring

Conclusion: Caution is the word when it comes to Information Security. In an era, when information is the power and wealth for an organisation, one cannot expect taking chances with it. Therefore, it is advisable not only to secure the physical access to the information, but also to install antivirus software, wherever required. ‘Prevention is better than cure’- goes strong in case of Information Security also, if we want to create competitiveness. Moreover Security is a continuous process, the preparedness of yesterday may not be sufficient for today. We have to review periodically to find the gaps and immediate action.

Section-VI

Chapter-27

Sample Questions

E2E3 Technical sample questions 1 of 3

Part-I Objective type-70 marks This section will have a combination of multiple choices, true/false and match the following type questions (maximum 50 questions). Few sample questions are given below:

1. Two main factors responsible for guiding the light waves in optical fibers are:

(a) Incident angle and Reflection. (b) Critical angle and total internal reflection (c) reflection and air to glass refraction. (d) None

2. SDH rings are commonly called as

(a) Self healing Ring. (b) Asynchronous ring (c) Dedicated Ring (d) Path switched

3. Max no. of EI can be mapped in STM-1 frame.

(a) 63 (b) 65 (c) 60 (d) 61

4. For synchronization, N/W synchronization exists at

(a) Bit level (b) Byte level (c) Frame level (d) At all –three level

5. Which is main meter used in OFC testing

(a) DTA (b) OTDR (c) Power meter (d) ANT-30

6. What is the basic service unit of cellular telephony?

(a) location area (b) cell (c) PLMN service area (d) MSC/VLR service area

7. Paging is done in

(a) Cell (b) Location area (c) Handover area (d) Routing area

8. Which of the following is not part of the mobile Switching System?

(a) EIR (b) BSC (c) HLR (d) VLR

9. EIR checks

(a) IMSI (b) TMSI (c) IMEI (d) MSRN

10. Which of the following MS can simultaneously handle voice and data call

(a) Class A (b) Class B (c) Class C (d) None of these

11. The minimum speed of BSNL broadband connection is:

(a) 128kbps (b) 256 kbps (c) 512kbps (d) 1Mbps

12. The HR Package has been developed by:

a. ITPC , Pune b. BSNL HQ c. ALTTC d. AP Circle

13. To secure the network, the following should be used.

(a) Antivirus (b) Firewall (c) Upgradation of software (d) all of them

14. Number of time slots in 2Mbps PCM are

(a) 26 (b) 30 (c) 31 (d) 32


15. Type of signaling used in modern telecom network is

(a) MF (b) Decadic (c) CCS no 7 (d) IP based

16. IAM in CCS 7 stands for

(a) Identity authentication message (b) Initial address message (c) International address message (d) Interconnect address message

17. NGN stands for

(a) New Generation Network (b) Next Generation Network (c) National Gateway Network (d) Notional Gateway Network

18. In packet switching, path of packets:

(a) is fixed (b) may be different (c) Generally same (d) combination

19. In sampling theorem sampling frequency Fs is related to highest signal frequency fh

(a) Fs >= 2fh (b) Fs > 2fh (c) Fs < 2fh (d) Fs =< 2fh

20. SCCP stands for

(a) Signalling Connection control point (b) Subscriber Charging control program (c) Special Customer care portal (d) Signalling Channel control point

21. The following protocols is used to distribute labels in MPLS-VPN:-

a) (a) RSVP (b) LDP (c) BGP (d) OSPF

22 Match the following (4 marks)

1. UMTS (a) Mobility management 2. MS (b) Grey list 3. Mobile Switching equipment (c) SIM 4. EIR (d) 3G

23. Match the following (4 marks)

(a) FPH (1) 0900xx (b) VCC (2) 1902xx (c) PRM (3) 1800xx (d) Televoting local (4) 1802xx

24 Match the following (4 marks)

(a) Foreign Key 1. SQL Statement (b) DML 2. Constraint (c) Trigger 3. Eliminate redundant data (d) Normalisation 4. Object

25 State True/False (Each question carries one mark)

1.The function of splitter in DSLAM and subs-premises is different. 2.The maximum distance of ADSL is 2 km. 3.The core routers in MPLS are not having any routing table. 4.The incoming packet to a router in MPLS will have the labels announced by

its immediate neighbor / peer.


Part-II

Subjective: Total marks-30 This section will have questions seeking 5-10 line answer and may ask to draw general block diagrams. The questions may offer choice and can be from any of the topics. Few sample questions are given below: 1 Write two main advantages of GPRS for operators and users respectively. 2 Draw block schematic of GSM architecture showing its main units.

3 What is the format of HRMS no (HR Staff No)?

4 List two types of threats to computer systems. What counter measures can be taken to minimize the risk?

5 Write down any four daily maintenance checks for engine alternator 6 Write down any four monthly maintenance checks for window/split AC. 7 Define NGN and write any four features of NGN. 8 What is Intelligent Network? Briefly explain any four IN services of BSNL 9 What are VPN's? List the different types of VPN provided by BSNL and

explain briefly any one of them?

10 Write down any three advantages of MPLS VPN. 11 What are the factors responsible for attenuation in the OF cable ? 12 Write any three limitation of PDH network and three advantage of SDH

over PDH.

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