Modern Wireless Communication

Systems

Presented by:

Maulik Patel

Outline• Overview Of Wireless Technology(1g,2g,2.5g,3g).• 2G: Second Generation Networks: TDMA/FDD Standards,

CDMA/FDD Standard, 2.5G Mobile Networks• 3G: Third Generation Networks, 3G Standards and

Access Technologies, 3G W-CDMA (UMTS)• GSM System Architecture, Radio Interface• Protocols, Localization and calling• Data Services: GPRS

Overview Of Wireless Technology• 1G TECHNOLOGY

• 2G TECHNOLOGY

• 2.5 TECHNOLOGY

• 3G TECHNOLOGY

WHAT IS WIRELESS ?

• The word wireless is dictionary defined “having no wires ” . In networking terminology , wireless is the term used to

describe any computer network where there is no physical wired connection between sender and receiver, but rather the network is connected by radio waves and or microwaves to maintain communications.

• Wireless networking utilizes specific equipment such as NICs and Routers in place of wires (copper or optical fibre).

1G Technology• 1G refers to the first generation of wireless telephone

technology, mobile telecommunications which was first introduced in 1980s and completed in early 1990s.

• It's Speed was upto 2.4kbps.• It allows the voice calls in 1 country.• 1G network use Analog Signal.• AMPS was first launched in USA in 1G mobile systems.

DRAWBACKS OF 1G

• Poor Voice Quality • Poor Battery Life • Large Phone Size• No Security • Limited Capacity• Poor Handoff Reliability

2G Technology• 2G technology refers to the 2nd generation which is based on GSM.• It was launched in Finland in the year 1991. • 2G network use digital signals.• It’s data speed was upto 64kbps.

Features Includes:

It enables services such as text messages, picture messages and MMS (multi media message).

It provides better quality and capacity

DRAWBACKS OF 2G

• 2G requires strong digital signals to help mobile phones work. If there is no network coverage in any specific area , digital signals would weak.

• These systems are unable to handle complex data such

as Videos.

2.5G Technology• 2.5G is a technology between the second (2G) and third (3G) generation of

mobile telephony.

• 2.5G is sometimes described as 2G Cellular Technology combined with GPRS.

Features Includes: Phone Calls Send/Receive E-mail Messages Web Browsing Speed : 64-144 kbps Camera Phones Take a time of 6-9 mins. to download a 3 mins. Mp3 song

3G Technology• 3G technology refer to third generation which was

introduced in year 2000s.

• Data Transmission speed increased from 144kbps- 2Mbps.

• Typically called Smart Phones and features increased its bandwidth and data transfer rates to accommodate web-based applications and audio and video files.

Features Of 3G Technology Providing Faster Communication

Send/Receive Large Email Messages

High Speed Web / More Security

Video Conferencing / 3D Gaming

TV Streaming/ Mobile TV/ Phone Calls

Large Capacities and Broadband Capabilities

11 sec – 1.5 min. time to download a 3 min Mp3 song.

2GIntroduction

• The 2g technology was the first U.S. cellular telephone system, deployed in Chicago in 1983

• It uses digital radio signals, while its predecessor, 1G, was based on analog radio signals.

• Capable of servicing complex commercial relationships and second generation of b-to-b ecommerce systems all across the world

• It uses circuit switched domain service.

TDMA/FDD Standards

• Global System for Mobile (GSM):

1. first fully digital system utilizing the 900 MHz frequency band 2. The initial GSM had 200 KHz radio channels, 8 full-rate or 16 half-rate TDMA channels per carrier, encryption of speech, low speed data services and support for SMS

• Interim Standard 136 (IS-136):

1. In this system, there were 3 full-rate TDMA users over each 30 KHz channel. 2. The need of this system was mainly to increase the capacity over the earlier analog system

Conti….

• Pacific Digital Cellular (PDC): This standard was developed in Japan. 1. The main advantage of this standard was its low transmission bit rate which led to its better spectrum utilization.

CDMA/FDD Standard

• Interim Standard 95 (IS-95): 1. Also known as CDMAOne, 2. uses 64 orthogonally coded users and code-words are transmitted simultaneously on each of 1.25 MHz channels. 3. Certain services are: - short messaging service, - slotted paging, - over-the-air activation, - enhanced mobile station identities etc.

Pros and Cons Of 2G

• Pros :- 1. The digital signals require very little battery power 2. SMS and email is one of the many 2g technology advantages 3. Improved privacy

• Cons :- 1. Weaker digital signal 2. Angular decay curve 3. Reduced range of sound

2.5G Mobile Networks

• Increased throughput rates in 2G to support modern Internet application, the new data centric standards were developed is known as 2.5G standard.

• Here, the main upgradation techniques are:

1. supporting higher data rate transmission for web browsing 2. supporting e-mail traffic 3. enabling location-based mobile service

Conti…• 2.5G networks also brought into the market some popular

application, Like

1. Wireless Application Protocol (WAP) 2. General Packet Radio Service (GPRS) 3. High Speed Circuit Switched Dada (HSCSD) 4. Enhanced Data rates for GSM Evolution (EDGE)

WHAT IS 3G TECHNOLOGY?

● NEXT GENERATION OF WIRELESS TECHNOLOGY THAT TRANSMITS WIRELESS DATA UPTO 2 MB/Sec.●VOICE●DATA●VIDEO

3G STANDARD

3G technology comprises three primary standards: ● W- CDMA (wideband code-division multiple access), ● CDMA2000, ● TD-CDMA (time-division CDMA).

Each standard is based on an upgrade path for at least one of today’s primary wireless interfaces: ● TDMA (time-division multiple-access),● GSM(Global system for mobile communication)● CDMA(Code division for multiple access

Overview Of 3G

FDMA

● FDMA puts each call on a separate frequency. ● Only one subscriber at any given time is assigned to a channel.● The channel therefore is closed to other conversations until the initial call is finished, or until it is handed-off to a different channel● A “full-duplex”  FDMA transmission requires two channels, one for transmitting and the other for receiving.● FDMA has been used for first generation analog systems.

TDMA●TDMA improves spectrum capacity by splitting each frequency into time slots. ● TDMA allows each user to access the entire radio frequency channel for the short period of a call. ● Other users share this same frequency channel at different time slots. ● The base station continually switches from user to user on the channel.  ●TDMA is the dominant technology for the second generation mobile cellular networks.●A narrow band that is 30 kHz wide.

CDMA●Enables a number of mobile phone users to talk simultaneously in the same area and in the same frequency band.●The cdma technique is also known as a 'spread spectrum' system as the digital code spreads the call across the spectrum bandwidth to transmit the signal.● Uses a special digital code for each user. This code is combined and transmitted with the voice signal of the individual user across the entire spectrum.●CDMA increases spectrum capacity by allowing all users to occupy all channels at the same time

WCDMA(UMTS)●Wide band or broad band is considered to include data rates from 64 Kbps to 2 Mbps.●Wideband channels can carry multiple signals in the same piece of frequency spectrum. ●Wideband CDMA uses nearly 5MHz per carrier●WCDMA allows simultaneous access to several voice, video and data services at once.

UMTS• Universal Mobile Telecommunications System (UMTS)

• UMTS is an upgrade from GSM via GPRS or EDGE• The standardization work for UMTS is carried out by Third Generation Partnership Project (3GPP)

• Data rates of UMTS are:• 144 kbps for rural• 384 kbps for urban outdoor• 2048 kbps for indoor and low range outdoor

• Virtual Home Environment (VHE)

Application Of 3G• Mobile TV• Video on demand• Video Conferencing• Telemedicine• Location-based services• Global Positioning System (GPS)

Advantage Of WCDMA• Large Number Of User Can Permitted And Large Number

Of Code Can Generate.• The maximal number of users is interference limited.• Without knowing the spreading code it is impossible to

recover the transmitted data.• In India, 3G is defined by telecom service providers as

minimum 2 Mbps to maximum 28 Mbps.• 3G networks offer greater security than their 2G

predecessors.

Disadvantage Of WCDMA• High Price To Help Cover the initial Demand And Fixed

Cost.

• Needs more towers the high density requires towers to be closer together.

Global System for Mobile Communications

Originally GSM stood for Groupe Speciale Mobile GSM to meet the following business objectives1. Support for international roaming2. Good speech quality3. Ability to support handheld terminals4. Low terminal and service cost5. Spectral efficiency6. Support for a range of new services and facilities7. ISDN compatibility

GSM System Hierarchy

GSM System Hierarchy

Consists at the minimum one administrative region assigned to one MSC (Mobile Switching Centre) Administrative region is commonly known as PLMN (Public Land Mobile Network) Each administrative region is subdivided into one or many Location Area (LA) One LA consists of many cell groups and each cell group is assigned to one BSC (Base Station Controller) For each LA, there will be at least one BSC while cells in one BSC can belong to different LAs

GSM Architecture

GSM Architecture

Cells are formed by the radio areas covered by a BTS (Base Transceiver Station) Several BTSs are controlled by one BSC Traffic from the MS (Mobile Station) is routed through MSC Calls originating from or terminating in a fixed network or other mobile networks is handled by the GMSC (Gateway MSC)

Operational Architecture of GSM

Entities in GSM

The Mobile Station (MS) - This includes the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). The Base Station Subsystem (BSS) - This includes the Base Transceiver Station (BTS) and the Base Station Controller (BSC). The Network and Switching Subsystem (NSS) - This includes Mobile Switching Center (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Equipment Identity Register (EIR), and the Authentication Center (AUC). The Operation and Support Subsystem (OSS) - This includes the Operation and Maintenance Center (OMC).

Mobile Station Mobile Station (MS) consists of two main elements: mobile equipment or mobile device (that is the phone without the SIM card) and Subscriber Identity Module (SIM) Terminals distinguished principally by their power and application SIM is installed in every GSM phone and identifies the terminal SIM cards used in GSM phones are smart processor cards with a processor and a small memory SIM card contains the International Mobile Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for authentication, and other security information

Radio subsystem• The Radio Subsystem (RSS) comprises the cellular mobile network up

to the switching centers• Components

– Base Station Subsystem (BSS):• Base Transceiver Station (BTS): radio components including

sender, receiver, antenna - if directed antennas are used one BTS can cover several cells

• Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (Um) onto terrestrial channels (A interface)

• BSS = BSC + sum(BTS) + interconnection

– Mobile Stations (MS)

System architecture: radio subsystem

• Interfaces– Um : radio interface– Abis : standardized, open interface with

16 kbit/s user channels– A: standardized, open interface with

64 kbit/s user channels

Um

Abis

A

BSS

radiosubsystem

network and switchingsubsystem

MS MS

BTSBSC MSC

BTS

BTSBSC

BTSMSC

Network and Switching Subsystem

Central component of the Network Subsystem is the Mobile Switching Center (MSC)

Signaling between functional entities in the Network Subsystem uses Signaling System Number 7 (SS7)

MSC together with Home Location Register (HLR) and Visitor Location Register (VLR) databases, provide the call-routing and roaming capabilities of GSM

MSC does the following functions: 1. It acts like a normal switching node for mobile

subscribers of the same network (connection between mobile phone to mobile phone within the same network)

Network and switching subsystem

• NSS is the main component of the public mobile network GSM– switching, mobility management, interconnection to other

networks, system control• Components

– Mobile Services Switching Center (MSC)controls all connections via a separated network to/from a mobile terminal within the domain of the MSC - several BSC can belong to a MSC

– Databases (important: scalability, high capacity, low delay)• Home Location Register (HLR)

central master database containing user data, permanent and semi-permanent data of all subscribers assigned to the HLR (one provider can have several HLRs)

• Visitor Location Register (VLR)local database for a subset of user data, including data about all user currently in the domain of the VLR

Mobile Services Switching Center

• The MSC (mobile services switching center) plays a central role in GSM

– switching functions– additional functions for mobility support– management of network resources– interworking functions via Gateway MSC (GMSC)– integration of several databases

• Functions of a MSC– specific functions for paging and call forwarding– mobility specific signaling– location registration and forwarding of location

information– provision of new services (fax, data calls)– support of short message service (SMS)– generation and forwarding of accounting and billing

information

Operation subsystem• The OSS (Operation Subsystem) enables centralized

operation, management, and maintenance of all GSM subsystems

• Components– Authentication Center (AUC)

• generates user specific authentication parameters on request of a VLR

• authentication parameters used for authentication of mobile terminals and encryption of user data on the air interface within the GSM system

– Equipment Identity Register (EIR)• registers GSM mobile stations and user rights• stolen or malfunctioning mobile stations can be

locked and sometimes even localized– Operation and Maintenance Center (OMC)

• different control capabilities for the radio subsystem and the network subsystem

AIR INTERFACEFrequency Allocation

Radio ChannelDOWNLINK935 - 960 MHz1805-1880 MHz

UPLINK890-915 MHz1710-1785 MHz

Air Interface

Cell Site Mobile

GSM Frequency Allocation

Each way the bandwidth for the GSM system is 25 MHz which provides 125 carriers uplink/downlink each having a bandwidth of 200 kHz. ARFCN (Absolute Radio Frequency Channel Numbers) denote a forward and reverse channel pair which is separated in frequency by 45 MHz. Practically, a guard band of 100 kHz is provided at the upper and lower end of the GSM 900 MHz spectrum and only 124 (duplex) channels are implemented.

GSM Frequency Allocation GSM uses TDMA and FDMAOne or more carrier frequencies are assigned to each base station and each of these carrier frequencies is then divided in time using a TDMA scheme where fundamental unit is called a burst period lasting approximately 0.577 ms. Eight burst periods are grouped into a TDMA frame of approximately 4.615 ms which forms the basic unit for the definition of logical channels. One physical channel is one burst period per TDMA frame while, normally, channels are defined by the number and position of their corresponding burst periods.

GSM Frequency Allocation

Carrier frequencies and TDMA frames

tch –traffic control channelSacch-slow associated control channel

What is GPRSGeneral Packet Radio Service

• General -> not restricted to GSM use (3rd generation systems)• Packet Radio -> enables packet mode communication over air • Service, not System -> existing BSS (partially also NSS) infrastructure is

used

Main benefits• Resources are reserved only when needed and charged accordingly• Connection setup times are reduced• Enables new service opportunities

Data Services: GPRS• Bearer services for GPRS offer end-to-end packet-

switched data transfer. Two types:• Point-to-point (PTP)

• Internet access• SMS messages

• Point-to-multipoint (PTM)• Unidirectional distribution of information (e.g. weather, news)• Conferencing services between multiple users

Quality of Service• QoS profiles can be defined using parameters derived from

service precedence, reliability, delay and throughput.• QoS profiles can be negotiated between the mobile user and

the network, per session, depending on current resources, and can affect billing

• Three priorities: High, Medium, Low• Three reliability classes that guarantee maximum values of

loss, duplication, mis-sequencing and corruption of packets• Delay defines maximum mean delay and 95-percentile delay• Throughput specifies peak and mean bit-rate

GPRS and Conventional GSM• GSM/GPRS services can be used in parallel. Three

classes of mobile station:• Class A – Simultaneous use of GSM and GPRS• Class B – Can register for both GSM and GPRS, but only use

one at a time• Class C – Can attach for only either GSM or GPRS (with the

exception of SMS messages)

Uplink/downlink - GPRS• The uplink channel is shared by a number of

mobiles, and its use is allocated by a BSC (Base Station Controller)

• The MS (Mobile Station) requests use of the channel in a “packet random access message”.

• The BSC allocates an unused channel to the mobile and sends a “packet access grant message” in reply

• The downlink is fully controlled by the serving BSC and random access is not needed

GPRS Architecture

SGSN: Serving GPRS Support NodeGGSN: Gateway GPRS Support Node

EIR – Equipment Identity RegisterAuC – Authentication Center

SGSN and GGSN• SERVING GPRS SUPPORT NODE (SGSN):

• Responsible for authentication, registration and mobility management of mobiles in the network.

• GATEWAY GPRS SUPPORT NODE (GGSN):• Acts as an interface and a router to external networks.• Contains routing information for GPRS mobiles which is used to tunnel packets

through the IP based internal backbone to the correct Serving GPRS Support Node.• Also collects charging information connected to the use of the external data networks

and can act as a packet filter for incoming traffic.

• Internal Backbone:• The internal backbone is an IP based network used to carry packets between different

GSNs.

Mobility Management• ACTIVE STATE:

• Data is transmitted between an MS and the network only when the MS is in the active state. Here, the SGSN knows the cell location of the MS.

• Packet transmission to an active MS is initiated by packet paging.• It notifies the MS of an incoming data packet.• Data transmission then proceeds on the channel indicated by the paging

message.• The purpose of the paging message – to simplify the process of receiving

packets.• The MS listens to only the paging messages instead of to all the data packets

in the downlink channels. This reduces battery usage significantly.

Mobility Management• STANDBY STATE:

• Only the routing area of the MS is known. (It can consist of one or more cells within a GSM location area).• When the SGSN sends a packet to an MS that is in the standby state, the MS must be paged.• A packet paging message is sent to the routing area.• MS relays its cell location to the SGSN to establish the active state.

• IDLE STATE:• Not possible to send messages to the MS from external data networks.• The MS does not have a logical GPRS context activated or any packet-switched public data network

(PSPDN) addresses allocated.

• ROUTING UPDATES:• When an MS that is in an active or a standby state moves from one routing area to another within the

service area of one SGSN, it must perform a routing update.• The routing area information in the SGSN is updated, and the success of the procedure is indicated in the

response message.

References• “Overview of The Gsm Sysyem And Protocol architechture” IEEE Paper

Published By Moe Rahema.• “Characterizing Data Services in a 3G Network” IEEE Paper Published By

Zhichao Zhu 2011.• “On Antena And Frequency Diversity In GSM related systems” IEEE Paper

Published By preben E.Mogensen And Jeroen wihard.• “Frequency Coordination Between UMTS And GSM System” IEEE Paper

Published By Jiang jindi Huawei Technologies.• “GPRS: Architechture, Protocols, And Air Interface” IEEE Paper Published

By Christian Bettstetter, Hans-Jotg Eberspacher and Jorg Eberspacher.