DETAILED REPORT

C-DOT SBM/MBM

1.1 The C-DOT DSS Family1.1.1 GENERAL

C-DOT DSS MAX is a universal digital switch which can be

configured for different applications as local, transit, or

integrated local and transit switch. High traffic/load handling

capacity up to 8,00,000 BHCA with termination capacity of

40,000 Lines as Local Exchange or 15,000 trunks as Trunk

Automatic Exchange, the C-DOT DSS family is ideally placed to

meet the different requirements of any integrated digital

network.

1.2. BASIC GROWTH/BUILDING MODULES

C-DOT DSS MAX exchanges can be configured using four basic

modules (Fig. 1.1)

Base Module

Central Module

Administrative Module

Input Output Module

i) BASE MODULE

The Base Module (BM) is the basic growth unit of the system. It

interfaces the external world to the switch. The interfaces may

be subscriber lines, analog and digital trunks, CCM and PBX

lines. Each Base Module can interface upto 2024 terminations.

The number of Base Modules directly corresponds to the

C-DOT MAX 1

exchange size. It carries out majority of call processing

functions and, in a small-exchange application, it also carries

out operation and maintenance functions with the help of the

Input Output Module.

In Single Base Module (SBM) exchange configuration, the Base

Module acts as an independent switching system and provides

connections to 1500 lines and 128 trunks. In such a

configuration, the Base Module directly interfaces with the

Input Output Module for bulk data storage, operations and

maintenance functions. Clock and synchronization is provided

by a source within the Base Module. It is a very useful

application for small urban and rural environments.

ii) CENTRAL MODULE

Central Module (CM) consists of a message switch and a space

switch to provide inter-module communication and perform

voice and data switching between Base Modules. It provides

control message communication between any two Base

Modules, and between Base Modules and Administrative

Module for operation and maintenance functions.

iii) ADMINISTRATIVE MODULE

Administrative Module (AM) performs system-level resource

allocation and processing function on a centralized basis. It

performs all the memory and time intensive call processing

support functions and also administration and maintenance

functions. It communicates with the Base Module via the

Central Module. It supports the Input Output Module for

providing man- machine interface.

iv) INPUT OUTPUT MODULE (I0M)

C-DOT MAX 2

Input, Output Module (IOM) consists of duplicated Input Output

Processor (IOP). The Input Output Processor (IOP) is a general-

purpose computer with UNIX Operating System. It is used as

the front-end processor in C-DOT DSS. It handles all the input

and output functions in C-DOT DSS. The IOP is connected to

AP/BP via HDLC links.

1.2 REMOTE SWITCH UNIT

Remote Switch Unit (RSU) is an integral part of C-DOT DSS

architecture. In order to realise a RSU, the normal BM can be

modified for remoting with the host exchange via 2 Mbps

digital links. The number of 2 Mbps links between the Main

Exchange and RSU is primarily determined by the traffic. A

maximum 16 PCMs can be provided between a RSU & Main

exchange. Analog and Digital trunk interfaces are also

implemented in RSU to support direct parenting of small

exchanges from RSU itself instead of parenting it to the main

exchange which will ultimately save the media required from

main exchange..

During standalone mode of operation, the local and incoming

terminating calls in RSU are switched and the metering

information of all the RSU subscribers is stored in the RSU. It is

sent to the host whenever the PCM links are available again.

1.3. SYSTEM FEATURES1.3.1 GENERAL FEATURES

This section includes system features related to the CTOD DSS

MAX. They are:

C-DOT MAX 3

TYPES OF SERVICES

The CDOT DSS of different capacities can be put to use at

various switching nodes in the telecommunication network.

MAX

Main Automatic Exchange MAX is expandable to large

capacities of order of 2000 lines or beyond. The MAX may have

Remote Modules (RM) and Remote Line Concentrators (RLC)

connected to it.

RAX

Rural Automatic Exchange (RAX) is a small exchange and is

expandable upto 2000 lines capacity. Single Base Module

configuration (i.e. CDOT SBM RAX with or without

concentration) comes under the RAX category.

TYPES OF APPLICATION

The system can be put to the following applications:

Replacements

The exchange can serve as replacement of an existing

switching system due to be phased out from the network.

New Exchanges

Wherever new exchanges are opened, the CDOT DSS MAX can

provide the switching network within the existing telecom

network.

Extensions

The capacity of an existing CDOT switching system can be

increased. For example if the capacity of an existing CDOT

exchange is 512 points, it can be increased, to say, 4000 lines.

TYPE OF SYSTEM

C-DOT MAX 4

The system is Stored Programme Controlled (SPC) which

makes it possible to work in attended/non-attended type of

working environment.

TYPE OF NETWORK

The switching network within the system is 4-wire digital.

TYPE OF COMPONENTS

The different type of components used include integrated

circuits, miniature relays, PCB, etc. The connecting scheme

between various modules emphasis connectorised hardware.

C-DOT MAX 5

C-DOT MAX 6

SYSTEM

ARCHITECTURE

FIG 1.1

2.1 CDOT SYSTEM CAPACITY

2.1.1 INTRODUCTION

The capacity of C-DOT DSS is defined in terms of the following

parameters:

• .The termination capacity expressed as the number of lines

and trunks

• The amount of traffic (in Erlangs) that can be switched

• The number of Busy Hour Call Attempts (BHCA) that can be

processed with a given call-mix while meeting the overall

service quality requirements

2.1.2. TERMINATION CAPACITY

A Terminal Card is the basic system element. It interfaces/

terminates the lines and trunks. The next higher element is a

Terminal Unit. The types of terminal cards and terminal units

used in C-DOT DSS along with its functions are explained in

H/W description. Termination capacity of a BM is 488 analog

terminals and that of LM is 768 analog terminals. A BM can be

concentrated with 2 LMs to provide maximum termination

capacity of 2024 analog lines. In case of a BM, a maximum of

256 B- channels can be provided for ISDN terminations at the

cost of 128 analog lines. In its maximum configuration of one

BM and 2 LMs with termination capacity of 2024 analog lines,

256 B-channels are provided at the cost of 512 analog lines.

One to one replacement of B-channels is planned in immediate

future.

C-DOT MAX 7

Table 2.1

Termination Capacity of System Elements

Sl System Element Termination Capacity1 Termination Cards (TC):

A Analog Line CardLCC – 8 Analog Subscribers

CCM – 8 CCB subscribers with

last two ports supporting 16-kHz B Analog Trunk Card TWT/ EMF – 8 Trunks

C A set of DTS/DTC

Cards

One 2-Mbps E-1 link as CAS/CCS

trunksD #7 PHC Card (SHM) 8 Protocol Handlers/ Signalling

LinksE ISDN-BRI Card 8 BRI (2B+D) Interface i.e. 16 B-

channelsF ISDN-PRI Card One PRI (30B+D) Interface i.e. 30

B-channels2 Terminal Unit (TU):

A Analog TU (ATU)16 Analog Terminal Cards (LCC/

CCM/ TWT/ EMF) to support any

combination of Lines & Trunks in B Digital TU (DTU) Four 2-Mbps E-1 links as CAS/

CCS7C #7 Signalling Unit

Module (SUM)

64 Nos., #7 Protocol

Handlers/signalling linksD ISDN Terminal Unit

(ISTU)

256 Bearer Channels to be

configured as BRI, PRI or any 3 Base Module (BM):

A Base Module (Line)480 Analog Subscribers. A

maximum of 256 B-Channels for

ISDN interface can be provided

B Line Module (LM)768 Analog subscriber lines. A

maximum of two LMs connected

with BM supports 2024 lines.C BM (Analog Trunks) 488 Analog Trunks

D BM (Digital Trunks) Fifteen 2-Mbps E-1 links as CAS/

CCS7E BM (Analog + Digital) Three possible configurations as

360 AT+ 4 PCMs/ 232 AT+ 8

C-DOT MAX 8

C-DOT MAX 9

Hardware Architecture

3.1 GENERAL

The hardware architecture of C-DOT DSS MAX is mapped

closely on the System Overview described in the previous

chapter. In the following sections, the hardware architecture of

each constituent module is described.

3.2 BASE MODULE (BM)Base Module (BM) is the basic building block of C-DOT DSS

MAX. It interfaces the subscribers, trunks and special circuits.

The subscribers may be individual or grouped PBX lines, analog

or digital lines. The trunks may be Two Wire Physical, E&M

Four Wire, E&M Two Wire, Digital CAS or CCS.

FIG: 3.1 BASE MODULE (BM)

CONFIGURATION

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C-DOT MAX 10