Summer Training ReportOn

Basic Telecom

Submitted in partial fulfillment

of the requirement for the award of the degree of

Bachelor of Technology

in

Electronics and Communication

By

Subhash Chandra Tank

Enrollment No. 11EC001351

Submitted to

Department of Electronics and Communication Engineering

Sir Padampat Singhania University

Udaipur – 313601, Rajasthan India

Under the supervision ofMr. PRAMOD TAILORJunior Telecom Officer

BSNLNimbahera, Rajasthan 312601

CERTIFICATE1

This is to certify that the Internship in ‘BSNL’ being submitted by Subhash Chandra Tank

,

In fulfilment of the requirement for the award of degree of Bachelor of Technology

in discipline of engineering, has been carried out under my supervision and guidance.

The matter embodied in this thesis has not been submitted, in part or in full, to any

other university or institute for the award of any degree, diploma or certificate.

Dr. Achintya Choudhury

Dean, School of Engineering

Sir Padampat Singhania University

Udaipur 313601 Rajasthan, India

2

Prof. Udayprakash R. Singh

Head of Department

Department of Electronics and

Communication

Sir Padampat Singhania University

Udaipur 313601 Rajasthan, India

3

ACKNOWLEDGEMENT

“It is not possible to prepare a project report without the assistance &

Encouragement of other people. This one is certainly no exception.”

On the very outset of this report, I would like to extend my sincere & heartfelt

obligation towards all the personages who have helped me in this endeavour.

Without their active guidance, help, cooperation & encouragement, I would not

have made headway in the project.

I am ineffably indebted to Mr. PRAMOD TAILOR for conscientious guidance and

Encouragement to accomplish this assignment.

I am extremely thankful and pay my gratitude to department of BSNL for their

Valuable guidance and support on completion of this project in its presently.

I extend my gratitude to SPSU for giving me this opportunity. I also acknowledge

with a deep sense of reverence, my gratitude towards my Parents and member of

my family, who has always supported me morally as well as economically.

At last but not least gratitude goes to all of my friends who directly or indirectly

Helped me to complete this project report.

Any omission in this brief acknowledgement does not mean lack of gratitude.

Thanking You

Subhash Chandra Tank

4

ABSTRACT

Spending a period of four weeks with the Telecommunication Networking.

The report on how the BSNL Basic Telecome Network work and how to exchange work

and how the company work with telecommunication Network.

This Report also contains the basic telecommunication that work with all team work of

employees and the exchange work.

I was in direct selling and, I realized that it is very difficult to understand the behaviour of

customers. I am saying this because even though I was associated with a brand,

sometimes it was difficult to convince the custom BSNL has a Quality

telecommunication system which is demonstrated through its ability to consistently

provide product and services that meets customer and applicable regulatory

requirements. It aims to enhance customer satisfaction through its effective services.

Previously electro mechanically exchange for use in India namely Strowger type

exchange, cross bar exchange were there. These Manual telephone exchanges

suffered from some disadvantages.

To overcome these an automatic exchange was introduced in this system. In this

system 1980’s PITHROTHA LTD. Imtroduced “C-DOT“ exchange in India.

Besides C-DOT exchange ILT exchange, E-10B exchange also proved of mild

stone in Telecommunication Sector to replace electromechanical exchages, which

were most sophisticated and modern latest techniques electronics exchanges.

There after it was OCB-283 exchange which proved very important exchange in this

series to replace electromechanical exchanges.

Now it is “WLL” & “GSM” mobiles which is also proved a mild stone in

telecommunication sector. It was 31st march 2002 when BSNL started these

GSM mobile and today it has provided almost 35 lacks mobiles in all over

country.

5

CONTENTS

CHAPTERNO.

PARTILULAR PAGE NO.

Cover Page 1

Certificate 2

Acknowledgement 3

Abstract 4

Contents 5-6

List of Figures 7

Introduction to BSNL 8

Profile of the Company 9-10

Facilities / Departments Visited 11

Chapter-1

Telecome Network 12-16

1.1 Call Setup 12

1.2 Electronic Exchange 13

1.3 Carrier Room 13

1.3.1 Conventional Leased

Line System

13

1.3.2 Managed Leased Line

Network

14

1.4 Main Distribution Frame 14

1.4.1 Function of MDF 14

1.5 Power Plant 15

1.6 How a Telecom Exchange

Work

15

1.7 Engine and Alternator 16

6

1.8 OMC 16

1.9 Switches 16

Chapter-2 Switching 17-20

2.1 C-DOT 18

Chapter-3 Mobile Communication 21-24

3.1 Generation Gap 21

3.2 How a call is connected 23

Chapter-4 CDMA 25-26

4.1 Advantage of CDMA 26

Chapter-5 GSM 27-30

5.1 GSM Subsystem 28

5.2 GSM Evoulation 29

5.3 Advantages for Operation 30

Chapter-6 Broadband 31-37

6.1 Feature of Broadband 32

6.2 Wire Line Broadband Technologies 32

6.2.1 ADSL 32

6.2.2 DSL 35

6.2.3 ISDN 35

6.2.4 Advantages 36

6.2.5 BPL 36

6.2.6 Applications of

Broadband

37

Chapter-7 Conclusion 38

References 39

7

List of Figures

FIGURE

NO.

Title of Figure Page

No.

FIG 1.1 How Line Reaches From Subscriber to Exchange 12

FIG 1.2 Main Distribution Frame 14

FIG 1.3 Block Diagram of Telephone Exchange 16

FIG 2.1 General Diagram of a Digital Switch 17

FIG 2.2 C-DOT Rax 19

FIG 2.3 The C-DOT DSS MAX Basic Architecture 20

FIG 3.1 Cell Phone and Base Station 22

FIG 4.1 Different b/w CDMA and Other Systems 26

FIG 5.1 GSM Network Architecture 29

FIG 5.2 Evalution of GSM 29

FIG 6.1 Broadband Connection 34

8

INTRODUCTION

The telephone is a telecommunication device that is used to transmit and receive

electronically or digitally encoded speech between two or more people conversing.

It is one of the most common household appliances in the world today. Most

telephone network which allows any phone user to communicate with almost any

other user.

Telecommunication networks carry information signals among entities, which are

geographically far apart. The entities are involved in the process of information

transfer that may be in the form of a telephone conversation or a file transfer

between two computers or message transfer between two terminals etc.

With the rapidelly growing traffic and untargerted growth of cyberspace,

telecommunication becomes a fabric of our life. The future challenges are

enormous as we anticipate rapid growth items of new services and number of user.

Telecommunication has evaluated and growth at an explosive rate in recent years

and will undoubtedly continue to do so.

The telecommunication links and switching were mainly designed for voice

communication. With the appropriate attachments/equipments, they can be used to

transmit data. A modern society, therefore needs new facilities including very

high bandwidth switched data networks, and large communication satellites with

small, cheap earth antennas.

9

COMPANY PROFILE

Company Name: Bharat Sanchar Nigam Ltd.

Type: State-owned enterprise

Founded: 15 September 2000

Headquarters: New Delhi, India

Industry: Telecommunications

Key people: R.K. Upadhyay (Chairman & MD)

Services: Fixed line and mobile telephony, Internet services, digital television, IPTV

Revenue : 271.28 billion (2013) 279.33 billion (2012)

Operating Income:    -79.55 billion (2013)  -88.21 billion (2012)

Net income:    -78.84 billion (2013)  -88.51 billion (2012)

Total assets:    956.89 billion (2013) 1018.35 billion (2012)

Total equity:    956.89 billion (2013) 1018.35 billion (2012)

Owner(s): Government of India

Employees: 2,44,891

Website: www.bsnl.co.in

10

Bharat Sanchar Nigam Limited is a state-owned telecommunications company

headquartered in New Delhi, India. BSNL is one of the largest Indian cellular service

providers, with over 87.1 million subscribers as of April 2011, and the largest land line

telephone provider in India. BSNL is India’s oldest and largest communication service

provider (CSP). It had a customer base of 90 million as of June 2008. It has footprints

throughout India except for the metropolitan cities of Mumbai and New Delhi, which are

managed by Mahanagar Telephone Nigam Limited (MTNL). As of June 30, 2010, BSNL

had a customer base of 27.45 million wire line and 72.69 million wireless subscribers.

BSNL is the only service provider, making focused efforts and planned initiatives

to bridge the Rural-Urban Digital Divide ICT sector. In fact there is no telecom operator

in the country to beat its reach with its wide network giving services in every nook &

corner of country and operates across India except Delhi & Mumbai. Whether it is

inaccessible areas of Siachen glacier and North-eastern region of the country BSNL

serves its customers with its wide bouquet of telecom services. BSNL is numerous

operator of India in all services in its license area.

The company offers wide ranging & most transparent tariff schemes designed to suite

every customer. BSNL cellular service, Cell One, has 55,140, 282 2G cellular customers

and 88,493 3G customers as on 30.11.2009. In basic services, BSNL is miles ahead,

with 85 per cent share of the subscriber base and 92 percent share in revenue terms.

BSNL has more than 2.5 million WLL subscribers and 2.5 million Internet Customers

who access Internet through various modes. BSNL has been adjudged as the NUMBER

ONE ISP in the country. BSNL has set up a world class multi-gigabit, multi-protocol

convergent IP infrastructure that provides convergent services like voice, data and video

through the same Backbone and Broadband Access Network. At present there are 0.6

Million broadband customers.

The company has vast experience in Planning, Installation, network integration and

Maintenance of Switching & Transmission Networks and also has a world class ISO

9000 certified Telecom Training Institute.

11

Facilities/ Departments Visited

Department/

Facility

Duration of visit Major

equipment/

Software

available

Name of

official

under whom

training was

carried out

Frome To

Working of

Telecom

network

May 5th May

10th

C-DOT ,

MDF, Telecom

Network

Mr. Pramod

Tailor

GSM, CDMA

and Landline

May 10th May

16th

Sanchar Soft,

KENAN FX,

and C-DOT

Mr. Pradeep

Navlakha

Broadband and

Telecome

May 16th May

23th

Switch Room,

OFC Room

Mr. Mahesh

Joshi

Exchange

Shifting

May 24th May

24th

Landline

Exchange

Mr. Mahesh

Joshi

Telecom

network

May 24th May

30th

C-DOT, WLL Mr. Pramod

Tailor

&

Mr. Mahesh

Joshi

12

Chapter-1

TELECOM NETWORK

This section includes brief introduction of how a call is processed when we

dial a call from basic telephone to another basic telephone or from basic to

mobile or vice versa.

1.1 CALL SETUP:

When a subscriber calls to another subscriber first its request goes to

the nearest switching centre that is PSTN (Public Switching

Telecommunication Network). Then it processes the caller and

subscriber’s number if it exists in the same BSC then call setup is

completed.

If subscriber is not in the same BSC (Base Switching Centre) then call

transfer to MSC (Main Switching Centre) then it transfers the call to

prior BSC then call setup is completed.

If Caller calls to a mobile subscriber then call transfer is done by MTSO

now call transfer is done on BTSs (Base Transceiver Station) and call

setup is completed.

FIG 1.1 HOW LINE REACHES FROM SUBSCRIBER TO EXCHANGE

13

FUNCTION OF EXCHANGE:

Exchange of information with subscriber lines with other exchange.

This is done by two type of signaling:

1. Inchannel signaling

2. Common channel signaling

Processing of signaling information and controlling the operation of

signaling network.

Charging and billing.

1.2: ELECTRONIC EXCHANGE:

All control functions by series of instructions are stored in memory.

Memories are modifiable and control program can always be rewritten.

For each call processing step decision is taken according to class of

service.

1.3: CARRIER ROOM:

Leased line connectivity is provided in carrier room. This room has two

parts:

1. Conventional leased line system

2. MLLN

1.3.1: CONVENTIONAL LEASED LINE SYSTEM:

It consists of modems and routers that are provided by the company

requesting for that network.

Connectivity of different ATM, banks etc. is provided by BSNL here.

For this, we have 4 modems (2 in Exchange, 1 at sender and 1 at

receiver)

Modems are used for short distances i.e. trans and receive part are

received here and local lead connection is given to the subscriber.

14

Local lead faults can be handled here but the trans and receive faults

can be handled by the department meant for it.

Accept 64Kbps or 2 Mbps.

For long distance communication we have MUXS and data is sent

through optical fibers. MUXS are present at both the ends.

1.3.2: MANAGED LEASED LINE NETWORK:

No open wiring.

Route can be changed by the computer software

In Agra Gate Exchange, we have 3 VMUX of type II.

1.4: MDF(MAIN DISTRIBUTION FRAME):

M.D.F. is a media between switching network and subscriber’s line. It is a

termination point within the local telephone exchange where exchange

equipment and terminations of local loops are connected by jumper wires.

FIG 1.2 MDF(REF- 1.4.1)

1.4.1: FUNCTIONS OF MDF:

All cable copper wires supplying services through user telephone lines

are terminated and distributed through MDF.

The most common kind of large MDF is a long steel rack accessible

from both sides. Each jumper is a twisted wire.

It consists of local connection and broadband connection frames for the

main Exchange area.

15

The MDF usually holds central office protective devices including heat

coils and functions as a test point between a line and the office.

It provides testing of calls.

It checks whether fault is indoor or external.

All lines terminate individually.

1.5: POWER PLANT:

It provides -48V to the switch rooms and 48V to the connections.

Batteries are artificially discharged once in a year for their

maintenance.

Cooling is provided through fans & AC.

There is earth region too for protection.

1.6: HOW A TELECOM EXCHANGE WORKS:

It require -48 Vdc.

A telephone exchange or telephone switch is a system of electronic comp

onents that

connects telephone calls. A central office is the physical building used to h

ouse inside plant equipment including telephone switches, which make

telephone calls “work” in the sense of making connections and relaying the

speech information.

The basic block diagram for a telecom exchange is as follows-

16

Fig 1.3 : Block diagram of telephone exchange

1.7: Engine and Alternator

It provides AC output in the event of commercial power supply failure. The

diesel engine provides the prime mover to the alternator so that the

alternating current is generated to support the exchange systems.

150 KV Generator with 6 Silinder, and it require 24 V DC for Starting

System

1.8: OMC (Operation and Maintenance Control)

It contains input-output processor terminals, visual display units, printers,

cartridges, etc. It controls the entire operation of exchange data and billing

data. The new connections, adding and removing of facilities to the

subscriber is done in the OMC room.

1.9: Switch

It provides the switching facility and connection to the outside of the

exchange. The switch room contains actual telephone switching hardware

such as cabinets, racks, slots and cards. Switching is the most important

part of the exchange process.

17

Chapter-2

SWITCHING 

A switch is defined as establishing a temporary connection from the

calling subscriber to the called subscriber. Switch is a device that makes

the connection and breaks the connection. It is a device that channels

incoming data from any of the multiple input ports to the specific input that

will take the data toward its intended destination.

A Digital switching system, in general, is one in which signals are switched

in digital form. These signals may represent speech or data. The digital

signals of several speech samples are time multiplexed on a common

media before being switched through the system.

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

highways. The digitalized speech samples are switched in two modes,

viz., Time Switching and Space Switching.

Fig 2.1 : General Diagram of a Digital Switch

18

AU : Subscriber rack for feeding current and other functionalities

Interface: Interface between main exchange and subscribers/Trunks

Switch: Main switching network and other exchange equipment

MDD: Magnetic Disk Drive for storing data

MTD: Magnetic Tape Drive for backup and regeneration of the

exchange

OMT: Operation and Maintenance terminal to issue various

commands.

Control: Processor to control peripherals and interfacing Main

Exchange.

Printer: To get hard copy for all the reports.

Different types of Electronic Switches are – 

(1) C-DOT : Indian Made

(2) E10B : France Made

(3) OCB : France Made

(4) EWSD : Germany Made

Of these, the most important ones include C-DOT and EWSD. Which are

mostly used now a days.

2.1 : C-DOT

The Centre for Development of Telematics (C-DOT) was established in

August 1984 as an autonomous body. Its goal was to develop

telecommunication technology to meet the needs of the Indian

telecommunication network.

In the initial years, a telecom revolution in rural India that was responsible

for all-round socio-economic development from global connectivity. As part

of its development process, C-DOT spawned equipment manufacturers

19

and component vendors. Research and development facilities were

located at its Delhi and Bangalore campuses.

Within a very short time, telecom switching products suited to Indian

conditions appeared in the form of small rural automatic exchanges

(RAXs) and medium size switches as SBMs for towns. This was followed

by higher capacity digital switches known as main automatic exchanges

(MAXs). C-DOT technology spread across the country through its licensed

manufacturers..

Beginning with digital switching systems, C-DOT developed products for

optical, satellite and wireless communication from circuit switching

technology, ATM and next generation networks. From a purely hardware

development centre, it diversified into development of telecom software

like IN, NMS, Data Clearing House and from a protected environment of

closed market to an open and competitive market.

While developing the RAX/MAX digital switches, C-DOT also evolved

processes and procedures for manufacturing the switches in Indian

factories which set up an Indian manufacturing vendor base. Later, C-DOT

projects included central monitoring systems for telecom security, for the

Indian government.

20

Fig 2.2 : C-DOT Rax

Block diagram :C-DOT DSS MAX exchange can be configured using four

basic modules

Base Module

Central Module

Administrative Module

Input Output Module

Fig 2.3: The C-DOT DSS MAX Basic Architecture

21

Chapter-3

MOBILE COMMUNICATION

 

A mobile phone, cell phone or hand phone is an electronic device used to

make mobile telephone calls across a wide geographic area, served by

many public cells, allowing the user to be mobile. By contrast, a cordless

telephone is used only within the range of a single, private base station, for

example within a home or an office.

A mobile phone can make and receive telephone calls to and from

the public telephone network which includes other mobiles and fixed-line

phones across the world. It does this by connecting to a cellular network

provided by a mobile network operator. In addition to telephony, modern

mobile phones also support a wide variety

of other services such as text messaging, MMS, email, Internet access, sh

ort range wireless communications (infrared, Bluetooth), business

applications, gaming and photography. Mobile phones that offer these

more general computing capabilities are referred to as smart phones.

3.1: Generation Gap

Generation#1

Analog [routines for sending voice]

All systems are incompatible

No international roaming

Generation#2

Digital [voice encoding]

Increased capacity

More security

Compatibility

22

Can use TDMA or CDMA for increasing capacity

Generation#2.5 

Packet-switching

Connection to the internet is paid by packets and not by connection

time.

Connection to internet is cheaper and faster [up to 56KBps]

Generation#3

The present future

Permanent web connection at 2Mbps

Internet, phone and media: 3 in 1

The standard based on GSM is called UMTS.

The EDGE standard is the development of GSM towards 3G.

The genius of the cellular system is the division of a city into small cells.

This allows extensive frequency reuse across a city, so that millions of

people can use cell phones simultaneously. In a typical analog cell-phone

system, the cell-phone carrier receives about 800 frequencies to use

across the city. The carrier chops up the city into cells. Each cell is

typically sized at about 10squaremiles (26 square ilometres). Cells are

normally thought of as hexagons on a big hexagonal grid, like this:

23

Fig 3.1: Cell Phones and base Stations

3.2 : HOW A CALL IS CONNECTED

When you first power up the phone, it listens for an SID on the control

channel. The control channel is a special frequency that the phone

and base station use to talk to one another about things like call set-up

and channel changing. If the phone cannot find any control channels to

listen to, it knows it is out of range and displays a “no service”

message.

When it receives the SID, the phone compares it to the SID

programmed into the phone. If the SIDs match, the phone knows that

the cell it is communicating with is part of its home system.

Along with the SID, the phone also transmits a registration request, and

the MTSO keeps track of your phone’s location in a database — this

way, the MTSO knows which cell you are in when it wants to ring your

phone.

The MTSO gets the call, and it tries to find you. It looks in its database

to see which cell you are in.

The MTSO picks a frequency pair that your phone will use in that cell

to take the call.

The MTSO communicates with your phone over the control channel to

tell it which frequencies to use, and once your phone and the tower

switch on those frequencies, the call is connected. Now, you are talking

by two-way radio to a friend.

As you move toward the edge of your cell, your cell’s base station

notes that your signal strength is diminishing. Meanwhile, the base

24

station in the cell you are moving toward (which is listening and

measuring signal strength on all frequencies, not just its own one-

seventh) sees

your phone’s signal strength increasing. The two base stations coordinate

with each other through the MTSO, and at some point, your phone gets a

signal on a control channel telling it to change frequencies. This

hand off switches your phone to the new cell.

Let’s say you’re on the phone and you move from one cell to another —

but the cell you move into is covered by another service provider, not

yours. Instead of dropping the call, it’ll actually be handed off to the other

service provider.

If the SID on the control channel does not match the SID programmed into

your phone, then the phone knows it is roaming. The MTSO of the cell

that you are roaming in contacts the MTSO of your home system, which

then checks its database to confirm that the SID of the phone you are

using is valid. Your home system verify your phone to the local MTSO,

which then tracks your  phone as you move through its cells. And the

amazing thing is that all of this happens within seconds.

25

Chapter- 4

CDMA

One of the basic concepts in data communication is the idea of allowing

several transmitters to send information simultaneously over a single

communication channel. This allows several users to share a band of

frequencies. This concept is called multiple access.

CDMA employs spread-spectrum technology and a special coding scheme

(where each transmitter is assigned a code) to allow multiple users to be

multiplexed over the same physicalchannel.

By contrast, time division multiple access (TDMA) divides access by time,w

hile frequency-division multiple access(FDMA) divides it by frequency.

CDMA is a form of spreadspectrumsignalling,

since the modulated coded signal has a much higher data bandwidth than

the data being communicated.

FDMA - Different users use different frequency 

TDMA - Different user use different time slotof one frequency 

CDMA - Different user use same frequency at the same time, but

with different spreading code

CDMA is a spread spectrum multiple access technique. A spread

spectrum technique spreading the bandwidth of the data uniformly for the

same transmitted power. Spreading code is a pseudo-random code that

has a narrow Ambiguity function, unlike other narrow pulse codes. In

CDMA a locally generated code runs at a much higher rate than the data

to be transmitted. Data for transmission is combined via bitwise

XOR(exclusive OR) with the faster code.

26

Each user in a CDMA system uses a different code to modulate their

signal. Choosing the codes used to modulate the signal is very important

in the performance of CDMA systems. The best performance will occur

when there is good separation between the signal of a desired user and

the signals of other users. The separation of the signals is made by

correlating the received signal with the locally generated code of the

desired user. If the signal matches the desired user’s code then the

correlation function will be high and the system can extract that signal. If

the desired user’s code has nothing in common with the signal the

correlation should be as close to zero as possible (thus eliminating the

signal); this is referred to as cross correlation. If the code is correlated with

the signal at any time offset other than zero, the correlation should be as

close to zero as possible. This is referred to as auto-correlation and is

used to reject multi-path interference.

4.1: Advantages of CDMA

Frequency reuse factor is 1. Network design and expanding become

much easier.

Large Coverage, almost 2 times than GSM, saves money for

operators.

High spectrum capacity 8—10 times than AMPS, 4²6 times than GSM.

High privacy, hard to wiretapping.

Perfect Power Control and voice activation make the MS power low,

healthy for body green mobile phone.

Use soft handoff, decreases call-drop rate.

27

CDMA – “make before break”---soft handoff

Other systems – “make after break”---hard handoff

Fig 4.1: Differences b/w CDMA and other systems

Chapter-5

GSM

GSM (Global System for Mobile Communications) is a standard set

developed by the  European Telecommunications

Standards Institute (ETSI) to describe technologies for second generation

(or “2G”) digital cellular networks. Developed as a replacement for first

generation analog cellular networks, the GSM standard originally

described a digital, circuit switched network optimized for full duplex voice

telephony. The standard was expanded over time to include first circuit

switched data transport, then packet data transport via GPRS. Packet data

transmission speeds were later increased via EDGE. The GSM standard is

succeeded by the third generation (or “3G”)UMTS standard developed by

the 3GPP. GSM networks will evolve further as they begin to incorporate

fourth generation (or “4G”) LTE Advanced standards.”GSM” is a trademark

owned by the GSM Association.

GSM is a cellular network, which means that mobile phones connect to it

by searching for cells in the immediate vicinity. There are five different cell

sizes in a GSM network² macro, micro, pico, femto and umbrella cells. The

coverage area of each cell varies according to the

28

implementation environment. Macro cells can be regarded as cells where

the base station antenna is installed on a mast or a building above

average roof top level. Micro cells are cells whose antenna height is under

average roof top level; they are typically used in urban areas. Pico cells

are small cells whose coverage diameter is a few dozen metres; they are

mainly used indoors. Femto cells are cells designed for use in residential

or small business environments and connect to the service provider’s

network via a broadband internet connection. Umbrella cells are used to

cover shadowed regions of smaller cells and fill in gaps in

coverage between those cells.

Cell horizontal radius varies depending on antenna height, antenna gain

and propagation conditions from a couple of hundred meters to several

tens of kilometres. The longest distance the GSM specification supports in

practical use is 35 kilometres (22 mi). There are also several

implementations of the concept of an extended cell,

where the cell radius could be double or even more, depending on the

antenna system, the type of terrain and the timing advance.

Indoor coverage is also supported by GSM and may be achieved by using

an indoor  microcell base station, or an indoor repeater with distributed

indoor antennas fed through power splitters, to deliver the radio signals

from an antenna outdoors to the separate indoor distributed antenna

system. These are typically deployed when a lot of call capacity is needed

indoors; for example, in shopping centres or airports. However, this is not

a prerequisite, since indoor coverage is also provided by in-building

penetration of the radio signals from any nearby cell. The modulation used

in GSM is Gaussian minimum-shift keying (GMSK), a kind of continuous-

phase frequency shift keying. In GMSK, the signal to be modulated onto

the carrier is first smoothened with a Gaussian low-pass filter prior to being

fed to a frequency modulator, which greatly reduces the interference

to neighbouring channels (adjacent-channel interference).

29

5.1: GSM subsystems

Network Subsystem: includes the equipments and functions related to end-to-end call.

Radio Subsystem: includes the equipments and functions related to the management of the connections on the radio path.

Operations and Maintenance subsystem: includes the operation and maintenance of GSM equipment for the radio and network interface.

-

Fig 5.1: GSM Network Architecture

5.2: GSM Evolution

30

Fig 5.2.: Evolution of GSM

5.3: Advantages for Operators

More revenue : By providing more than a mobile connection. Also

operator can charge on the basis of type and amount of content accessed.

Huge Potential Market for Data Services: Mobile Phone and Internet,

both are fastest growing technologies and GPRS is the merger of two.

Fast Roll-out and Continuous Network Expansion: GPRS is an integral

part of GSM.

 

GPRS uses excess voice capacity for data: GPRS Packets are

transmitted in short, free periods between busy hour calls.

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Chapter-6

BROADBAND

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 kilo bits per second (kbps) to an individual subscriber from

the Point Of Presence (POP) of the service provider is called Broadband.

Data rates are defined in terms of maximum download because network and

server conditions significantly affect the maximum speeds that can be

achieved and because common consumer broadband technologies such

as ADSL are “asymmetric” supporting much lower maximum upload data

rate than download. In practice, the advertised maximum bandwidth is not

always reliably available to the customer; physical

Link quality can vary, and ISPs usually allow

a greater number of subscribers than their backbone connection or neighb

ourhood accessnetwork can handle, under the assumption that most users

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will not be using their full connection capacity very frequently. This

aggregation strategy (known as a contended service) works more often

than not, so users can typically burst to their full bandwidth most of the

time however, peer-to-

peer (P2P) filesharing systems, often requiring extended durations of high 

bandwidth usage, violate these assumptions, and can cause major

problems for ISPs. In some cases the contention ratio, or a download cap,

is agreed in the contract, and businesses and other customers, who need

a lower contention ratio or even an uncondensed service, are typically

charged more. When traffic is particularly heavy, the ISP can deliberately

throttle back user traffic, or just some kinds of traffic. This is known as

traffic shaping. Careful use of traffics happing by the network provider can

ensure quality of service for time critical services even one extremely busy

networks, but overuse can lead to concerns about network neutrality if

certain types of traffic are severely or completely blocked.

6.1: FEATURES OF BROADBAND

Fast connection to the Internet

Access to the services which would otherwise be impossible on a slower

dial up connection. These include facilities such as downloading music or

video footage, listening to your favourite radio station or downloading (or

sending) large attached files with emails.

“Always-on” connection

Means that you are permanently connected to the internet; hence no need

to dial up connection every time you want to surf the web, send email, etc.

Flat-rate billing

If you choose an uncapped rate there will be no additional charges for the

time you are online. You can use it as much or as little as you would like,

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for a fixed fee. Some connections are available at a lower cost, but limit

you to the amount of data being downloaded (known as ‘capped rate’).

Dedicated connection

Simultaneous use of both telephone & data line.

6.2: WIRE LINE BROADBAND TECHNOLOGIES :

6.2.1: ADSL (A symmetric Digital Subscriber Line)

ADSL exploits the copper wires which have a much greater bandwidth or

range of frequencies than that demanded for voice without disturbing the

line’s ability to carry phone conversations. The A stands for asymmetric,

meaning that data transmission rate is not the same in both directions i.e.,

more bandwidth, or data-carrying capacity, is devoted to data travelling

downstream-from the Internet to your PC-than to upstream data travelling

from your PC to the Internet. The reason for the imbalance is that,

generally upstream traffic is very limited to a few words at a time, like for

example ±an URL request and downstream traffic, carrying graphics,

multimedia, and shareware program downloads needs the extra capacity.

An ADSL circuit connects an ADSL modem on each end of a twisted pair

telephone line, creating three information channels

1. A high speed downstream channel

2. A medium speed duplex channel

3. A basic telephone service channel The basic telephone service

channel is split off from the digital modem by filters, thus guaranteeing

uninterrupted basic telephone service, even if ADSL fails.

6.2.1.1: Features of ADSL

Allows simultaneous access to the line by the telephone and the

computer 

In case of power/ADSL failure, data transmission is lost but basic

telephone service will be operational

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ADSL Provides 16-1000 kbps upstream and 1.5-24 Mbps downstream.

It can work up to a distance of 3.7 to 5.5 km depending upon the speed

required.

6.2.1.2: Advantages of ADSL

You can leave your Internet connection open and still use the phone

line for voice calls.

The speed is much higher than a regular modem

DSL doesn’t necessarily require new wiring; it can use the phone line

you already have.

In BSNL, Broadband Access Network, there has to be an ADSL modem

on either end of the telephone line. One end of the line, terminated at

Subscriber’s premises is first connected to the splitter which filter out the

low frequency voice to be connected to the telephone instrument. The

higher frequency, which carries the data is connected to the modem. The

connectivity is shown in the figure 1 given below.

Fig 6.1: Broadband Connections

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The other end is terminated at service providers end which also has

similar arrangement. But at service providers point, numerous ADSL lines

are terminated and there has to be equal number of splitters and ADSL

modems. So instead of separate splitters & modems, it is aggregated into

single nit called Digital Subscriber Line Access Multiplexer (DSLAM). So

one side of the DSLAM interfaces the subscriber lines and the other side

interfaces to the core network through several LAN switches. Before being

given access to the subscriber, subscriber is authenticated based on

username and password by the BRAS. After authentication(verification of

username & password), subscriber is authorised to access the

Providers core network and in turn is connected to whatever service or

content the subscriber demands and accounting is initiated based on

either time based or volume based billing. The LAN Switch collocated with

the Core router is termed as Tier ± 1 Switch and all other LAN switches

which aggregate the DSLAM are called Tier -2 switches. DSLAMs can

also be aggregated to Tier -1switch.

The various components in the Broadband Access Network are

Customer Premises Equipment(CPE) (ADSL Modem & Splitter)

Digital Subscriber Line Access Multiplexer (DSLAM)

LAN Switches: for aggregating DSLAM (Tier -1 & Tier -2 Switch)

Broadband Remote Access Server (BRAS)

6.2.2: DSL

DSL is a family of technologies that provides digital data transmission over

the wires of a local telephone network. DSL originally stood for digital

subscriber loop. In telecommunications marketing, the term Digital

Subscriber Line is widely understood to mean Asymmetric Digital

Subscriber Line (ADSL), the most commonly installed technical variety of

DSL. DSL service is delivered simultaneously with regular telephone on

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the same telephone line. This is possible because DSL uses a higher

frequency. These frequency bands are subsequently separated by

filtering.

The data throughput of consumer DSL services typically ranges from 256

Kb/s to 20 Mbit/s in the direction to the customer (downstream), depending

on DSL technology, line conditions, and service-level implementation. In

ADSL, the data throughput in the upstream direction, (i.e. in the direction

to the service provider) is lower, hence the designation of asymmetric

service. In Symmetric Digital Subscriber Line (SDSL) service, the

downstream and upstream data rates are equal.

6.2.3: ISDN

Integrated Service Digital Network (ISDN) is one of the oldest broadband

digital access methods for consumers and businesses to connect to the

Internet. It is a telephone data service standard. A basic rate ISDN line

(known as ISDN-BRI) is an ISDN line with 2 data “bearer” channels (DS0 -

64 Kbit/s each). Using ISDN terminal adapters (erroneously called

modems), it is possible to bond together 2 or more separate ISDN-BRI

lines to reach bandwidths of 256 Kbit/s or more. The ISDN channel

bonding technology has been used for video conference applications

and broadband data transmission.

6.2.4: Advantages:

Constant data rate at 64 Kbit/s for each DS0 channel.

Two way broadband symmetric data transmission, unlike ADSL.

One of the data channels can be used for phone conversation without

disturbing the data transmission through the other data channel. When

a phone call is ended, the bearer channel can immediately dial and re-

connect itself to the data call.

Call setup is very quick.

Low latency

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ISDN Voice clarity is unmatched by other phone services.

Caller ID is almost always available for no additional fee.

Maximum distance from the central office is much greater than it is for

DSL.

6.2.5: BPL

Broadband over power lines (BPL), also known as power-line Internet or

power band, is the use of PLC technology to provide broadband Internet

access through ordinary power lines. A computer (or any other device)

would need only to plug a BPL “modem” into any outlet in an equipped

building to have high-speed Internet-access.

BPL my offer benefits over regular cable or DSL connections: the extensiv

e infrastructurealready available appears to allow people in remote

locations to access the Internet with relatively little equipment investment

by the utility. Also, such ubiquitous availability would make it much easier

for other electronics, such as televisions or sound systems, to hook up.

Cost of running wires such as Ethernet in many buildings can be

prohibitive; Relying on wireless has number of predictable problems

including security, limited maximum throughput and inability to power

devices efficiently.

6.2.6: APPLICATIONS OF BROADBAND 

Basic WWW browsing and Email access

Run Servers (Web / FTP)

Business tariff, can depend on company

Some technologies are asymmetric (cable, ADSL)

Video On Demand (VOD)

Audio Streams (Internet Radio)

Fast File Transfers (Possibility of downloading large files in short period

of time)

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Chapter-7

CONCLUSION

Bharat Sanchar Nigam Ltd. Formed in October 2000 is the world’s 7th

largest Telecommunications company providing comprehensive range of

telecom services in India: Wired-line, CDMA mobile, GSM mobile, Internet,

Broadband, Carrier Service, MPLS-VPN,VSAT, VoIP services, IN

services, etc. Presently it is one of the largest and leading public

sector unit in India.

The training was aimed at providing the students with basic knowledge

about telecommunications and the working of telecom exchanges. The

various aspects regarding the working of telecommunications, the various

modules in the telecom exchange and their importance in the exchange

process was explained. Both wired and wireless (mobile) communication

39

aspects were dealed with. Mobile communication ± both CDMA and GSM

± was extensively covered. Also, information about broadband internet and

its requirements was provided.

Along with technical lecture sessions, practical sessions were also

conducted where the telecom exchanges and their equipment were shown

and explained.

REFERENCES

BSNL In-plant training material

www.bsnl.co.in

www. .wikipedia.org

Telecommunication system engineering by Roger L Freeman

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