The document provides details about Subhash Chandra Tank's summer training report on basic telecom. It includes a cover page, certificate from his supervisor certifying the completion of the internship, acknowledgements where he thanks various individuals for their support and guidance, and an abstract summarizing the key activities and learnings from the internship. The report is submitted in partial fulfillment of the degree requirements for a Bachelor of Technology in Electronics and Communication from Sir Padampat Singhania University.

1. 1
Summer Training Report
On
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 of
Mr. PRAMOD TAILOR
Junior Telecom Officer
BSNL
Nimbahera, Rajasthan 312601

2. 2
CERTIFICATE
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
Prof. Udayprakash R. Singh
Head of Department
Department of Electronics and Communication
Sir Padampat Singhania University
Udaipur 313601 Rajasthan, India

3. 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. 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. 5
CONTENTS
CHAPTER
NO.
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. 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. 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. 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. 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. 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. 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. 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

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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. 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.

15. 15
 It consists of local connection and broadband connection frames for the
main Exchange area.
 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 TELECOMEXCHANGE WORKS:
It require -48 Vdc.
A telephone exchange or telephone switch is a system of electronic compo
nents 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. 16
Fig1.3: 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 with6 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. 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.
Fig2.1: General Diagram of a Digital Switch

18. 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 and
component vendors. Research and development facilities were located at
its Delhi and Bangalore campuses.

19. 19
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.
Fig 2.2 : C-DOT Rax

20. 20
Blockdiagram :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. 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
 Can use TDMA or CDMA for increasing capacity

22. 22
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 22ilometres). Cells are normally thought of as
hexagons on a big hexagonal grid,like this:
Fig 3.1: Cell Phones and base Stations

23. 23
3.2 : HOW A CALL ISCONNECTED
 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 anycontrol 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 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

24. 24
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. 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.
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

26. 26
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.
CDMA – “make before break”---soft handoff
Other systems – “make after break”---hard handoff
Fig 4.1: Differences b/w CDMA and other systems

27. 27
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
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.

28. 28
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).
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.
-

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Fig 5.1: GSM Network Architecture
5.2: GSM Evolution
Fig 5.2.: Evolution of GSM

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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 downloadbecause 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
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

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concerns about network neutrality if certain types of traffic are severely or
completely blocked.
6.1: FEATURESOFBROADBAND
 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, 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 (Asymmetric 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

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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
 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

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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
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

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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 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

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(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
 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

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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 OFBROADBAND
 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 inIndia.
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
aspects were dealed with. Mobile communication ± both CDMA and GSM ±
was extensively covered. Also, informationabout 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.

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REFERENCES
 BSNL In-plant training material
 www.bsnl.co.in
 www. .wikipedia.org
 Telecommunication system engineering by Roger L Freeman