1. 1.
INDUSTRIAL TRAINING-1
Partial Fulfilment of
B. Tech-Computer Science and Engineering
In
Individual Project with Professor Ms. A.Nithyakalyani
Dept. of Computer Science and Engineering, SRM University
From 01.07.2015 to 14.07.2015
By
NISHANT BHARTI
Register No.1031310579
Report submitted to Professor Ms. A.Nithyakalyani
(Class In-Charge)
Department of Computer Science and Engineering,
SRM University, School of Computing, Faculty of Engineering and
Technology

2. 2.
BONAFIDE CERTIFICATE
This is to certify that NISHANT BHARTI of 3rd
year, B.Tech,
Computer Science and Engineering, bearing Registration Number- 1031310579
has completed his one month of Internship as a research project during the
academic year 2015-16 as a partial fulfillment of the B.Tech course under
Professor Ms. A.Nithyakalyani, Dept. of Computer Science and Engineering,
SRM University, Chennai (India)
Signature of the Guide Signature of HOD
Date: 23rd
September, 2015
Ms. A.Nithyakalyani
Professor
Department of Computer Science & Engineering
Mrs. E. Poovammmal, M.E. (PhD)
Professor
Department of Computer Science & Engineering

3. 3.
ACKNOWLEDGEMENT
We place our deep sense of gratitude to our beloved Chancellor, SRM
University for providing us with the requisite infrastructure throughout the course.
We are extremely grateful to the Head of the Department (CSE), Mrs. E.
Poovammmal, for having encouraged and helped us throughout the course of our
project. Without her supervision and feedback, it would have been really hard for
us to finish our project in a timely manner. Thus, we feel deeply obliged for her
support.
We are highly obliged to our guide, Mr. Alok Kumar, J.E., Training
Instructor (BSNL, Munger) for having assisted and mentored us so diligently in
the process of preparing our project. Without her persistent support and co-
operation, we couldn’t have accomplished our ideas.
We also take the opportunity to extend our heartfelt thanks to our respected
Class-in-charge, Ms. A.Nithyakalyani for her support and impeccable guidance.

4. 4.
TABLE OF CONTENTS
LIST OF FIGURES:
Figures Description Page no.
Fig.01 Diagram of a Simple Selector 9
Fig.02 Two Motion Final Selector 10
Fig.03 Switching System Room 11
Fig.04 Overview of Fiber Optic System 16
Fig.05 Stem Index Multimode Fiber 18
Fig.06 Graded Index Multimode Fiber 18
Fig.07 Single Mode Fiber 19
Fig.08 Macro and Micro Bending 20
Fig.09 GSM Overview 24
Fig.10 Internet Connectivity in a Network 30

5. 5.
CONTENTS
Serial No. Title Page No:
01. COMPANY PROFILE
7
02. INTRODUCTION
8
03. ABOUT THE EXCHANGE
10
04. LOCAL AND TRUNK LINE
13
05. PCM
14
06. FIBER OPTICS COMMUNICATON
16
07. GSM TECHNOLOGY
26
08. CDMA TECHNOLOGY
28
09. INTRODUCTION TO INTERNET AND
BROADBAND 30
10. CONCLUSION
34

6. 6.
COMPANY PROFILE
Every day we make phone calls from our telephone sets quite easily but are unaware of
the technology used behind it. The technologies used in telecommunication is a bit complicated
but at the same time interesting too.
Here it has been tried to give an idea of the different technologies used for
telecommunication by one of the biggest service provides to India, i.e., BHARAT SANCHAR
NIGAM LTD.
The service provided by BSNL to its customers is:-
 Basic local telephony
 National and International call service
 Mobile Communication
 Internet Service
The basic telephony i.e., the local call facility provided to the consumers by BSNL comprises of
the following:-
1. Exchange
2. Main Distribution Frame
3. Line Connection
4. Power Plant
The exchange is the basic part of telecommunication system. It is through this exchange
that a subscriber gets connected to different parts of the world by means of a telephone. There
are different types of exchanges depending upon the technology used.

7. 7.
INTRODUCTION
All industries operate in a specific environment which keeps changing and the firms in the
business need to understand it to dynamically adjust their actions for best results. Like minded
firms get together to form associations in order to protect their common interests. Other stake
holders also develop a system to take care of their issues. Governments also need to intervene for
ensuring fair competition and the best value for money for its citizens. This handout gives
exposure on the Telecom Environment in India and also dwells on the role of international
bodies in standardizing and promoting Telecom Growth in the world.
The Indian postal and telecom sectors saw a slow and uneasy start. In 1850, the first
experimental electric telegraph line was started between and. In 1851, it was opened for the use
of. The Posts and Telegraphs department occupied a small corner of the Public Works
Department, at that time.
Subsequently, the construction of 4,000 miles (6,400 km) of telegraph lines connecting Kolkata
(then Calcutta) and Peshawar in the north along with Agra, (then Bombay) through Sindwa
Ghats, and well as and was started in November 1853. , who pioneered the and in India,
belonged to the Public Works Department, and worked towards the development of telecom
throughout this period. A separate department was opened in 1854 when telegraph facilities were
opened to the public.
In 1880, two namely The Ltd. and The Anglo-Indian Telephone Company Ltd.
approached to establish the permission was refused on the grounds that the establishment of
telephones was a Government monopoly and that the Government itself would undertake the
work. In 1881, the Government later reversed its earlier decision and a license was granted to
the Limited of for opening telephone exchanges at ,and and the first formal telephone service
was established in the country. On the 28th January 1882, Major E. Baring, Member of the’s
Council declared open the Telephone Exchanges in Calcutta, Bombay and Madras. The
exchange in Calcutta named the "Central Exchange” was opened at third floor of the building at
7, Council House Street, with a total of 93 subscribers. Later that year, Bombay also witnessed
the opening of a telephone exchange.
Further milestones and developments
 1907 - First Central Battery of telephones introduced in 1913-1914 - First Automatic Exchange
installed in Kanpur.
 1927 - Radio-Telegraph system between the UK and India, with beam stations at Khandi and
Dhundh.
 1933 - System inaugurated between the UK and India.
 1953 - 12 Channel Carrier Systemoduced.
 1960 - First Route commissioned between Delhi and Kanpur.

8. 8.
 1975 - First System commissioned between Mumbai city and andheri Telephone Exchanges.
 1979 - First optical fiber system for local junction commissioned at Pune.
 1980 - First satellite earth station for domestic communications established at Scikandarabad.
 1983 - First analog signal Stored Program Control exchange for trunk line commissioned at
Mumbai.
 1984 – c-dot exchange established for indigenous development and production
of Digital Exchanges.
 1995 - First mobile telephone service started on non-commercial basis on 15 August 1995
in Delhi
 1995 - Internet Introduced in India starting with Delhi, Bombay, Calcutta, Chennai and Pune on
15 August.
Modern policies
 All Villages shall receive telecom facilities by the end of 2002.
 A Communication Convergence Bill introduced in the Parliament on August 31, 2001 is
presently before the Standing Committee of Parliament on Telecom and IT.
 National Long Distance Service (NLD) is opened for unrestricted entry.
 The International Long Distance Services (ILDS) have been opened to competition.
 The basic services are open to competition.
 In addition to the existing three, a fourth cellular operator, one each in four metros and thirteen
circles, has been permitted. Cellular operators have been permitted to provide all types of mobile
services including voice and non-voice messages, data services and public call office utilizing
any type of network equipment, including circuit and/or package switches that meet certain
required standards.
 Policies allowing private participation have been announced as per the New Telecom Policy
(NTP), 1999 in several new services, which include Global Mobile Personal Communication by
Satellite (GMPCS) Service, digital Public Mobile Radio Trunked Service (PMRTS) and Voice
Mail/ Audiotex/ Unified Messaging Services.
 Wireless Local Loop has been introduced to provide telephone connections in urban, semi-urban
and rural areas promptly.
 Two telecom PSUs, VSNL and HTL have been disinvested.
 Steps are being taken to fulfill Universal Service Obligation (USO), funding, and administration.
 A decision to permit Community Phone Service has been announced.
 Multiple Fixed Service Providers (FSPs) licensing guidelines were announced.
 Internet Service Providers (ISPs) have been allowed to set up International Internet Gateways,
both Satellite and Landing stations for submarine optical fiber cables.
 Two categories of infrastructure providers have been allowed to provide end-to-end bandwidth
and dark fiber, right of way, towers, duct space etc.
 Guidelines have been issued by the Government to open up Internet telephony (IP).

9. 9.
ABOUT THE EXCHANGE
In the field of, a telephone exchange or telephone switch is a system of electronic
components that connects telephone calls. A central office is the physical building used to
house equipment including telephone switches, which make "work" in the sense of making
connections and relaying the speech information.
TYPE’S OF EXCHANGE
 Manual Exchange
 Strowger Exchange
 Cross bar Exchange
 Electronics Exchange (Analog and Digital Exchange)
MANUAL EXCAHNGE
With manual service, the customer lifts the receiver off-hook and asks the operator to
connect the call to a requested number. Provided that the number is in the same central office,
the operator connects the call by plugging into the jack on the switchboard corresponding to the
called customer's line. If the call is to another central office, the operator plugs into the trunk for
the other office and asks the operator answering (known as the "inward" operator) to connect the
call.
STROWGER EXCHANGE
Strowger developed a system of automatic switching using an electromechanical switch
based around electromagnets and pawls. With the help of his nephew (Walter S. Strowger) he
produced a working model in 1888 .selector starts in the 'home' position and with each 'impulse'
the wiper contacts would progress round the output bank to the next position. Each output would
be connected to a different subscriber, thus the caller could connect to any other subscriber who
was connected to that bank, without any manual assistance from an operator.
Fig.01. Diagram of a simple Selector

10. 10.
In Figure 2 (above), the selector has 10 outputs, so a caller can choose to connect to any of 10
different subscribers by dialing any digit from 1 to 0 (0=10). This sort of automatic selector is
known as a Uni-Selector, as it moves in just one plane (Rotary).
By mounting several arcs of outlets on top of each other, the number of outlets can be
increased significantly but the wipers are then required to move both horizontally to select a
bank and then vertically to move around that bank to the required outlet. Such a selector is
known as a Two-Motion Selector. Two-motion selectors typically have 10 rows of 10 outlets,
thus 100 possible outlets altogether. A two-motion selector can therefore accept two dialed digits
from a subscriber and route the call to any of 100 numbers. The selector 'wipers' always start in
their resting 'home' position. The first digit moves the selector vertically up to the corresponding
level and then the second digit moves the wipers around the contacts of that level. This is shown
in figure 3, below.
Fig.02. a Two-Motion "Final" Selector
The type of selector shown above is known as a Final Selector as it takes the final two
digits of the number dialed. Most numbers dialed are several digits longer, and therefore pass
through a chain of selectors. Selectors previous to the Final Selectors are different; they are
called Group Selectors. Group selectors take only ONE digit from the caller, and step up the
number of levels according to the digit dialed. The rotary movement is then automatic; the
wipers search around that level to find a free outlet - i.e. the next free selector in the chain. This
is covered in more depth later.
CROSS BAR EXCAHNGE
In , a crossbar switch (also known as cross-point switch, crosspoint switch, or matrix
switch) is a connecting multiple inputs to multiple outputs in a matrix manner. Originally the
term was used literally, for a matrix switch controlled by a grid of crossing . A crossbar switch is
an assembly of individual switches between multiple inputs and multiple outputs. The switches
are arranged in a matrix. If the crossbar switch has M inputs and N outputs, then a crossbar has a
matrix with M x N cross-points or places where the "bars" cross. At each crosspoint is a switch;
when closed, it connects one of M inputs to one of N outputs. A given crossbar is a single layer,

11. 11.
non-blocking switch. Collections of crossbars can be used to implement multiple layer and/or
blocking switches. A crossbar switching system is also called a co-ordinate switching system.
ELECTRONICS EXCHANGE
It is based on the automatic control by stored programmed in computer linked to it. It
cover all the main drawbacks of above mentioned exchange. It may be digital or analog but
mostly digital electronics exchanges are now common. It base on the principal Time Division
Switching or Space Division Switching. Space division switching is used for analog electronics
exchange and time division switching is used for digital exchange.
Fig.03 Switching System Room
Space Division switching System
In a space Division Switching system, a continuous physical path is set up between input
and output terminations. This path is separate for each connection and is held for the entire
duration of the call. Path for different connections is independent of each other. Once a
continuous path has been established., Signals are interchanged between the two terminations.
Such a switching network can employ either metallic or electronic cross points. Previously,
usage of metallic cross-points using reed relays and all were favored. They have the advantage of
compatibility with the existing line and trunk signaling conditions in the network.
Time Division Switching System
In Time Division Switching, a number of calls share the same path on time division
sharing basis. The path is not separate for each connection, rather, is shared sequentially for a
fraction of a time by different calls. This process is repeated periodically at a suitable high rate.
The repetition rate is 8 KHz, i.e. once every 125 microseconds for transmitting speech on
telephone network, without any appreciable distortion. These samples are time multiplexed with

12. 12.
staggered samples of other speech channels, to enable sharing of one path by many calls. The
Time Division Switching was initially accomplished by Pulse Amplitude.
DIGITAL CARD
It is programmed data card which is used for automatic control of call set up and call
termination as well as providing various services to the customer. There are three types of digital
card which are as follow
1) TERMINATION CARD
2) SERVICE CARD
3) CONTROL CARD
Termination card: its main aim to connect the customer on trunk line .other
features of terminating card is battery feed, over voltage protection,check weather
call is STD or LOCAL or ISD
Service card: the service like dial tone ,call waiting ,call confrencing etc is
given by this card.
Control card: it is there to see whether the call has been established or not. If
established then requisite unit has been established or not.
Local and trunk Network
Trunk Lines
The term Trunk Line in telecommunications refers to the high-speed connection
between telephone central offices in the. Trunk lines are always digital. The wiring between
central offices was originally just pairs of twisted copper wire (the twists in the wiring prevented
things known as crosstalk and noise). Because it is expensive to string up (or lay trenches for
buried cables), the phone company researched ways in which to carry more data over the existing
copper lines. This was achieved by using. Later, when fiber-optic technology became available,
phone companies upgraded their trunk lines to fiber optics and used statistical time-division
multiplexing, , coarse or dense wave division multiplexing and optical switching to further
improve transmission speeds.
The signaling information exchanged between different exchanges via inter exchange
trunks for the routing of calls is termed as Inter exchange Signaling. Earlier in band /out of band
frequencies were used for transmitting signaling information. Later on, with the emergence of
PCM systems, it was possible to segregate the signaling from the speech channel. A trunk line is

13. 13.
a connecting (or other switching equipment), as distinguished from local loop circuit which
extends from telephone exchange switching equipment to individual or information
origination/termination equipment. When dealing with a private branch exchange (PBX), trunk
lines are the phone lines coming into the PBX from the telephone provider. This differentiates
these incoming lines from extension telephone lines that connect the PBX to (usually) individual
phone sets. Trunking saves cost, because there are usually fewer trunk lines than extension lines,
since it is unusual in most offices to have all extension lines in use for external calls at once.
Trunk lines transmit voice and data in formats such as analog, digital signal 1, ISDN or primary
rate interface. The dial tone lines for outgoing calls are called DDCO (Direct Dial Central
Office) trunks.
A travelling over a trunk line is not actually flowing any faster. The electrical signal on a
voice line takes the same amount of time to traverse the wire as a similar length trunk line. What
makes trunk lines faster is that the has been altered to carry more data in less time using more
advanced multiplexing and techniques. If you compared a voice line and a trunk line and put
them side by side and observed them, the first pieces of information arrive simultaneously on
both the voice and trunk line. However, the last piece of information would arrive sooner on the
trunk line. No matter what, you can't break the laws of physics. Electricity over copper or laser
light over fiber optics, you cannot break the speed of light--though that has rarely stopped
uneducated IT or IS managers from demanding that cabling perform faster instead of upgrading
equipment.
Trunk lines can contain thousands of simultaneous calls that have been combined using.
These thousands of calls are carried from one central office to another where they can be
connected to a de-multiplexing device and switched through digital access cross connecting
switches to reach the proper exchange and local phone number.
What is Trunking?
In telecommunications systems, Trunking is the aggregation of multiple user circuits
into a single channel. The aggregation is achieved using some form of multiplexing.
PCM
A long distance or local telephone conversation between two persons could
be provided by using a pair of open wire lines or underground cable as early as mid of
19th
century. However, due to fast industrial development and an increased telephone
awareness, demand for trunk and local traffic went on increasing at a rapid rate. To
cater to the increased demand of traffic between two stations or between two subscribers

14. 14.
at the same station we resorted to the use of an increased number of pairs on either the
open wire alignment, or in underground cable. This could solve the problem for some
time only as there is a limit to the number of open wire pairs that can be installed on
one alignment due to headway consideration and maintenance problems. Similarly
increasing the number of open wire pairs that can be installed on one alignment due to
headway consideration and maintenance problems. Similarly increasing the number of
pairs to the underground cable is uneconomical and leads to maintenance problems.
It, therefore became imperative to think of new technical innovations which could exploit the
available bandwidth of transmission media such as open wire lines or underground cables to
provide more number of circuits on one pair. The technique used to provide a number of circuits
using a single transmission link is called Multiplexing.
Basic Requirements for PCM System:
To develop a PCM signal from several analogue signals, the following processing steps are
required:
1. Filtering
2. Sampling
3. Quantization
4. Encoding
5. Line Coding
Duplexing Methodology:
Duplexing is the technique by which the send and receive paths are separated over the medium,
since transmission entities (modulator, amplifiers, demodulators) are involved.
There are two types of Duplexing:
1. Frequency Division Duplexing (FDD)
2. Time Division Duplexing (TDD)
Frequency Division Duplexing (FDD): Different frequencies are used for send and receive
paths and hence there will be a forward band and reverse band. Duplexer is needed if
Simultaneous Transmission (send) and Reception (receive) Methodology is adopted. Frequency
separation between forward band and reverse band is constant.

15. 15.
Time Division Duplexing (TDD): TDD uses different time slots for transmission and
reception paths. Single radio frequency can be used in both the directions instead of two as in
FDD. No duplexer is required. Only a fast switching synthesizer, RF filter path and fast antenna
switch are needed. It increases the battery life of mobile phones.
FIBER-OPTICS COMMUNICATION
Fiber Optics: The use and demand for optical fiber has grown tremendously and optical-
fiber applications are numerous. Telecommunication applications are widespread, ranging from
global networks to desktop computers. These involve the transmission of voice, data, or video
over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber
designs in one of several cable designs.
Carriers use optical fiber to carry plain old telephone service (POTS) across their nationwide
networks. Local exchange carriers (LECs) use fiber to carry this same service between central
office switches at local levels, and sometimes as far as the neighborhood or individual home
(fiber to the home [FTTH]).
Optical fiber is also used extensively for transmission of data. Multinational firms need secure,
reliable systems to transfer data and financial information between buildings to the desktop
terminals or computers and to transfer data around the world. Cable television companies also
use fiber for delivery of digital video and data services. The high bandwidth provided by fiber
makes it the perfect choice for transmitting broadband signals, such as high-definition television
(HDTV) telecasts. Intelligent transportation systems, such as smart highways with intelligent
traffic lights, automated tollbooths, and changeable message signs, also use fiber-optic-based
telemetry systems.
Another important application for optical fiber is the biomedical industry. Fiber-optic systems
are used in most modern telemedicine devices for transmission of digital diagnostic images.
Other applications for optical fiber include space, military, automotive, and the industrial sector.
ADVANTAGES:
Fiber Optics has the following advantages:
• SPEED: Fiber optic networks operate at high speeds - up into the gigabits
• BANDWIDTH: large carrying capacity
• DISTANCE: Signals can be transmitted further without needing to be "refreshed" or
strengthened.
• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other
nearby cables.
• MAINTENANCE: Fiber optic cables costs much less to maintain.

16. 16.
Fiber Optic System:
Optical Fiber is new medium, in which information (voice, Data or Video) is transmitted through
a glass or plastic fiber, in the form of light, following the transmission sequence give below :
(1) Information is encoded into Electrical Signals.
(2) Electrical Signals are converted into light Signals.
(3) Light Travels down the Fiber.
(4) A Detector Changes the Light Signals into Electrical Signals.
(5) Electrical Signals are decoded into Information.
- Inexpensive light sources available.
- Repeater spacing increases along with operating speeds because low loss fibers
are used at high data rates.
Fig.04 Overview of Fiber Optic System
Principle of Operation - Theory
 Total Internal Reflection - The Reflection that Occurs when a Ligh Ray Travelling in
One Material Hits a Different Material and Reflects Back into the Original Material

17. 17.
without any Loss of Light.
PROPAGATION OF LIGHT THROUGH FIBER
The optical fiber has two concentric layers called the core and the cladding. The
inner core is the light carrying part. The surrounding cladding provides the difference refractive
index that allows total internal reflection of light through the core. The index of the cladding is
less than 1%, lower than that of the core. Typical values for example are a core refractive index
of 1.47 and a cladding index of 1.46. Fiber manufacturers control this difference to obtain
desired optical fiber characteristics. Most fibers have an additional coating around the cladding.
This buffer coating is a shock absorber and has no optical properties affecting the propagation of
light within the fiber. Figure shows the idea of light travelling through a fiber. Light injected
into the fiber and striking core to cladding interface at greater than the critical angle, reflects
back into core, since the angle of incidence and reflection are equal, the reflected light will again
be reflected. The light will continue zigzagging down the length of the fiber. Light striking the
interface at less than the critical angle passes into the cladding, where it is lost over distance. The
cladding is usually inefficient as a light carrier, and light in the cladding becomes attenuated
fairly. Propagation of light through fiber is governed by the indices of the core and cladding by
Snell's law.
Such total internal reflection forms the basis of light propagation through a optical fiber. This
analysis consider only meridional rays- those that pass through the fiber axis each time, they are
reflected. Other rays called Skew rays travel down the fiber without passing through the axis.
The path of a skew ray is typically helical wrapping around and around the central axis.
Fortunately skew rays are ignored in most fiber optics analysis.
The Specific Characteristics of light propagation through a fiber depends on many factors,
including
- The size of the fiber.
- The composition of the fiber.
- The light injected into the fiber.
Jacket
Cladding
Core
Cladding
Angle of
reflection
Angle of
incidence
Light at less than
critical angle is
absorbed in jacket
Jacket
Light is propagated by
total internal reflection
Jacket
Cladding
Core
(n2)
(n2)
Fig. Total Internal Reflection in an optical Fibre

18. 18.
50m and a cladding diameter of 125m.
FIBER TYPES
The refractive Index profile describes the relation between the indices of the core and
cladding. Two main relationships exist:
(I) Step Index
(II) Graded Index
The step index fiber has a core with uniform index throughout. The profile shows a sharp step at
the junction of the core and cladding. In contrast, the graded index has a non-uniform core. The
Index is highest at the center and gradually decreases until it matches with that of the cladding.
There is no sharp break in indices between the core and the cladding.
By this classification there are three types of Fibers:
(I) Multimode Step Index Fiber (Step Index Fiber)
(II) Multimode graded Index Fiber (Graded Index Fiber)
(III) Single- Mode Step Index Fiber (Single Mode Fiber)
STEP-INDEX MULTIMODE FIBER has a large core, up to 100 microns in
diameter. As a result, some of the light rays that make up the digital pulse may travel a direct
route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause
the different groupings of light rays, referred to as modes, to arrive separately at a receiving
point. The pulse, an aggregate of different modes, begins to spread out, losing its well-defined
shape. The need to leave spacing between pulses to prevent overlapping limits bandwidth that is,
the amount of information that can be sent. Consequently, this type of fiber is best suited for
transmission over short distances, in an endoscope, for instance.
Fig.05 Step Index Multimode Fiber
GRADED-INDEX MULTIMODE FIBER contains a core in which the refractive
index diminishes gradually from the center axis out toward the cladding. The higher refractive
index at the center makes the light rays moving down the axis advance more slowly than those
near the cladding.
Fig.06 Graded Index Multimode Fiber
Also, rather than zigzagging off the cladding, light in the core curves helically because of
the graded index, reducing its travel distance. The shortened path and the higher speed allow

19. 19.
light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in
the core axis. The result: a digital pulse suffers less dispersion.
SINGLE-MODE FIBER has a narrow core (eight microns or less), and the index of
refraction between the core and the cladding changes less than it does for multimode fibers.
Light thus travels parallel to the axis, creating little pulse dispersion. Telephone and cable
television networks install millions of kilometers of this fiber every year.
Fig.07 Single Mode Fiber
OPTICAL FIBRE PARAMETERS
Optical fiber systems have the following parameters.
1) Wavelength.
2) Frequency.
3) Window.
4) Attenuation.
5) Dispersion.
6) Bandwidth.
9.1 WAVELENGTH
It is a characteristic of light that is emitted from the light source and is measures in nanometers
(nm). In the visible spectrum, wavelength can be described as the colour of the light.
For example, Red Light has longer wavelength than Blue Light, Typical wavelength for fibre use
are 850nm, 1300nm and 1550nm all of which are invisible.
FREQUENCY
It is number of pulse per second emitted from a light source. Frequency is measured in
units of hertz (Hz). In terms of optical pulse 1Hz = 1 pulse/ sec.
WINDOW
A narrow window is defined as the range of wavelengths at which a fibre best operates.
ATTENUATION
Attenuation is defined as the loss of optical power over a set distance, a fibre with lower
attenuation will allow more power to reach a receiver than fibre with higher attenuation.
Attenuation may be categorized as intrinsic or extrinsic.

20. 20.
INTRINSIC ATTENUATION
It is loss due to inherent or within the fibre. Intrinsic attenuation may occur as
(1) Absorption - Natural Impurities in the glass absorb light energy.
(2) Scattering - Light Rays Travelling in the Core Reflect from small Imperfections into a
New Pathway that may be Lost through the cladding.
Fig. 10 Scattering
EXTRINSIC ATTENUATION
It is loss due to external sources. Extrinsic attenuation may occur as –
(I) Macro bending - The fiber is sharply bent so that the light travelling down the fibre
cannot make the turn & is lost in the cladding.
Fig.08 Micro and Macro bending
(II) Micro bending - Micro bending or small bends in the fibre caused by crushing
contraction etc. These bends may not be visible with the naked eye.
 Attenuation is measured in decibels (dB). A dB represents the comparison between
the transmitted and received power in a system.
BANDWIDTH
It is defined as the amount of information that a system can carry such that each pulse of light is
distinguishable by the receiver.
Light
Ray
Light is lost
Light
Ray

21. 21.
System bandwidth is measured in MHz or GHz. In general, when we say that a system has
bandwidth of 20 MHz, means that 20 million pulses of light per second will travel down the fibre
and each will be distinguishable by the receiver.
NUMBERICAL APERTURE
Numerical aperture (NA) is the "light - gathering ability" of a fibre. Light injected into
the fiber at angles greater than the critical angle will be propagated. The material NA
relates to the refractive indices of the core and cladding.
NA = n1
2
- n2
2
Where n1 and n2 are refractive indices of core and cladding respectively.
In general, fibers with a high bandwidth have a lower NA. They thus allow fewer modes means
less dispersion and hence greater bandwidth. A large NA promotes more modal dispersion, since
more paths for the rays are provided NA, although it can be defined for a single mode fibre, is
essentially meaningless as a practical characteristic. NA in a multimode fibre is important to
system performance and to calculate anticipated performance.
Numerical Aperture of fiber
* Light Ray A: Did not Enter Acceptance Cone - Lost
* Light Ray B: Entered Acceptance Cone - Transmitted through the Core by Total Internal
Reflection.
OFC Splicing
Splices are permanent connection between two fibres. The splicing involves cutting of the edges
of the two fibers to be spliced.
Splicing Methods
The following three types are widely used :
1. Adhesive bonding or Glue splicing.
2. Fusion splicing
Adhesive Bonding or Glue Splicing
This is the oldest splicing technique used in fiber splicing. After fiber end preparation, it is
axially aligned in a precision V–groove. Cylindrical rods or another kind of reference

22. 22.
surfaces are used for alignment. During the alignment of fiber end, a small amount of
adhesive or glue of same refractive index as the core material is set between and around the
fiber ends. A two component epoxy or an UV curable adhesive is used as the bonding agent.
Fusion Splicing
The fusion splicing technique is the most popular technique used for achieving very low
splice losses. The fusion can be achieved either through electrical arc or through gas flame.
The process involves cutting of the fibers and fixing them in micro–petitioners on the fusion
splicing machine. The fibers are then aligned either manually or automatically core aligning (in
case of S.M. fiber ) process. Afterwards the operation that takes place involve withdrawal of the
fibers to a specified distance, preheating of the fiber ends through electric arc and bringing
together of the fiber ends in a position and splicing through high temperature fusion
MOBILE COMMUNICATION
A mobile phone uses radio wave signal for its connectivity with the subscriber.
Mobile Phone Towers
The mobile phone works on the frequency signal and each mobile phone
connection has its own frequency. These frequencies are sending from the basic lower station
tower. Each tower has a range of 5 km in the city circle and there are a number of towers in the
city to provide connectivity to each mobile phone subscriber. The city is divided into imaginary
hexagon as its area plans out and each hexagon point has a tower for providing frequency signals

23. 23.
to the mobile subscriber. When the mobile sends signals to the base tower then it is called uplink
signal. When the base tower sends signal to the mobile then its downlink signals on the highways
the range of base tower of sending signal to the mobile phone subscribers is 25 km.
Basic terms in mobile communication are:-
1. MSC: TAX for mobile phones
2. HLR: Home Location Register
3. TRC: Traffic Controller
4. VLR: Visitors Location Register
5. MNC: Mobile Network Code
6. BSC: Base Station Control
MSC:
It acts as a trunk automatic exchange (TAX). All the switching is done here in this TAX.
Each and every call made by the mobile subscribers is first collected from the base station are
send to the MSC where all the necessary verification of the subscriber is made and then the
switching of the call is made by the MSC. The OSS is a component within the MSC which
maintains the MSC. The functions of OSS are maintenance of MSC.
HLR:
The Home Location Register stores each and every data of the mobile subscriber. Before the
call is switched for the mobile subscriber the MSC verifies the subscriber and all the
verification data is provided by the HLR. When the subscriber is on roaming facility, the
MSC of that area collects all the necessary information of the subscriber from its home MSC
through its HLR.

24. 24.
TRC:
The traffic controller controls the traffic for MSC and also controls the traffic of subscriber
trying to make contact with the MSC when call is made or received.
VLR:
The Visitor Location Register keeps a track record of subscribers who are on roaming facility
and all the records of the visitor coming from a different MSC area.
MNC:
Each and every country and its states have a unique Mobile Network Code (MNC) which
makes a difference between the mobile subscriber of two different countries and also within
the states. The MNC for India is 404and for Jharkhand BSNL mobile is INA76 where INA
refers to the Indian Network.
BSC:
The Base Station acts as important media for call transfer and call receiving for the mobile
subscribers. It sends frequency signals for the connectivity of mobile subscriber. The BSC is
connected to its towers through 2 MB link and is directly connected to the MSC where all
call switching takes place for the mobile subscribers. Each base station is provided 124
frequencies and a time slot of 8 channels for every call.
Fig.09 GSM Overview
GSM Network Components
The GSM network is divided into two systems. Each of these systems is comprised of a
number of functional units which are individual components of the mobile network. The two
systems are:

25. 25.
Switching System (SS)
Base Station System (BSS)
GSM networks are operated, maintained and managed from computerized centers.
Subscriber Identity Module (SIM)
SIM card is the key feature of the GSM. It contains information about the subscriber and
must be plugged into the ME to enable the subscriber to use the network with the exception
of emergency calls MS can only be operated if a valid SIM is present.
These store three types of subscriber related information:
1. Fixed data stored before the subscription is sold such as authentication key and security
algorithms.
2. Temporary network data such as the location area of the subscriber and forbidden
PLMNS.
3. Service data such as language preference advice of charge.
There are two types of SIM cards:-
ID-SIM: The format and layout of the ID-SIM complies with ISO standards for integrated
circuit cards.
PLUG-In SIM: The plug-in SIM is smaller than the ID-SIM and is intended for semi
permanent installation in the MNS.
INTODUCTION TO GSM TECHNOLOGY
What is GSM?
If you are in Europe, Asia or Japan and using a mobile phone then most probably you must be
using GSM technology in your mobile phone.
 GSM stands for Global System for Mobile Communication and is an open, digital
cellular technology used for transmitting mobile voice and data services.

26. 26.
 The GSM emerged from the idea of cell-based mobile radio systems at Bell Laboratories
in the early 1970s.
 The GSM is the name of a standardization group established in 1982 to create a common
European mobile telephone standard.
 The GSM standard is the most widely accepted standard and is implemented globally.
 The GSM is a circuit-switched system that divides each 200 kHz channel into eight 25
kHz time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the
1.9GHz and 850MHz bands in the US.
 The GSM owns a market share of more than 70 percent of the world's digital cellular
subscribers.
 The GSM makes use of narrowband technique for transmitting signals.
 The GSM was developed using digital technology. It has an ability to carry 64 kbps to
120 Mbps of data rates.
 Presently GSM support more than one billion mobile subscribers in more than 210
countries throughout of the world.
 The GSM provides basic to advanced voice and data services including Roaming service.
Roaming is the ability to use your GSM phone number in another GSM network.
A GSM digitizes and compresses data, then sends it down through a channel with two
other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800
MHz frequency band.
Specifications for different Personal Communication Services (PCS) systems vary
among the different PCS networks. The GSM specification is listed below with important
characteristics.
Modulation:
Modulation is a form of change process where we change the input information into a
suitable format for the transmission medium. We also changed the information by
demodulating the signal at the receiving end.
The GSM uses Gaussian Minimum Shift Keying (GMSK) modulation method.
Access Methods:
Because radio spectrum is a limited resource shared by all users, a method must be devised to
divide up the bandwidth among as many users as possible.GSM chose a combination of
TDMA/FDMA as its method. The FDMA part involves the division by frequency of the total
25 MHz bandwidth into 124 carrier frequencies of 200 kHz bandwidth. One or more carrier
frequencies are then assigned to each BS. Each of these carrier frequencies is then divided in
time, using a TDMA scheme, into eight time slots. One time slot is used for transmission by
the mobile and one for reception. They are separated in time so that the mobile unit does not
receive and transmit at the same time.

27. 27.
Transmission Rate:
The total symbol rate for GSM at 1 bit per symbol in GMSK produces 270.833 K
symbols/second. The gross transmission rate of the time slot is 22.8 Kbps.
GSM is a digital system with an over-the-air bit rate of 270 kbps.
Frequency Band:
The Uplink Frequency Range specified for GSM is 933 - 960 MHz (basic 900 MHz band
only). The Downlink Frequency Band 890 - 915 MHz (basic 900 MHz band only).
Speech Coding:
GSM uses linear predictive coding (LPC). The purpose of LPC is to reduce the bit rate. The
LPC provides parameters for a filter that mimics the vocal tract. The signal passes through
this filter, leaving behind a residual signal. Speech is encoded at 13 kbps.
Access Network:
Access network, the network between local exchange and subscriber, in the Telecom
Network accounts for a major portion of resources both in terms of capital and manpower. So
far, the subscriber loop has remained in the domain of the copper cable providing cost
effective solution in past. Quick deployment of subscriber loop, coverage of inaccessible and
remote locations coupled with modern technology has led to the emergence of new Access
Technologies. The various technological options available are as follows:
1. Multi Access Radio Relay
2. Wireless in Local Loop
3. Fiber in the Local Loop
Wireless in Local Loop (WILL)
Fixed Wireless telephony in the subscriber access network also known as Wireless in Local
Loop (WLL) is one of the hottest emerging market segments in global telecommunications
today. WLL is generally used as “the last mile solution” to deliver basic phone service
expeditiously where none has existed before. Flexibility and expediency are becoming the
key driving factors behind the deployment of WILL.

28. 28.
WLL shall facilitate cordless telephony for residential as well as commercial complexes
where people are highly mobile. It is also used in remote areas where it is uneconomical to
lay cables and for rapid development of telephone services. The technology employed shall
depend upon various radio access techniques, like FDMA, TDMA and CDMA.
SPREAD SPECTRUM PRINCIPLE
Originally Spread spectrum radio technology was developed for military use to counter the
interference by hostile jamming. The broad spectrum of the transmitted signal gives rise to
“Spread Spectrum”. A Spread Spectrum signal is generated by modulating the radio
frequency (RF) signal with a code consisting of different pseudo random binary sequences,
which is inherently resistant to noisy signal environment.
A number of Spread spectrum RF signals thus generated share the same frequency spectrum and
thus the entire bandwidth available in the band is used by each of the users using same frequency
at the same time.
Frequency of Operation: 824-849 MHz and 869-894 MHz
Duplexing Method: Frequency Division Duplexing (FDD)
Access Channel per carrier: Maximum 61 Channels
RF Spacing: 1.25 MHz
Coverage: 5 Km with hand held telephones and approx.
20 km with Fixed units.
Hand Offs in CDMA

29. 29.
As the phone moves through a network the system controller transfers the call from one
cell to another, this process is called “handoff”. Handoffs maybe done with the assistance
of the mobile or the system controller will control the process by itself. Handoffs are
necessary to continue the call as the phone travels. Handoffs may also occur in idle state
due to mobility.
Types of Handoffs in CDMA: There are primarily three types of Handoffs in CDMA. They are
 Soft
 Hard and
 Idle.
The type of handoff depends on the handoff situation.
To understand this we should know the cellular concept used in CDMA.
CDMA frequency- reuses planning (cellular concept):
Each BTS in a CDMA network can use all available frequencies. Adjacent cells can
transmit at the same frequency because users are separated by code channels, not
frequency channels. BTSs are separated by offsets in the short PN code this feature of
CDMA, called "frequency reuse of one," eliminates the need for frequency planning
Soft Handoff:
A soft handoff establishes a connection with the new BTS prior to breaking the connection
with the old one. This is possible because CDMA cells use the same frequency and because
the mobile uses a rake receiver. The CDMA mobile assists the network in the handoff. The
mobile detects a new pilot as it travels to the next coverage area. The new base station then
establishes a connection with the mobile. This new communication link is established while
the mobile maintains the link with the old BTS.
Soft handoffs are also called "make-before-break." Soft handoff can take place only when the
serving cell and target cell are working in the same frequency.
INTRODUCTION TO INTERNET AND BROADBAND
INTERNET
The internet connection requires a computer which has Internet Explorer software
signal and analog signal to digital signal, a telephone line connection. The data is

30. 30.
sent through telephone line connection to the local exchange, from where it is
then sent to the main exchange.
The main exchange consists of a Node. The Node consists of a control card and a modem from
where it is sent to its main. Node is in the form of packets. It has two parts- LAN and Control
Card.
Fig.10 Internet connectivity in a Network
The main Node is connected to the main server which is located at New Delhi. From here it
is sent to gateway, which is connected to the World Wide Web (WWW)
INTERNET CONNECTIVITY
Telephone Local Exchange (through PCM) LAN
Control Card (routers, packet switching) Modem
WAN Patna (through OFC, B2 Node) Delhi
Network Connection Gateway

31. 31.
OVERVIEW OF BROAD BAND
Definition of Broad Band:
Band Broadband is often called high-speed Internet, because it usually has a high rate
of data transmission. In general, any connection to the customer of 256 kbit/s or more is
considered broadband.
HOW IS BROADBAND DIFFERENT FROM DIAL-UP SERVICE?
 Broadband service provides higher speed of data transmission—Allows more content to
be carried through the transmission “pipeline.”
 Broadband provides access to the highest quality Internet services—streaming media,
VoIP (Internet phone), gaming and interactive services. Many of these current and newly
developing services require the transfer of large amounts of data which may not be
technically feasible with dial-up service. Therefore, broadband service may be
increasingly necessary to access the full range of services and opportunities that the
Internet can offer.
 Broadband is always on—does not block phone lines and no need to reconnect to
network after logging off.
What is Broadband Service?
Broadband refers to a connection that has capacity to transmit large amount of data at high
speed. Presently a connection having download speeds of 256 kbps or more is classified as
broadband. When connected to the Internet broadband connection allows surfing or downloading
much faster than a dial-up or any other narrowband connections. BSNL offers 2 Mbps minimum
download speed for its Broadband connections.
Requirement for providing Broad Band connection
 Personal Computer
 ADSL Modem
 Land Line Connection
 Splitter for separating telephone from Personal computer.
Services available through Broadband

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 High speed Internet Access: This is the always-on Internet access service with speed
ranging from 256 kbps to 8 Mbps.
 Bandwidth on Demand: This will facilitate customer to change bandwidth as per his / her
requirement. For example a customer with 256 kbps can change to 1 Mbps during the video
Conferencing session.
 Multicasting: This is to provide video multicast services, video-on-demand etc. for
application in distance education, telemedicine etc.
 Dial VPN Service: This service allows remote users to access their private network
securely over the NIB-II infrastructure.
 Video and Audio Conferencing:
 Content based Services: Like Video on Demand, Interactive Gaming, Live and time shifted
TV
 Video on Demand: Customers can view any movie of their choice from a pool of movies
stored in a central server. The movies can be viewed either on a TV or a PC.
 Audio on Demand: It is a similar service where person can listen to any music of his
choice.
 TV channels through broadband connection: The TV channels may be available in the
broadband connection. In fact, there may be other new channels, particularly the
educational and scientific channels, depending on demand. Additional equipments required
in the customer's premises are
 Set Top Box (STB) - The STB converts the digital IP based signal to a form
compatible with the TV set.
 PC and TV
The TV services envisaged are:
i. S-VoD: Subscription based Video Content, as in Pay Channels.
ii. Video-On-Demand
iii. N-VoD: Near Video-On-Demand. NVOD provides playouts on fixed time
bands which people can watch against payment.
iv. T-VOD: Transaction or Pay-Per-View service.
The video content will have Hindi, international and regional movies, music, soaps and
serials, sports, news, interactive gaming, e-learning and niche channels. "The driver in
entertainment will be on-demand movies, interactive gaming, broadband Internet
connectivity and e-learning,"
 Billing: To provide a means to bill for the aforesaid services by either time-based or
volume-based billing. It shall provide the customer with the option to select the services
through web server To provide both pre-paid and post paid broadband services
 IP Telephony
 Messaging: plain and feature rich,
 Multi-site MPLS VPN with Quality of Service (QoS) guarantees.
 Wi-Fi
 Web hosting & web co-location.
 Lease line service.

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CONCLUSION
The working in the project was an interesting and an all together learning experience.
New technologies, new progress and new competition are the order of the day. The core area to
look for is highly fragmented and information intense activity sequence that involves a number
of player and audiences.
The project mainly revolves around: EWSD, TAX, internet node, mobile communication,
and WLL and intelligence network.
The emphasis of the different parts of the project is to throw light on the systems working
in Munger (Bihar) Main Exchange. The project also deals with modern technologies attributes
and the scope of implementation of the same in Patna. The area under study was limited to Patna
Main Exchange.
The scope of the study is very vast and the topic under study deals with the volatile
technology world. After the study, suggestions and strategy has been formulated keeping in view
the limitations of the field.
Evolution of this technological world is occurring every minute. Thanks to
Telecom and Web Technologies, countries are coming closer day by day.