1

Table of contents

1. Acknowledgement

2. Certificate

3. Preface

4. Introduction

5. Making a Telephone Call

6. Working of Basic Telecommunication Network

7. Leased Lines

8. Intranet

9. Corporate Network

10. WIFI (Wireless Fidelity)

11. WiMAX

12. Global system for mobile communication (GSM)

13. General Packets for Radio Services (GPRS)

14. CDMA (Code Division Multiple Access)

15. Fiber Optic Transmission System

16. Conclusion

2

ACKNOWLEDGEMENT

It is with profound gratitude that I express my deep indebtedness to all the employees

of B.S.N.L. without whose support and guidance it would not have been possible for

this training to have materialized and taken a concrete shape. I owe my personal

thanks to my trainers in charge MR. ANANAD PRAKASH SINGH –(SDE) who

extended full support and co-operation at every stage of my training period. I would

also like to take this opportunity to acknowledge the guidance from

DR. DEEPAK ARYA (HOD of computer science engg.) and for undergoing training at a

reputed company like B.S.N.L.

I am also indebted to my parents and friends for their constant encouragement and

helping me in my endeavor. Last, but not the least, I would like to thank everyone

who has contributed for the successful completion of my training.

DESHBANDHU KUMAR

130240101020

(B. TECH VII SEMESTER – C.S.E)

3

CERTIFICATE

I hereby declare that the work which is being presented in this

training report entitled “SUMMER TRAINING”, towards the

partial fulfillment for the award of Bachelor of Technology in

Computer Science Engineering, submitted in the Department of

Computer Science Engineering at

Roorkee Institute of Technology, Roorkee, is record of my

work carried out from under the Guidance of B.S.N.L CTTC.

DATE: -

4

PREFACE

Organizations are made up of people and function through people. Without people,

organizations cannot exist. The resources of men, money, material, machinery, and

mechanism are connected, coordinated and utilized through people. Engineers need to

concentrate more on mechanism and the way in which things have been made. The

need of training arises for doing things yourself, understanding its way.

Practical exposure for doing things makes a person conversant to the technicalities

involved in any job. In view of such benefits, imparting of vocational training has

been made an integral part of any academic structure.

In B.S.N.L., training is given to Engineering Aspirants to secure future in the dynamic

world of telecommunications. Today telecommunication industry is one of the very

fastest growing industries in the world.

In this order, I have taken 40 days BSNL training. In my report, I try to introduce

Leased line concepts, WIMAX, Wi-Fi, optical fiber concepts and overview of

Intranet.

5

INTRODUCTION TO BSNL

India is the fourth largest telecom market in Asia after China, Japan and South Korea.

The Indian telecom network is the eighth largest in the world.

TYPE: COMMUNICATION SERVICE PROVIDER

COUNTRY: INDIA

AVAILABLITY: NATIONAL EXCEPT DELHI & MUMBAI

OWNER: THE GOVERNMENT OF INDIA

WEBSITE: www.bsnl.co.in

1.1 HOW BSNL CAME IN TELECOM MARKET:

The initial phase of telecom reforms began in 1984 with the creation of Center for

Department of Telematics (C-DOT) for developing indigenous technologies and

private manufacturing of customer premise equipment. Soon after, the Mahanagar

Telephone Nigam Limited (MTNL) and Videsh Sanchar Nigam Limited (VSNL)

were set up in 1986.The Telecom Commission was established in 1989. A crucial

aspect of the institutional reform of the Indian telecom sector was setting up of an

independent regulatory body in 1997 – the Telecom Regulatory Authority of India

(TRAI), to assure investors that the sector would be regulated in a balanced and fair

manner. In 2000, DoT corporatized its services wing and created Bharat Sanchar

Nigam Limited.

1.2 INSTITUTIONAL FRAMEWORK:

It is defined as the system of formal laws, regulations, and procedures, and informal

conventions, customs, and norms, that broaden, mold, and restrain socio-economic

activity and behavior. The country has been divided into units called Circles, Metro

Districts, Secondary Switching Areas (SSA), Long Distance Charging Area (LDCA)

and Short Distance Charging Area (SDCA).

In India, DoT is the nodal agency for taking care of telecom sector on behalf of

government.

Its basic functions are:

• Policy Formulation

• Review of performance

• Licensing

• Wireless spectrum management

• Administrative monitoring of PSUs

• Research & Development

• Standardization/Validation of Equipment

6

1.3 BSNL CONTRIBUTION TO DEVELOPMENT OF TELECOM:

Bharat Sanchar Nigam Limited was formed in year 2000 and took over the service

provider’s role from DOT. BSNL’s roadmap for providing customer with access to

the latest telecommunications services without losing sight of universal service access

has been by way of utilizing optimally the existing infrastructure and accelerating

advances in technological component by innovative absorption.

ACHIEVEMENTS OF BSNL:

• BSNL has a customer base of over 9 crores and is the fourth largest integrated

telecom operator in the country.

• BSNL is the market leader in Broadband, landline and national transmission network.

• BSNL is also the only operator covering over 5 lakh village with telecom connectivity.

• Area of operation of BSNL is all India except Delhi & Mumbai.

MAKING A TELEPHONE CALL

A telephone call starts when the caller lifts the handsets of the base. Once the dial

tone is heard, the caller uses a rotary or a push button dial mounted either on the

handset or on the base to enter a sequence of digits, the telephone number of called

party. The switching equipment from the exchange removes the dial tone from the

line after the first digit is received and after receiving the last digit, determines the

called party is in the same exchange or a different one. If the called is in the same

exchange, burst of ringing current is applied to the called party’s line. Each telephone

contains a ringer that responds to specific electric frequency. When the called, party

answers the telephone by picking up the handset, steady start to flow in the called

party’s line and is detected by the exchange. The exchange than stops applying

ringing and sets up the connection between the caller and the called party. If the called

party is in different exchange from the caller, the caller exchange set up the

connection over the telephone network to the called party’s exchange. The called

party then handles the process of ringing, detecting an answer, and notifying the

calling and billing machinery when the call is completed. When conversation is over,

one or both parties hang up by replacing their handset on the base, stopping the flow

of current. The exchange when initiates the process of taking down the connection,

including notifying billing equipment of the duration of the call if appropriate.

7

WORKING OF BASIC TELECOMMUNICATION 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.

2.1 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 2.1 HOW LINE REACHES FROM SUBSCRIBER TO EXCHANGE

(REF- 1)

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.

8

2.2 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.

2.3 CARRIER ROOM:

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

1. Conventional leased line system

2. MLLN

2.3.1 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.

• 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.

2.3.2 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.

2.4 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 2.2 MDF

(REF- 4)

9

2.4.1 FUNCTIONS OF MDF:

• All cable copper wires supplying services through user telephone lines are

terminated and distributed through MDF.

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

sides. Each jumper is a twisted wire.

• It consists of local connection and broadband connection frames for the main

Exchange area.

• 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.

2.5 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.

10

LEASED LINES

3.1 INTRODUCTION:

A leased line (dedicated line) is a permanent fiber optic or telephone connection

between two points set up by a telecommunications carrier. They can be used for

telephone, data, or Internet services. Businesses use a leased line to connect to

geographically distant offices because it guarantees bandwidth for network traffic. For

example, a bank may use a leased line in order to easily transfer financial information

from one office to another. Customers generally pay a flat monthly rate for the service

depending on the distance between the two points. Leased lines do not have telephone

numbers. The information sent through the leased line travels along dedicated secure

channels, eliminating the congestion that occurs in shared networks.

3.2 DRAWBACKS OF TRADITIONAL LEASED LINE CIRCUITS:

1. Limited range of services - Only Plain Leased Line Service, Data cards

support only up to 64 kbps, no support for N x 64 Kbps.

2. From Operator point of view in case of Leased Line Circuit different boxes

from different vendors so difficult to manage & control.

3. No Centralized Monitoring or alarm or performance monitoring.

The solution to this is MLLN.

3.3 MLLN (MANAGED LEASED LINE NETWORK):

The MLLN service is specially designed mainly for having effective control and

monitoring on the leased line so that the down time is minimized and the circuit

efficiency is increased. This mainly deals with data circuits ranging from 64 Kbps to

2048 Kbps.

11

3.3.1 MLLN FEATURES:

1. MLLN is an integrated, fully managed, multi service digital network platform

through which service provider can offer a wide range of service at an optimal

cost to business subscriber.

2. Using NMS, MLLN can provide high speed Leased Line with improved QoS,

high availability & reliability.

3. Except for connecting the local lead to the MODEM all operations &

maintenance is carried out through ROT (Remote Operating Terminal).

4. NMS supports service provisioning, Network optimization, planning & service

monitering.

5. System offers end to end circuit creation and modification, circuit loop testing &

fault isolation, automatic rerouting of traffic in case of trunk failure, software

programmability of NTU etc.

6. Banking, Financial institution, Stock market, paper industry, broadcasting &

Internet service Provider are the main customers for MLLN.

3.3.2 MLLN ADVANTAGES:

1. 24 hrs Performance Monitoring of the circuit.

2. Circuit fault reports generated proactively.

3. On Demand the Bandwidth can be increased.

4. Low lead time for new circuit provisioning.

5. Protection against the failure of the circuit through recovery Management

process either automatic or manually.

6. Long drive on single copper pair.( for 64 kbps – 7 kms & for 2mbps – 3.5 kms)

7. Centrally managed from ROT connected to the NMS.

12

INTRANET

4.1 INTRANET:

• Smaller private version of Internet. It uses Internet protocols to create

enterprise-wide network which may consists of interconnected LANs.

• It may or may not include connection to Internet.

• Intranet is an internal information system based on Internet technology and web

protocols for implementation within a corporate organization.

• This implementation is performed in such a way as to transparently deliver the

immense informational resources of an organization to each individual’s desktop

with minimal cost, time and effort.

• The Intranet defines your organization and displays it for everyone to see.

4.2 FEATURES OF INTRANET:

1. It is scalable.

2. It is Interchangeable.

3. It is platform independent

4. It is Hardware independent.

5. It is vendor independent.

4.3 WHY INTRANET FOR AN ORGANIZATION:

• Quick access to voice, video, data and other resources needed by users.

• Variety of valuable Intranet applications improves communication and

productivity across all areas of an enterprise.

• A 21st Century Telephone.

• An ISO Tool.

• A Target Marketing Tool.

• A Decision-Making Tool.

• A Complete Communication Tool.

13

FIG 4.1 INTRANET NETWORK (REF- 5)

4.4 APPLICATIONS OF INTRANET:

• Publishing Corporate documents.

• Access into searchable directories.

• Excellent Mailing Facilities.

• Proper Sharing of Information.

• Developing Groupware Applications.

4.5 TECHNICAL OVERVIEW OF THE INTRANET TECHNOLOGY

Intranet runs on open TCP/IP network, enable companies to employ the same type of

servers and browser used for World Wide Web for internal applications distributed

over the corporate LAN.

A typical Intranet implementation involves a high-end machine called a server which

can be accessed by individual PCs commonly referred to as clients, through the

network.

The Intranet site setup can be quite inexpensive, especially if your users are already

connected by LAN.

14

CORPORATE NETWORK

5.1 INTRODUCTION:

A corporate network (CN) is a closed and private computer network that affords

secure communications between geographically dispersed LANs of an enterprise.

Traditional networks

• Informal

• Socially oriented

• Had geographical boundaries

• Were expertise specific

• No access to corporate

resources

• Not self sufficient

• Not self sustainable

• No corporate governance

policies

An ideal network

• Formal

• Business oriented

• International infrastructure &

exposure

• Comprehensive expertise

• Access to substantial corporate

resources

• self sufficient

• Self sustainable

• Governed by strict values and

principles

TABLE 5.1 DIFFERERCES BETWEEN TRADITIONAL AND IDEAL

NETWORKS (REF- 2)

The requirement in a Corporate Network is same as ideal network.

5.2 WHY DO BUISNESSES HAVE CORPORATE NETWORK?

A business implements a corporate network to share applications and data between

different computing devices and users in different locations. Unless the application is

web based or database driven, this usually means copying files back and forth

between a network drive and a local computer, where a desktop application is used to

read and/or edit the files.

The increasing need to access corporate data from anywhere has led to changes in the

nature of applications, in current model of corporate network.

A typical corporate network has the following characteristics:

• Many LAN segments.

• More than one network protocol (IP or IPX).

• OSPF-configured areas, if it uses IP.

• Dial-up connectivity for users connecting from home or while traveling.

• Connectivity to external networks.

• Demand-dial connections to branch offices.

• Dedicated circuits to branch offices.

• A corporate network typically uses different types of network media. The

different office segments can be on 10-MB Ethernet or Token Ring networks,

15

but the backbone network used for connecting the different networks and

hosting servers is usually made up of 100-MB Ethernet. Connectivity to external

networks (the Internet) is over leased lines. Connectivity to branch offices is

either over dial-up line or dedicated media (leased lines).

FIG 5.1 CORPORATE NETWORK (REF- 5)

5.3 FEATURES OF CORPORATE NETWORK SECURITY:

• Complete bullet-proof protection of the remote computers you have on your

network.

• Executable patches can be easily uploaded to all your remote computers and

executed remotely.

• Easy and intuitive configuration without lots of complicated configuration files.

Everything is configured through the stand-alone GUI interface from any

location where TCP/IP connection to your corporate network can be established.

• You do not need to physically visit your workstations when you need to change

security settings or install patches.

• The remote client service application is bullet-proof. Your users will not be able

to disable, uninstall or delete it.

• All traffic between the server and the clients is encrypted. All local files are

encrypted as well.

• The server service application and the remote client service application work as

NT services under Windows NT/2000/XP and higher therefore they will keep

working in the logoff mode.

16

WI-FI (WIRELESS FIDELITY)

6.1 WI-FI NETWORK:

A Wi-Fi network provides the features and benefits of traditional LAN technologies

such as Ethernet and Token Ring without the limitations of wires or cables. It

provides the final few meters of connectivity between a wired network and the mobile

user. WIFI is a wireless LAN Technology to deliver wireless broad band speeds up to

54 Mbps to Laptops, PCs, PDAs, dual mode Wi-Fi enabled phones etc.

6.2 WORKING OF WI-FI NETWORK:

In a typical Wi-Fi configuration, a transmitter/receiver (transceiver) device, called the

Access Point (AP), connects to the wired network from a fixed location using

standard cabling. A wireless Access Point combines router and bridging functions, it

bridges network traffic, usually from Ethernet to the airwaves, where it routes to

computers with wireless adapters. The AP can reside at any node of the wired

network and acts as a gateway for wireless data to be routed onto the wired network.

It supports only 10 to 30 mobile devices per Access Point (AP) depending on the

network traffic. Like a cellular system, the Wi-Fi is capable of roaming from the AP

and re-connecting to the network through another AP. Like a cellular phone system,

the wireless LAN is capable of roaming from the AP and re-connecting to the network

through other APs residing at other points on the wired network. This can allow the

wired LAN to be extended to cover a much larger area than the existing coverage by

the use of multiple APs such as in a campus environment. It may be used as a

standalone network anywhere to link multiple computers together without having to

build or extend a wired network.

FIG 6.1WI-FI NETWORK (REF- 5)

End users access the Wi-Fi network through Wi-Fi adapters, which are implemented

as cards in desktop computers, or integrated within hand-held computers. Wi-Fi

17

wireless LAN adapters provide an interface between the client Network Operating

System (NOS) and the airwaves via an antenna.

6.3 BENEFITS OF WI-FI:

Wi-Fi offers the following productivity, conveniences, and cost advantages over

traditional wired networks:

• Mobility: Wi-Fi systems can provide LAN users with access to real-time

information anywhere in their organization.

• Installation Speed and Simplicity: Installing a Wi-Fi system can be fast and easy

and can eliminate the need to pull cable through walls and ceilings.

• Installation Flexibility: Wireless technology allows the network to go where

wire cannot go.

• Reduced Cost-of-Ownership: While the initial investment required for Wi-Fi

hardware can be higher than the cost of wired LAN hardware, overall

installation expenses and life-cycle costs can be significantly lower.

• Scalability: Wi-Fi systems can be configured in a variety of topologies to meet

the needs of specific applications and installations. Configurations are easily

changed and range from peer-to-peer networks suitable for a small number of

users to full infrastructure networks of thousands of users that allows roaming

over a broad area.

• It offers much high speed up to 54 Mbps which is very much greater than other

wireless access technologies like CORDECT, GSM and CDMA.

6.4 LIMITATIONS OF WI-FI:

• Coverage: A single Access Point can cover, at best, a radius of only about 60

meters. For 10 square kms area roughly 650 Access Points are required, where

as CDMA 2000 1xEV-DO require just 09 sites.

• Roaming: It lacks roaming between different networks hence wide spread

coverage by one service provider is not possible, which is the key to success of

wireless technology.

• Backhaul: Backhaul directly affects data rate service. Wi-Fi real world data

rates are at least half of their theoretical peak rates due to factors such as signal

strength, interference and radio overhead. Backhaul reduces the remaining

throughput further.

• Interference: Wi-Fi uses unlicensed spectrum, which mean no regulator recourse

against interference. The most popular type of Wi-Fi, ‘802.11’b uses.

18

WIMAX

7.1 WIRELESS BROADBAND SERVICES:

There are two fundamentally different types of broadband wireless services. The first

type attempts to provide a set of services similar to that of the traditional fixed-line

broadband but using wireless as the medium of transmission. This type, called fixed

wireless broadband, can be thought of as a competitive alternative to DSL or cable

modem. The second type of broadband wireless, called mobile broadband, offers the

additional functionality of portability, nomadicity and mobility.

WI-MAX is an acronym that stands for World-wide Interoperability for

Microwave Access and this technology is designed to accommodate both fixed and

mobile broadband applications.

7.2 SALIENT FEATURES OF WIMAX:

• OFDM-based physical layer.

• Very high peak data rates.

• Scalable bandwidth and data rate support.

• Adaptive modulation and coding (AMC).

• Link-layer retransmissions.

• Support for TDD and FDD OFDMA.

• Flexible and dynamic per user resource allocation.

• Support for advanced antenna techniques.

• Quality-of-service support.

• Robust security.

• Support for mobility.

• IP-based architecture.

19

7.3 EVOLUTION OF BROADBAND WIRELESS:

1. NARROWBAND WIRELESS LOCAL-LOOP SYSTEMS: The first

application for which a wireless alternative was developed and deployed was voice

telephony. These systems, called wireless local-loop (WLL). WLL systems based on

the digital-enhanced cordless telephony (DECT) and code division multiple access

(CDMA) standards continue to be deployed in these markets. During the same time,

several small start-up companies focused solely on providing Internet-access services

using wireless, antennas to be installed at the customer premises. These early

systems typically offered speeds up to a few hundred kilobits per second. Later

evolutions of license-exempt systems were able to provide higher speeds.

2. FIRST-GENERATION BROADBAND SYSTEMS: As DSL and cable modems

began to be deployed, wireless systems had to evolve to support much higher speeds

to be competitive. Very high speed systems, called local multipoint distribution

systems (LMDS), supporting up to several hundreds of megabits per second, were

developed.

In the late 1990s, one of the more important deployments of wireless broadband

happened in the so-called multi channel multipoint distribution services (MMDS)

band at 2.5GHz. The MMDS band was historically used to provide wireless cable

broadcast video services, especially in rural areas where cable TV services were not

available. The first generations of these fixed broadband wireless solutions were

deployed using the same towers that served wireless cable subscribers. These towers

were typically several hundred feet tall and enabled LOS coverage to distances up to

35 miles, using high-power transmitter.

The advent of satellite TV ruined the wireless cable business, and operators were

looking for alternative ways to use this spectrum. A few operators began to offer one-

way wireless Internet-access service, using telephone line as the return path.

3. SECOND-GENERATION BROADBAND SYSTEMS: Second-generation

broadband wireless systems were able to overcome the LOS issue and to provide

more capacity. This was done through the use of a cellular architecture and

implementation of advanced-signal processing techniques to improve the link and

system performance under multi path conditions. Many solved the NLOS problem by

using such techniques as orthogonal frequency division multiplexing (OFDM), code

division multiple access (CDMA), and multi antenna processing.

4. WIMAX AND OTHER BROADBAND WIRELESS TECHNOLOGIES:

WIMAX is not the only solution for delivering broadband wireless services. WiMAX

occupies a somewhat middle ground between Wi-Fi and 3G technologies when

compared in the key dimensions of data rate, coverage, QoS, mobility, and price.

20

7.3 WIMAX NETWORK ARCHITECTURE:

The overall network may be logically divided into three parts:

1. Mobile Stations (MS) used by the end user to access the network.

2. The access service network (ASN), which comprises one or more base stations

and one or more ASN gateways that form the radio access network at the edge.

3. Connectivity service network (CSN), which provides IP connectivity and all the

IP core network functions.

ASN-ACCESS SERVICES NETWORK

NAP-NETWORK ACCESS PROVIDER

CSN- CORE SERVICES NETWORK

NSP- NETWORK SERVICES PROVIDER

BS- BAS STATION

HA-HOME AGENT

FA-FOREGN AGENT

AAA-AUTHENTICATION AUTHONZATION & ACCOUNTING

FIG 7.1 WIMAX NETWORK ARCHITECTURE (REF- 3)

BASE STATION (BS): The BS is responsible for providing the air interface to the

MSS. Additional functions that may be part of the BS are micro mobility management

functions, such as handoff triggering and tunnel establishment, radio resource

management, QoS policy enforcement, traffic classification, DHCP (Dynamic Host

Control Protocol) proxy, key management, session management, and multicast group

management.

21

ACCESS SERVICE NETWORK GATEWAY (ASN-GW): The ASN gateway

typically acts as a layer 2 traffic aggregation points within an ASN. Additional

functions that may be part of the ASN gateway include intra-ASN location

management and paging, radio resource management and admission control, caching

of subscriber profiles and encryption keys, AAA client functionality, establishment

and management of mobility tunnel with base stations, QoS and policy enforcement,

and foreign agent functionality for mobile IP, and routing to the selected CSN.

CONNECTIVITY SERVICE NETWORK (CSN): The CSN provides connectivity

to the Internet, ASP, other public networks, and corporate networks. The CSN is

owned by the NSP and includes AAA servers that support authentication for the

devices, users, and specific services. The CSN also provides per user policy

management of QoS and security. The CSN is also responsible for IP address

management, support for roaming between different NSPs, location management

between ASNs, and mobility and roaming between ASNs, subscriber billing and inter

operator settlement, inter-CSN tunneling to support roaming between different NSPs.

GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM)

In wireless communication, every region is divided into cells. Cell size is constant for

whole system. GSM is a form of multiplexing, which divides the available bandwidth

among the different channels. Most of the times the multiplexing used is either TDM

(Time division multiplexing) or FDM (Frequency Division Multiplexing). SM differs

from its predecessor technologies in that both signaling and speech channels are

digital, and thus GSM is considered a second generation (2G) mobile phone system.

FIG 8.1 (REF- 4)

8.1 MAIN FEATURES OF GSM:

• Support for voice and data services

• Better frequency efficiency, smaller cells and more customers per cell

• High audio quality and reliability for wireless, uninterrupted phone calls at higher

speeds (e.g. from cars, trains) i.e. high transmission quality.

• Authentication via chip-card and PIN.

• Worldwide connectivity.

22

8.2 GSM SUBSYSTEMS:

• RADIO SUBSYSTEM (RSS)

• NETWORK AND SWITCHING SUBSYSTEM (NSS)

8.2.1 RADIO SUBSYSTEM:

MOBILE STATION (MS):

A mobile unit is a transmitter as well as receiver too. It has a SIM (Subscriber Identity

Module) which gives a unique identity of a subscriber. Every mobile unit has a unique

IMIE (International Mobile Equipment Identity) number.

BASE TRANSCEIVER STATION (BTS):

• A base transceiver station or cell site (BTS) is a piece of equipment that facilitates

wireless communication between user equipment (UE) and a network.

• It encodes, encrypts, modulates and feeds the RF signal to antenna.

• It produces time and frequency synchronization signals.

• It does power control and frequency hopping too.

BASE STATION CONTROLLER (BSC):

• Its main work is to control several transceivers.

• Switching between BTSs

• Managing of network resources

• Mapping of radio channels

8.2.2 NETWORK AND SWITCHING SUBSYSTEM:

This subsystem does mainly switching, mobility management, interconnection to

other networks, system control.

COMPONENTS:

1. MOBILE SERVICES SWITCHING CENTRE (MSC):

It controls all connections via a separated network to/from a mobile terminal within

the domain of the MSC – several BSC can belong to a MSC.

2. DATABASES:

Home Location Register (HLR):

Central master database containing user data, permanent and semi-permanent data of

all subscribers assigned to the HLR (one provider can have several HLRs).

Visitor Location Register (VLR):

Local database for a subset of user data, including data about all user currently in the

domain of the VLR.

23

8.2.3FUNCTION OF MAIN SWITCHING CENTER (MSC):

• Manages communication between GSM and other network (PSTN, Data

Network and GPRS).

• Call setup basic switching, call handling.

• Location register

• Billing for subscriber

8.3 FEATURES OF GSM:

• GSM is already used worldwide with over 450 million subscribers.

• International roaming permits subscribers to use one phone throughout Western

Europe. CDMA will work in Asia, but not France, Germany, the U.K. and other

popular European destinations.

• GSM is mature, having started in the mid-80s. This maturity means a more stable

network with robust features. CDMA is still building its network.

• The availability of Subscriber Identity Modules, which are smart cards that

provide secure data encryption give GSM m-commerce advantages.

GENERAL PACKET RADIO SERVICE (GPRS)

General packet radio service (GPRS) is a packet oriented mobile data service

available to users of the 2G cellular communication systems, global system for mobile

communications (GSM), as well as in the 3G systems. In 2G systems, GPRS provides

data rates of 56-114 kbps. It provides moderate speed data transfer, by using unused

time division multiple access (TDMA) channels.

Its supported protocols are Internet Protocol (IP), Point to Point Protocol (PPP) and

X.25.

GPRS data transfer is typically charged per megabyte of traffic transferred, while data

communication via traditional circuit switching is billed per minute of connection

time, independent of whether the user actually is using the capacity or is in an idle

state. GPRS is a best effort packet switched service, as opposed to circuit switching,

where a certain Quality of service (QoS) is guaranteed during the connection for non-

mobile users.

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GPRS extends the GSM circuit switched data capabilities and makes the following

services possible:

• “Always on” Internet access

• Multimedia messaging service (MMS)

• Push to talk over cellular (PoC/PTT)

• Instant messaging and presence – wireless village

• Internet applications for smart devices through wireless application protocol

(WAP)

• Point to Point (P2P) service: inter-networking with the internet (IP).

• Increase message sending speed 30 messages per minute approximately.

CODE DIVISION MULTIPLE ACCESS (CDMA)

Code Division Multiple Access (CDMA) consistently provides better capacity for

voice and data communications that other commercial mobile technologies, allowing

more subscribers to connect at any given time, and it is the common platform on

which 3G technologies are built.

CDMA is a spread spectrum technology, allowing many users to occupy the same

time and frequency allocations in a given band/space. As it names implies, CDMA

assigns unique codes to each communication to differentiate it from others in the

same spectrum resources, CDMA enables many more people to share the airwaves at

the same time than do alternative technologies.

10.1 ADVANTAGES OF CDMA:

• Increased cellular communications security.

• Simultaneous conversations

• Increased efficiency, meaning that the carrier can serve more subscribers.

• Smaller phones

• Low power requirements and little cell-to-cell coordination needed by

operators.

• Extended reach-beneficial to rural users situated far from cells.

10.2 DISADVANTAGES OF CDMA:

• Due to its proprietary nature, all of CDMA’s flaws are not known to the

engineering community.

• CDMA is relatively new, and the network is not as mature as GSM.

• CDMA cannot offer international roaming, a large GSM advantage.

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10.3 DIFFERENCE BETWEEN CDMA AND GSM:

• The GSM stands for global system for mobile communication and CDMA for

code division multiple accesses.

• GSM is a form of multiplexing, which divides the available bandwidth among

the different channels. Most of the times the multiplexing used are either TDM

(Time Division Multiplexing) or FDM (Frequency Division Multiplexing). On

the other hand, CDMA is a type of multiple access scheme (which means

allotting the given bandwidth to multiple users) and makes use of spread

spectrum technique which is essentially increasing the size of spectrum.

• In CDMA, each user is provided a unique code and all the conversations

between 2 users are coded. This provides a greater level of security to CDMA

users than the GSM ones.

FIBER OPTIC TRANSMISSION SYSTEM

11.1 INTRODUCTION:

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.

FIG 11.1 OPTICAL FIBER TRANSMISSION (REF- 1)

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11.2ARCHITECTURE OF 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. 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.

FIG 11.2 PROPAGATION OF LIGHT THROUGH FIBRE (REF- 1)

11.3 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)

(I) STEP-INDEX MULTIMODE FIBER: It 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. This type of

fiber is best suited for transmission over short distances, in an endoscope, for instance.

(II) GRADED-INDEX MULTIMODE FIBER: It 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. A digital pulse suffers less

dispersion.

(III) SINGLE-MODE FIBER: It 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.

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11.4 ADVANTAGES OF FIBRE OPTICS:

• 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.

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CONCLUSION

Engineering student will have to serve in the public and private sector industries and

workshop based training and teaching in classroom has its own limitation. The lack of

expo sure to real life, material express and functioning of industrial organization is the

measure hindrance in the student employment.

In the open economy era of fast modernization and tough competition, technical

industries should procedure pass out as near to job function as possible.

Practical training is one of the major steps in this direction. I did my training from

BSNL, Bharatpur which is one of the best-known communication service provider

companies of India. The training helps me in gaining in depth knowledge of the

working of telephone exchange, various technologies of BSNL –GSM, GPRS,

WIMAX, Wi-Fi, MLLN and optical fiber transmission.

In the end, I hereby conclude that I have successfully completed my industrial training

on the above topics.