Seminar on Practical Training at BSNL

Presented by:Ayush Anand

B. Tech , ECE , 7th SemSri Balaji College of Engineering & Technology, Jaipur

“Telecommunication”

Introduction

• 4th largest telecommunication company in Asia and 7th largest in the world.

• Provides GSM and basic telephony service and first company in India providing 3G technology.

• More than 3 lacs of employees, officers and engineers are working at present.

Glimpse at Company Profile

WHAT IS WIRELESS ?The word wireless is dictionary defined “having no wires ” .In networking terminology , wireless is the term used to describe any computer network where there is no physical wired connection between sender and receiver, but rather the network is connected by radio waves and or microwaves to maintain communications.

Wireless networking utilizes specific equipment such as NICs and Routers in place of wires (copper or optical fibre).

Multiple Access Schemes

• Frequency Division Multiple Access (FDMA)• Time Division Multiple Access (TDMA)• Code Division Multiple Access (CDMA)

3 orthogonal Schemes:

Frequency Division Multiple Access

• Each mobile is assigned a separate frequency channel for the duration of the call.

• Sufficient guard band is required to prevent adjacent channel interference.

• Usually, mobile terminals will have one downlink frequency band and one uplink frequency band

• Different cellular network protocols use different frequencies

Time Division Multiple Access

• Time is divided into slots and only one mobile terminal transmits during each slot.

• Each user is given a specific slot. No competition in cellular network

Code Division Multiple Access

• Use of orthogonal codes to separate different transmissions• Each symbol of bit is transmitted as a larger number of

bits using the user specific code – Spreading• Bandwidth occupied by the signal is much larger than the

information transmission rate• But all users use the same frequency band togetherOrthogonal among users

Evolution of Cellular Networks

1G 2G 3G 4G2.5G

GSM architecture

Global System for Mobile CommunicationServicesArchitecture

GSM Services• Voice, 3.1 kHz• Short Message Service (SMS) • 1985 GSM standard that allows messages of at most 160

chars. (incl. spaces) to be sent between handsets and other stations

• Over 2.4 billion people use it; multi-billion $ industry• General Packet Radio Service (GPRS)• GSM upgrade that provides IP-based packet data

transmission up to 114 kbps• Users can “simultaneously” make calls and send data• GPRS provides “always on” Internet access and the

Multimedia Messaging Service (MMS) whereby users can send rich text, audio, video messages to each other

• Performance degrades as number of users increase• GPRS is an example of 2.5G telephony – 2G service

similar to 3G

GSM Frequencies• Originally designed on 900MHz range, now

also available on 800MHz, 1800MHz and 1900 MHz ranges.• Separate Uplink and Downlink frequencies• One example channel on the 1800 MHz

frequency band, where RF carriers are space every 200 MHz

1710 MHz 1880 MHz1805 MHz1785 MHz

UPLINK FREQUENCIES DOWNLINK FREQUENCIES

UPLINK AND DOWNLINK FREQUENCY SEPARATED BY 95MHZ

Architecture of GSM

Network subsystemPerforms call processing and subscriber related functions. It includes:

MSC: Mobile Switching CentreHLR: Home Location RegisterVLR : Visitor Location RegisterAuC: Authentication CentreEIR: Equipment Identity RegisterGMSC:Gateway MSC.

The functions carried out by the MSC are listed below:

Call ProcessingCall SwitchingOperations And Maintenance SupportInternetwork Networking

When the MSC provides the interface with the other networks in the GSM network it is known as a Gateway MSC.

Mobile Switching Centre

Subscriber ID (IMSI & MSIN).

Current location of subscriber.

Subscriber status (registered/unregistered)

Authentication key and AUC functionality.

Mobile subscriber roaming number.

Home Location Register

• Provides local database for subscriber when they are away from home.

It contains:• Mobile status(busy/free/no ans)

• Location area identity(LAI)

• TMSI AND MSIN .

Visitor Location Register

• Provides authentication and encryption.

• Ensures confidentiality of each cell.

• Protects network operators from frauds.

• Associated with HLR.

• Takes place each time the subscriber initializes” on the system.

Authentication Centre

• Centralized database for validating the IMEI (International Mobile Station Eqipment Identity).

• It contains three lists-White ListBlack ListGrey List

Eqipment Identity Register

Base Transceiver Station

• Maintains air interface and minimize transmission problems.

• Radio level power control.• BTS identification.• Ciphering (Encryption).• Speech processing.

Base Station Controller

It is connected to MSC.Controls one or more

BTS.Switches traffic and

signaling to/from BTSs and MSC.

Controls handover performed by BTS.

Frequency allocation and power control.

• A leased line is a telecommunications path between twopoints that is available 24 hours a day for use by a designated user (Individual or company).

• These leased lines can carry data, voice and videoinformation. It is not shared in common among multiple users as dialup line.

DEPARTMENT : MLLN

DEPARTMENT : C-DOT

• It stands for Center for Development of Telematics

• Digital Telephone Exchange runs on this technique

• Call processing of Landline Networks

• STD / ISD / LOCAL

DEPARTEMNT: Transmission

• Optical fiber communication

• Splicing

• Detection of faults

• Rectification

Thanks for your attention !

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