A SEMINAR REPORT ON CELLULAR SYSTEM Introduction to cellular system The cellular concept was developed and introduce by the bell laboratories in the.

A SEMINAR REPORT

ON

CELLULAR SYSTEM

Introduction to cellular system The cellular concept was developed and introduce by the bell laboratories in the early 1970.One of the successful initial implementation of the cellular concept was the advanced mobile phone system (AMPS). Thus the system of cellular system is divide a large geographic service area into cells with diameters from 2 to 50 km, each of which is allocated a number of radio frequency (RF) channel. One of many reasons for developing a cellular mobile

telephone system and developing it in many cities is the operational limitations of conventional mobile telephone systems: limited services capability, poor service performance, and inefficient frequency spectrum utilization.

Cellular IdentifiersCellular Identifiers

In AMPS, a cell phone subscription is identified using three numbers:

– Electronic Serial Number (ESN): unique 32 bit number programmed into the cell when it was manufactured.

– Mobile Identification Number (MIN): 10 digit phone number.

– System Identification Code (SID): Unique 5 bit code assigned by the FCC to each service provider.

Multiple Access MethodsMultiple Access Methods

There are three common technologies used by cell-phone networks for transmitting information: – Frequency division multiple access (FDMA) – Time division multiple access (TDMA) – Code division multiple access (CDMA)

FDMA puts each call on a separate frequency band. TDMA assigns each call a certain portion of time on a

designated frequency band. CDMA gives a unique code to each call and spreads it

over the available frequencies.

TDMA: A Digital Cellular TDMA: A Digital Cellular MethodMethod

The benefit of digital cellular systems over the FDMA analog systems can be seen by looking a simple gain offered by a digital TDMA system.

This gain is result of a property of human speech. Human speech (generally sound) is caused by minute

changes in the air pressure. When a caller speaks on his/her phone, the microphone

records these varying pressure changes into varying electronic signals.

For example, here is a graph showing the analog wave created by saying the word "hello“.

CDMA StandardCDMA Standard

All users transmit in the same wide-band chunk of spectrum.

Each user's signal is spread over the entire bandwidth by a unique spreading code.

At the receiver, that same unique code is used to recover the signal.

CDMA systems need to put an accurate time-stamp on each piece of a signal; they reference the GPS system for this information.

Features of GSM:Good subjective speech quality Low terminal and service cost Support for international roaming Ability to support handheld terminals Support for range of new services and facilities Spectral efficiency ISDN compatibility

The GSM architecture is based on three parts:-

The Mobile Station

The Base Station Subsystem

The network subsystem

Mobile Station:

The mobile station (MS) consists of the mobile equipment (the terminal) and a smart card called the Subscriber Identity Module (SIM).

Each mobile device has a globally unique IMEI (international mobile equipment identity) and each SIM has a IMSI (international mobile subscriber identity),which is used to identify and authorize the subscriber for various services.

Base Station Subsystem: The Base Station Subsystem is composed of two parts, the Base Transceiver Station (BTS) and the Base Station Controller (BSC).The Base Transceiver Station houses the radio transceivers that define a cell and handles the radio-link protocols with the Mobile Station. The Base Station Controller manages the radio resources for one or more BTSs. The BSC is the connection between the mobile station and the Mobile service Switching Center (MSC).

Network subsystem:The MSC is the central component of the network subsystem. It communicates with all the BSCs and is responsible for providing all the functionalities to mobile devices like registration authentication,call routine etc. a network also,usually, as GMSC(gateway MSCs) to communicate with external(landline)networks like ISDN,PSTN etc. Register like HLR (home location register) stores information about the current location of subscribers of the network. VLR (visitor location register) covers one or more cells and stores information about the subscribers currently under its area of influence.

What happens when you What happens when you receive a call?receive a call?

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

Recall: control channel is special frequency that the phone and base station use to talk to each other about things like call setup and channel changing, etc.

If phone cannot find any control channels, then it is out of range and it lights up the “No Service” light.

CONCLUSION

In this paper I gave the general flavor of GSM and the philosophy behind its design.

GSM is compatible with the Integrated Services Digital Network (ISDN) that is evolving in most industrialized countries, and Europe in particular (the so-called Euro-ISDN)

GSM is also the first system to make extensive use of the Intelligent Networking concept, in which services like 800 numbers are concentrated and handled from a few centralized service centers, instead of being distributed over every switch in the country.

GSM is a very complex standard, but that is probably the price that must be paid to achieve the level of integrated service and quality offered while subject to the rather severe restrictions imposed by the radio environment