SIX MONTH INDUSTRIAL TRAINING REPORT

(JAN – JUNE 2011)

Submitted in the partial fulfilment of the requirements

for the 8th semester curriculum of degree of

Bachelor of Technology

in

Electronics and communication Engineering

Of

PUNJAB TECHNICAL UNIVERSITY, JALANDHAR

Under the guidance of: Er.Sukhdev Singh(HOD)

Submitted By:

(Name of the Teachers/ Industry Instructor) Name:Jagveer Singh

Inst Roll No:8214/08-L

Uni. Regd. No:80302508013

Department of Electronics & Communication Engineering

GURU TEG BAHADUR INSTITUTE OF ENGINEERING & TECHNOLOGY

CHHAPIAN WALI (MALOUT)

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CERTIFICATE

Certified that this six month industrial Training (Date from Jan. To June)

done by (Jagveer Singh, Uni. Regd. No.-80302508013.) in partial fulfilment of

requirements for the 8th

semester of Bachelor of Technology, Electronics &

communication Engg. Submitted to Guru Teg Bahadur Khalsa Institute of

Engineering & Technology, Chhapianwali (Malout) is a record to student’s

own work carried under.

------Er. Gaurav Nagpal-----

This has not been submitted to any other university or Institute as a part of

curriculum of any degree to

the best of my knowledge.

(Name :Jagveer Singh)

(HOD, Er. Sukhdev Singh)

GTBKIET, Chhapianwali (Malout)

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Table of Contents

ACKNOWLEDGEMENT .................................................................. 3

COMPANY PROFILE ........................................................................ 4

INTRODUCTION ............................................................................... 6

EVOLUTION OF GSM ...................................................................... 9

DESCRIPTION ................................................................................. 11

EVOLUTION OF CDMA..................................................................33

CONCLUSION ................................................................................. 43

BIBLIOGRAPHY ............................................................................. 46

ANNEXURE………………………………………………………..47

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ACKNOWLEDGEMENT

I take this opportunity with much pleasure to express my sincere thanks and gratitude to Miss

Monika Mehta (Manager), Kross infotel ltd. Chandigarh. It gives me immense pleasure to extend my

gratitude towards Er. Gaurav Nagpal (Quality Engineer), Kross infotel ltd. Chandigarh and the

entire Network.

In addition, I wish to thank Kross infotel ltd. Chandigarh office to provide me the opportunity to

acquire the experience of knowing the corporate world and also providing the required facilities, well

working systems, besides complete collection of all latest technology software’s.

I am especially grateful to the professors and lecturers of our institute ‘G.T.B.K.I.E.T’, who has been

training us, since the first day, with the knowledge and support in the most lucid manner.

It was really a good experience working in a professionally managed firm and learning from such

good and knowledgeable people. I hope it will really help me in future.

(Jagveer Singh)

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COMPANY PROFILE

Kross infotel ltd. Chandigarh formerly known as vender of Reliance , Tata

Indicom,Videocon is an Indian company offering telecommunication services in

around country. It is the largest cellular service provider in India, single-

country mobile operator and fifth largest telecom operator in the world in terms

of subscriber base. It also offers fixed line services and broadband services. It

offers its telecom services under the Kross infotel brand and is headed by Mr.

Sandeep Dhillon, who is the Chairman & Managing Director of the Company.

The company also provides land-line telephone services, under the trade name

‘Touchtel’ and broadband Internet access (DSL) in over 96 cities in India.

Kross infotel is known for being the first vender company in the world to

outsource everything except marketing and sales and finance. Its network (base

stations, microwave links, etc.) is maintained by Ericsson and Nokia Siemens

Network, business support by IBM and transmission towers by another

company. Ericsson agreed for the first time, to be paid by the minute for

installation and maintenance of their equipment rather than being paid up front.

During the last financial year (2009-10), Kross infotel has roped in a strategic

partner Alcatel-Lucent to manage the network infrastructure for the Telemedia

Business.

The tabulated summary of various partnering companies is as under:

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Network

Equipment

Mobile Services Nokia Siemens, Ericsson, Huawei

Telemedia & Long Distance

Services

Nokia Siemens, Juniper, Cisco, Alcatel Lucent,

ECI, Tellabs

Information Technology IBM

Call Centre Operations IBM Daksh, Hinduja TMT, Teleperformance,

Mphasis, First source & Aegis

The company is structured into four strategic business units:

Mobile,

Telemedia,

Enterprise, and

Digital TV

The mobile business offers services in country across the Indian Subcontinent .

The Telemedia business provides broadband, IPTV and telephone services in 89

Indian cities. The Digital TV business provides Direct-to-Home TV services

across India. The Enterprise business provides end-to-end telecom solutions to

corporate customers and national and international long distance services to

telcos. In June 2010, Kross infotel as part of its global expansion strategy

acquired Zain Telcom of Kuwait. Kross infotel through the Zain deal .

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INTRODUCTION

.

GSM stands for ‘Global Services for Mobile communication' and is an open,

digital cellular technology used for transmitting mobile voice and data services.

GSM supports voice calls and data transfer speeds of up to 9.6 kbit/s, together

with the transmission of SMS (Short Message Service).

This technology is globally accepted and most popular among all countries. It is

started in Europe to integrate all countries with wireless communication. Earlier

each country in Europe has its own standard for wireless communication ,so due

to this a person cannot use the same mobile in two different country and cannot

even communicate with the same mobile in different countries, so due to this

fragmentation problem occurred. So to overcome this problem European Union

(EU) came with GSM technology that is accepted by whole continent and

standardized by ITU-T. It is a 2 G technology and world’s first cellular

technology and it is most popular 2G technology. Today GSM operator has

largest customer base. In India total cellular operator have more than 550

million customers and GSM has more than 400 million customer bases alone. It

is a second generation cellular standard developed to cater voice services and

data delivery using digital modulation.

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Objectives of GSM

To eliminate the fragmentation problem in European Union.

To allow interaction with ISDN and PSTN.

The Goals of GSM

Improved spectrum efficiency

International roaming

Low-cost mobile sets and base stations

High-quality speech

Compatibility with ISDN and other telephone

Company services.

Support for new services

Specifications and Characteristics for GSM:

Frequency band – the frequency range specified for GSM is 1,850 to

1,990 MHz (mobile station to base station).

Duplex distance – the duplex distance is 80 MHz. Duplex distance is the

distance between the uplink and downlink frequencies. A channel has two

frequencies, 80 MHz apart.

Channel separation – the separation between adjacent carrier frequencies.

In GSM, this is 200 kHz.

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Modulation – Modulation is the process of sending a signal by changing

the characteristics of a carrier frequency. This is done in GSM via

Gaussian minimum shift keying (GMSK).

Transmission rate – GSM is a digital system with an over-the-air bit rate

of 270 kbps.

Access method – GSM utilizes the time division multiple access (TDMA)

concept. TDMA is a technique in which several different calls may share

the same carrier. Each call is assigned a particular time slot.

Speech coder – 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.

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EVOLUTION OF GSM

In 1982, the European Conference of Postal and Telecommunications

administrations (CEPT) created the Group Special Mobile (GSM) to develop a

standard for a mobile telephone system that could be used across Europe. In

1987, a memorandum of understanding was signed by 13 countries to develop a

common cellular telephone system across Europe. Finally the system created by

SINTEF led by Torleiv Maseng was selected.

In 1989, GSM responsibility was transferred to the European

Telecommunications Standards Institute (ETSI) and phase I of the GSM

specifications were published in 1990. The first GSM network was launched in

1991 by Radio linja in Finland with joint technical infrastructure maintenance

from Ericsson. By the end of 1993, over a million subscribers were using GSM

phone networks being operated by 70 carriers across 48 countries.

GSM around the world

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GSM statistics in India

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DESCRIPTION

The basic architecture of the GSM is described in the figure below:

The abbreviations used in the figure above are described herein under:

HLR- Home Location Register:

HLR is database, which holds very important information of subscribers. It is

mostly known for storing and managing information of subscribers. It contains

subscriber service profile, status of activities, information about locations and

permanent data of all sorts. When new connections are purchased, these

subscribers are registered in HLR of mobile phone companies.

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MS-Mobile station:

It consists of mobile equipment and SIM. At the time of manufacturing, an

international mobile equipment number (IMEI) is programmed in ME.A SIM is

required to activate the GSM services. A international mobile subscriber

identification (IMEI) number is programmed along with security parameter and

algorithm. The called number is not linked to ME but to SIM.A SIM has

following data stored in it. MSISDN (mobile subscriber isdn) IMSI

(international mobile subscriber identity) - 15 digit number. TMSI (temporary

mobile subscriber identity) – 4 octets, allocated by VLR, continuously

changed.IMEI (international mobile equipment identity) unique, permanently

assigned to MS.

AUC- Authentication Center:

AUC is small unit which handles the security end of the system. Its major task

is to authenticate and encrypt those parameters which verify user’s

identification and hence enables the confidentiality of each call made by

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subscriber. Authentication center – AUC makes sure mobile operators are safe

from different frauds most likely to happen when hackers are looking for even

smallest loop wholes in systems.

MSC- Mobile Services Switching Center:

MSC is also important part of SS, it handles technical end of telephony. It is

build to perform switching functionality of the entire system. It’s most

important task is to control the calls to and from other telephones, which means

it controls calls from same networks and calls from other networks. Toll

ticketing, common channel signaling, network interfacing etc are other tasks

which MSC is responsible for.

.

VLR- Visitor Location Register:

VLR performs very dynamic tasks; it is database which stores temporary data

regarding subscribers which is needed by Mobile Services Switching Center-

MSC VLR is directly connected to MSC, when subscribe moves to different

MSC location, Visitor location register – VLR integrates to MSC of current

location and requests the data about subscriber or Mobile station (MS) from the

Home Location Register –HLR. When subscriber makes a call the Visitor

location register-VLR will have required information for making call already

and it will not required to connect to Home Register Location - HRL again.

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BSS-The Base Station System:

The base station system have very important role in mobile communication.

BSS are basically outdoor units which consist of iron rods and are usually of

high length. BSS are responsible for connecting subscribers (MS) to mobile

networks. All the communication is made in Radio transmission. The Base

station System is further divided in two systems. These two systems, they are

BSC, and BTS.

BTS – The Base Transceiver Station:

Subscriber, MS (Mobile Station) or mobile phone connects to mobile network

through BTS; it handles communication using radio transmission with mobile

station. As name suggests, Base transceiver Station is the radio equipment

which receive and transmit voice data at the same time. BSC control group of

BTSs.

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BASE TRANSIEVER STATION (BTS)

BSC – The Base Station Controller:

The Base Station normally controls many cells; it registers subscribers,

responsible for MS handovers etc. It creates physical link between subscriber

(MS) and BTS, then manage and controls functions of it. It performs the

function of high quality switch by handover over the MS to next BSC when MS

goes out of the current range of BTS, it helps in connecting to next in range

BTS to keep the connection alive within the network. It also performs functions

like cell configuration data, control radio frequency in BTS.

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SIM-Subscriber Identity Module:

One of the key features of GSM is the Subscriber Identity Module, commonly

known as a SIM card. The SIM is a detachable smart card containing the user's

subscription information and phone book. This allows the user to retain his or

her information after switching handsets. Alternatively, the user can also change

operators while retaining the handset simply by changing the SIM.

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OSS -The Operation and Support System:

OMC- Operations and maintenance center is designed to connect to equipment

of MSC- Mobile Switching Center and BSC-Base Station Controller. The

implementation of OMC is called OSS-The Operations and Support

System.OSS helps in mobile networks to monitor and control the complex

systems. The basic reason for developing operation and support system is to

provide customers a cost effective support and solutions. It helps in managing,

centralizing, local and regional operational activities required for GMS

networks.

Authentication & Encryption:

Authentication: - Whenever a MS requests access to a network, the network

must authenticate the MS. Authentication verifies the identity and validity of the

SIM card to the network and ensures that the subscriber is authorized access to

the network.

Encryption:- In GSM, encryption refers to the process of creating

authentication and ciphering crypto variables using a special key and an

encryption algorithm.

Ciphering:- Ciphering refers to the process of changing plaintext data into

encrypted data using a special key and a special encryption algorithm.

Transmissions between the MS and the BTS on the Um link, are enciphered.

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Ki:- The Ki is the individual subscriber authentication key. It is a 128-bit

number that is paired with an IMSI when the SIM card is created. The Ki is

only stored on the SIM card and at the Authentication Center (AuC). The Ki

should never be transmitted across the network on any link.

RAND:- The RAND is a random 128-bit number that is generated by the Auc

when the network requests to authenticate a subscriber. The RAND is used to

generate the Signed Response (SRES) and Kc crypto variables.

Signed Response:- The SRES is a 32-bit crypto variable used in the

authentication process. The MS is challenged by being given the RAND by the

network; the SRES is the expected correct response. The SRES is never passed

on the Um (Air) interface. It is kept at the MSC/VLR, which performs the

authentication check.

A3 Algorithm:- The A3 algorithm computes a 32-bit Signed Response (SRES).

The Ki and RAND are inputted into the A3 algorithm and the result is the 32-bit

SRES. The A3 algorithm resides on the SIM card and at the AuC.

A8 Algorithm:- The A8 algorithm computes a 64-bit ciphering key (Kc). The

Ki and the RAND are inputted into the A8 algorithm and the result is the 64-bit

Kc. The A8 algorithm resides on the ISM card and at the AuC.

Kc:- The Kc is the 64-bit ciphering key that is used in the A5 encryption

algorithm to encipher and decipher the data that is being transmitted on the Um

interface.

A5:- The A5 encryption algorithm is used to encipher and decipher the data that

is being transmitted on the Um interface. The Kc and the plaintext data are

inputted into the A5 algorithm and the output is enciphered data. The A5

algorithm is a function of the Mobile Equipment (ME) and not a function of the

SIM card. The BTS also makes use of the A5 algorithm.

There are three versions of the A5 algorithm:

A5/1:- The current standard for U.S. and European networks. A5/1 is a stream

cipher.

A5/2:- The deliberately weakened version of A5/1 that is intended for export to

non-western countries. A5/2 is a stream cipher.

A5/3:- A newly developed algorithm not yet in full use. A5/3 is a block cipher.

Triplets: - The RAND, SRES, and Kc together are known as the Triplets. The

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AuC will send these three crypto variables to the requesting MSC/VLR so it can

authenticate and encipher.

GSM Control Channels:

1. The Broadcast Channel [BCH].

2. The Common Control Channel [CCCH]

3. The Dedicated Control Channel [DCCH]

1. The Broadcast Channel [BCH]:

It operates on the forward link of specific ARFCN within each cell, and

transmits data only in the first time slot (TS0) of certain GSM frames.

It serves as a TDMA bacon channel for any nearby mobile to identify & lock

on to.

It provides synchronization for all mobiles within the cell.

It is occasionally monitored by mobiles in neighboring cell so that received

power MAHO decisions may be made by out of cell users.

The BCH is defined by three separate channels.

a. Broadcast Control Channel [BCCH].

b. Frequency Correction Channel [FCCH].

c. Synchronization Channel [SCH].

a) Broadcast Control Channel [BCCH]

It is a forward control channel that is used to broadcast following

information.

Cell & Network Identity.

Operating characteristics of cell such as current control channel structure,

channel availability and congestion.

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List of channels that are currently in use within the cell.

Information about BCCH is carried for the neighboring cells.

b) Frequency Correction Channel [FCCH]

It is a special data burst which occupies TS0 for the very first GSM frame &

is repeated every 10 frames within a control channel multi frame.

It allows each subscriber unit to synchronize its internal frequency to the

exact frequency of the BTS.

c) Synchronization Channel [SCH]:

It is broadcast in TS0 of the frame immediately following the FCCH frame.

It is also repeated every 10 frames within the control channel multi frame.

It is used to identify serving the BTS that is it is GSM BTS (Mobile transmits

BSIC (Base Station Identity Code); BSIC can only be decoded by GSM BTS.

It allows mobile to frame synchronize with BTS.

2. Common Control Channel [CCCH]

On the Broadcast channel ARFCN, these channels occupy TS 0 of every

GSM frame that is not otherwise used by the BCH.

The CCCH consists of three different channels,

o Paging Channel [PCH]

o Random Access Channel [RACH]

o Access Grant Channel [AGCH]

a. Paging Channel [PCH]:

It is used to broadcast the following information.

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Paging Signals from the BTS to all mobiles in the cell, & notify a specific

mobile of an incoming call which originates from PSTN.

The IMSI of the target subscribers, along with a request for acknowledgement

from the mobile unit on the RACH.

b. Random Access Channel [RACH]:

It is used for,

To acknowledge a Page from the PCH.

To originate call.

All mobiles must access or respond to PCH alert within TS 0 of a GSM

frame.

c. Access Grant Channel [AGCH]:

It is used for:

To respond RACH sent by a mobile in the previous CCCH frame.

To carry data this instructs the mobile to operate in a particular physical

channel with a particular dedicated control channel.

3. Dedicated Control Channels [DCCH]:

These channels are bi directional & have the same format & function on both

forward & reverse link.

They may exist in any time slot & on any ARFCN except TS 0.

a) Stand Alone Dedicated Control Channel [SDCCH].

b) Slow Associated Control Channel [SACCH].

c) Fast Associated Control Channel [FACCH].

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a) Stand Alone Dedicated Control Channel [SDCCH]:

It is used to send authentication and alert messages as the mobile

synchronizes itself with the frame structure and waits for TCH.

It is used for location updating.

b) Slow associated Control Channel [SACCH]:

It is always associated with a TCH or a SDCCH & maps onto the same

physical channel.

On the forward link it is used to send changing control information to the

mobile, such as transmit power level instructions.

The reverse SACCH carries information about the received signal

strengths, quality of TCH & BCH measurement results from neighboring

cells.c) Fast Associated Control Channel [FACCH]:

It is assigned whenever a SDCCH has not been dedicated for a particular

user and there is a urgent message to be conveyed.

It is assigned only to a traffic channel & relies on frame stealing to gain

access to the traffic channel.

Value added services

Call waiting:

With Call Waiting on a Hutch phone, you can receive and hold an incoming call

when you are already talking to another person. When this service is activated,

the network notifies you of a new incoming call while you have a call in

progress, which means that if another person tries calling you midway through a

conversation, he/she will hear a message informing him/her that your line is

busy, while you will hear beeps at intervals.

Call Divert:

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In case you are busy in a meeting, or if your cell phone is switched off, you can

forward incoming calls to a landline or another mobile phone - where someone

can receive messages on your behalf. You can also forward an incoming call

while speaking to someone.

Voice response services:

By using these services one can access information, download ringtones and

logos, and more. For this one has to just dial and speak on a no. for the desired

service. With Hutch World, one can enjoy a host of GPRS-based services

exclusively on Hutch GPRS phone. From astrology to photo messaging,

gaming, chat, news and even internet access.

Mail:

One can now send an SMS - without even using a mobile phone, from wherever

they are. All they need to do is type in their message and send it as e-mail.

Roaming:

Roaming is defined as the ability for a cellular customer to automatically make

& receive voice calls, send & receive data, or access other services when

traveling outside the geographical coverage area of the home network, by means

of using a visited network.

If the visited network is in the same country as the home network, this is known

as National Roaming. If the visited network is outside the home country, this is

known as International Roaming (the term Global Roaming has also been used).

If the visited network operates on a different technical standard than the home

network, this is known as Inter-standard roaming.

GSM Roaming, which involves roaming between GSM networks, offers the

convenience of a single number, a single bill and a single phone with worldwide

access to over 205 countries. The convenience of GSM Roaming has been a key

driver behind the global success of the GSM Platform.

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Mobile subscriber identities in GSM

International Mobile Subscriber Identity (IMSI):

An IMSI is assigned to each authorized GSM user. It consists of a mobile

country code (MCC), mobile network code (MNC) (to identify the PLMN), and

a PLMN unique mobile subscriber identification number (MSIN). The IMSI is

the only absolute identity that a subscriber has within the GSM system. The

IMSI consists of the MCC followed by the MNC and MSIN and shall not

exceed 15 digits.

Temporary Mobile Subscriber Identity (TMSI)

A TMSI is a MSC-VLR specific alias that is designed to maintain user

confidentiality. It is assigned only after successful subscriber authentication.

The correlation of a TMSI to an IMSI only occurs during a mobile subscriber’s

initial transaction with an MSC (for example, location updating). Under certain

condition (such as traffic system disruption and malfunctioning of the system),

the MSC can direct individual TMSIs to provide the MSC with their IMSI.

Mobile Station ISDN Number:

The MS international number must be dialed after the international prefix in

order to obtain a mobile subscriber in another country. The MSISDN numbers

is composed of the country code (CC) followed by the National Destination

Code (NDC), Subscriber Number (SN), which shall not exceed 15 digits. Here

too the first two digits of the SN identify the HLR where the mobile subscriber

is administrated.

The Mobile Station Roaming Number (MSRN):

The MSRN is allocated on temporary basis when the MS roams into another

numbering area. The MSRN number is used by the HLR for rerouting calls to

the MS. It is assigned upon demand by the HLR on a per-call basis. The MSRN

for PSTN/ISDN routing shall have the same structure as international ISDN

numbers in the area in which the MSRN is allocated. The HLR knows in what

MSC/VLR service area the subscriber is located. At the reception of the MSRN,

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HLR sends it to the GMSC, which can now route the call to the MSC/VLR

exchange where the called subscriber is currently registered.

International Mobile Equipment Identity:

The IMEI is the unique identity of the equipment used by a subscriber by each

PLMN and is used to determine authorized (white), unauthorized (black), and

malfunctioning (gray) GSM hardware. In conjunction with the IMSI, it is used

to ensure that only authorized users are granted access to the system.

Subscriber Authentication Key (Ki):

It is used to authenticate the SIM card.

Pin Unblocking Key (PUK)

In case of PIN, the PUK is needed for unlocking the SIM again. PUK is

numeric only, with eight digits. If a correct PUK is entered, an indication is

given to the user. After 10 consecutive incorrect entries the SIM is blocked.

Either the IMSI or the MSISDN Number may access the subscriber data. Some

of the parameters like IAI will be continuously updated to reflect the current

location of the subscriber. The SIM is capable of storing additional information

such as accumulated call charges. This information will be accessible to the

customer via handset key entry.

Personal Identity Number (PIN)

It is used to unlock the MS. If one enters the wrong PIN three times it will lock

the SIM. The SIM can be protected by use of PIN password.

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GSM Frequency Bands

There are a total of fourteen different recognized GSM frequency

bands. These are defined in 3GPP TS 45.005.

Band Uplink

(MHz)

Downlink

(MHz) Comments

380 380.2 - 389.8 390.2 - 399.8

410 410.2 - 419.8 420.2 - 429.8

450 450.4 - 457.6 460.4 - 467.6

480 478.8 - 486.0 488.8 - 496.0

710 698.0 - 716.0 728.0 - 746.0

750 747.0 - 762.0 777.0 - 792.0

810 806.0 - 821.0 851.0 - 866.0

850 824.0 - 849.0 869.0 - 894.0

900 890.0 - 915.0 935.0 - 960.0

P-GSM, i.e. Primary

or standard GSM

allocation

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Band Uplink

(MHz)

Downlink

(MHz) Comments

900 880.0 - 915.0 925.0 - 960.0

E-GSM, i.e.

Extended GSM

allocation

900 876.0 - 915 921.0 - 960.0 R-GSM, i.e. Railway

GSM allocation

900 870.4 - 876.0 915.4 - 921.0 T-GSM

1800 1710.0 -

1785.0

1805.0 -

1880.0

1900 1850.0 -

1910.0

1930.0 -

1990.0

There are three different frequency bands on which mobile phones are usually

operates and these are Dual Band, Tri-Band and Quad Band.

Dual Band : Dual frequency band operates on 900MHz and 1800 MHz,

that means mobile phone that supports dual band can be operated

anywhere in the world where 900 MHz and 1800 MHz frequencies are

used. Dual Band GSM networks usually found in all continents Europe,

Asia, Africa, Australia and South America.

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Tri-Band: three frequencies are supported in Tri Band, these frequencies

are 900 MHz, 1800MHz and 1900 MHz Tri band is also supported all

around the world these days.

Quad-Band: Quad Band supports four frequencies which are 850 MHz,

900 MHz, 1800 MHz , 1900 MHz Quad band also enables GSM phones

to road almost anywhere in the world. All countries support GSM

networks hence make communication possible.

Handover:

Handover, or handoff as it is called in North America, is the switching of an on-

going call to a different channel or cell. There are four different types of

handover in the GSM system, which involve transferring a call between

Channels (time slots) in the same cell,

Cells (Base Transceiver Stations) under the control of the same Base

Station Controller (BSC),

Cells under the control of different BSCs, but belonging to the same

Mobile services Switching Center (MSC), and

Cells under the control of different MSCs.

The first two types of handover, called internal handovers, involve only one

Base Station Controller (BSC). To save signaling bandwidth, they are managed

by the BSC without involving the Mobile service Switching Center (MSC),

except to notify it at the completion of the handover. The last two types of

handover, called external handovers, are handled by the MSCs involved. Note

that call control, such as provision of supplementary services and requests for

further handoffs, is handled by the original MSC.

Handovers can be initiated by either the mobile or the MSC (as a means of

traffic load balancing). During its idle time slots, the mobile scans the

Broadcast Control Channel of up to 16 neighboring cells, and forms a list of the

six best candidates for possible handover, based on the received signal strength.

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This information is passed to the BSC and MSC, and is used by the handover

algorithm.

The algorithm for when a handover decision should be taken is not specified in

the GSM recommendations. There are two basic algorithms used, both closely

tied in with power control. This is because the BSC usually does not know

whether the poor signal quality is due to multipath fading or to the mobile

having moved to another cell. This is especially true in small urban cells.

The 'minimum acceptable performance' algorithm [Bal91] gives precedence to

power control over handover, so that when the signal degrades beyond a certain

point, the power level of the mobile is increased. If further power increases do

not improve the signal, then a handover is considered. This is the simpler and

more common method, but it creates 'smeared' cell boundaries when a mobile

transmitting at peak power goes some distance beyond its original cell

boundaries into another cell.

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Key Features

SIM (Subscriber Identity Module)

It is a memory device which is used to store the information of user such as user

privacy number, 4 digit PIN number, subscriber identification number and user

information. Called number is not associated with mobile station but to SIM.

Increased Capacity

It provides better channel capacity than analog system. It provides 25KHZ per

user, that means eight conversation per 200KHZ channel pair(a channel pair

consists of a forward channel and a reverse channel). Channel coding and

modulation provided to enhance the channel capacity and from this 12 DB is

achieved as a channel to interference ratio(C/I ration), as compare to 18db of

analog system.

Frequency Hopping

It is a feature of GSM system in which frequency in a single channel

continuously hops and resultant provides a better coverage to a specific area.

Mobile Assisted Handover (MAHO)

GSM uses Mobile assisted handover technique. The mobile itself carries out

the signal strength and quality measurement of its server and signal strength

measurement of its neighbors. This data is passed on the Network which then

uses sophisticated algorithms to determine the need of handover.

Discontinuous Transmission

In this GSM has a advantage of preventing system from interference and noise

by offsetting the silent time between the conversation and by blocking the

undesired signals.

Support of Short Service Message (SMS)

GSM has a advantage of short service messages assisted by paging channel of

system.

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Frequency Reuse

GSM has a advantage of frequency reuse pattern from which same frequency

can be used in different cells. Normally 124 carriers are provided by the GSM

system and if we multiply it with the 7 time slots used for traffic than we get

868 numbers of calls can be made and that is very less in number. so to

overcome this problem same RF carrier is used for several conversation in

different cells and for this there is regular pattern is defined. The pattern to be

used depends on the traffic requirement and spectrum availability. Some typical

patter are 4/12 , 7/21 etc.

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Future Opportunities for GSM:

2nd Generation

GSM -9.6 Kbps (data rate)

2.5 Generation ( Future of GSM)

HSCSD (High Speed ckt Switched data)

Data rate : 76.8 Kbps (9.6 x 8 kbps)

GPRS (General Packet Radio service)

Data rate: 14.4 - 115.2 Kbps

EDGE (Enhanced data rate for GSM Evolution)

Data rate: 547.2 Kbps (max)

3 Generation

WCDMA(Wide band CDMA)

Data rate : 0.348 – 2.0 Mbps

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CDMA TECHNOLOGY

CODE DIVISION MULTIPLE ACCESS What is CDMA?

One of the most important concepts to any cellular telephone system is

that of "multiple access", meaning that multiple, simultaneous users can be

supported. In other words, a large number of users share a common pool of

radio channels and any user can gain access to any channel (each user is not

always assigned to the same channel). A channel can be thought of as merely a

portion of the limited radio resource which is temporary allocated for a specific

purpose, such as someone's phone call. A multiple access method is a definition

of how the radio spectrum is divided into channels and how channels are

allocated to the many users of the system.

CDMA is a "spread spectrum" technique in which each phone in a cell

uses a distinct code known to the base station to communicate with the base

station. All frequencies in one cell can be used in other cells.

The CDMA Cellular Standard

With CDMA, unique digital codes, rather than separate RF frequencies or

channels, are used to differentiate subscribers. The codes are shared by both the

mobile station (cellular phone) and the base station, and are called "pseudo-

Random Code Sequences." All users share the same range of radio spectrum.

For cellular telephony, CDMA is a digital multiple access technique

specified by the Telecommunications Industry Association (TIA) as "IS-95".

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In March 1992, the TIA established the TR-45.5 subcommittee with the

charter of developing a spread-spectrum digital cellular standard. In July of

1993, the TIA gave its approval of the CDMA IS-95 standard.

IS-95 systems divide the radio spectrum into carriers which are

1,250 kHz (1.25 MHz) wide. One of the unique aspects of CDMA

is that while there are certainly limits to the number of phone

calls that can be handled by a carrier, this is not a fixed number.

Rather, the capacity of the system will be dependent on a number

of different factors.

Current Cellular Standard

Different types of cellular systems employ various methods of multiple

access. The traditional analog cellular systems, such as those based on the

Advanced Mobile Phone Service (AMPS) and Total Access Communications

System (TACS) standards, use Frequency Division Multiple Access (FDMA).

FDMA channels are defined by a range of radio frequencies, usually expressed

in a number of kilohertz (kHz), out of the radio spectrum.

For example, AMPS systems use 30 kHz "slices" of spectrum for each

channel. Narrowband AMPS (NAMPS) requires only 10 kHz per channel.

TACS channels are 25 kHz wide. With FDMA, only one subscriber at a time is

assigned to a channel. No other conversations can access this channel until the

subscriber's call is finished, or until that original call is handed off to a different

channel by the system.

A common multiple access method employed in new digital cellular

systems is Time Division Multiple Access (TDMA). TDMA digital standards

include North American Digital Cellular (known by its standard number IS-54),

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Global System for Mobile Communications (GSM), and Personal Digital

Cellular (PDC).

TDMA systems commonly start with a slice of spectrum, referred to as

one "carrier". Each carrier is then divided into time slots. Only one subscriber at

a time is assigned to each time slot, or channel. No other conversations can

access this channel until the subscriber's call is finished, or until that original

call is handed off to a different channel by the system.

For example, IS-54 systems, designed to coexist with AMPS systems,

divide 30 kHz of spectrum into three channels. PDC divides 25 kHz slices of

spectrum into three channels. GSM systems create 8 time-division channels in

200 kHz wide carriers.

Multiple Access Comparison

It is easier to understand CDMA if it is compared with other multiple

access technologies. The following sections describe the fundamental

differences between a Frequency Division Multiple Access Analog technology

(FDMA), a Time Division Multiple Access Digital technology (TDMA) and a

Code Division Multiple Access Digital technology (CDMA).

FDMA - Frequency Division Multiple Access

FDMA is used for standard analog cellular. Each user is assigned a

discrete slice of the RF spectrum. FDMA permits only one user per channel

since it allows the user to use the channel 100% of the time. Therefore, only the

frequency "dimension" is used to define channels.

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TDMA - Time Division Multiple Access

The key point to make about TDMA is that users are still assigned a

discrete slice of RF spectrum, but multiple users now share that RF carrier on a

time slot basis. Each of the users alternate their use of the RF channel.

Frequency division is still employed, but these carriers are now further sub-

divided into some number of time slots per carrier.

A user is assigned a particular time slot in a carrier and can only send or

receive information at those times. This is true whether or not the other time

slots are being used. Information flow is not continuous for any user, but rather

is sent and received in "bursts." The bursts are re-assembled at the receiving

end, and appear to provide continuous sound because the process is very fast.

CDMA - Code Division Multiple Access

IS-95 uses a multiple access spectrum spreading technique called Direct

Sequence (DS) CDMA.

Each user is assigned a binary, Direct Sequence code during a call. The

DS code is a signal generated by linear modulation with wideband

Pseudorandom Noise (PN) sequences. As a result, DS CDMA uses much wider

signals than those used in other technologies. Wideband signals reduce

interference and allow one-cell frequency reuse.

There is no time division, and all users use the entire carrier, all of the

time.

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CDMA Technology

Though CDMA's application in cellular telephony is relatively new, it is

not a new technology. CDMA has been used in many military applications, such

as anti-jamming (because of the spread signal, it is difficult to jam or interfere

with a CDMA signal), ranging (measuring the distance of the transmission to

know when it will be received), and secure communications (the spread

spectrum signal is very hard to detect).

Spread Spectrum

CDMA is a "spread spectrum" technology, which means that it spreads

the information contained in a particular signal of interest over a much greater

bandwidth than the original signal.

The standard data rate of a CDMA call is 9600 bits per second (9.6

kilobits per second). This initial data is "spread," including the application of

digital codes to the data bits, up to the transmitted rate of about 1.23 megabits

per second. The data bits of each call are then transmitted in combination with

the data bits of all of the calls in the cell. At the receiving end, the digital codes

are separated out, leaving only the original information which was to be

communicated. At that point, each call is once again a unique data stream with a

rate of 9600 bits per second.

Traditional uses of spread spectrum are in military operations. Because of

the wide bandwidth of a spread spectrum signal, it is very difficult to jam,

difficult to interfere with, and difficult to identify. This is in contrast to

technologies using a narrower bandwidth of frequencies. Since a wideband

spread spectrum signal is very hard to detect, it appears as nothing more than a

slight rise in the "noise floor" or interference level. With other technologies, the

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power of the signal is concentrated in a narrower band, which makes it easier to

detect.

Increased privacy is inherent in CDMA technology. CDMA phone calls

will be secure from the casual eavesdropper since, unlike an analog

conversation, a simple radio receiver will not be able to pick individual digital

conversations out of the overall RF radiation in a frequency band.

Synchronization

In the final stages of the encoding of the radio link from the base station

to the mobile, CDMA adds a special "pseudo-random code" to the signal that

repeats itself after a finite amount of time. Base stations in the system

distinguish themselves from each other by transmitting different portions of the

code at a given time. In other words, the base stations transmit time offset

versions of the same pseudo-random code. In order to assure that the time

offsets used remain unique from each other, CDMA stations must remain

synchronized to a common time reference.

The primary source of the very precise synchronization signals required

by CDMA systems is the Global Positioning System (GPS). GPS is a radio

navigation system based on a constellation of orbiting satellites. Since the GPS

system covers the entire surface of the earth, it provides a readily available

method for determining position and time to as many receivers as are required.

"The Balancing Act"

CDMA cell coverage is dependent upon the way the system is designed.

In fact, three primary system characteristics - Coverage, Quality and Capacity -

must be balanced off of each other to arrive at the desired level of system

performance.

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In a CDMA system these three characteristics are tightly inter-related.

Even higher capacity might be achieved through some degree of degradation in

coverage and/or quality. Since these parameters are all intertwined, operators

can not have the best of all worlds: three times wider coverage, 40 times

capacity, and "CD" quality sound. For example, the 13 kbps vocoder provides

better sound quality, but reduces system capacity as compared to an 8 kbps

vocoder.

Operators will have the opportunity to balance these parameters to best

serve a particular area. The best balance point may change from cell site to cell

site. Sites in dense downtown areas may trade off coverage for increased

capacity. Conversely, at the outer edges of a system, capacity could be

sacrificed for coverage area.

CDMA Benefits

When implemented in a cellular telephone system, CDMA technology offers

numerous benefits to the cellular operators and their subscribers. The following

is an overview of the benefits of CDMA.

1. Capacity increases of 8 to 10 times that of an AMPS analog system and

4 to 5 times that of a GSM system.

2. Improved call quality, with better and more consistent sound as

compared to AMPS systems

3. Simplified system planning through the use of the same frequency in

every sector of every cell

4. Enhanced privacy

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5. Improved coverage characteristics, allowing for the possibility of fewer

cell sites

6. Increased talk time for portables

7. Bandwidth on demand

CDMA for Cellular

When implemented in a cellular telephone system, CDMA technology offers

numerous benefits to the cellular operator and their subscribers. These can be

summarized as follows:

Capacity increases: 8 to 10 times that of an AMPS analog system, and 4

to 5 times that of a GSM system.

Improved call quality: CDMA will provide better and more consistent

sound as compared to AMPS. Cellular telephone systems using CDMA

should be able to provide higher quality sound and phone calls than

systems based on other technologies.

Simplified system planning: Engineers will no longer have to perform the

detailed frequency planning which is necessary in analog and TDMA

systems.

Enhanced privacy: Increased privacy over other cellular systems, both

analog and digital, is inherent in CDMA technology.

Increased talk time and standby time for portables: Because of precise

power control and other system characteristics, CDMA subscriber units

normally transmit at only a fraction of the power of analog and TDMA

phones

Advanced Features: These include Multiple/High Quality Vocoders,

Short Messaging Services, Over-the-Air-Activation, Sleep Mode, and

Data/Fax.

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CDMA for Personal Communications Services (PCS)

Personal Communications Services (PCS) is anticipated to be the

"omnipresent" wireless communication system of the future - a vehicle through

which people can communicate to whomever they want, whenever they want,

wherever they want.

CDMA is a strong solution for PCS because it offers higher capacity and

increased range of coverage. By requiring fewer cell sites than traditional

analog and other digital systems, CDMA is viewed as the most cost effective

technology for PCS.

From enhanced spectral efficiency to improved call quality and feature

flexibility, CDMA offers a host of key benefits to wireless PCS operators.

Specifically, benefits which are especially relevant to PCS operators include:

Increased Capacity: In the long run, carriers who provide greater capacity

from the same spectrum will experience lower operating expenses than

operators who choose less spectrum-efficient technologies.

Audio Quality: CDMA has a number of unique features which provide a

superior, robust RF communications path to digital communications. The

qualities that allow CDMA to provide high quality voice performance

also ensure superior dropped call performance over existing cellular

systems.

Vocoder Flexibility: Different Vocoders can be used for product and

service differentiation.

Decreased Blocking: System capacity in CDMA is flexible and has a

"soft" limit. As a result, blocking is decreased since capacity can grow in

response to user demand.

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Enhanced Coverage: CDMA reduces the number of cells needed for

coverage compared to other air interfaces, while preserving robust audio

quality.

Low Deployment Cost: With a large advantage in link margin

(approximately 5 dB), a CDMA system requires approximately half the

number of cell sites for the same coverage area and system loading. This

efficiency lowers equipment and site acquisition costs, and is especially

cost-effective for new system deployment.

Motorola's SC™ hardware and software platform makes CDMA even more

attractive for PCS, considering its ability to grow with the needs of the market.

For example, MCC cards, which contain the traffic channels on the system, are

added to networks as customers' market penetration increases and more

subscribers are supported. In addition, the digital strategies Motorola employs in

its designs will ensure that in the future, the SC™ products have excellent

potential to decrease in size and in cost.

CDMA for Wireless Local Loop (WiLL™)

In many developing countries, there is tremendous demand for new business

and residential telephone service. More and more operators are looking to

wireless technologies to rapidly provide thousands of new subscribers with high

quality telephone service at a reasonable price. Motorola has introduced a set of

Wireless Local Loop (WiLL™) systems which can meet the telephony

requirements of many communities.

Existing landline operators can extend their network with WiLL™.

Cellular operators can capitalize on their current network to deliver

residential service with WiLL™.

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New service providers can quickly deploy non-traditional WiLL™

solutions to rapidly meet a community's telephony needs.

The unique features and benefits of CDMA make it an excellent technology

choice for fixed wireless telephone systems.

In a fixed telephony environment, CDMA is estimated to provide up to

15-20 times the capacity of an AMPS cellular system, resulting in the highest

capacity cellular-based offering for wireless local loop applications. The key to

this increased WiLL™ capacity is that, in a fixed environment, CDMA power

control is able to very accurately track required power, thereby resulting in

reduced overall transmission power and increased capacity. Subscribers in a

fixed environment require less RF power to achieve quality communications,

therefore more subscribers can be placed on a CDMA channel.

In addition, CDMA optimizes use of the radio spectrum, which is an

increasingly scarce resource worldwide. CDMA's single cell frequency re-use

capability and non-contiguous bandwidth requirement, along with its extended

coverage range, simplifies RF planning and implementation. This allows an

operator to invest in fewer cell sites with faster deployment, ultimately giving

the service provider increased and quicker access to revenues.

CONCLUSION

During the period of Evolution of mobile communication technologies various

systems were introduced and deployed to achieve standardization in mobile

industry, but all the efforts were failed. Multiple issues were sustained like

incompatibility of systems, development of digital radio frequency. That is,

when GSM (Global System for Mobile Communication) Technology was

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introduced and problems like standardization, incompatibility etc were

overcame. TDMA solution was chosen in 1987, it is narrowband system and

TDMA standards for Time Division Multiple access.

In 1991 in Finland. GSM based mobile phones are operated on TDMA Systems,

in TDMA single radio frequency is offered to users with any interference. After

all these years, GSM is now the largest mobile communication technology

worldwide, all manufacturers of Mobile phones develop their products based on

GSM, and all mobile companies provide their subscribers GSM networks.

GSM technology facilitates with high speed integrated data, voice data, fax,

mail, voice mail and mostly used SMS feature. GSM also make sure that all the

communication made between networks are secured and protected from

intruders and frauds.

.SM actually brought the concept of being Mobile way beyond the limits. It

enabled us to communicate across the continents.

GSM supports multiple frequency levels like 900 MHz, 1800 MHz, 1900 MHz

1900MHz frequency is used in North America where as 1800MHz is used in

other parts of the world. Different frequency bands are used by different mobile

phone operators.

Moreover, there are over 700 GSM networks available in the world operating in

their respective countries and providing international roaming services courtesy

GSM technology. There are over 2 billion GSM subscribers in the world.

Countries which are using GSM networks on larger scales are Russia, china

Pakistan, United States, India.

Giver the above facts and very good voice quality, support useful services and

standards, delivered by GSM, it is expected that GSM shall remain the

prominent technology for offering the mobile telephony.

The CDMA digital interface also allows for a number of complex and

unique features such as variable rate vocoders; robust error correction;

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frequency, space and time diversity; and multipath immunity. These features all

contribute to improved system and call quality.

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BIBLIOGRAPHY

1. http://en.wikipedia.org/wiki/GSM

2. http://www.gsmworld.com/ourwork/mobile_broadband/service_mar

k/index.htm

3. http://www.gsmworld.com/technology/index.htm

4. http://searchmobilecomputing.techtarget.com/definition/GSM

5. http://en.wikipedia.org/wiki/Code_division_multiple_access

6. http://www.webopedia.com/welcomead/

7. www.search.com

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Annexure

GSM: Global System for Mobile Communication

CEPT: Conference of European Posts and Telecommunications

ISDN: Integrated Services Digital Network

SIM: Subscriber Identity Module

VAS: Value Aided Services

BSS: The Base Station Subsystem

NSS: The Network and Switching Subsystem

OSS: The Operation and Support Subsystem

FDMA: Frequency Division Multiple Access

TDMA: Time Division Multiple Access

HLR: Home Location Register

MS: Mobile station

VLR: Visitor Location Register

AUC: Authentication Center

MSC: Mobile Services Switching Center

BTS : The Base Transceiver Station