GSM Technology

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Global

SystemFor

MobileCommunication

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Discussion Points

• What is GSM?• Evolution of GSM • Worldwide Deployment of GSM • GSM vs. CDMA• Generations of GSM• GSM architecture• Services of GSM• Characteristics and features• Advantages of GSM• Disadvantages of GSM• Applications of GSM• Conclusion• References

Prepared by :Avani Trambadiya

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What is GSM?

• The Global System for Mobile communications is a digital cellular communications system. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide.

– Formerly it was “Groupe Spéciale Mobile” (founded in 1982)

– now: Global System for Mobile Communication.


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Evolution of GSM

• 1982: Conference of European Post and Telecommunications (CEPT) formed Group Speciale Mobile called GSM.


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Worldwide Deployment


• 930 networks in 222 countries and regions.

• More than 3 billion subscribers worldwide.

• More than 80% worldwide market share.

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GSM CDMAStands for Global System for Mobile

communicationCode Division Multiple Access

Storage Type SIM (subscriber identity module) Card

Internal Memory

Global market share 75% 25%

Dominance Dominant standard worldwide except the U.S.

Dominant standard in the U.S

Data transfer GPRS/E/3G/4G/LTE EVDO/3G/4G/LTE

Network Every cell has a corresponding network tower, which serves the mobile phones in that cellular area.

There is one physical channel and a special code for every device in the coverage network. Using this code, the signal of the device is multiplexed, and the same physical channel is used to send the signal.

International roaming Most Accessible Less Accessible

Frequency band Multiple (850/900/1800/1900 MHz)

Single (850 MHz)

Network service SIM specific. User has option to select handset of his choice.

Handset specific

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Generations of GSM

• 1st generation:- Analog mobile technologies :- AMPS , TACS & NMT.

• 2nd generation:- digital mobile technologies :- GSM , CDMA

• 2.5generation:- Enhancement of GSM:- GPRS

• 3rd generation:- Technologies coursed by ITU-IMT

• The following table lists the key events in the GSM evolution

• AMPS—Advanced Mobile Phone System• TACS----Total Access Communication System.• NMT----Nordic Mobile Telephones


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GSM Architecture• Mobile Station (MS)

Mobile Equipment (ME)Subscriber Identity Module (SIM)

• Base Station Subsystem (BSS)Base Transceiver Station (BTS)Base Station Controller (BSC)

• Network Switching Subsystem (NSS)Mobile Switching Center (MSC)Home Location Register (HLR)Visitor Location Register (VLR)Authentication Center (AUC)Equipment Identity Register (EIR)


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Mobile Station (MS)

The Mobile Station is made up of two entities:

1. Mobile Equipment (ME)

2. Subscriber Identity Module (SIM)


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Mobile Station (MS)

Mobile Equipment• Portable hand held device • Uniquely identified by an IMEI Voice

and data transmission • Monitoring power and signal quality of

surrounding cells for optimum handover.

Subscriber Identity Module (SIM)• Smart card contains IMSI• Allows user to send and receive calls.• Encoded network identification details

- Key Ki,Kc and A3,A5 and A8 algorithms

• Protected by a password or PIN• Can be moved from phone to phone


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Base Station Controller (BSC)

Base Transceiver Station (BTS):• Encodes,encrypts,multiplexes,modulat

es and feeds the RF signals to the antenna.

• Frequency hopping• Communicates with MS and BSC• Consists of Transceivers (TRX) units

Base Station Controller (BSC)• Manages Radio resources for BTS• Assigns Frequency and time slots for

all MS’s in its area• Handles call set up• Transco ding and rate adaptation

functionality• Handover for each MS• Radio Power control • It communicates with MSC and BTSPrepared by :Avani Trambadiya

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Network Switching Subsystem (NSS)

• Home Location Registers (HLR)- permanent database about mobile subscribers in a large

service area (generally one per GSM network operator) - database contains IMSI,MSISDN, prepaid/postpaid,

roaming restrictions, supplementary services.

• Visitor Location Registers (VLR)- Temporary database which updates whenever new MS

enters its area, by HLR database- Controls those mobiles roaming in its area - Reduces number of queries to HLR - Database contains IMSI, TMSI,MSISDN ,MSRN, Location

Area, authentication key


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Network Switching Subsystem (NSS)

• Authentication Center (AUC) - Protects against intruders in air interface- Maintains authentication keys and algorithms and

provides security triplets ( RAND, SRES, Kc)- Generally associated with HLR

• Equipment Identity Register (EIR)- Database that is used to track handsets using the IMEI

(International Mobile Equipment Identity)- Made up of three sub-classes: The White List, The Black

List and the Gray List- Only one EIR per PLMN


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GSM Architecture


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GSM Operation from speech to radio wave

Speech decoding

Channel decoding

De-interleaving

Burst Formatting

De-ciphering

DemodulationModulation

Ciphering

Burst Formatting

Interleaving

Channel Coding

Speech coding

Radio Interface

Speech Speech

13 Kbps

22.8 Kbps

22.8 Kbps

33.6 Kbps

33.6 Kbps

270.83 Kbps

Speech decoding

Channel decoding

De-interleaving

Burst Formatting

De-ciphering

DemodulationModulation

Ciphering

Burst Formatting

Interleaving

Channel Coding

Speech coding

Radio Interface

Speech Speech

13 Kbps

22.8 Kbps

22.8 Kbps

33.6 Kbps

33.6 Kbps

270.83 KbpsPrepared by :Avani Trambadiya

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GSM Services

• Tele-services• Bearer or Data Services • Supplementary services


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Tele-services

• Telecommunication services that enable voice communication via mobile phones.

• Offered services - Mobile telephony

- Emergency calling


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Bearer Services

• Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps

• Short Message Service (SMS) – up to 160 character alphanumeric data transmission

to/from the mobile terminal• Unified Messaging Services(UMS)• Group 3 fax• Voice mailbox• Electronic mail


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Supplementary Services

Call related services :• Call Waiting

- Notification of an incoming call while on the handset• Call Hold

- Put a caller on hold to take another call• Call Barring

- All calls, outgoing calls, or incoming calls• Call Forwarding

- Calls can be sent to various numbers defined by the user• Multi Party Call Conferencing - Link multiple calls together


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Characteristics of GSM

• Fully digital system.• Security against fraud• Enhance privacy • Full international roaming capability.• Support for new services.• Compatibility with ISDN.• Support of Short Message Service (SMS).• Good subjective voice quality.


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Advantages of GSM

• Better Quality of speech• Data transmission is

supported• New services offered due

to ISDN compatibility• International Roaming

possible• Large market• Crisper, cleaner quieter

calls


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Disadvantages of GSM

• Dropped and missed calls

• Less Efficiency

• Security Issues


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Applications of GSM

• Mobile telephony• GSM-R• Telemetry System

- Fleet management - Automatic meter

reading - Toll Collection - Remote control and

fault reporting of DG sets

• Value Added Services


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Conclusion

• The mobile telephony industry rapidly growing and that has become backbone for business success and efficiency and a part of modern lifestyles all over the world.

• In this session I have tried to give and over view of the GSM system. I hope that I gave the general flavor of GSM and the philosophy behind its design.

• The GSM is standard that insures interoperability without stifling competition and innovation among the suppliers to the benefit of the public both in terms of cost and service quality.


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References

• www.slideshare.com• www.wikipidia.com• www.seminarsonly.com• www.gsmarena.com• www.gsm-architecture.blogspot.com


http://www.slideshare.com/

http://www.wikipidia.com/

http://www.seminarsonly.com/

http://www.gsmarena.com/

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