2 GSM Essentials

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GSM900DCS1800

GSM Essentials

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ObjectivesUpon completion of the module the student should be able to:– Name the key terms in mobile communications– List the main improvements from 1G to 2G mobile communications

systems– Identify events in GSM evolution

Introduction to GSM

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Radio Transmission

• 1873 J.C. Maxwell - Electromagnetic theory

• 1895 G. Marconi - First radio transmission

• 1901 First transatlantic transmission

• 1906 R. Fesseden - First transmission of human voice

• 1909 First Broadcast Transmission

• 1946 First car phone service

First Steps in Wireless Communications

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DuplexSimplex

one-waytwo-way

Transmission

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cell = supply area

Base station

Downlink (DL)

Uplink(UL)

Single Cell System

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• Arles

• Nimes

• Avignon

• Salon-de-Provence

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• Cavaillon

• Orange

• Carpentras

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Aix-en-Provence

Coverage

Cellular System

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Mobile phone is active, e.g. a call takes place

Continued service without interruption

Handover

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Location Area 1

Location Area 2

Location Area 3

no Location Update

Location Update

Location Area=

registrationarea of onesubscriber

Location Areas and Paging

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1. No Roaming2. Only Speech3. Supplementary services not available4. No security5. Problems & limitations in radio interface

1st Generation Limitations

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Roaming=

ability to use the infrastructure of

differentoperator‘s

GSM subscriberfrom Spain

Can use GSM networkin Australia, based on aroaming agreement between home operatorand visited operator

Example:

Roaming

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GSM Radio Interface Organisation: FDD and FDMA

UPLINK DOWNLINK

GSM900: 890 MHz - 915 MHz 935 MHz - 960 MHz

GSM1800: 1710 MHz - 1785 MHz 1805 MHz - 1880 MHz

1 2 3 ...

Channel 1 - 124 1 - 374

200 kHz

1 2 3 ...

Duplex frequency 45 MHz / 95 MHz

guard band

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TDMA frame= 8 timeslots

=8x.577ms

=4.615ms

01

23

45

76

01

23

45

76

01

23

45

200 kHz

Physical channel, e.g. allocated to one

subscriber with FR voice &no frequency hopping

frequency

time

TDMA frame

GSM Radio Interface Organisation: TDMA

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A

NMSNMS

NSSNSSBSSBSS

O&M

Air

MS

Network Switching Subsystem

• Switching• Mobility Management• Connection Management• Charging

Base Station Subsystem

• Radio Resource Management• Radio Link Management

Network Management System

• Fault Management• Configuration Management• Performance Management

GSM PLMN Organisation

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01 General Description of a GSM PLMN

02 Services03 Network Functions04 MS - BSS Interface05 Radio Path06 Speech Processing Functions07 Terminal Adaptation Functions08 BSS - MSC Interface09 Network Inter Working10 Service Inter Working11 Type Approval Procedures12 Operation and Maintenance[..] removed

GSM Technical Specifications

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Global System for Mobile Communications

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• GSM uses radio frequencies efficiently and, because of the digital radio path, the system tolerates more inter cell disturbances.

• The average quality of speech achieved is better than that in existing analogue systems.

• Data transmission is supported throughout the system.• Speech is encrypted and subscriber information security is

guaranteed.• Due to ISDN compatibility, new services are offered as compared

to the analogue systems.• International roaming is technically possible within all the

countries concerned.• The large market toughens the competition and lowers the prices

both for investments and usage.

Advantages of GSM

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•1982 CEPT initiated a new system, GSM

•1985 CEPT made decision on time schedule and action plan

•1986 CEPT tested eight experimental systems in Paris

•1987 Memorandum of Understanding (MoU), allocation of the frequencies

– 890-915 uplink (from mobile to base station)

– 935-960 downlink (from base station to mobile)

Evolution of GSM (1)

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•1988 The European Telecommunications Standard Institute (ETSI) was created; includes members from administrations, industry and user groups

•1989 Final recommendations and specifications

•1.7.1991 First official call in the world with GSM

•1992 Australian operators were the first non-European signatories of the GSM MoU

•1992 New frequency allocation: GSM1800

– 1710-1785 uplink

– 1805-1880 downlink


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•1993 Roaming agreements between several operators are established. By December 1993 there were 32 GSM networks operating in 18 areas.

•1994 The first GSM network in Africa was launched in South Africa. The GSM Phase 2 data/fax bearer services were launched. By December 1994 there were 69 GSM networks in operation.

•1995 There were 117 GSM networks operating around the world. The GSM phase 2 standardisation was completed, including adaptation for GSM 1900 (PCS 1900).


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•1996 By December 1996 there were 120 networks operating. The 8K SIM was launched in addition to Pre-Paid GSM SIM cards.

•1997 Zimbabwe and Mozambique implement GSM networks.

•1998 Over 2 million GSM 1900 users in the USA and a total of 120 million GSM 900/1800/1900 users worldwide. The first High Speed Circuit Switched Data (HSCSD) trials in Singapore.


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•1999 First GPRS call in a live network. 200 million subscribers exceeded and 344 networks in 127 countries (August 1999).Location Based Services StandardisedOpen Service Access (OSA) StandardisedGSM 850 supportFirst UMTS Release – evolutionary concept based on GSM

•2000 First GPRS networks launched.


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•2001 GSM 700 supportMultimedia Messaging Service (MMS) standardised

•2002 IP Multimedia Subsystem (IMS) standardisedMore than 40 operators launched MMSMore than 120 operators offer GPRS commercially (Oct. 2002)About 880 Million GSM subscribers (Dec. 2002)460 GSM networks on air in 164 countries (Sep. 2002)


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Review Questions for“Introduction to GSM“

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1. Name advantages of cellular systems as opposed to single cell systems. •The supply area of a single cell system is limited.

A cellular systemcan offer mobile services to a region, or even nation-wide.

•Handover procedures offer continuous service for a moving subscriber.

•The cell size can be adjusted (e.g. in GSM900, the cell radius ranges from 0.5 to 35 km). By decreasing the cell radius, thus increasing the numbers of cells in one geographical area, the available radio interface capacity can be increased.

Review

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2. Explain the difference between handover and the location update procedure.

A handover takes place during a call, when the mobile phone is moved from one cell to the next. It is required for service continuation. (The mobile phone is in the so-called ”dedicated mode“.)

A location update takes place when the mobile phone is moved into a new cell belonging to a new administrative area, known as the ”location area“. A location update only takes place when the mobile phone is in so-called ”Idle mode,“ i.e. no calls takes place.

Review

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3. Which of the following is a requirement for GSM specifications?

a) The system must be compatible with existing mobile standards.

b) The system must be standardised globally.c) The system must be built without causing any major

changes in the existing Public Switched Telephone Networks (PSTN).

d) All of the above.

Review

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4. Which of the following two statements are generally seen as advantages of GSM over analogue networks?

a) Data transmission is supported in the whole GSM network.

b) It is only possible to use an analogue mobile telephone in one’s own network.

c) GSM mobile stations can be used in other digital mobile networks, for instance in NMT and TACS networks.

d) GSM is a more secure system than analogue systems with respect to subscriber information and transmission.

Review

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5. Match the year in the left-hand column with the corresponding significant GSM event in the middle column.

Year Event Correct year

1982 Allocation of GSM frequencies

2000 Experimental test in Paris

1995 Frequency allocation for GSM 1800

1989 First official GSM call in the world

1991 Initiation of a new system

1987 ETSI begins the specification work for UMTS

1992 Final recommendations Phase 1

1999 Phase 2 recommendations frozen

1986 Total GSM subscribers exceeds 300 million

1982

1986

1992

1991

1995

1999

1989

1994

2000

Review

2 GSM Essentials

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