GSM DETAILS

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GSM COMPLETE DETAILS

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GSM Global System for Mobiles1

TOPICS GSM CONCEPTS GSM SYSTEM ARCHITECTURE IDENTITIES USED IN GSM GSM CHANNELS GSM RADIO LINK MOBILITY MANAGEMENT CALL MANAGEMENT RADIO RESOURCE MANAGEMENT2

TOPICS GSM CONCEPTS GSM SYSTEM ARCHITECTURE IDENTITIES USED IN GSM GSM CHANNELS GSM RADIO LINK MOBILITY MANAGEMENT CALL MANAGEMENT RADIO RESOURCE MANAGEMENT3

Telecom Basics Communication Voice and Data Analog and Digital Circuit Switched and Packet Switched Media - Copper Wire, Co-axial cable, Air, Optical Fibre Networks -PSTN, ISDN, PDN and Mobile Networks

4

Background to GSM 1G : Advanced Mobile Phone Service (AMPS) Analog, Circuit Switched, FDMA, FDD

2G : Digital Advanced Mobile Phone Service (D-AMPS) Digital, Circuit Switched, FDMA, FDD

2G : Global System for Mobile (GSM) Digital, Circuit Switched, FDMA and TDMA, FDD

2G : Code Division Multiple Access (CDMA) Digital, Circuit Switched, FDMA, SS, FDD

5

GSM History

6

Development of the GSM Standard1982: Groupe Spcial Mobile (GSM) created Description of GSM features 1993: 1985: List of recommendations settled 1995: The GSM-MoU has 62 signatories in 39 countries worldwide. Specifications of GSM phase 2 are frozen. GSM MoU joins 3GPP (UMTS) GPRS Trials begins 1992: Official commercial launch of GSM service in Europe. First Launch in Finland 1984:

1987:

Initial MoU (Memorandum of Understanding) aside the drafting of technical specifications was signed by network operators of 13 countries: Validation and trials, of the radio interface. First system trials are demonstrated at the Telecom 91 exhibition.

1999:

1988:

2000:

480M GSM subscribers Worldwide First GPRS Networks roll out

1991:

End 2002: 792M GSM subscribers Worldwide 7

GSM Specifications12 SERIES OPERATION AND MAINTENANCE 11 SERIES EQUIPMENT AND TYPE APPROVAL SPECIFICATIONS 01 SERIES GENERAL 02 SERIES SERVICE ASPECTS 03 SERIES NETWORK ASPECTS

10 SERIES SERVICE INTERWORKING

04 SERIES MS-BSS INTERFACE AND PROTOCOLS

09 SERIES NETWORK INTERWORKING

05 SERIES PHYSICAL LAYER ON THE RADIO PATH. 06 SERIES SPEECH CODING SPECIFICATIONS

08 SERIES BSS TO MSC INTERFACES

07 SERIES TERMINAL ADAPTERS FOR MOBILE STATIONS

Increasing GSM Data RatesUMTS E/GPRSphoto report video clip video report clip video report clip video report clip video report clip

web

photo

ISDN PSTN

e-mail web

photo

e-mail

web

photo

GSM0

e-mail

web

photo

10 sec

1 min

10 min

1 hour

Transmission Time

GPRS = General Packet Radio Service HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution UMTS = Universal Mobile Telecommunication System

Wireless Data Technology Options2M1M

throughput kbps

p100 k

ket acEDGE

64 k

it rcu ci

HSCSD

UMTS

10 k

14.4 9.6

GPRS

1k

Time frame 1998 1999 2000 2001 2002GPRS = General Packet Radio Service HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution UMTS = Universal Mobile Telecommunication System 10

Circuit-Switched or Packet-SwitchedCircuit mode

Packet mode B CC

AA

FA

F

F

D A C

H F GC D A C D A

G H

G H F

G H F

C

G

G

D

D

D

H

E

H

11

Multiple Access Technique Multiple Access Achieved by dividing the available radio frequency spectrum, so that multiple users can be given access at the same time. FDMA - Frequency Division Multiple Access ( eg: GSM each Frequency channel is 200KHz) TDMA - Time Division Multiple Access ( eg: GSM each frequency channel is divided into 8 timeslots) CDMA - Code Division Multiple Access (eg: IS95- Each User data is coded with a unique code) 12

Duplex Technique Duplex - How the up link and Down link of a user is separated FDD - Frequency Division Duplex (eg:In GSM the up link and down link of a user is separated by 45MHz )

TDD - Time Division Duplex (the up link and down link of a user will be at the same frequency but at different Time )

13

GSM Concepts Cellular Structure2 2 7 1 6 5 3 4 6 5 7 1 Cellular Networking technology that breaks geographic area into cells shaped like honey comb Cell is the radio coverage area of one base transceiver station14

What are the types in GSM Network? GSM-900 (Channels 125 operating band 900Mhz carrier spacing 200khz spacing 45Mhz) GSM -1800 (Channels 374 spacing 95Mhz) GSM -1900(Used in USA)

15

GSM Band Allocations (MHz)GSM systems Uplink Downlink Band Duplex Spacing Duplex channels

GSM 450 GSM 480

GSM 850 GSM 900 E-GSM (900) R-GSM (900) GSM 1800 GSM 1900

450.4-457.6 478.8-486824-849 890-915 880-915 876-880 1710-1785 1850-1910

460.4-467.6 2x7.2 488.8-496 2x7.2869-894 935-960 925-960 921-925 1805-1880 1930-1990 2x25 2x35 2x04 2x75 2x60

2x25

10 10

45 45 45 41 95 80

35 35

124 124 174 40 374 299

Frequencies are in MHz Carrier frequency = ARFCN = Absolute Radio Frequency Channel Number

GSM Family Radio Band SpectrumUplink450.4 457.6 478.8 486 824 849

GSM 450

GSM 480

GSM 850

Downlink Uplink876 880

460.4

467.6

488.8

496

869

894

MHz

915 915 890 915 P-GSM E-GSM GSM 1800 GSM 1900 1710 1785 1850 1910

R-GSM 921 925 935 960 960 960 1805 1880 1930 1990

Downlink

MHz

Traffic/Signaling Trafficbla bla bla...

Signaling

RING ! riiiiing

Network

MS

GSM - Network StructureUm BTS BSC Abis A MSC B C GMSC E Abis A MSC E PSTN X.25 VLR X.25 OMC Server 19 F EIR H VLR HLR

MS BTS

AuC

BSC Um BTS

GSM System specificationsFrequency band Uplink Downlink Duplex Frequency Spacing Carrier separation Frequency Channels Time Slots /Frame(Full Rate) Voice Coder Bit Rate Modulation Air transmission rate Access method Speech Coder 890 - 915 MHz 935 - 960MHz 45MHz 200KHz 124 8 13Kbps GMSK 270.833333 Kbps FDMA/TDMA RPE-LTP-LPC20

Paired Radio Channels in GSMCase of GSM 900Uplink890 MHz Frequency 915 MHz 935 MHz

DownlinkFrequency

BTS 960 MHz

0

channel #

124 Example: Channel 48

0

channel #

124

Duplex spacing = 45 MHz Frequency band spectrum = 2 x 25 MHz Channel spacing = 200 kHz21

GSM Time Division MultiplexFrame and Physical ChannelsTime-slot TDMA frame TDMA frameTS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

(frames repeat continuously)

Time0 4.615 ms 9.23 ms

Physical channel # 2 = recurrence of time-slot # 2

Physical ChannelBTS With FHtime

BTS Without FH

n+1

TDMAsn TS 0 n-1 MS27

MS1

MS31

FDMA

2

// 124

ARFCN

Radio Link Aspects From Speech to RF SignalBlah... Blah... Blah...Digitizing and Source Coding Channel Coding

Blah Blah Blah...Source Decoding

Channel Decoding

Interleaving

De-interleaving

Ciphering

Deciphering

Burst Formatting Modulating

Burst De-formatting Demodulating

Speech and user's data Idle mode Signaling

Functions of the Radio InterfaceCommunication modeBTS

BTS-1

BTS-2

Access TechniquesUplink 890 MHz to 915 MHz Down Link 935 MHz to 960 MHz 25 MHz divided into 125 channels of 200 KHz bandwidthUP 890.0 890.2 890.4 914.8 915.0

DOWN 935.0

935.2

935.4

959.8

960.0

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Access Techniques ...Time Division Multiple Access Each carrier frequency subdivided in time domain into 8 time slots Each mobile transmits data in a frequency, in its particular time slot - Burst period = 0.577 milli secs. 8 time slots called a TDMA frame. Period is .577 * 8 = 4.616 milli secs0.577 ms 0 1 2 3 4 5 6 727

4.616 ms

28

Fundamentals960 MHz 959.8MHz

124 123 . 2 1

TS: Time slot

DOWNLINK200KHz

935.2 Mhz 935 MHz

0 1

GSM utilizes two bands(TDMAMHz. 890-915 Downlink of 25 frame) = 8 TS MHz band is used for uplink while the 935960 MHz is used for downlink. The frequency bands are divided into 200 KHz wide channels called ARFCNs (Absolute Radio Frequency Channel Numbers) i.e. Data burst = 156.25 bit periods = 576.9s there are 125 ARFCNs out of which only 124 are used. Each ARFCN supports 8 users with each user transmitting / receiving on a particular time Delay 0 1 2 3 4 5 6 7 slot (TS).

2 3

4 5 6 7

915 MHz 914.8 MHz

124 123 . 2 1

45 MHzUPLINK200KHz

Uplink (TDMA frame)

890.2 MHz 890 MHz

The technology

Therefore 1 TDMA frame = 156.25 x 8 = 1250 bits and has a duration of 576.92s x 8 = 4.615 ms 29

GSM Delays Uplink TDMA FramesBTS sideThe start of the uplink TDMA is delayed of three time-slotsTDMA Frame (4.615 ms)

0 R

1 R

2 R

3 R

4 R

5 R

6 R

7 R

Downlink TDMABTS

T

T

T Down link

T

T

T

T Up link

T

MSs sideMS1 R

T

MS2

R

T

Fixed transmit delay of three time-slots

Timing Advance

1 - Propagation Delay

M2

d2

d1>>d2

M1

BTS Frame reference

TS0

TS1

TS2

TS3

TS4

TS5