2 GSM Overview

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GSM Overview

October 2006, Telenor Pakistan

Prepared by

Montri Thanaphakawat


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GSM Details

Global System for Mobile Communication

UL:890-915MHz, DL:935-960MHz Channel: 1 - 124, BW: 200kHz

TDMA:Time Division Multiple Access

Lower C/I stricts. More powerful capability


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GSM 900 :

GSM 1800 :

Channel spacing 200kHz

Usual bandwidth values (GSM900):5 ..8 MHz per operator in one or more sub-bands

890 915 935 960

duplex distance : 45 MHz

1710 1785 1805 1880

duplex distance : 95 MHz

Operator A Operator B Op. BOp. Anot allocated

Digital Transmission


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Telenor G900&G1800 Frequency Allocation Strategy

1. BCCH Frequency Ch. 64 79 (15 ch)

2. Guard Band Frequency Ch. 63 and 80 (2 ch)

3. RF Hopping for GSM900 Frequency Ch. 81 86 (6 ch)

4. RF Hopping Frequency for GSM1800 Frequency Ch. 587 625 (39 ch)

GSM 900 Frequency

GSM 1800 Frequency


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Digital TransmissionTDMA : Time Division Multiple Access

T = Allocated time

t

A

Slot for user 1

Slot for user 2

Slot for user 3

Slot for user 5

Slot for user 7

Slot for user 8

Slot for user 4

Slot for user 6


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Burst Period

0 7

TDMA frame = 4.615 ms

= BURST PERIOD

0

0 0

f s


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Network Element


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GSM System

HLR

AUC

EIR

VLR

NMC

SUBSCRIBER

DATABASE

OPEN SYSTEMS

CONNECTION

INTERFACE TOOTHER NETWORKS

MSC

MSC/GMSC

ANTENNA

SYSTEM

ANTENNA

SYSTEM

OMCOMC

BTS

BTS

BTS

BTS

BTS

BTS

BSC

BSC

VLR

BSS SS

Um

Abis

A


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NETWORK ELEMENTS OF THE BSS

OMC

MSCBSC

BTS

MS

BSS

TRU

BTS

TRU

BTSTRU

TCSM2


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Base Transceiver Station timing Broadcast Control Channels (BCCH) and Common Control

Channels (CCCH) forwarding MS and BTS measurements to the BSC maintaining synchronisation between the MS and the BTS

detecting RACHs (Random Access Channels) from the MS rate adaptation channel coding and decoding on the radio path interleaving and deinterleaving on the radio path encryption and decryption on the radio path

performing frequency hopping GMSK modulation, demodulation, up / down conversion and power

amplifying transmitter RF signal combining

receiver RF signal filtering, amplifying and multicoupling reporting idle traffic channel quality to the BSC interface to the BSC / Mobile Station


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Transmission

provides Abis interface

reallocates the Traffic andsignalling channels in the BTS


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PCM Branching0

1 TSL0 TSL1 TSL2 TSL32 TSL4 TSL5 TSL6 TSL7

3 TSL0 TSL1 TSL2 TSL3






















25 TRXSIG1 TRXSIG1 TRXSIG2 TRXSIG2






31 *OMUSIG

TRX 1

TRX 2

TRX 3

TRX 4

TRX 5

TRX 6

TRX 7

TRX 8

TRX 9

TRX 10

TRX 11

TRX 12


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Base Station Controller

terrestrial channel management configuration and management of traffic

channels frequency hopping control paging BTS and MS power control idle channel quality monitor quality and field strength control for active

channels

handover control maintenance of BTS / BSC / TC interfaces to the OMC / BTS / TC


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BSC with 384 TRX Capacity


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Transcoder

considered as part of the BSC

normally at the MSC site used for converting the bit rate of traffic

channels between 64 and 16 kbit/s

speech activity detection

framing and synchronisation of the

vocoder block interfaces to the MSC / BSC


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INTERFACES IN THE GSM NETWORK

Abis interface A interface

Ater interface

TCSM LTG

BSC

TCSM LTG

TCSM LTG

BSC

TCSM LTG

MSC


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A interface - between MSC and TC

- 2 Mbit/s interface Ater interface

- between TCSM and BSC - 2 Mbit/s interface Abis interface

- between BSC and BTS - 2 Mbit/s interface

- structure depends on the connection type and signalling (64kbit/s or 16kbit/s) used

Air interface - between BTS and MS - TDMA frame for sending signals intended for various users on the same

radio frequency in different time slots.

X.25 - between MSC / BSC and OMC

- two ways to implement * analogue X.25 between BSC and OMC * digital X.25 between MSC and OMC

INTERFACES IN THE GSM NETWORK


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RF Planning and Optimization


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Scope of NW Planning

Customer requirements External information sources

subscriber forecasts terrain & morphological data coverage requirement population data

quality of service bandwidth available

recommended sites frequency co-ordinationconstraints

Network design number and configuration of BS

antenna systems specification Network performance

BSS topology grade of service (blocking)

dimensioning of transmission line outage calculations

frequency plan interference probabilities

network evolution strategy quality observation

Network Planningdata acquisition

sites survey and selectionfield measurement evaluationNW design and analysistransmission planning

Network Planningdata acquisition

sites survey and selectionfield measurement evaluationNW design and analysistransmission planning


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Cellular Planning Principle

Transmissionplan

Transmissionplan Coverage

plan

Coverageplan

Freq.&inter-ference plan

Freq.&inter-ference plan Final NW

topology

Final NWtopology

Parameterplan

Parameterplan

Initial NWdimensioningInitial NWdimensioning

marketing

Business

plan

Traffic

assumptions


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Optimization process

For improvement of the network after it is launched and

filled up by subscribers

Collect /analyse

drive testmeasuremts

Collect /analyse

drive testmeasuremts

Collect /

analysecomplaints

Collect /

analysecomplaints

Collect /analyseOMC

statistics

Collect /analyse

OMCstatistics

Propose /

implementchanges

Propose /

implementchanges

Repeatprocess until

agreed quality

Repeatprocess until

agreed quality

Pre-analysis:Generalnetworkcheck

Pre-analysis:General

networkcheck


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Why Network need Optimization

Maximize network quality as perceived by subscriber

+

Maximize the network quality as perceived by

operator

=

Maximize the revenue with a Minimum Investment

Quality

Subscriber

Time

Optimisation Optimisation


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Planning vs. Optimising Thorough network planning from start can reduce the

optimization effort significantly!

In a poorly planned network, achievableoptimisation effects without major re-design are

rather marginal

A close link between the two activities is necessaryBe involved

Feedback result


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Planning and Optimization Tools

ASSET Coverage Prediction, Frequency planning, Adjacentplanning

Mapinfo, MCOM Site location, Antenna direction, Frequencychecking, Adjacent checking

TEMS Drive Test tool to check Coverage, Quality of network

Network Doctor to check BSC and BTS statistic that datacollected from OMC

MML command to check Site configuration, BSC and BTSAlarm

Statistic monitoring tool Cell daily statistic such as Dropcall rate, Call Setup Success Rate, Handover and Quality


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End

&

Question ???

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