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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
4 TSL4 TSL5 TSL6 TSL7
5 TSL0 TSL1 TSL2 TSL3
6 TSL4 TSL5 TSL6 TSL7
7 TSL0 TSL1 TSL2 TSL3
8 TSL4 TSL5 TSL6 TSL7
9 TSL0 TSL1 TSL2 TSL3
10 TSL4 TSL5 TSL6 TSL7
11 TSL0 TSL1 TSL2 TSL3
12 TSL4 TSL5 TSL6 TSL7
13 TSL0 TSL1 TSL2 TSL3
14 TSL4 TSL5 TSL6 TSL7
15 TSL0 TSL1 TSL2 TSL3
16 TSL4 TSL5 TSL6 TSL7
17 TSL0 TSL1 TSL2 TSL3
18 TSL4 TSL5 TSL6 TSL7
19 TSL0 TSL1 TSL2 TSL3
20 TSL4 TSL5 TSL6 TSL7
21 TSL0 TSL1 TSL2 TSL3
22 TSL4 TSL5 TSL6 TSL7
23 TSL0 TSL1 TSL2 TSL3
24 TSL4 TSL5 TSL6 TSL7
25 TRXSIG1 TRXSIG1 TRXSIG2 TRXSIG2
26 TRXSIG3 TRXSIG3 TRXSIG4 TRXSIG4
27 TRXSIG5 TRXSIG5 TRXSIG6 TRXSIG6
28 TRXSIG7 TRXSIG7 TRXSIG8 TRXSIG8
29 TRXSIG9 TRXSIG9 TRXSIG10 TRXSIG10
30 TRXSIG11 TRXSIG11 TRXSIG12 TRXSIG12
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 ???