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7/31/2019 My Notes_gsm Slides
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Uke Kurniawan Usman - 20051
GSM Fundamental
ByUke Kurniawan Usman
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Agenda
Network Architecture
Functional Layer of GSM Air InterfaceSystem Capacity
Anti Interference TechnologyNetwork PlanningNumbering arrangement
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MSC/VLR
HLR/
AUC EIR SC/VM
OMC
BSC
BTSPSTNISDNPSPDN
MS
BSS
MSS
Um
Abis
BIEA
FC
H
MSC/VLR
E
GSM Network Structure
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Base Transceiver Station (BTS)
Wireless transmissionWireless diversityWireless channel encryptionConversion between wired and wireless signalsFrequency Hopping
BaseBand Unit:voice and data speed adapting and channel coding
RF Unit:modulating/demodulating, transmitter and receiverCommon Control Unit:
BTS operation and maintenance
GSM Network EntityBase Transceiver Station
( BTS )
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Managing Wireless network-BSSMonitoring BTS
Controls:Wireless link distribution between MS and BTSCommunication connection and disconnectionMS location, handover and pagingVoice encoding, transecoding (TC), rate, adaptation,The operation and maintenance functions of BSS.
Base Station Controller
( BSC )
GSM Network Entity
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holds all the switching functionsmanages the necessary radio resources,
updating the location registration
carrying out the inter-BSC and inter-MSC tender
Inter-working with other networks (IWF).
GSM Network Entity
Mobile Service Switching Center
( MSC )
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Manages the mobile subscribers database
subscriber information
part of the mobile location information
3 identities essentialthe International Mobile subscriber Identitythe Mobile station ISDN Numberthe VLR address
GSM Network Entity
Home Location Register
( HLR )
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Visitor Location Register
( VLR )
dynamically stores subscriber information needed to handleincoming/outgoing calls
Mobile Station Roaming NumberWhen a roaming mobile enters an MSC area. This MSC
warns the associated VLR of this situation; the mobile entersa registration procedure through which it is assigned a
mobile subscriber roaming number (MSRN)
Temporary Mobile Subscriber Identity, if applicableThe location area in which the mobile has beenregistered
Data related to supplementary service parameters
GSM Network Entity
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AUC/EIR
Authentication Center(s) (AUC)Providing the authentication key used forauthorizing the subscriber access to theassociated GSM PLMN.
Equipment Identity Register(s) (EIR)
Handling Mobile Station Equipment Identity
GSM Network Entity
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Agenda
Network Architecture
Functional Layer of GSM Air InterfaceSystem Capacity
Anti Interference TechnologyNetwork PlanningNumbering arrangement
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O AM
S ervice carrie r
CM
MM
RR
Subsc riber
Tran smissi on
Overview: Function Layers of GSM-1
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CM
MM
RR
LAPDm
MS
RR
LAPDm
Um
LAPD
BTSM
LAPD
Abis
RR
BTSM SCCP
MTP3
BS SAP
BTS BSC
MTP2
SCCP
MTP3
BS SAP
MTP2
CM
MM
MSC
A
Protocol Stack Structure of GSM
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Agenda
Network Architecture
Functional Layer of GSMAir Interface System Capacity
Anti Interference TechnologyNetwork PlanningNumbering arrangement
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Concept: channel is composed of a
series of timeslots of periodicity. Different signalenergies are distributed intodifferent timeslots. Theadjacent channel interferenceis restricted by connectionchoosing from time to time. Sothe useful signal is passedonly in the specified timeslot.
GSM adopts TDMA/FDMA modechannel width: 200KHzeach channel has 8 timeslots
User 1
User 2
User 3
Frequency
time
TDMA
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GSM Timeslot and Frame structure
time
Frequency
BP15/26ms
200KHz
interval
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Frequency Resource
GSM900 :up: 890~915MHz
down: 935~960MHzduplex interval: 45MHzbandwidth: 25MHz frequency interval: 200KHz
GSM1800 :up: 1710-1785MHzdown: 1805-1880MHzduplex interval: 95MHz working bandwidth: 75MHz frequency interval: 200KHz
EGSM900 :up: 880~890MHz
down: 925~935MHzduplex interval: 45MHzbandwidth: 10MHz frequency interval: 200KHz
GSM1900MHz:up:1850~1910MHzdown:1930~1990MHzduplex interval: 80MHz working bandwidth: 60MHz
frequency interval: 200KHz
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1800MHz
1900MHz
900MHzWhich one?
Single Band Network General Priority
High
Low
Reason
For Subscriber For Operator
PropagationCharacteristic
New Operator
Frequency Resource
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1800MHz
1900MHz
900MHz
Single Band Network
Single Band
Dual Band
Triple BandIn a sense, the network determines the handsetscan be selected.But nowadays, most handsets support dual band.
Frequency Resource
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Propagation characteristic
Cellcoverage radius :
The higher the propagationfrequency
The higher the propagation loss
The smaller the cell coverage radius.
900MHz
1800MHz
1900MH z
Single Band Network
Frequency Resource
We know
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0 2045 2046 2047321 2044
3210 4947 48 50
0 24 251
1 super high frame = 2048 super frame = 2715648 TDMA frame
1 super frame = 1326 TDMA frame 6.12s
0 1 2524 504910
1 multiplex frame = 26 TDMA frames 120ms 1 multiplex frame = 51 TDMA frame
0 1 765432
1 TDMA frame = 8 timeslot 120/26 = 4.615ms
BCCHCCCH
SDCHSACCH/TCHFACCH
Timeslot and Frame structure
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0 1 765432
8 9 151413121110
16 17 232221201918
The physical channel adopts FDMA and TDMA techs.On the time domain, a specified channel occupies thesame timeslots in each TDMA frame, so it can beidentified by the timeslot number and frame number.
Physical Channel
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channel
TCH
CCH
Voice CH
Data CH
FR Voice Traffic Channel (TCH/FS)
HR Traffic Channel (TCH/HS)
4.8Kbit/s HR TCH (TCH/H4.8)
9.6Kbit/s FR TCH(TCH/F9.6)
4.8Kbit/s FR TCH (TCH/F4.8)
BCH
FCCH (down)SCH (down)BCCH (down)
CCCHRACH (up)AGCH (down)PCH (down)
DCCHSDCCHFACCHSACCH
14.4Kbit/s FR TCH (TCH/F14.4)
Enhanced FR Traffic Channel (TCH/EFR)
Channel Type-Summary
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Channel Type
Traffic Channel
Transmit voice and data
Signaling Channeltransmit the signaling and synchronous data between BTS andMS.
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Channel Type
BCH :Frequency Correction CHannel FCCH
-- for MS error correctionSynchronous Channel SCH)
-- for MS frame synchronization and BTS recognizationBroadcasting Control CHannel BCCH
-- broadcasting information(cell selection information, etc..)
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Channel Type
DCCH
Self-help Dedicated Control Channel SDCCH for channel distribution information transmission
Slow Associated Control Channel SACCH combined with one traffic channel or SDCCH, to transmit some
specific information of user informationFast Associated Control Channel FACCH
combined with one traffic channel, taking the same signal asSDCCH. It occupies the service channel to transmit signalinginformation.
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Structure of 51-frame Control CH
SF B C
R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R
51 Frame
SF C C SF C C SF C C I
R R R R R R R R R R
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3
SF C C
R R R R R R R R R R
III
D0 D1 D2 D3 D4 D5 D6 D7 A4 A5 A6 A7 I II
A1 A2 A3 III
A5 A6 A7 III
D0 D1 D2 D3 D4 D5 D6 D7 A0
D0 D1 D2 D3 D4 D5 D6 D7 A4
SF B C SF C C SF D0 D1 SF D2 D3 ISF A0 A1
SF B C SF C C SF D0 D1 SF D2 D3 ISF A2 A3
D3
D3
R R
R R
A2 A3
A0 A1
D2
D2
SF
SF
D0 D1
D0 D1
R R R R R R R R R R R R R R R R R R R R R R R
R R R R R R R R R R R R R R R R R R R R R R R
F FCCH S SCHB BCCH C CCCH(CCCH=PCH+AGCH+RACH)R RACH D SDCCHA SACCH/C I idle
BCCH+CCCH(Downlink)
BCCH+CCCH(uplink)
8 SDCCH/8(Downlink)
8 SDCCH/8(uplink)
BCCH+CCCH+4SDCCH/4(Downlink)
BCCH+CCCH+4SDCCH/4
(uplink)
(a) FCCH+SCH+BCCH+CCCH
(b) SDCCH/8(0,...,7)+SACCH/C8(0,...,7)
(c) FCCH+SCH+CCCH+SDCCH/4(0,...,3)+SACCH/C4(0,...,3)
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Channel Combination Type
Several logic channels combine together in some way to form
some specific types of channel to transmit user data or signalinginformation. They are called combined channels. One combinedchannel can be mapped to a physical channel.
There are the following combined channels:a TCH/F + FACCH/F + SACCH/TFb TCH/H(0,1) + FACCH/H(0,1) + SACCH/TH(0,1)c TCH/H(0,0) + FACCH/H(0,1) + SACCH/TH(0,1) + TCH/H(1,1)d FCCH + SCH + BCCH + CCCHe FCCH + SCH + BCCH + CCCH + SDCCH/4(0...3) + SACCH/C4(0...3)f BCCH + CCCHg SDCCH/8(0 ..7) + SACCH/C8(0 .. 7)
CCCH = PCH + RACH + AGCH
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Small capacity cell with only 1 TRX TN0: FCCH+SCH+CCCH+BCCH+SDCCH/4(0,_,3)+SACCH/C4(0,_,3);TN1-7 : TCH/F+FACCH/F+SACCH/TF
The medium-size cell with 4 TRXs 1TN0 group: FCCH+SCH+BCCH+CCCH;2 SDCCH/8(0,_,7)+SACCH/C8(0,_,7);
29 TCH/F+FACCH/F+SACCH/TF
Channel Assignment inside cells
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Large-size cell with 12 TRXs 1 TN0 group: FCCH+SCH+BCCH+CCCH;
1 TN2 group, 1 TN4 group and 1 TN6 group: BCCH+CCCH;5 SDCCH/8(0,_,7)+SACCH/C8(0,_,7);87 TCH/F+FACCH/F+SACCH/TF
Channel Assignment inside cells
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Agenda
Network Architecture
Functional Layer of GSM Air InterfaceSystem Capacity
Anti Interference TechnologyNetwork PlanningNumbering arrangement
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Capacity
When the traffic is very low, and no possibility for quickincrement, Omni-directional cell is used in common.Otherwise, we suggest to adopt the sector cell.
Note: TRX-transceiver,each TRX handles 1 frequency.
Coverage AreaSector cell is often used to enlarge the cell coverageradius because of the higher antenna gain.For special coverage ,such as road coverage, two-sector cell is adopted firstly.
BTS Mode
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Erlang :
the traffic intensity of a totally occupied channel (i.e.the call hour of a unit hour or the call minute of a unitminute). For example, the traffic of a channel occupiedfor 30 minutes in an hour is 0.5 Erlang)
GOS:
defined as the probability of call blocking or theprobability when the call delay time is longer than agiven queuing time.
System capacity
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Agenda
Network Architecture
Functional Layer of GSM Air InterfaceSystem CapacityAnti Interference Technology Network PlanningNumbering arrangement
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Reasons for Interference
The transmission path is very complex, ranging
from the simple line-of-sight transmission toencountering such terrain as buildings, hills andtrees. Wireless channels are extremelyunpredictable.
Abrupt drop, or fading, of signal strength in theland mobile wireless channel is quite common. Thefading feature of the mobile channel depends on theradio wave propagation environment .
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Reasons for interference
Environmental factors:
Terrain (mountains, hills, plains, water bodies, etc.); The quantity, heights, distribution and materials of
buildings; The vegetation of the region; Weather conditions; Natural and artificial electromagnetic noises; Frequency; How MS is moved.
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Co-Channel Interference
Conception:the interference among the signals of co-channel cells is called co-channel interference.
Result from :Frequency reuse
Reduction method:co-channel cells must physically bespaced at a minimum interval to ensureadequate isolation of transmissions.
Interference
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Adjacent Channel InterferenceConception:
The signal interference from the frequencyadjacent to that of the signal used is calledadjacent channel interference.
Reduction method:accurate filtering and channel allocation(maximizing channel intervals of thecell). Interval of frequency reuse inter-cellinterference, such as C/I, C/A
Interference
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FH technology
Dynamic power control (DPC)
Discontinuous Transceiving (DTX)
Diversity receiving technique
Solution -Anti-interference
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Reason :counteract Rayleigh Fading
scatter interference among multiple calls
Types :Base band frequency hoppingkeeps the transmission and receiving frequency of eachcarrier unit unchanged, but merely sends FU transmissiondata to different carrier units at different FN moments.radio frequency hoppingcontrols the frequency synthesizer of each transceiver,making it hop according to different schemes in different time
slots.
Frequency Hopping Technique
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Discontinuous Speech Transmission (DTX)
TRAU BTS
BTS MS
Speech frame
480 ms
comfort noise frame
Two aims can be achieved by adopting DTX mode:lower the total interference electric level in the air
save transmitter power.
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The multi-path propagation of radio signals causesmagnitude fading and delay time.
Space Diversity (antenna diversity)
Polarization Diversityorthogonal polarization diversity.
horizontal polarization and vertical polarization.
Frequency DiversityThe working principle of this technology is thatsuch fading wont take place on the frequencyoutside the coherence bandwidth of the channel.
Diversity Reception Technology
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Agenda
Network Architecture
Functional Layer of GSM Air InterfaceSystem Capacity
Anti Interference TechnologyNetwork Planning Numbering arrangement
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4 3 reuse mode: one group includes 3 sectors /site ,12 frequency whichare distributed to 4 sites. Every site owns 3 frequency.
Frequency Reuse
A3
D2B1
C3
B2D1
D3
A2C1
B3
C2A1
B3
C2A1
A3
A1B1
D1
D3D2
C3
B2A1
C3D2
C3
C1
D2B1C2A1
A2C1
D3
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A3
C2B1
B3
A2C1
C3
B2A1
A3
C2B1
B3
A2C1
B3
A1C1
A1
A3A2
C3
B2A1
A3A3
C3
C1
B2A1B2A1
A2C1
B3
Frequency Reuse
3 3 reuse mode: one group includes 3 sectors /site ,9 frequency which aredistributed to 3 sites. Every site owns 3 frequency.
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AgendaNetwork Architecture
Functional Layer of GSM Air InterfaceSystem Capacity
Anti Interference TechnologyNetwork Planning Numbering arrangement
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Numbering Arrangement
International Mobile Subscriber Identification number(IMSI)
It identifies a unique international universal number of a
mobile subscriber, which consists of MCC+MNC+MSIN.1) MCC: country code, 4602 MNC: network code, 00 or 013 MSIN: subscriber identification, H1H2H3H4 9XXXXXX,
H1H2H3H4: subscriber registering place
H1H2: assigned by the P&T Administrative Bureau(operator )to different provinces, to each provinceH3H4: assigned by each province/city
the IMSI of user will be written into the SIM card byspecific device and software and be stored into the HLRwith other user information.
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It is the subscriber number commonly
used. China uses the TDMA independentnumbering plan:
CC+NDC+ H1H2H3H4 +ABC
CC: country code, 86NDC: network code, 135 139, 130H1H2H3H4: HLR identification code
ABCD: mobile subscriber number inside
each HLR
Mobile Subscriber ISDN Number MSISDN
Numbering Arrangement
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International Mobile Equipment Identification code
(IMEI)
It will uniquely identify a mobile station. It is a
decimal number of 15 digits. Its structure is:
TAC+FAC+SNR+SP
TAC=model ratification code, 6 digitsFAC=factory assembling code, 2 digitsSNR=sequence code, 6 digitsSP=reserved, 1 digit
Numbering Arrangement
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Mobile Subscriber Roaming Number (MSRN)
The MSRN is temporarily distributed to thesubscriber by the VLR according to the request
by the HLR when this subscriber is called. TheMSRN is released and can be assigned to other subscriber later.
CC + NDC + 00 + M1M2M3 + ABCCC: country code, 86NDC: mobile network code, 135 139, 130M1M2: same as the H2H3 of MSISDN
ABC: 000 -- 999
Numbering Arrangement
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Temporarily Mobile Subscriber Identification Number(TMSI)
To insure the IMSI security, the VLR willassign an unique TMSI number for theaccessed subscriber. It is used locally onlyand is a 4-byte TMSI number BCD code.
Numbering Arrangement