my notes_gsm slides

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





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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


Functional Layer of GSMAir Interface System Capacity



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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





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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


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



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


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



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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



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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



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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.


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