1、GSM,吴伟民 电子与信息工程系 ,1,+,+,+,2,CONTENTS,+ History+ GSM Network Architecture1- BTS Description2- BSC Description3- MSC Description4- VLR Description5- HLR Description6- MS Description+ Area Configuration+ Frequency description+ TDMA Frame,Mobile in IDLE Mode1-FCCH Channel2- SCH Channel3- BCCH Channel3-
2、Roaming NotionHow to call a mobile?1- PCH ChannelMobile in communication 1- RACH Channel2- AGCH Channel3- Maximal Configuration for Common channels4- Minimal Configuration forCommon channels,+,+,Mobile in communication,5- SDCCH Channel6- SACCH Channel,7- Multiplexing Channel: SDCCH - SACCH8- FACCH/T
3、CH Channel,9- Multiplexing Channel: FACCH/TCH - SACCH 10- Communication example,11- Voice Codec,Subscriber Confidentiality,1- Subscriber Identity,2- Subscriber Authentication3- Ciphering Mode,3,CONTENTS,+,+,+,GSM Services,+,Layer 3,1- Supplementary Services,2 - SMSGSM Protocol,1 RR Layer2 MM Layer3
4、CM Layer,1 Global ArchitectureRadio Interface- LAPDm4,CONTENTS,+,Abis Interface1 Physical Layer2 - LAPD3- Layer 3 -RSL,+,A - Interface1 MTP 22 MTP 33 SSCP4 BSSAP,5,CONTENTS,1987,1989,1990,1992,1994,HISTORY,19821994,Group Special Mobile is bornTechnical Radio Transmission is selected, prototype is do
5、ne in 1986GSM Members have created Technical Comity Technique (TC) of ETSI. First Technical Standard Draft were written.GSM 900: Stage 1 of GSM Specification was done. Adaptation of DCS 1800 was started.First European Network using GSM 900 was openedStage 2 of GSM900 AND DCS1800 was done including h
6、alf-rate.Several evolutions : Stage 2+,6,GSM NETWORK ARCHITECTURE,3 Sub-Networks :,Radio Sub-System (BSS Base Station Sub-System),Wire Network Sub-System (NSS Network Sub-System),Operation and Maintenance Sub -System,(OSS, Operation Sub-System, not explained in this course),7,4,GSM NETWORK ARCHITECT
7、URE,BSS,NSSB,VLR,D,HLR,BTS,Abis,BSC,A,D,MSC,E,P,Abis,B VLR,S,Abis,BSC,A,T N,MSC 4,MS,8,BTS DESCRIPTION,Base Transceiver Station,Include Receivers and Transmiters : TRX.,Radio Transmission : modulation, demodulation, eqalization,Code Corrector, Encryption.,Acces to physical TDMA Frame (Time Division
8、Multiple Access).,Power Measurements and Quality Measurements, not used by BTS,9,BTS DESCRIPTIONConfiguration in STARBTS,Abis,BSC,A,BTSBTS,AbisAbis,10,BTS DESCRIPTIONConfiguration in Chain,BTS,BTS,BTS,Abis,BSC,A,11,BSC DESCRIPTION,Base Station Controller,Intelligent Entity of BSS.,Manage radio resou
9、rces on each TRX.,Allocation of physical channels.,Tx Power Control for MS and BTS on each communication (in theory).,HandOver Procedures : when mobile switches cell during,communication.,12,MSC DESCRIPTION,Mobile-service Switching Center,Management communications between MS and different MSCs.,GMSC
10、 : GateWay MSC.,Direct link with external networks,PSTN (Public Switched Telephone Network).ISDN (Integrated Services Digital Network),MSC protocol uses between entities.,13,VLR DESCRIPTION,Visitor Location Register,Database including subscriber information relevant to area location.,VLR could be in
11、volved with MSC (same computer).,Subscriber Information: Ciphering Keys, Temporary Identity, Supplementary Services (roaming international, Call Fowarding ).,14,HLR DESCRIPTION,Home Location Register,Register Database for all subscribers defined by PLMN (CU and CMCC).,International Mobile Subscriber
12、 Identity: IMSI.,Subscriber Call Number (MSISDN : 06 62 H1H2 XX XX).,Supplementary Services of (roaming services,call forwarding, second call .).,VLR number where subscriber is stored.,Authentication Center (AUC) includes,15,MS DESCRIPTIONMobile StationTerminal Equipment including SIM card.Access to
13、 PLMN Services.Manage Uplink Physical Layer (TDMA Frame)Terminal Equipment has unique IMEI number,Mobile Class : from 1 to 5,0.8W to 20W,16,AREA CONFIGURATION,Cell Information,Includes 4 to 10 TRX (frequencies).,Cell Paremeters:,Country Number (MCC) PLMN Number (MNC) Cell Number (Cell Id) Cell Color
14、 (BSIC),Main Frequency (main cell) Secondary frequencies Access Control for MS,Neighbour Cells LAC Number,Dimension : from 100m to 30 km.,17,AREA CONFIGURATION,LAC Definition (Location Area Code),Group of cells involves in a PLMN.,Cellular Engineering : 1 MSC for one LAC.,MS monitors in continue if
15、it is changing of LAC.,LAC number is stored in registering subscriber s VLR entity LAI:MCC+MNC+LAC,18,AREA CONFIGURATION,LAC 75021,F12,F5,F6,F3,F8,F11,F20,F4,F7,F22,F2,F1,F10,F30,F15,F6,F8,F3,LAC 75020,F1,F5,F9,Main Frequency19,AREA CONFIGURATION,BSIC number is used for descriminating 2 cells using
16、same Main Frequency.,Usually, same BSIC number is set in area group of cells.,BSIC number is not in relation with LAC number,20,FREQUENCY BANDS GSM 900, Primary Band Extended Band,890 915 MHz in Uplink 935 960 MHz in Downlink 880 890 MHz in Uplink,925 935 MHz in Downlink DCS 1800 1710 1785 MHz in Up
17、link 1805 1880 MHz in Downlink PCS 1900 1850 1910 MHz in Uplink 1930 1990 MHz in Downlink GSM 850 824 849 MHz in Uplink 869 894 MHz in Downlink21,FREQUENCY BANDS, ARFCN, The carrier spacing is 200kHz, Fl(n): frequency value of the carrier ARFCN in “lower band” Fu(n): frequency value of the carrier A
18、RFCN in “upper band”,22,TDMA NotionNotion of Time Division, Time Slot or Slots (Slot : corresponding of short period in frame).,Tslot = (75/130) x10-3 s,0.5769 ms,Each slot has a number from 0 to 7 in TDMA frameTDMA Frame has 8 slots, with duration of 4.6152 ms.Burst : data signal, Physical Informat
19、ion stores inside one TimeSlot.23,TDMA Notion1 TDMA Frame,0 1 2 3 4 5 6 71 Slot,Carrier,BTS,4,Data Bits Encrypted,TSCTraining Sequence Code,Data Bits Encrypted,3 bits,58 bits,26 bits,58 bits,3 bits,24,25,TDMA NotionFrame Division,120 ms,235.8ms,0 1 2,23242526- multiframe0 1 20 1 2,0 1 2,48495051- mu
20、ltiframe48 49 5023 24 25,superframe,0,1,2,2045 2046 2047,Hyperframe = 3h 28 mn 53 760msEach TDMA Frame includes a Number relevant to HyperframeFN (Frame Number from 1 to 2 715 648),MOBILE IN IDLE MODE,MS selects in continue the best cell(the strenghest Rx signal in dBm).,Check if detected PLMN corre
21、sponds to its Home PLMN,Identify cell parameters for accessing to cell,(incoming call or outgoing call).,Check if decoded LAC number has changed,Selects in continue the best Main Cell,26,MOBILE IN IDLE MODE,FCCH Channel,Specific Burst transmits each 50 ms,5 times/per 51 multiframe,- Used by MS to sy
22、nchonize in frequency,- Sinus signal transmitted around f0 + 1625/24kHz,- Transmit in TS0 in Main Frequency,- Position in 51-multiframe :,0, 10 , 20, 30, 40,MS processes first Power Detection on reception of,FCCH channel,27,MOBILE IN IDLE MODESCH ChannelTiming Synchronization is done with SCH Channe
23、l on Main FrequencySpecific Burst transmits each 50 ms in time slot 0 ms5 times/per 51 multiframe1 Slot,Data Bits Encrypted,Long Training Sequence Code,Data Bits Encrypted,3 bits,39 bits,64 bits,39 bits,3 bits,28,MOBILE IN IDLE MODE,SCH Channel,FCCH,SCH,FS,FS,FS,FS,FS,0 1 2,10,20,30,40,50,0 1 2 3 4
24、5 6 7,SCH channel includes 2 parameters:,1 TDMA Frame,- Number of Frame called FN- Color Code of Cell: BSIC (Base Tranceiver Station Identity Code)* BCC = TSC of normal burst, BS Colour Code (3 bits)* NCC = PLMN Code, Network Colour Code (3 bits)29,30,MOBILE IN IDLE MODEBCCH ChannelTransmit logical
25、network information :- Area Location Number : LAC,- Cell Access parameters,RACH Channel Description,- Common Channel Organisation-Neighbour Cells List, description of main frequencyfor each neighbour- CI: Cell Identity- Information for detecting PCH Channel (incoming call)Channel encoded in 4 normal
26、 Bursts, 1 time/per 51 multiframe,MOBILE IN IDLE MODE,Roaming Notion,MOBILE MUST BE CALLED EVERYWHERE,+,NETWORK CAN NOT STORE CELL ID,FOR EVERY MOBILE,=,NETWROK REGISTERS IN VLR,LAC NUMBER DECODED BY MOBILE,31,MOBILE IN IDLE MODERoaming NotionLAC 92010CI 2Mobile shall transmit to network,CI 1CI 5,CI
27、 3LAC 92011,LAC number decodedCI3 broadcasts new LAC numberFor this mobileLocation Updating.32,HOW TO CALL A MOBILE ?,PCH Channel,This Paging channel broadcast subscriber identity joinedMobile lists in continue this channel,4 subscribers can be simulanemous called,Subscriber Identity:,IMSI stores in
28、 HLR and SIM card.,MCC : Mobile Contry Code, France 208 China 460,MNC : Mobile Network Code, PLMN Number,MSIN : subscriber number inside PLMN,33,HOW TO CALL A MOBILE ?,For Paging a mobile, network uses shorter identity than IMSI,TMSI (Temporary IMSI),Registered in VLR and SIM Card,TSMI is reallocate
29、d every communication by network (VLR),If network can not match this TMSI, otherwise mobile shall transmit,IMSI,34,35,HOW TO CALL A MOBILE ?,SFR,- TMSI 1052 (0612251120),MSC,- LAC 75010,- TMSI 1052,BSC,VLR10 - TMSI 1052IMSI XX,- TMSI 1052,BSC,HLR 25,PS T,N,- TMSI 1052LAC 75010,- 0612251120 - VLR 10
30、- IMSI XX,HOW TO CALL A MOBILE ?,亲爱的，,你晚上带面包回来吧!,When mobile receives a Paging Message including its Id,It shall start Paging Response procedure,IT S ALWAYS MOBILE THAT TRIGS A COMMUNICATION,36,MOBILE IN COMMUNICATION,GSM Communication includes:,1- Location Updating ,2 Incoming Call or Mobile Termin
31、ating Call ,3 Outgoing Call or Mobile Originating Call ,4 - Emergency Call ,5 - SMS received or send ,6 - Supplementary Services,37,MOBILE IN COMMUNICATION,RACH Channel,When mobile want to access to network, specific burst is sent In RACH Channel,Mobile includes random number or Random Reference or
32、identifying its communications,GSM feature : mobile can move, it can loose synchronization with cell,TDMA (reception or transmission).,Timing delay shall be processing in continue when mobile sends bursts,distance estimation between MS and BTS,38,MOBILE IN COMMUNICATIONRACH ChannelSpecific Burst in
33、uplink slot 01 Slot,SynchronizationSequence,Data Bits,Guarding Period252s Max,8 bits,41bits,36 bits,3 bits,252s of guarding period corresponds to maximum cell of37.8 kmBTS estimates distance between Mobile and itself,Using guarding period:This distance is Called Timing Advance (TA)39,MOBILE IN COMMU
34、NICATION,AGCH Channel,Channel encoded with 4 normal bursts, in dowlink slot 0 - Used for replying to mobile access network,-Includes all parameters for mobile for switching in dedicated mode, Random Reference set by mobile (avoiding collision), distance between mobile and BTS (TA), step of 550m, fre
35、quency (ARFCN) and Time Slot used for dedicated channel,reserved by BSC for each communication.,40,C,MOBILE IN COMMUNICATIONMaximal Configuration for Common ChannelsOnly with 51- multiframe and slot 0,FCCH,SCH,BCCH,C = PCH or AGCH,Downlink Way (BTS towards MS),FS B,C FS C,C FS C,C FS C,C FS C,012,10
36、,20,30,40,50,Uplink Way,RACH,R R R R R R R R R R R R RR R R R R R R R R R R R R R R R RR R R R R R R R R R R RR R R R R R R R R,0,10,20,30,40,50,41,MOBILE IN COMMUNICATIONMinimal Configuration for Common Channels,FCCH,SCH,BCCH,C = PCH or AGCH,Downlink Way (BTS towards MS),FS B,C FS C,C FS D0,D1 FS D
37、2 D3 FS,A0 /A2,A1 /A3,0,10,20,30,40,50,Di : SDCCHi,Ai : SACCHi,Uplink Way,RACH,D3,RR,A0 /A2,A1 /A3,R R R R R R R R R R R R R R R R R R R R R R R,D0,D1,RR,D2,0,10,20,30,40,50,42,MOBILE IN COMMUNICATION1 Slot = 0.5769ms1 Burst includingt 2x 58 data bits,Data Bits Encrypted,TSC,Data Bits Encrypted,3 bi
38、ts,58 bits,26 bits,58 bits,3 bits,0 1 2 3 4 5 6 71 TDMA Frame= 8 slots51 TDMA Frames,Carrier,10 20 Common Channel only in Slot N 0SCHBCCH,30,40CCCH = PCH or AGCH,50,1 slot,4 slots,4 slots,43,MOBILE IN COMMUNICATION,SDCCH Channel,First Dedicated Channel assignes for communication :,Transmit Control m
39、essages,Channel encoded with 4 normal burst :,Processing:,Subscriber authentication,Cyphering communication,Call Information,(voice/data, call number),44,MOBILE IN COMMUNICATIONSACCH ChannelDedicated Channel used for one communication,Transmits following information:, Timing Delay,TA, MS Transmissio
40、n Power Control Link Radio Quality estimated by MS Neighbour Measurements done by MS45,MOBILE IN COMMUNICATIONMultiplexing SDCCH-SACCH51 - Multiframe,D0,D1 D2 D3 D4 D5 D6,D7,A0/ A1/ A2/ A3/A4 A5 A6 A7,0,10,20,30,40,50,A1/ A2/ A3/A5 A6 A7,D0 D1 D2,D3 D4 D5 D6 D7 A0/A4,Di = SDCCHi Channel Ai = SACCHi
41、Channel associated with SDCCHi46,47,LE MOBILE EN COMMUNICATIONFACCH-TCH ChannelSpeech Channel, trnasmitted- either data,- or voiceIn case of mobile needs to transmit control messageTCH switchs to FACCH channel.For example when mobile changes of main cell (HandOver procedure),Data Bits Encrypted,TSC,
42、Data Bits Encrypted,3 bits,57 bits,26 bits,57 bits,3 bits,Bit = 0 TCH Channel Bit = 1 FACCH Channel,MOBILE IN COMMUNICATIONMultiplexing FACCH/TCH-SACCH26 -Multiframe,TT T T,T T T T F F F F F F F F T T T T,A T T T T T T T T T T T T I,0 1 2,12,25,T : TCH,F : FACCH,A : SACCH,I : IDLE,In IDLE slot MS ca
43、n process neighbour measurements48,MOBILE IN COMMUNICATIONExample of communicationSFRCI 1,CI2,SFR,49,MOBILE IN COMMUNICATIONExample of communicationIMobile Status : IDLE,Actions :,Detect strengthest cell using FCCH Channel:CI1 is selectedDecode SCH Channel of CI1and done fine timing synchronization
44、on CI1Decoder BCCH Channel of CI1 and check Whether CI1 is its Home PLMNMonitors PCH Channel , in case of incoming call Monitors neighbour cells reception50,II,MOBILE IN COMMUNICATIONExample of communicationMobile Status: User starting communication,Actions :,Mobile sends Burst Random Accesor Access
45、 Burst in RACH ChannelNetwork detects Burst RA, and calculates TABSC allocates SDCCHi ChannelNetwork replies into AGCH Channel to MS All parameters describing SDCCHi Channel(frequency, TS, FN) Radio information for MS (TA, Power Tx control)51,II,MOBILE IN COMMUNICATION,Example of communication,Mobil
46、e synchronize finely in Uplink (using TA) And starts to exchange control messages into SDCCHi Channel.,Mobile transmits Service Requirement in SDCCHiChannel: Mobile Originating Call including TMSI.VLR (controlling area including CI1) identities,subscribers TMSI, and processes authentication procedur
47、e And ciphering mode.,Now GSM communication can support voice service,In allocation TCH Channel.,52,MOBILE IN COMMUNICATION,Example of communication,MSC requires BSC to activate voice channel,BSC allocates TCHi channel,Network replies into SDCCHi Channel all parameters,describing TCHi Channel (frequ
48、ency, TS, FN) Radio information for MS (TA, Power Tx control)Mobile synchronize finely in Uplink (using TA),And starts to contine exchanging control messages into,FACCH/TCHi Channel.,Connection end-users is done,They can speak,53,III,54,MOBILE IN COMMUNICATIONExample of communicationMobile Status: U
49、ser moving CI1 to CI2,Actions :,Mobile measures neighbour cells strength signal,Of CI1 ( BA List ).Mobile selects 6 best neighbour cells andEstimates quality reception and strength signalReception of its main cell CI1These information are sent to BSC thhrough Measurement Report control message inSACCH.channelBSC detects that CI2 Rx Level is better than CI1.Communication shall switch to CI2, HandOver to CI2 is processing,
