1、Agenda. GSM900/DCS1800 . The GSM Network & Air Interface . Technical Basics . Speech Coding . Types of Channel . Making a Phone Call Global System for Mobile( Groupe Special Mobile )G S M1982Groupe Special Mobile?is created within CEPT1986A Permanent Nucleus is set up1987 Main radio transmission tec

2、hniques are chosen, based on prototype evalution (1986)1989GSM becomes an ETSI technical committe1990The phase 1 GSM 900 specifications are finalized1991First systems are running 1992 All major European GSM 900 operators begin commercial operator GSM Development History Speech Services Data Services

3、 Short Message Services (SMS) Supplementary Services Subscriber Identity Module (SIM) Security FunctionGSM / DCS1800 FunctionalitiesRF AspectsTDMA0.3GMSK ModulationBurst Power TransmissionNeighbour Cells MeasurementHoppingUplink / Downlink DTxBER & Receiver Testing GSM900/DCS1800/PCS1900GSM Frequenc

4、y Range890 - 915 MHz Uplink / MS Transmit935 - 960 MHz Downlink / BS TransmitDuplex Offset 45 MHzChannel Spacing 200kHzChannel numbering 1 - 124Transmission Speed 270 Kbits DCS1800 Frequency Range1710 - 1785 MHz Uplink / MS Transmit1805 - 1880 MHz Downlink / BS TransmitDuplex Offset 95 MHzChannel Sp

5、acing 200kHzChannel numbering 512 - 885Transmission Speed 270 Kbits GSM Primary Band890900910920930940950960Freq45 MHzUplink ( Mobile to Base )Downlink ( Base to Mobile )DCS1800 Primary Band17101735176017851800182518501875Freq95 MHzUplink ( Mobile to Base )Downlink ( Base to Mobile )Carriers at the

6、border of the GSM band890.2890.4890.6890.8FreqGSM band200 kHzCarriers at the border of the DCS1800 band1710.21710.41710.61710.8FreqDCS1800 band200 kHzGSM NetworksBSCBTSBTSBTSBSSBSCBTSBTSBTSBSSMSCMSCOMCOMCADCNMCVLRVLRHLRAUCEIRInterface to other networkMSGSM NetworksTerminology:MS- Mobile Station (移動臺

7、)BSS- Base Station System (基站系統(tǒng))BTS- Base Transceiver Station (基站收發(fā)臺)BSC- Base Station Controller (基站控制器)MSC- Mobile Switching Centre (移動業(yè)務交換中心)OMC- Operations and Maintenance Centre (操作與維護中心)NMC- Network Management Centre (網絡管理中心)AUC- Authentication Centre (鑒權中心)HLR- Home Location Register (歸屬位置寄存器

8、)VLR- Visitors Location Register (來訪位置寄存器)EIR- Equipment Identity Register (設備標識寄存器)MSCBSCBSCBSCPSTNBTSBTSBTSAir InterfaceAbis InterfaceSS#7SS#7GSM InterfaceMSGMSK Modulation110010110010PSKGuassian FilterSpectrum 200kHzFcFc + 67.708KHzFc + 67.708KHz+67.708KHz-67.708KHzData Type ?0Data Type ?1Modulat

9、ion401234567123456FrequencyAmplitudeARFCNTimeslotPhysical Channel isan ARFCN and TimeslotTDMA and FDMATDMA and FDMATerminology:FDMA - Frequency Division Multiple AccessTDMA - Time Division Multiple AccessARFCN - Absolute RF Channel NumberTS - TimeslotPhysical - The Combination of a TS number Channel

10、s and ARFCN.Logical - Are Mapped on Physical Channels Channels10us10us10us10us8us8us3311575726 148 Active Bits, 546.42us 147 Useful Bits542.8us-70dB-30dB-6dB+4dB-6dB-30dB-70dBTol -1.0dBTol +1.0dBGSM TDMA Power BurstPower Time Template542.8 us / 147 Bits1081010810TimePower-700dBUpper LimitLower Limit

11、ActualusNormal BurstPower Time Template321.23 us / 87 Bits1081010810TimePower-700dBUpper LimitLower LimitActualusAccess Burst87 bitsUplink & DownlinkDownlink / MS Receive5670123456701342067012345671342Uplink / MS Transmit5Uplink & DownlinkARFCN02473601350614725312645724603571321045670123456700345670

12、123451ARFCNUPLINKDOWNLINK45MHz. Uplink Lags Downlink by 3 Timeslot periods. Uplink and Downlink use same Timeslot Number. Uplink and Downlink use same Channel Number (ARFCN). Uplink and Downlink use different bands(45MHz apart for GSM900)Frequency HoppingMODCouplerSwitchSynthRegisterControlUplink BS

13、 1BS 2MonitoringRX LevRX QualDownlink 165124165124Home BS20ms BlocksSpeech CoderBits Ordered260 Bits260 Bits5013278. RELP and LTP Coder RELP- Residual-Excited Linear Prediction Coder LTP- Long Term Prediction. Converts Speech to Low Data Rate. 20ms Speech makes 260Bits. Output 13kbit/sVery Important

14、 BitsImportant BitsOther BitsSpeech CoderError CorrectionType Ia 50Type Ib 132Type II 7850132783Type IaCRCType IbType IIBlock Code256625663478Re-ordering37878Half rate convolutional code456 Bits from 20ms of SpeechType IaType IbType IbType IaTailType IICRC262 BitsIn456 BitsOutDiagonal Interleaving45

15、6 Bits from 20ms of Speech456 Bits from 20ms of Speech575757575757575757575757575757575757575757575757575757575757TCHTraffic Channel (TCH) Bursts Carry Two 57 Bits Blocks (114) Each120ms of Speech = 456x6 = 2736 bits2736/114 = 24 bursts I.e. 24frames(mobile transmits once per frame)Multiframe has 26

16、 frames in 120msThere are 2 spare frames厖 One SACCH, one Idle 中國最大的資料庫下載Speech to Radio / Radio to SpeechChannelcodingSpeechDigitizing and Source codingInterleavingBurst formatting CipheringModulationChanneldecodingSpeechSource decodingDe-interleavingBurst formatting DecipheringDemodulationMS Camp o

17、n Flow ChartMS Turn OnMS searches channelsand orders by signalstrengthMSStongestBCCHFCCH on BCCH and adjusts timebaseSCH on BCCH and fine tunes timebase & timingDecode BCCH & store info Is BCCHin PLMN ?MSNext StongestBCCHYESNOYESNONOLocation =Previous Location?YESYESMS camped on - listens for page,

18、can request serviceUsing SACCH - adjust power, TA & report RX QualetcMS goes to the assigned SDCCH ( Freq., timeslot, . )for authentication + location UpdateMS sendsRACHBS assigns SDCCH to MS using the CCCH Orignated CallBS pages MS usingthe CCCH MS sends RACHBS ORIGINATED CALLMS ORIGINATED CALLMS r

19、esponds withRACH BS assigns MS to SDCCH or TCHMS transmits and receives speech on TCHTCHUsing the FACCH onTCH authentication &location updateUsing the SDCCH, authentication,call setup, and TCH assignmentUsing the SACCH, BS commands MS to adust power + timing, MSreports power + Rx quality of BCCH + adjacent BCCHMS transmits + receives speechon TCHUsing the SACCH on TCH, MSreports power + Rx quality , BScommands MS to adjust power ,TADuring inactive timeslots, MS measures adjacent cells, BCCHCall disconnected by MS or BSSubscriber Identity Module ( SIM )SIM contains ( at least ) following i