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SMART Communications, Inc. SYSTRA Introduction to GSM There was an increasing need for telecommunication services which prompted CEPT tospecify a common mobile system for Western Europe later to be called GSM ( GlobalSystem for Mobile ) GSM later on spread throughout Eastern Europe, Africa, Asia and Australia. GSM system primary requirements: 1. There should be several network operators in each country to encouragecompetition. 2. The GSM system must be an open system. 3. The GSM network must be built without causing any major modificationsto the existing Public Switched Telephone Networks ( PSTN ). Advantages of GSM Efficient use of radio frequencies and more tolerant to interference. Quality of speech is better than analog systems. Data transmission is supported. Speech is encrypted and subscriber information security is guaranteed. New services can be offered due to compatibility with ISDN system. International roaming is possible. Competition and large market results in lower prices. Traffic Management Objectives Name the three subsystems of GSM. Explain the mobility concept ( handover, location update, paging ). Describe how mobile originated and mobile terminated calls are handled in GSM. GSM subsystems BSC MSC VLR GMSC HLR NMS MS BSS NSS Air A O&M A-bis NSS Functions: 1. Mobility Management 2. Subscriber Data Handling 3. Signalling ( towards othernetwork elements ) 4. Call Control 5. Charging 6. Locating a subs for mobile terminated calls. GSM subsystems BSC MSC VLR GMSC HLR NMS MS BSS NSS Air A O&M A-bis BSS Functions: 1. Radio Path Control, BTS and TC control, Sync withMSC. 2. Air and A interface signalling, Connection establishment. 3. Mobility management, Speech Transcoding 4. Collection of Statistical data GSM subsystems BSC MSC VLR GMSC HLR NMS MS BSS NSS Air A O&M A-bis NMS Functions: 1. Fault Management 2. Configuration Management 3. Performance Management MSISDN = CC +NDC +SN CC = Country Code NDC = National Destination Code SN = Subscriber # IMSI = MCC + MNC + MSIN ( fixed 15 digits ) MCC = Mobile Country Code MNC = Mobile Network Code MSIN = Mobile Subscriber Identification # LAI = MCC + MNC + LAC MCC = Mobile Country Code (of visiting country) MNC = Mobile Network Code(of serving PLMN) LAC = Location Area Code BTS 1 BSC 1 MSC VLR1 MSC VLR2 LAI 1 MS B First time Location Update (1) Loc Up HLR IMSI Request IMSI HLR DB MSISDNIMSIVLR AddressSub. Data 63+918+9499247 310+02+1234567890vlr2servicesLoc Up + TMSI Authen BTS 1 BSC 1 MSC VLR1 MSC VLR2 LAI 1 MS B Generic Location Update TMSI + LAI HLR Loc Up + new TMSI TMSI IMSI Security Info Subscriber Info Update Del old data Authentication MS BSSMSCVLRHLR LOCATION UPDATE REQUEST REQUEST SUBS ID SEND SUBS ID REQUEST SUBS INFO SEND SUBS INFO AUTHENTICATION AUTHENTICATION RESPONSE HLR UPDATE PSTN BTS 1 BSC 1 MSC VLR1 MSC VLR2 HLR HLR Enquiry HLR DB MSISDN IMSI VLR AddressSub. Data 63+918+9499247 310+02+1234567890vlr2servicesVLR DB IMSIMSRN LAI DATA 310+02+1234567890 1services LAI 1 MSRN POOL MS B IMSI A B Call Establishment (PSTNO-MT) MSISDN MSISDN (B) CC+NDC + SN 63 9189499247 IMSI = MCC+MNC+MSIN MSRN = CC+NDC+SN MSISDN PSTN BTS 1 BSC 1 MSC VLR1 MSC VLR2 LAI 1 MS A B Call Establishment (MO-PSTNT) MSISDN MSISDN (A) CC+ NDC + SN 63 25113580 HLR VLR DB IMSIMSRNLAIServices 2Speech BTS 1 BTS 2 BSC 2 BSC 1 MSC VLR1 MSC VLR2 HLR HLR Enquiry LAI 1 LAI2 MSRN MS MS B IMSI B C Call Establishment (MO-MT) MSISDN MSISDN (C) CC+NDC+ SN 63 9189499247 IMSI = MCC+MNC+MSIN MSRN = CC+NDC+SN MSISDN HLR DB MSISDNIMSIVLR AddressSub. Data 63+918+9499247 310+02+1234567890vlr1servicesHandover (1) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR A B Measurement Report Handover (2) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A I am OK Handover (3) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A Measurement Report Handover (4) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A I am OK Handover (5) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A Measurement Report Handover (6) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A I am OK Handover (7) MSC/VLR 1 MSC/VLR 2 BSC1 BSC2 BSC3 BTS4 BTS3 BTS2 BTS1 PSTN HLR B A Review Questions 1. Which is the following does not contain subscriber data? a) HLR b) VLR c) MSC d) SIM 2. The format of IMSI is: a) CC + NDC + SN b) MCC + MNC + MSIN c) MCC + MNC + LAC d) Operator specific 32 bit number 3. The three subsystem of GSM are: a) NMS, PSTN, MS b) NMS, BSS, MS c) NSS, BSS, MS d) NSS, BSS, NMS 4. Which of the following will result in a HLR Enquiry? a) PSTN originated PSTN terminated call b) Mobile originated PSTN terminated call c) PSTN originated Mobile terminated call d) None of the above 5. A Location area 1. Is a geographical area under one BSC. 2. Is equal to one MSC area. 3. Is equal to one cell. 4. Is identified by a unique Location Area Identity. 6. Which of the following combination best describes the BSS. 1. BSC, TC, BTS 2. MS, BSC, BTS 3. TC, Submultiplexer, BTS 4. BSC, BTS, MS 7. The BSS 1. Is responsible for radio network control. 2. Is located between Air and A interfaces. 3. Gets synchronization from MSC 4. All of the above. 8. Name two reasons for performing a handover. 9. Name 4 different handover cases. Transmission Objectives Differentiate between physical and logical channels. List and describe the twelve different types of logical channels and their functions. Describe how air interface properties affect the transmission of speech between MS and network and explain GSM solutions to these problems. Describe the main function of transcoders. List 3 BSC/BTS connections. ACCESS METHODS FDMACDMA TDMA Frequency Division Code DivisionTime Divisionf1 f2 f3 4}4} 4 4 4 } } } *+4^==*+4^= ****** 4444444 ======== TDMA is used in GSM system FRAME STRUCTURE 1 TDMA Frame = 8 TDMA Time Slots 01234567 4.615 ms TailDataFTrainingDataFTail Or Speech Flag 3 000 57 1 261573 Burst 148 bits 156.25 bits0.577 ms Basic TDMA frame, timeslot and burst structure FDT TT TT T SDT TT TT T BDT TT TT T BDT TT TT T BDT TT TT T BDT TT TT T CDT TT TT T CDT TT TT T CDT TT TT T CDT TT TT T FDT TT TT T SDT TT TT T CD A T AT A T CDT TT TT T CDT TT TT T CDT TT TT T TS0TS1TS2 TS3 TS4TS5 TS6 TS7 4.615 ms . . . . . . . . . . . . . . . . . . . . . . . . 1 Frame(Downlink - BTS transmit) 1 carrier = 200 kHz F = FCCH S = SCH B = BCCH C = PCH or AGCH D = SDCCH A = SACCH T = TCH RDT TT TT T RDT TT TT T RDT TT TT T RDT TT TT T RDT TT TT T R DT TT TT T RDT TT TT T RD T TT TTT RDT TT TT T RDT TT TT T RDT TT TT T RD T TT TT T RD A IAIAI RD T TT TT T RDTTT TT T RD T TT TT T TS0TS1TS2 TS3 TS4TS5 TS6 TS7 4.615 ms . . . . . . . . . . . . . . . . . . . . . . . . 1 Frame (Uplink - Mobile transmit) 1 carrier = 200 kHz R = RACH A = SACCH T = TCH LOGICAL CHANNELS On every physical channel, a number of logical channels are mapped. Each logicalchannel is used for a specific purpose. 11 Logical Channels in the GSM system: 2 are used for Traffic 9 are used for Control Signaling LOGICAL CHANNELS TRAFFIC CHANNELS (TCH) Full Rate Channel Half Rate Channel CONTROL CHANNELS (with horrible abbreviations!) Broadcast Channels (BCH) Frequency Correction Channel (FCCH) Synchronization Channel (SCH) Broadcast Control Channel (BCCH) Common Control Channels (CCCH) Paging Channel (PCH) Random Access Channel (RACH) Access Grant Channel (AGCH) Dedicated Control Channels (DCCH) Stand alone Dedicated Control Channel (SDCCH) Slow Associated Control Channel (SACCH) Fast Associated Control Channel (FACCH) Hey! Dont shout at me, lower your power... BROADCAST CHANNELS all downlink! FCCH SCHTDMA#BSIC... BCCH Hey. Im a GSM xmitter! GSM? GSM!!! LAneigborscell infomax power... Okok COMMON CONTROL CHANNELS PCH downlink only Hello! You have a call. RACH uplink only Hello! I have to set up a call. I need SDCCH. AGCH downlink only Ok. Use SDCCH. DEDICATED CONTROL CHANNELS uplink and downlink SDCCH SACCH timing advance MS power FACCH handover On SDCCH: -call set up signaling -location updating -periodic registration -IMSI attach/detach -SMS -facsimile etc.. On SACCH -mobile transmits signal strength on ncell quality Dont shout at me/ I cant hear you. FADINGS signal level (dB) log (distance) global mean value log normal fading local mean value slow fading shadowing long-term fading rayleigh fading fast fading short-term fading so many names to make life worst! FAST FADING signal level (dB) log (distance) present due to the fact that the mobile antenna is lower than the surrounding structures such as trees and buildings.( Multipath propagation ) peak-to-peak distance is ~ lambda/2 (in GSM ~ 17 cm) affects the signal quality and can lead to signal level below the receiver sensitivity. SOLUTIONS: use more power at the transmitter (providing a fadingmargin). use space diversity. SLOW FADING signal level (dB) log (distance) if we smooth out the fast fading, the signal variation received is called the local mean or the slow fading. caused by obstructions near the mobile such as buildings, bridges and trees and this may cause a rapidchange of the local mean (in the range of 5 to 50 meters). ( Shadowing ) because slow fading reduces the average strength received, the total coverage from the transmitter is reduced. SOLUTION: fading margin must be used. Concept of Multiplexing Network Planning Objectives List the main steps of the radio network planning process. Define the main radio network parameters. Explain how frequencies are reused. THE CELL PLANNING PROCESSTraffic and Coverage Analysis Nominal Cell PlanSurveys System Design Implementation System Tuning TRAFFIC DATA Based on ERICSSON Initial PlanningSystem Growth THE CELL PLANNING PROCESS Traffic and Coverage Analysis Nominal Cell PlanSurveys System Design Implementation System Tuning TRAFFIC DATA Based on ERICSSON Initial PlanningSystem Growth geographical area. expected need of capacity. cell