Gsm fundamentals

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Gsm fundamentals

  1. 1. INTRODUCTION, GSM-FUNDAMENTALS PRESENTED TO NIGERIAN SOCIETY OF ENGINEERS- ELECTRICAL DIVISION( NIGERIAN INSTITUTION OF ELECTRICAL AND ELECTRONICS ENGINEERS-NIEEE) BY 2
  2. 2. ContentsBasic Concepts of Cellular Mobile SystemGSM Network ComponentsTerrestrial InterfaceService Area and Number PlanningChannels on The Air Interface 3 Engr
  3. 3. The Frequency Spectrum GSM 900 EGSM GSM EGSM GSM880 890 915 925 935 960 MHz Duplex Separation: 45MHz Channel Bandwidth: 200KHz 4 Engr
  4. 4. The Frequency Spectrum DCS 1800 Base Station Receive Base Station Transmit1710 1785 1805 1880MHz Duplex Separation: 95MHz Channel Bandwidth: 200KHz 5 Engr
  5. 5. Frequency Re-UseWhat is Frequency Re-Use?Because frequency resource of mobile system isvery limited,different Subscribers must use the samefrequency in different place.Of course, the quality of communication must beensured. 6
  6. 6. Frequency Re-Use How can we reuse frequency? 27(Site)X 1(Cell) 7 3Re-use 2 1 6 4 5 7 Engr
  7. 7. Frequency Re-Use4(Site)X 3(Cell) 5 1Re-use 7 9 6 3 2 5 11 8 10 1 4 9 6 12 7 2 3 10 5 11 1 9 8 Engr
  8. 8. CELL OmniOmni-Directional Cells 1 120 Degree Sectors 1 120 degree 2 3 9 Engr
  9. 9. ContentsBasic Concepts of Cellular Mobile SystemGSM Network ComponentsTerrestrial InterfaceService Area and Number PlanningChannels on The Air InterfaceRadio TechnologiesThe Future Development 10
  10. 10. GSM Network Components NSS AUC HLR EIROSS OMC MSC/VLR PSTN SIMME BTS BSC MS BSS 11 Engr
  11. 11. Mobile Station—MSMS=ME+SIMInternational Mobile Equipment Identity (IMEI) – Mobile EquipmentInternational Mobile SubscriberIdentity (IMSI) – Subscriber Identity Module 12 Engr
  12. 12. Subscriber Identity Module – SIM International Mobile Subscriber Identity (IMSI) Temporary Mobile Subscriber Identity (TMSI) Location Area Identity (LAI) Subscriber Authentication Key (Ki) Mobile Station International Standard Data Network (MSISDN), it is optional. 13 Engr
  13. 13. Base Station Subsystem – BSS MSC The Base Station Controller – BSC The Base Transceiver BSS TC/SM Station – BTS The Trans-coder – TC and Sub multiplexer BSC (SM) BTS 14 Engr
  14. 14. The Network Switching System NSS AUC HLR OMC EIR EC PSTN MSC/VLR IWFMobile Switching Center – MSCHome Location Register – HLRVisitor Location Register – VLREquipment Identity Register – EIRAuthentication Center – AUC BSSInter-Working Function – IWFEcho Cancellor – EC 15 Engr
  15. 15. Mobile Service Switching Center – MSCCall ProcessingOperations and Maintenance SupportInter-network & Inter-workingBilling 16 Engr
  16. 16. Home Location Register – HLR Subscriber ID (IMSI and MSISDN) Current subscriber VLR (current location) Supplementary service information Subscriber status (registered/deregistered) Authentication key and AuC functionality 17 Engr
  17. 17. Visitor Location Register – VLR Mobile Status(IMSI detached/ attached) Location Area Identity(LAI) Temporary Mobile Subscriber Identity(TMSI) Mobile Station Roaming Number(MSRN) 18 Engr
  18. 18. Equipment Identity Register – EIR •White List •Black List IMEI Is Checked against White List •Grey List If NOT found, checked against Grey/Black ListIf NOT found, checked IMEIagainst White List Is Checked against Black/Grey ListindicationsIf found, returns a Blackor Grey List indicator 19 Engr
  19. 19. Operation and Maintenance Sub System OSS(NMC)OMC OMC OMC Region2 Region 3 Region 1 20 Engr
  20. 20. Operation and Maintenance Center – OMCOMC – R: OMC assigned specifically tothe Base Station SubsystemOMC – S: OMC assigned specifically tothe Network Switching Subsystem 21 Engr
  21. 21. OMC Functional Architecture Event/Alarm Security Management Management MMI OS DB Fault ConfigurationManagement Management Performance Management 22 Engr
  22. 22. GSM Interface D HLR G H VLR VLR C AUC EIR B F MSC MSC EIWF EC EC IWF A TC Um Abis MS BTS BSC 23 Engr
  23. 23. SigL1: 2MBps Trunks HLR OMC AUC IWF EIR MSC/VLR MSC/VLR EC EC TC BSC PSTNBTS BTS 24 Engr
  24. 24. 2MBps Trunks Typical Configuration TS 0 TS 1-15 TS16 TS 17-31 TS = Time slotTS# Used for 0 Frame Alignment /Error Checking /Signaling1-15 Traffic 16 CCS7 Signaling (Other TS may also the used)17-31 Traffic 25 Engr
  25. 25. ContentsBasic Concepts of Cellular Mobile SystemGSM Network ComponentsTerrestrial InterfaceService Area and Number PlanningChannels on The Air InterfaceRadio TechnologiesThe Future Development 26 Engr
  26. 26. Physical and Logical ChannelsThe physical channel is the medium over whichthe information is carriedThe logical channels consist of the informationcarried over the physical channel TDMA FRAME 0 1 2 3 4 5 6 0 7 Timeslot The information carried in one time slot is called a “burst” 27 Engr
  27. 27. Traffic Channel TCH Traffic Channels Normal Burst Speech DataTCH/FS TCH/HS TCH/9.6 TCH/2.4TCH Traffic ChannelTCH/FS Full rate Speech ChannelTCH/HS Half rate Speech ChannelTCH/9.6 Data Channel 9.6kb/sTCH/4.8 Data Channel 4.8kb/s TCH/4.8TCH/2.4 Data Channel 2.4Kb/s 28 Engr
  28. 28. Control Channel CCH Control Channels DCCH BCCH SDCCH ACCH BCCH Synch. CH. FACCH SACCH CCCH SCH FCCHBroadcast Control Channel – BCCH RACHCommon Control Channel – CCCH CBCHDedicated Control Channel – DCCHAssociated Control Channel – ACCH PCH/AGCH 29 Engr
  29. 29. Broadcast Control Channel – BCCHThe information carried on the CCHBCCH is monitored by the mobileperiodically when it is switched BCCHon and not in a call downlink onlyBCCH:Broadcast Control ChannelFCCH: Frequency Correction Synch.Channel BCCH ChannelsSCH: Synchronization Channel SCH FCCH 30 Engr
  30. 30. Common Control Channel – CCCH CCHThe CCCH is responsible fortransferring control informationbetween all mobiles and theBTS. CCCHRACH: Random Access ControlChannelPCH: Paging Channel RACH CBCHAGCH: Access Grant Control uplink downlinkChannelCBCH:Cell Broadcast Channel PCH/AGCH downlink 31 Engr
  31. 31. Dedicated Control Channel – DCCHDCCH is assigned to a single CCHmobile connection for call setupor for measurement and handoverpurpose. DCCHSDCCH: Standalone DedicatedControl ChannelACCH: Associated ControlChannel SDCCH ACCHSACCH: Slow Associated ControlChannelFACCH:Fast Associated ControlChannel FACCH SACCH 32 Engr
  32. 32. How to use these channel?Power-off state Search for frequency correction pulse FCCH Search for synchronous pulse SCH Unscramble system information BCCH Idle state Snoop into paging message PCH Send access pulse RACH Allocate signaling channel AGCHDedicated mode Set up the call SDCCH Allocate voice channel FACCH Conversation Release the call TCH Idle state FACCH 33 Engr
  33. 33. GSM Multiframe TDMA Frames 0 1 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 70 1 2 3 4 46 47 48 49 50 51 – Frame Multiframes CONTROL CHANNELS 34 Engr
  34. 34. Timeslots and TDMA FramesHigher Capacity Cell 0 1 2 3 4 5 6 0 7 Broadcast Traffic Dedicated 0 1 2 3 4 5 6 0 7 TrafficLow Capacity Cell 0 1 2 3 4 5 6 0 7 Combined Traffic 35 Engr
  35. 35. GSM Multiframe TDMA Frames 0 1 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 70 1 2 3 4 21 22 23 24 25 26 – Frame Multiframes TRAFFIC CHANNELS 36 Engr
  36. 36. ContentsBasic Concepts of Cellular Mobile SystemGSM Network ComponentsTerrestrial InterfaceService Area and Number PlanningChannels on The Air InterfaceRadio Technologies 37 Engr
  37. 37. Modulation Techniques Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM)– phase modulation can be implemented easily for digital signals, this is the method used for the GSM air interfaces. Phase Modulation is known as Phase Shift Keying when applied to digital signals 38 Engr
  38. 38. Gaussian Minimum Shift Keying (GMSK) Phase1 0 0 1 1 Gaussian Modulator Digital Filter 39 Engr
  39. 39. Battery LifePower Control Voice Activity Detection – VAD Discontinuous Transmission – DTX Discontinuous Reception – DRX 40 Engr
  40. 40. Power ControlBoth Uplink and Downlink 8Wpower settings can becontrolled independentlyand individually. 0.8W 5WSaves radio battery powerReduces co-channel andadjacent channel interference 41 Engr
  41. 41. VAD & DTX Without DTXEncoding the speech silences at a rate of 500 bit/s rather than the full 13Kb/s.If the mobile does With DTX not transmit during ‘silence’ there is a reduction in the overall power output requirement Comfort Noise 42 Engr
  42. 42. DRXDRX allows the mobile station to effectively “switch off” during times when reception is deemed unnecessary.BCCH Multiframe P = Paging ChannelPPPPPP BCCH PP MS Being MS in MS receive System MS in paged listen mode listen mode information 43 Engr
  43. 43. Multipath Fading•Diversity•Frequency Hopping Time Dispersion 44 Engr
  44. 44. Diversity Approx. 10 wavelengthsWhen diversity is implemented two antennas are situated at the receiver. These antennas are placed several wavelengths apart to ensure minimum correlation between the two receive paths. Compare orThe two signals are then add signalscombined, this ensures that alow signal strength is less likelyto occur. Resultant Signal 45 Engr
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