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gsm

  1. 1. GSMGlobal Systemfor Mobiles 1
  2. 2. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 2
  3. 3. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 3
  4. 4. Telecom Basics• Communication – Voice and Data – Analog and Digital – Circuit Switched and Packet Switched – Media - Copper Wire, Co-axial cable, Air, Optical Fibre – Networks -PSTN, ISDN, PDN and Mobile Networks 4
  5. 5. Background to GSM• 1G : Advanced Mobile Phone Service (AMPS) • Analog, Circuit Switched, FDMA, FDD• 2G : Digital Advanced Mobile Phone Service (D-AMPS) • Digital, Circuit Switched, FDMA, FDD• 2G : Global System for Mobile (GSM) • Digital, Circuit Switched, FDMA and TDMA, FDD• 2G : Code Division Multiple Access (CDMA) • Digital, Circuit Switched, FDMA, SS, FDD 5
  6. 6. GSM History 6
  7. 7. Development of the GSM Standard1982: Groupe Spécial Mobile (GSM) 1992: Official commercial launch of created GSM service in Europe. First Launch in Finland1984: Description of GSM features 1993: The GSM-MoU has 62 signatories in 39 countries1985: List of recommendations settled worldwide.1987: Initial MoU (Memorandum of 1995: Specifications of GSM phase 2 Understanding) aside the drafting are frozen. of technical specifications was signed by network operators of 13 1999: GSM MoU joins 3GPP (UMTS) countries: GPRS Trials begins1988: Validation and trials, of the radio 2000: 480M GSM subscribers interface. Worldwide First GPRS Networks roll out1991: First system trials are demonstrated at the Telecom 91 End 2002: 792M GSM subscribers exhibition. Worldwide 7
  8. 8. GSM Specifications 01 SERIES 12 SERIES GENERAL 02 SERIES OPERATION AND MAINTENANCE SERVICE ASPECTS 11 SERIES 03 SERIES EQUIPMENT AND TYPE NETWORK ASPECTSAPPROVAL SPECIFICATIONS 10 SERIES 04 SERIES SERVICE INTERWORKING MS-BSS INTERFACE AND PROTOCOLS 09 SERIES 05 SERIES NETWORK PHYSICAL LAYER ON THE INTERWORKING RADIO PATH. 08 SERIES 06 SERIES BSS TO MSC INTERFACES 07 SERIES SPEECH CODING TERMINAL ADAPTERS SPECIFICATIONS FOR MOBILE STATIONS
  9. 9. Increasing GSM Data Rates video UMTS photo report clip video E/GPRS web photo report clip video ISDN e-mail web photo report clip video PSTN e-mail web photo report clip video GSM e-mail web photo report clip 0 10 sec 1 min 10 min 1 hour GPRS = General Packet Radio ServiceTransmission HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution Time UMTS = Universal Mobile Telecommunication System
  10. 10. Wireless Data Technology Options 2M 1M ketthroughput kbps p ac it rcu 100 k EDGE 64 k ci HSCSD UMTS 14.4 10 k GPRS 9.6 Time frame 1k 1998 1999 2000 2001 2002 GPRS = General Packet Radio Service HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution UMTS = Universal Mobile Telecommunication System 10
  11. 11. Circuit-Switched or Packet-SwitchedCircuit modePacket mode A →F A F B →F A C →H →G D A CF →G C D AH F →G C →G →H C D AF →G C G D →H D →H D H E 11
  12. 12. Multiple Access Technique• Multiple Access – Achieved by dividing the available radio frequency spectrum, so that multiple users can be given access at the same time.• FDMA - Frequency Division Multiple Access – ( eg: GSM each Frequency channel is 200KHz)• TDMA - Time Division Multiple Access – ( eg: GSM each frequency channel is divided into 8 timeslots)• CDMA - Code Division Multiple Access – (eg: IS95- Each User data is coded with a unique code) 12
  13. 13. Duplex Technique• Duplex - How the up link and Down link of a user is separated• FDD - Frequency Division Duplex – (eg:In GSM the up link and down link of a user is separated by 45MHz )• TDD - Time Division Duplex – (the up link and down link of a user will be at the same frequency but at different Time ) 13
  14. 14. GSM Concepts - Cellular Structure 2 2 7 Cellular7 3 1 Networking technology 1 6 that breaks geographic6 4 5 area into cells shaped 5 like honey comb Cell is the radio coverage area of one base transceiver station 14
  15. 15. What are the types inGSM Network?• GSM-900 (Channels 125 operating band 900Mhz carrier spacing 200khz spacing 45Mhz)• GSM -1800 (Channels 374 spacing 95Mhz)• GSM -1900(Used in USA) 15
  16. 16. GSM Band Allocations (MHz) Duplex DuplexGSM systems Uplink Downlink Band Spacing channelsGSM 450 450.4-457.6 460.4-467.6 2x7.2 10 35GSM 480 478.8-486 488.8-496 2x7.2 10 35GSM 850 824-849 869-894 2x25 45 124GSM 900 890-915 935-960 2x25 45 124E-GSM (900) 880-915 925-960 2x35 45 174R-GSM (900) 876-880 921-925 2x04 41 40GSM 1800 1710-1785 1805-1880 2x75 95 374GSM 1900 1850-1910 1930-1990 2x60 80 299 Frequencies are in MHz Carrier frequency = ARFCN = Absolute Radio Frequency Channel Number
  17. 17. GSM Family Radio Band SpectrumUplink 450.4 457.6 478.8 486 824 849 GSM 450 GSM 480 GSM 850Downlink 460.4 467.6 488.8 496 869 894 MHz 915Uplink 915 876 880 890 915 1710 1785 1850 1910 P-GSM E-GSM GSM 1800 GSM 1900 R-GSM 921 925 935 960 1805 1880 1930 1990 960 MHzDownlink 960
  18. 18. Traffic/SignalingTraffic «bla bla bla...»Signaling « RING ! » riiiiing Network
  19. 19. MS GSM - Network Structure Um BTS VLR HLR BSC Abis MSC A B HMS C AuC BTS GMSC E F Abis EIR A E MSC BSC PSTN Um BTS X.25 VLR X.25 OMC Server 19
  20. 20. GSM System specifications Frequency band Uplink 890 - 915 MHz Downlink 935 - 960MHz Duplex Frequency Spacing 45MHz Carrier separation 200KHz Frequency Channels 124 Time Slots /Frame(Full Rate) 8 Voice Coder Bit Rate 13Kbps Modulation GMSK Air transmission rate 270.833333 Kbps Access method FDMA/TDMA Speech Coder RPE-LTP-LPC 20
  21. 21. Paired Radio Channels in GSM Case of GSM 900 Uplink Downlink BTS890 MHz Frequency 915 MHz 935 MHz Frequency 960 MHz0 channel # 124 0 channel # 124 Example: Channel 48 Duplex spacing = 45 MHz Frequency band spectrum = 2 x 25 MHz Channel spacing = 200 kHz 21
  22. 22. GSM Time Division Multiplex Frame and Physical ChannelsTime-slot TDMA frame TDMA frame TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 (frames repeat continuously) Time 0 4.615 ms 9.23 ms Physical channel # 2 = recurrence of time-slot # 2
  23. 23. Physical Channel BTS BTS time Without FH With FH n+1TDMAs 7 n TS 0n-1 MS1 MS2 MS3 1 // FDMA 2 124 ARFCN
  24. 24. Radio Link Aspects• From Speech to RF Signal Blah... Blah... Blah... Blah… Blah… Blah... Digitizing and Source Decoding Source Coding Channel Coding Channel Decoding Interleaving De-interleaving Ciphering Deciphering Burst Formatting Burst De-formatting Modulating Demodulating
  25. 25. Functions of the Radio Interface • Speech and users data CommunicationIdle mode • Signaling mode BTS BTS-1 BTS-2
  26. 26. Access Techniques Uplink 890 MHz to 915 MHz Down Link 935 MHz to 960 MHz 25 MHz divided into 125 channels of 200 KHz bandwidthUP 890.0 890.2 890.4 914.8 915.0DOWN 935.0 935.2 935.4 959.8 960.0 26
  27. 27. Access Techniques ...Time Division Multiple Access Each carrier frequency subdivided in time domain into 8 time slots Each mobile transmits data in a frequency, in its particular time slot - Burst period = 0.577 milli secs. 8 time slots called a TDMA frame. Period is .577 * 8 = 4.616 milli secs 0.577 ms 0 1 2 3 4 5 6 7 4.616 ms 27
  28. 28. 28
  29. 29. Fundamentals 960 MHz 959.8MHz 124 TS: Time slot 123DOWNLINK ……. GSM utilizes two bands(TDMAMHz. 890-915 Downlink of 25 frame) = 8 TS …… MHz band is used for uplink while the 935- 2 960 MHz is used for downlink. 200KHz 935.2 Mhz 1 0 1 2 3 4 5 6 7 The frequency bands are divided into 200 935 MHz KHz wide channels called ARFCNs (Absolute Radio Frequency Channel Numbers) i.e. Data burst = 156.25 bit periods = 576.9μs there are 125 ARFCNs out of which only 124 915 MHz are used. 914.8 MHz 124 Each ARFCN supports 8 users with each user 45 MHz 123 200KHz ……. slot (TS). 0 1 2 3 4 5 6 7 transmitting / receiving on a particular time Delay UPLINK …… 2 Uplink (TDMA frame) 890.2 MHz 1 890 MHz Therefore 1 TDMA frame = 156.25 x 8 = 1250 bits The technology and has a duration of 576.92μs x 8 = 4.615 ms 29
  30. 30. GSM Delays Uplink TDMA FramesBTS side The start of the uplink TDMA TDMA Frame (4.615 ms) is delayed of three time-slots 0 1 2 3 4 5 6 7 R R R R R R R R Downlink TDMA BTS T T T T T T T T Down UpMSs side link link MS1 R T MS2 R T Fixed transmit delay of three time-slots
  31. 31. Timing Advance 1 - Propagation Delay M2 d2 d1>>d2 M1BTS Frame reference TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 Propagation Delay τp Bits Overlapping MSs transmit
  32. 32. Timing Advance 2 - Without Timing Advance: CollisionTX BTS CAN W HAT GSM HOW W HEN WHATRX BTS yes the ms-isdn TARX MS1 CANTX MS1 +3TS yesRX MS2 W HATTX MS2 theRX MS3 GSM DTX MS3 D ms-isdnRX MS4 HOWTX MS4RX MS5TX MS5 Propagation Delay W HENRX MS6 WHATTX MS6RX MS7TX MS7RX MS8TX MS8 32
  33. 33. Timing Advance 3 - With Timing Advance: No CollisionTX BTS CAN WHAT GSM HOW WHEN WHATRX BTS yes the ms-isdnRX MS1 CANTX MS1 +3TS - TA yesRX MS2 WHATTX MS2 D theRX MS3 GSMTX MS3 D ms-isdnRX MS4 HOWTX MS4RX MS5 WHENTX MS5 Propagation DelayRX MS6 WHATTX MS6RX MS7TX MS7 Timing Advance = 2 * Propagation DelayRX MS8TX MS8 33
  34. 34. GSM in comparison with otherStandards• GSM gives mobility without any loss in Audio quality• Encryption techniques used gives high security in the air Interface and also use of SIM.• Bit Interleaving for high efficiency in Transmission.• Variable Power (Power budgeting- extend battery life)• Minimum Interference.• Features-CCS7 Signaling – SMS (Short Message Services) – Emergency Calls – CELL Broadcast 34
  35. 35. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 35
  36. 36. MS GSM - Network Structure Um BTS VLR HLR BSC Abis MSC A B HMS C AuC BTS GMSC E F Abis EIR A E MSC BSC PSTN Um BTS X.25 VLR X.25 OMC Server 36
  37. 37. GSM Network SS Switching AUC System External PSTN & VLR HLR EIR PDN N/W OMC MSCMS Mobile StationBTS Base transceiver SystemBSC Base Station ControllerMSC Mobile Switching Center BSS BSC Base StationHLR Home Location RegisterVLR Visitor Location Register BTS SystemEIR Equipment Identity RegisterAUC Authentication Center MS 37OMC Operation And Maintenance Center
  38. 38. GSM Architecture GSM VMSC SMSCAir interface B S C A AUC interface HLR Abis interface TRAU MSC PSTN B VLR BTS S BTS C BTS EIR OMCS BTS BTS BTS Network and switching subsystem Mobile A interface SS7 / speech Station X.25 OMCR SS7 Base Station System 38
  39. 39. Mobile Equipment(ME)• Frequency and Time Synchronization• Voice encoding and transmission• Voice encryption/decryption functions• Power measurements of adjacent cells• Display of short messages• International Mobile Equipment Identifier (IMEI) 39
  40. 40. SIM• Portable Smart Card with memory (ROM-6KB to 16KB-A3/A8 algorithm, RAM- 128KB TO 256KB, EEPROM- 3KB to 8KB )• Static Information – International Mobile Subscriber Identity(IMSI) – Personal Identification Number (PIN) – Authentication Key (Ki)• Dynamic Information – Temporary Mobile Subscriber Identity(TMSI) – Location Area Identity (LAI) – Phone memories, billing information – Ability to store Short Messages received 40
  41. 41. SIM-Card and GSM MobileEquipment Global GSM Mobility Card = + The Smart Card to use GSM Contains: - IMSI SIM-Card
  42. 42. The SIM-Card Functions Credit Card Size µ SIM-Card Global GSM Mobility Card 15 mm The Smart Card to use 25 mm GSMPermanent data: - Unique mobile subscriber identity Microchip with stored through IMSI number and PIMSI user information for Packet Mode - Authentication parameter Ki, - Authentication algorithm A3, Removable data: - Generating encryption key Kc - Temporary Mobile Subscriber Number, algorithm A8, - Location Area Identification - Routing Area Identification (Packet mode) - PIN code.
  43. 43. Subscriber Identification IMSI MS - ISDN Mobile Station - International Mobile Subscriber Identity Nature Integrated Services Digital Network Nb Similar to ISDN, Conformity with E212 Conformity with E164/E213 Identify a PLMN Identify the subscriber National Significant Mobile Number worldwide of a PLMN MCC MNC MSIN CC NDC SN Format H1 H2 x x x ......... x x x M1 M2 xx xx xx xx Country Mobile Mobile Mobile Subscriber National Mobile Subscriber CodeMeaning Country Network Ident. Nb (where Destination (national definition) Code Code H1 H2 = Identity of HLR subscription Code * M1 M2 = nbr of logical HLR within the home PLMN has been made)Nb. digits 3 2 max 10 1 to 3 2 to 4 total max 15 *This code does not identify a geographical area but an operator
  44. 44. Description Stored in SIM Card Global GSM Mobility Card MCC MNC The Smart Card to use = = 208 (France) 71(APBSNL) 234 (G-B) 72(TNBSNL)262 (Germany) 20 (Bytel) IMSI = 15 digits max GSM404,405(India) Mobile Mobile Mobile Subscriber Identification Number (MSIN) Country Network Code Code H1 H2 X X X X X X 3 digits 2 digits 10 digits max NMSI Temporary Mobile Subscriber Identity LAI 4 octetsMobile MobileCountry Network Location Area Code Routing Area CodeCode Code LAC RAC3 digits 2 digits RAI
  45. 45. Description Stored in the Network MS-ISDN (15 digits max)Country National Subscriber Number (SN) Must be dialed toCode Destination make a call to Code M1 M2 X X X X X X X X X X X X X mobile3 digits max 2 or 3 digits 10 digits max subscriber MSRN Roaming Number (RN) Is a PSTN-like National number used toCountry reach a roaming DestinationCode MS Code Is a PSTN-like number to track the NationalCountry MS that hands overCode Destination HO-number to another MSC Code during call-in-state NDC = 9448(BSNL-karnataka)CC = 33 (France) 9845,9880(Airtel) 091(India) 9886(Hutch) 001(US) 45 = 660, 661, 618 (Bytel)
  46. 46. Descriptor Embodied in the MobileEquipment IMEI enables the operator to check the Mobile Equipment Identity at call setup and make sure that no stolen or unauthorized MS is used in the GSM network E D YP VE T O R APP TAC FAC SNR SP Type Approval Serial NumbeR (SPare) Code Final Assembly Code
  47. 47. International Mobile Equipment Identity (IMEI) E D T YP OVE R APP TAC FAC SNR SP Type Approval Serial number (SPare) Code Final Assembly Code IMEI: #06# 351475 60 926514 4 *
  48. 48. MS Classmark Power classes Classmark For GMSK modulation Revision level GSM GSM GSM Class 400/850/900 1800 1900 RF power 1 1 W** 1 W** Encryption algorithm 8 W* 2 0.25 W 0.25 W Frequency 3 5W 4W 2W Short message 4 2 W** LoCation Services 5 0.8 W MS Positioning Method For 8-PSK modulation 8-PSK modulation GSM GSM GSM Class Multi-slot class 400/850/900 1800 1900 E1 2W 1W 1W Multi-band E2 0.5 W 0.4 W 0.4 W* Typical value for car mounted E3 0.2 W 0.16 W 0.16 W** Typical value for handheld
  49. 49. Base Transceiver Station(BTS)• Handles the radio interface to the mobile station.• Consists of one or more radio terminals for transmission and reception• Each Radio terminal represents an RF Channel• TRX and MS communicates over Um interface• Received data transcoding• Voice encryption/decryption• Signal processing functions of the radio interface• Uplink Radio channel power measurements 49
  50. 50. Base Station Controller (BSC)• Provides all the control functions and physical links between the MSC and BTS• External Interfaces – ‘Abis’ interface towards the BTS – ‘A’ interface towards the MSC• Monitors and controls several BTSs• Management of channels on the radio interface• Alarm Handling from the external interfaces• Performs inter-cell Handover• Switching from ‘Abis’ link to the ‘A’ link• Interface to OMC for BSS Management 50
  51. 51. Mobile Switching Center(MSC)• Performs call switching• Interface of the cellular network to PSTN• Routes calls between PLMN and PSTN• Queries HLR when calls come from PSTN to mobile user• Inter-BSC Handover• Paging• Billing 51
  52. 52. Home Location Register(HLR)• Stores user data of all Subscribers related to the GMSC – International Mobile Subscriber Identity(IMSI) – Users telephone number (MS ISDN) – Subscription information and services – VLR address – Reference to Authentication center for key (Ki)• Referred when call comes from public land network 52
  53. 53. Visitor Location Register (VLR)• Database that contains Subscriber parameters and location information for all mobile subscribers currently located in the geographical area controlled by that VLR• Identity of Mobile Subscriber• Copy of subscriber data from HLR• Generates and allocates a Temporary Mobile Subscriber Identity(TMSI)• Location Area Code• Provides necessary data when mobile originates call 53
  54. 54. Authentication Center (AuC)• Stores Subscriber authentication data called Ki, a copy of which is also stored in in the SIM card• Generates security related parameters to authorize a subscriber (SRES-Signed RESponse)• Generates unique data pattern called Cipher key (Kc) for user data encryption• Provides triplets - RAND, SRES & Kc, to the HLR on request. 54
  55. 55. EIR (Equipment Identity Register)• EIR is a database that contains a list of all valid mobile station equipment within the network, where each mobile station is identified by its International Mobile Equipment Identity(IMEI).• EIR has three databases., – White list - For all known,good IMEI’s – Black list - For all bad or stolen handsets – Grey list - For handsets/IMEI’s that are on observation 55
  56. 56. Location Area Identity• LAI identifies a location area which is a group of cells..• It is transmitted in the BCCH.• When the MS moves into another LA (detected by monitoring LAI transmitted on the BCCH) it must perform a LU.• LAI = MCC + MNC + LAC – MCC= Mobile Country Code(3 digits), identifies the country – MNC= Mobile Network Code(1-2 digits), identifies the GSM- PLMN – LAC= Location Area Code, identifies a location area within a GSM PLMN network. The maximum length of LAC is 16 bits,enabling 65536 different location areas to be defined in 56 one GSM PLMN.
  57. 57. Interfaces and Protocols Digital Networks ISUP Abis A E LAPD BSSAP TUP MAPUm LAPDm F MAP B POTS MAP C D G 57
  58. 58. GSM Entities and Signaling Architecture 58
  59. 59. GSM Protocols• CM - Connection Management• MM - Mobility Management• RR - Radio resource• LAPDm - LAPD for mobile• LAPD - Link Access Procedure for D channel• BTSM - BTS Management Part• BSSAP - BSS Application Part (BSC - MSC)• DTAP - Direct Transfer Application Part (MS - MSC)• MAP - Mobile Application Part• MTP - Message Transfer part of SS7• SCCP - Signalling Connection Control Part of SS7• TCAP - Transaction Capabilities Application Part• ISUP - ISDN User Part 59
  60. 60. Functional Plane of GSM MS BTS BSC MSC/VLR HLR GMSC CC MM RRTrans MS BTS BSC MSC/ HLR GMSC VLR 60
  61. 61. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTIFIERS USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 61
  62. 62. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 62
  63. 63. Channels : differentiatingbetween Physical and LogicalchannelsPhysical channels : The combination of an ARFCNand a time slot defines a physical channel.Logical channels : These are channels specified byGSM which are mapped on physical channels. 63
  64. 64. Channel conceptPhysical channel:One timeslot of a TDMA-frame on one carrieris referred to as a physical channel.There are 8 physical channels per carrier inGSM,channel 0-7(timeslot 0-7)Logical channel:A great variety of information must betransmitted between BTS and the MS,for e.g.user data and control signaling.Dependingon the kind of information transmitted werefer to different logical channels.These logicalchannels are mapped on physical 64channel.
  65. 65. Logical Channels on Air interface LOGICAL CHANNELS COMMON DEDICATED CHANNELS CHANNELS BROADCAST COMMON DEDICATED TRAFFIC CHANNELS CONTROL CONTROL CHANNELS CHANNELS CHANNELS FCCH SCH BCCH SDCCH SACCH FACCH PCH RACH AGCH TCH/F TCH/H TCH/EFR 65
  66. 66. Logical channels Logical channels Control channels Traffic channels Half Full CCCH DCCH BCH rate rateFCCHSCH BCCH CBCH PCH AGCH RACH SDCCH SACCH FACCH 66
  67. 67. Broadcast channels BCH• Broadcast Channel-BCH – Alloted one ARFCN & is ON all the time in every cell. Present in TS0 and other 7 TS used by TCH.• Frequency correction channel-FCCH – To make sure this is the BCCH carrier. – Allow the MS to synchronize to the frequency. – Carries a 142 bit zero sequence and repeats once in every 10 frames on the BCH.• Synchronization Channel-SCH – This is used by the MS to synchronize to the TDMA frame structure within the particular cell. – Listening to the SCH the MS receives the TDMA frame number and also the BSIC ( in the coded part- 39 bits). 67 – Repeats once in every 10 frames.
  68. 68. Broadcast channels BCH ...• BCCH – The last information the MS must receive in order to receive calls or make calls is some information concerning the cell. This is BCCH. – This include the information of Max power allowed in the cell. – List of channels in use in the cell. – BCCH carriers for the neighboring cells,Location Area Identity etc. – BCCH occupies 4 frames (normal bursts) on BCH and repeats once every Multiframe. – This is transmitted Downlink point to multipoint.• Cell Broadcast Channel - CBCH – Used for the Transmission of generally accessible information like Short Message Services(SMS) 68
  69. 69. Common Control ChannelsCCCH• CCCH- – Shares TS-0 with BCH on a Multiframe.• Random access channel-RACH: – Used by Mobile Station for requesting for a channel. When the mobile realizes it is paged it answers by requesting a signaling channel (SDCCH) on RACH. RACH is also used by the MS if it wants to originate a call. – Initially MS doesn’t know the path delay (timing advance), hence uses a short burst (with a large guard period = 68.25 bits). – MS sends normal burst only after getting the timing advance info on the SACCH. – It is transmitted in Uplink point to point. 69
  70. 70. Common Control ChannelsCCCH ..• Access Grant Channel-AGCH – On request for a signaling channel by MS the network assigns a signaling channel(SDCCH) through AGCH. AGCH is transmitted on the downlink point to point.• Paging Channel-PCH – The information on this channel is a paging message including the MS’s identity(IMSI/TMSI).This is transmitted on Downlink, point-to-multipoint. 70
  71. 71. Dedicated Control Channels-DCCH• Stand alone dedicated control channel(SDCCH)• AGCH assigns SDCCH as signaling channel on request by MS.The MS is informed about which frequency(ARFCN) & timeslot to use for traffic.• Used for location update, subscriber authentication, ciphering information, equipment validation and assignment of TCH.• This is used both sides, up and Downlink point-point. 71
  72. 72. Dedicated Control Channels-DCCH• Slow associated control channel-SACCH – Transmission of radio link signal measurement, power control etc. – Average signal strengths(RXLev) and quality of service (RXQual) of the serving base station and of the neighboring cells is sent on SACCH (on uplink). – Mobile receives information like what TX power it has to transmit and the timing advance. It is associated with TCH or SDCCH• Fast associated control channel-FACCH – Used for Hand over commands and during call setup and release. FACCH data is sent over TCH with stealing flag set 72
  73. 73. Traffic Channels-TCH• TCH carries the voice data.• Two blocks of 57 bits contain voice data in the normal burst.• One TCH is allocated for every active call.• Full rate traffic channel occupies one physical channel(one TS on a carrier) and carries voice data at 13kbps• Two half rate (6.5kbps) TCHs can share one physical channel. 73
  74. 74. GSM Channels GSM ChannelsTraffic Channels Control Channels (TCHs) Broadcast Common Control Dedicated Control Channels Channels Channels (BCHs) (CCCHs) (DCCHs) (down uplink) Full Half Downlink Downlink Uplink rate rate Fast Slow TCH /F TCH /H FCCH SCH BCCH PCH AGCH CBCH RACH SDCCH FACCH SACCHTraffic Multiframing Signaling Multiframing Traffic Multiframing 74
  75. 75. The Logical Channels on Radio Interface TS 0123456 7 BTS MS FCCH TCHFrequency correction Traffic (speech-data) SCH FACCHSynchronization Associated Signaling BCCHBroadcast control RACH Radio Measurement + SMS SACCHAccess request SDCCH Dedicated Signaling PCHSubscriber paging CBCH Broadcast info AGCHAnswer to Access request FCCH CBCHBroadcast info SCH M.S. Pre-synchronization SDCCHDedicated Signaling BCCH SACCHSys InFo 5, 6 + SMS RACH Access request PCHTraffic (speech data) Subscriber paging TCH AGCHAssociated Signaling Answer to Access request FACCH 75
  76. 76. Logical Channel Description (1/2) SACCH MESSAGES TCH MESSAGESMeasures: - power level of the communication • Speech - quality level of the communication • Data - level on the beacon frequency of • Handover Access message (uplink) the neighboring cells• Timing Advance• Power Control• SMS FACCH MESSAGES • Connection establishment from SDCCH to TCH SDCCH MESSAGES • End validation of a SDCCH-TCH commutation• Request for a SDCCH assignment • Characteristics of the future used BS• Request for the end of channel after handover assignment • Connection establishment to BS after• Order of commutation from SDCCH to handover TCH • Validation of an handover• SMS 76
  77. 77. Logical Channel Description FCCH MESSAGES AGCH MESSAGES (2/2)• no message is sent (all bits 0) • For dedicated channel assignment: - frequency number - slot number - frequency hopping description SCH MESSAGES - Timing Advance (1st estimation)• Frame Number - MS identification• Base Station Identity Code (BSIC) CBCH MESSAGES BCCH MESSAGES • Specific information (weather, road information• System Information type 1, 2, 2bis, 2ter, 3, 4, 7, 8 (idle mode) RACH MESSAGES • Service request: - emergency call PCH MESSAGES - answer to an incoming call - outgoing call• messages containing a mobile - short message identity for a call, a short message - call re-establishment or an authentication - inscription 77
  78. 78. GPRS Channels DL PDTCHPBCCH PACCH PPCH BSC PTCCH GPRSPAGCH PCUSN PNCH CORE NETWORK PDTCHPRACH Packet PACCH Common PTCCH Control UL CHannels Packet PDCH = Packet Data Traffic CHannel CHannels PBCCH 78
  79. 79. Traffic and Control Multiframing Traffic channel Control channel Frame 4.615 ms TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS TS 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 726 traffic frames = 120 ms 0 1 2 3 4 21 22 23 24 25 0 1 2 3 4 46 47 48 49 50 1326frames 0 1 2 3 4 51 x 26 traffic frames = 6.12 s 46 47 48 49 50 0 1 2 3 26 x 51 control frames = 6.12 s 22 23 24 25 0 1 2 3 4 5 2042 2043 2044 2045 2046 2047 1 Hyperframe = 2,715,648 frames= 3h 28 min. 53 s 760 ms 79
  80. 80. 80
  81. 81. 81
  82. 82. Logical Channel Mapping 1 - Traffic Channel Combination TFull Rate - Downlink & Uplink 26 frames = 120 ms T T T T T T T T T T T T A T T T T T T T T T T T T time Half Rate - Downlink & Uplink 26 frames = 120 msT0 T1 T0 T1 T0 T1 T0 T1 T0 T1 T0 T1 A0 T1 T0 T1 T0 T1 T0 T1 T0 T1 T0 T1 T0 A1 time T : TCH Ti : TCH A : SACCH Ai : SACCH : IDLE sub-channel no. i sub-channel no. i 82
  83. 83. Logical Channel Mapping 2 - Dedicated Signaling Channel Combination A A A ADownlink 51 frames = 235 msD0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3D0 D1 D2 D3 D4 D5 D6 D7 A4 A5 A6 A7 timeUplink 51 frames = 235 msA5 A6 A7 D0 D1 D2 D3 D4 D5 D6 D7 A0A1 A2 A3 D0 D1 D2 D3 D4 D5 D6 D7 A4 time A : SACCH D : SDCCH : IDLE 83
  84. 84. Logical Channel Mapping 3 - Common Channel Combination Downlink Multiframe mMultiframe Multiframem-1 51 frames = 235.38 ms m+1 C FS B C FS C C FS C C FS C C FS C C FS B Frames repeat continuously time PCH/AGCH Physical Channel BTS ARFCN (n) TS (s) MS SCH BCCH FCCH Uplink 51 frames = 235.38 ms R R R RR R R RR R R RR R R RR R R RR R R RR R R RRR R R R R RR R R RR R R RR RR RR R R R time : PCH / F : FCCH S : SCH B : BCCH C AGCH R : RACH : IDLE 84
  85. 85. Logical Channel Mapping 4 - Common Channel Combination Downlink 51 frames = 235 ms FS B C FS C C FS D0 D1 FS D2 D3 FS A0 A1 FS B C FS C C FS D0 D1 FS D2 D3 FS A2 A3 time Uplink 51 frames = 235 ms D3 RR A2 A3 RRRRRRRRRRRRRRRRRRRRRRR D0 D1 RR D2 D3 RR A0 A1 RRRRRRRRRRRRRRRRRRRRRRR D0 D1 RR D2 time : AGCHF : FCCH S : SCH B : BCCH C /PCH R : RACH A : SACCH D : SDCCH : IDLE 85
  86. 86. 86
  87. 87. Why 26 and 51 per Multiframe? Frames0 1 10 20 30 40 50 0 1FS B C FS C C FS C C FS C C FS C C FS TTTTTTTTTTTTATTTTTTTTTTTT TTTTTTTTTTTTATTTTTTTTTTTT 01 12 25 0 1 12 25 Downlink message Uplink message Mobile Rx Rx Tx Rx Rx Tx Rx Rx Tx activity (n) (n) (n)Neighboring BTS(downlink) Measurement Windows 87
  88. 88. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 88
  89. 89. From Speech to Radio Transmission Speech Digitizing and Source Step 1 source coding decoding Channel Channel Step 2 coding decoding Interleaving De-interleavingStep 3 Burst deformatting Burst formatting Deciphering Step 4 Ciphering Demodulation Step 5 Modulation equalization Step 6 Diversity Transmission 89
  90. 90. GSM Radio Link• Speech Coding -Done at Transcoder of BSC and MS – The Linear Predictive Coder uses RPE-LTP(Regular Pulse Excitation- Long Term Prediction) – Converts 64kbps voice to 13kbps(260 bits every 20ms)• Channel Coding - Done at BTS and MS – Uses Convolution Coding and CRC (Cyclic Redundancy Check) – Converts 13 kbps to 22.8 kbps (456 bits per 20ms) 90
  91. 91. GSM Radio Link• Bit Interleaving - Done at BTS and MS• Encryption - Done at BTS and MS – EX OR data with cipher block, which is generated by applying A5 Algorithm to the Ciphering Key(Kc)• Multiplexing - Done at BTS• Modulation - Done at BTS and MS – GMSK(Gaussian filtered Minimum Shift Keying) – Phase change of +90 for 0 and -90 for 1 91
  92. 92. Why Digitizing and Coding theSpeech? SPEECH TRANSMISSION BETWEEN MOBILE AND NETWORK BSS MS SPEECH MUST BE DIGITIZED AND CODED Better Quality Lower Rate 64 kbit/s
  93. 93. Speech Quality – Source Coding Codec Type Mean Opinion Score Rate (kb/s) (MOS) PCM A law 4.25 64 GSM EFR 4.2 12.2 CDMA 13 4.2 13 D-AMPS 4 8 GSM FR 3.8 13 CDMA 8 3.4 8 Quality MOS Listening Effort RequiredExcellent 5 Complete relaxation possible, no effort.Good 4 Attention necessary, no appreciable effort.Fair 3 Moderate effort.Poor 2 Considerable effort.Bad 1 No meaning understood with feasible effort. 93
  94. 94. Speech Coding BP A/D SPEECH ENCODER CHANNEL CODING To modulator Every 20ms 160 samples 1A 1B 2 BAND Every 125μ s value is taken PASS Data rate = 160 * 13/20ms 300 Hz - sampled from analog 50 132 78 signal and quantised by = 104 kbps 3.4 kHZ 13 bit word 3 crc bits Data rate = 13/125*10 -6 Four 0 bits for codec = 104 kbps 50 3 132 4 Conv coding rate = 1/2 delay = 4 Linear Predictive Coding & Regular Long term prediction analysis Pulse Excitation Analysis 1. Previous sequences stored in memory 378 coded bits 781. Generates 160 filter coeff 2. Find out the correlation between the2. These blocks sorted in 4 sequence present seq. And previous sequences 1,5,9,…37 / 2,6,10----38/ 3. Select the highest correlation sequence 456 bits in 20 ms = 22.8 kbps 3,7,11…39/8,12,16…40 4. Find a value representing the difference 57 x 8 = 4563. Selects the sequence with most between the two sequences. 1A = Filter Coeffenergy Reduces data rate = 26 kbps/2 = 13 kbps block ampl, LTP ie 260 bits in 20ms paramsSo data rate = 104/4 = 26 kbps 1B = RPE pointers & pulses 2 = RPE pulse & filter params CHANNEL LP D/A SPEECH DECODER DECODING 94
  95. 95. Channel Processing in GSM Overview for Full Rate 20 ms Speech blocks 20 ms 20 ms A B CCodec dependent Codec dependent Codec dependent Source coding Channel coding A 456 bits B 456 bits C 456 bits A A A A B B B B B B B B 8 Sub blocks C C C C 5 6 7 8 Interleaving 1 2 3 4 5 6 7 8 1 2 3 4 of 57 bits A5 A6 A7 A8 B5 B6 B7 B8 8 Bursts B1 B2 B3 B4 C1 C2 C3 C4Normal 3 57 bits 1 26 bits 1 57 bits 3 burst Tail Information CRL Training CRL Information Tail 95
  96. 96. 96
  97. 97. Channel Processing in GSM Overview for Half Rate 20 ms Speech blocks 20 ms 20 ms A B CCodec dependent Codec dependent Codec dependent Source coding Channel coding A 228 bits B 228 bits C 228 bits A A A A B B B B 4 Sub blocks C C C C 1 2 3 4 Interleaving 1 2 3 4 1 2 3 4 of 57 bits A3 A4 B3 B4 4 Bursts B1 B2 C1 C2Normal burst 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 97
  98. 98. Interleaving: TCH Full Rate 0 1 2 3 4 5 6 7 8 ... ... 452 453 454 455 456 coded bits Divide 456 bits in 8 sub-blocks 0 1 2 3 4 5 6 7 57 Rows 8 9 10 11 12 13 14 15 reordering • • • • • • • • • • • • • • • • & • • • • • • • • partitioning out 448 449 450 451 452 453 454 455 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 diagonal interleaving bit interleaving burstb0 b1 b56 b0 b1 b56 98
  99. 99. Burst Formatting Normal Burst 1 frame: 4.615 ms 0 1 2 3 4 5 6 7 Training Guard DATA S S DATA sequence Band3 57 1 26 1 57 3 8.25 Burst 148 bits Guard 156.25 bits duration (0.577 ms) 99
  100. 100. Burst Formats Frequency Correction Burst (FCCH) Guard Tail Data Tail Period3 bits 142 fixed bits (0) 3 bits 8.25 bits 156.25 bits duration (0.577 ms) Synchronization Burst (SCH) Guard Tail Data Extended Training Sequence Data Tail Period3 bits 39 encrypted bits 64 synchronization bits 39 bits 3 bits 8.25 bits 156.25 bits duration (0.577 ms) 100
  101. 101. Burst Formats Normal Burst Tail Data Training Sequence Data Tail Guard Period3 bits 57 encrypted bits 1 26 bits 1 57 encrypted bits 3 bits 8.25 bits 156.25 bits (0.577 ms) Dummy Burst GuardTail Dummy Sequence Training Sequence Dummy Sequence Tail Period3 bits 58 mixed bits 26 midamble bits 58 mixed bits 3 bits 8.25 bits 156.25 bits (0.577 ms) Access Burst Training Tail Sequence Data Tail Guard Period 8 bits 41 synch bits 36 encrypted bits 3 bits 68.25 bits 156.25 bits (0.577 ms) 101
  102. 102. Ciphering Burst to be Data S S Data transmittedPlain data: 0 1 1 1 0 0 1 0.....Ciphering sequence: 0 0 0 1 1 0 1 0.....XOR:Ciphered data (transmitted): 0 1 1 0 1 0 0 0.....Ciphered sequence: 0 0 0 1 1 0 1 0.....XOR:Recovered data: 0 1 1 1 0 0 1 0..... Received S Training S Data Data burst sequence 102
  103. 103. Interleaving Encoded speech blocks - Diagonal Interleaving 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 Even bits 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 Odd bits Bn-4 Bn-3 Bn-2 Bn-1 Bn Bn+1 Bn+2 Bn+3 Encoded control channel blocks - Rectangular Interleaving57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 Even bits 57 57 57 57 57 57 57 57 57 57 57 57 Odd bits Bn-4 Bn-3 Bn-2 Bn-1 Bn Bn+1 Bn+2 Bn+3 Tb Coded Data F Training Sequence F Coded Data Tb Gp 3 57 1 26 1 57 3 8.25 103
  104. 104. Burst• The information format transmitted during one timeslot in the TDMA frame is called a burst.• Different Types of Bursts – Normal Burst – Random Access Burst – Frequency Correction Burst – Synchronization Burst 104
  105. 105. Normal Burst 156.25 bits 0.577 msT Coded Data S T. Seq. S Coded Data T GP3 57 1 26 1 57 3 8.25 Tail Bit(T) :Used as Guard Time Coded Data :It is the Data part associated with the burst Stealing Flag :This indicates whether the burst is carrying Signaling data (FACCH) or user info (TCH). Training Seq. :This is a fixed bit sequence known both to the BTS & the MS.This takes care of the signal deterioration. 105
  106. 106. 156.25 bits 0.577 msT Training Sequence Coded Data T GP3 41 36 3 68.25 Random Access Burst 156.25 bits 0.577 msT Fixed Bit Sequence T GP3 142 3 8.25 Freq. Correc. Burst 156.25 bits 0.577 ms T Coded Data Training Sequence Coded T GP 3 39 64 Data 39 3 8.25 Synchronization Burst 106
  107. 107. Transmission on the radio channels • A timeslot has a duration of .577 m seconds (148 Bits) • 8 timeslots(8 x 0.577 = 4.62 ms) form a TDMA frame • If a mobile is assigned one TS it transmits only in this time slot • and stays idle for the other 7 with its transmitter off, called bursting • The start on the uplink is delayed from downlink by 3 TS periods • One TS = duration of 156.25 bits, and its physical contents is • called a burstDownlink 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7BTS > MS Uplink 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 MS > BTS 107 Offset
  108. 108. Timing AdvanceMS1 0 1 2 3 4 5 6 7 MS1 0 1 2 3 4 5 6 7near nearMS2 MS2 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7far far At AtBTS BTS 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 108
  109. 109. Frames Types On UmInterface• TDMA Frame – 8 Time slots (Burst Period) – Length is 4.62 ms(8 * 0.577ms)• 26-TDMA Multiframe – 26 TDMA Frames (24 TCH, SACCH, Idle) – 120 ms (26 * 4.62ms)• 51-TDMA Multiframe – 26 TDMA Frames (FCCH, SCH, BCCH, SDCCH, CCCH) – 235.6 ms (51 * 4.62ms) 109
  110. 110. Frames Types On UmInterface• Super Frame – 51* 26 TDMA Frames – 6.12 S• Hyper Frame – 2048 * 51* 26 TDMA Frames – 3 Hours, 28 Minutes, 53 Secs and 760 ms 110
  111. 111. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 111
  112. 112. Mobility Management• Mobility Management (MM)• Location updating- normal,periodic, IMSI attach• Paging• Security Management – Preventing unauthorized users- authentication – Maintaining Privacy of users- ciphering• Providing roaming facility• MM functionality mainly handled by MS, HLR, MSC/VLR. 112
  113. 113. Network Attachment• Cell Identification • MS scans complete GSM frequency band for highest power • Tunes to highest powered frequency and looks for FCCH. Synchronizes in frequency domain • Get training sequence from SCH which follows FCCH. Synchronizes in time domain. • Accesses BCCH for network id, location area and frequencies of the neighboring cells. • Stores a list of 30 BCCH channels 113
  114. 114. Network Attachment…..• PLMN Selection • Get the operator information from SIM.• Cell Selection • Selected cell should be a cell of the selected PLMN • Signal strength should be above the threshold. • Cell should not be barred• Location Update • Register with the network by means of location updation procedures. 114
  115. 115. MS Location UpdateMS BTS BSC (registration) (G)MSC VLR HLRAction Channel Request (RACH) Channel Assignment (AGCH) TMSI + old LAI Location Update Request (SDCCH) Authentication Request (SDCCH) Authentication Response (SDCCH) Comparison of Authentication param Accept LUP and allocTMSI (SDCCH) Ack of LUP and TMSI (SDCCH) Entry of new area and identity into VLR and HLR Channel Release (SDCCH) 115
  116. 116. Security - Authentication MSKi RAND Authentication center provides RAND to Mobile A3 AuC generates SRES using SRES Ki of subscriber and RAND Mobile generates SRES MS BTS AuC using Ki and RAND Mobile transmits SRES to BTS RAND BTS compares received SRES SRES with one generated SRES by AuC Auth Result 116
  117. 117. Security - Ciphering MS Ki RAND A8 Data sent on air interface ciphered for security Kc Um interface A5 and A8 MS Network Kc algorithms used to Kc cipher dataData Ciphered Data A5 A5 Ciphering Key is Data never transmitted on air 117
  118. 118. TOPICS• GSM CONCEPTS• GSM SYSTEM ARCHITECTURE• IDENTITIES USED IN GSM• GSM CHANNELS• GSM RADIO LINK• MOBILITY MANAGEMENT• CALL MANAGEMENT• RADIO RESOURCE MANAGEMENT 118
  119. 119. Communication Management(CM)• Setup of calls between users on request• Routing function i.e. Choice of transmission segments linking users• Point to Point Short message services 119
  120. 120. GSM Actors NSS BSS MSC Public Switched BSC Telephone Network BTS VLR HLR AUC Fixed subscriberMobile subscriber
  121. 121. PLMN Selection Yes Yes Is there an up to date found PLMNs list? No Creation of a found PLMN list manual automatic mode mode The user selects a The MS selects the first PLMN from the PLMN from the preferred displayed PLMNs PLMNs list (if it is not in the forbidden PLMNs list) No (manual) Cell Selection succeed? Yes Selection of the No (automatic) next preferred End of PLMN possible PLMN selection
  122. 122. PLMN Selection• Constitution of the "Found PLMN list" Listen to all the frequencies of the GSM spectrum: power level measurement (124 channels in GSM and average on these 900, 374 in GSM 1800 measurements and 299 in GSM 1900 Select the best frequencies according to the power level (30 in GSM 900 and 40 in GSM 1800) Memorize the beacon frequencies in the precedent selection => Create the Found PLMN list
  123. 123. Initial Cell Selection List of the frequencies of the selected PLMN Selection of Eligible cell? another PLMN No Yes C1 Computation for Suitable cell: eligible cells - cell of the selected PLMNEligible cell - cell not barred - C1 > 0 Suitable cell? No Yes Look for the cell with the best C1 in the suitable cells list PLMN set in the IMSI Attach forbidden PLMN list End of Cell Selection Rejected? No Yes
  124. 124. Cell SelectionPurpose: get synchronizationwith the GSM networkprior establishing any communication. 1 1 BTS-5 1 BTS-4 1 H 2 FCC 1 3BTS-3 5 SCH 4 CH BC BTS-1 This cell BTS-2
  125. 125. Immediate Assignment MS BTS BSC MSC CHANNEL REQUEST 1 CHANNEL REQUIRED RACH 2 CHANNEL ACTIVATION 3 Immediate 4 CHANNEL ACTIVATION Assignment ACK. IMMEDIATE ASSIGNMENT IMMEDIATE ASSIGNMENT 5 5 COMMAND AGCH CM SERVICE REQUEST 6 SDCCH or TCHOR LOCATION UPDAT. REQU. 6 SDCCH or TCH
  126. 126. Registration: the Very First LocationUpdate 1 BSS IMSI 2 2 4 MSC 4 BSC TMSI 5 TMSI 6 5 BTS 2 Release 6 4 TMSI 5 LAI HLR VLR IMSI 3 IMSI VLR id TMSI LAI
  127. 127. Intra – VLR Location Update 1 BSS TMSI + old LAI 22 MSC BSC new TMSI 3 3 BTS 4 4 2 New TMSI TMSI 3New LAI VLR IMSI TMSI LAI IMSI not Required

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