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gsm
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- 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. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 3
- 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. 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.
- 7. Development of theGSM Standard 1982: Groupe Spécial Mobile (GSM) 1992: Official commercial launch of created GSM service in Europe. First Launch in Finland 1984: Description of GSM features 1993: The GSM-MoU has 62 signatories in 39 countries 1985: 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 begins 1988: Validation and trials, of the radio 2000: 480M GSM subscribers interface. Worldwide First GPRS Networks roll out 1991: First system trials are demonstrated at the Telecom 91 End 2002: 792M GSM subscribers exhibition. Worldwide 7
- 8. GSM Specifications 01 SERIES 12 SERIES GENERAL 02 SERIES OPERATION AND MAINTENANCE SERVICE ASPECTS 11 SERIES 03 SERIES EQUIPMENT AND TYPE NETWORK ASPECTS APPROVAL 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. Increasing GSM DataRates 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 Service Transmission HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution Time UMTS = Universal Mobile Telecommunication System
- 10. Wireless Data TechnologyOptions 2M 1M ket throughput 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. Circuit-Switched or Packet-Switched Circuitmode Packet 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. 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. 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. GSM Concepts - Cellular Structure 2 2 7 Cellular 7 3 1 Networking technology 1 6 that breaks geographic 6 4 5 area into cells shaped 5 like honey comb Cell is the radio coverage area of one base transceiver station 14
- 15. What are thetypes in GSM 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. GSM Band Allocations(MHz) Duplex Duplex GSM systems Uplink Downlink Band Spacing channels GSM 450 450.4-457.6 460.4-467.6 2x7.2 10 35 GSM 480 478.8-486 488.8-496 2x7.2 10 35 GSM 850 824-849 869-894 2x25 45 124 GSM 900 890-915 935-960 2x25 45 124 E-GSM (900) 880-915 925-960 2x35 45 174 R-GSM (900) 876-880 921-925 2x04 41 40 GSM 1800 1710-1785 1805-1880 2x75 95 374 GSM 1900 1850-1910 1930-1990 2x60 80 299 Frequencies are in MHz Carrier frequency = ARFCN = Absolute Radio Frequency Channel Number
- 17. GSM Family RadioBand Spectrum Uplink 450.4 457.6 478.8 486 824 849 GSM 450 GSM 480 GSM 850 Downlink 460.4 467.6 488.8 496 869 894 MHz 915 Uplink 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 MHz Downlink 960
- 18. Traffic/Signaling Traffic «bla bla bla...» Signaling « RING ! » riiiiing Network
- 19. MS GSM - Network Structure Um BTS VLR HLR BSC Abis MSC A B H MS C AuC BTS GMSC E F Abis EIR A E MSC BSC PSTN Um BTS X.25 VLR X.25 OMC Server 19
- 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. Paired Radio Channelsin GSM Case of GSM 900 Uplink Downlink BTS 890 MHz Frequency 915 MHz 935 MHz Frequency 960 MHz 0 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. GSM Time DivisionMultiplex Frame and Physical Channels Time-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. Physical Channel BTS BTS time Without FH With FH n+1 TDMAs 7 n TS 0 n-1 MS1 MS2 MS3 1 // FDMA 2 124 ARFCN
- 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. Functions of theRadio Interface • Speech and user's data Communication Idle mode • Signaling mode BTS BTS-1 BTS-2
- 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 bandwidth UP 890.0 890.2 890.4 914.8 915.0 DOWN 935.0 935.2 935.4 959.8 960.0 26
- 27. Access Techniques ... TimeDivision 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.
- 29. Fundamentals 960MHz 959.8MHz 124 TS: Time slot 123 DOWNLINK ……. 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. GSM Delays UplinkTDMA Frames BTS 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 Up MSs side link link MS1 R T MS2 R T Fixed transmit delay of three time-slots
- 31. Timing Advance 1 - Propagation Delay M2 d2 d1>>d2 M1 BTS Frame reference TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 Propagation Delay τp Bits Overlapping MSs transmit
- 32. Timing Advance 2 - Without Timing Advance: Collision TX BTS CAN W HAT GSM HOW W HEN WHAT RX BTS yes the ms-isdn TA RX MS1 CAN TX MS1 +3TS yes RX MS2 W HAT TX MS2 the RX MS3 GSM D TX MS3 D ms-isdn RX MS4 HOW TX MS4 RX MS5 TX MS5 Propagation Delay W HEN RX MS6 WHAT TX MS6 RX MS7 TX MS7 RX MS8 TX MS8 32
- 33. Timing Advance 3 - With Timing Advance: No Collision TX BTS CAN WHAT GSM HOW WHEN WHAT RX BTS yes the ms-isdn RX MS1 CAN TX MS1 +3TS - TA yes RX MS2 WHAT TX MS2 D the RX MS3 GSM TX MS3 D ms-isdn RX MS4 HOW TX MS4 RX MS5 WHEN TX MS5 Propagation Delay RX MS6 WHAT TX MS6 RX MS7 TX MS7 Timing Advance = 2 * Propagation Delay RX MS8 TX MS8 33
- 34. GSM in comparisonwith other Standards • 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. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 35
- 36. MS GSM - Network Structure Um BTS VLR HLR BSC Abis MSC A B H MS C AuC BTS GMSC E F Abis EIR A E MSC BSC PSTN Um BTS X.25 VLR X.25 OMC Server 36
- 37. GSM Network SS Switching AUC System External PSTN & VLR HLR EIR PDN N/W OMC MSC MS Mobile Station BTS Base transceiver System BSC Base Station Controller MSC Mobile Switching Center BSS BSC Base Station HLR Home Location Register VLR Visitor Location Register BTS System EIR Equipment Identity Register AUC Authentication Center MS 37 OMC Operation And Maintenance Center
- 38. GSM Architecture GSM VMSC SMSC Air 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. 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. SIM • Portable SmartCard 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. SIM-Card and GSMMobile Equipment Global GSM Mobility Card = + The Smart Card to use GSM Contains: - IMSI SIM-Card
- 42. The SIM-Card Functions Credit Card Size µ SIM-Card Global GSM Mobility Card 15 mm The Smart Card to use 25 mm GSM Permanent 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. 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 Code Meaning 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. Description Stored inSIM 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 GSM 404,405(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 octets Mobile Mobile Country Network Location Area Code Routing Area Code Code Code LAC RAC 3 digits 2 digits RAI
- 45. Description Stored inthe Network MS-ISDN (15 digits max) Country National Subscriber Number (SN) Must be dialed to Code Destination make a call to Code M1 M2 X X X X X X X X X X X X X mobile 3 digits max 2 or 3 digits 10 digits max subscriber MSRN Roaming Number (RN) Is a PSTN-like National number used to Country reach a roaming Destination Code MS Code Is a PSTN-like number to track the National Country MS that hands over Code 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. Descriptor Embodied inthe Mobile Equipment 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. International Mobile EquipmentIdentity (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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Interfaces and Protocols Digital Networks ISUP Abis A E LAPD BSSAP TUP MAP Um LAPDm F MAP B POTS MAP C D G 57
- 58. GSM Entities andSignaling Architecture 58
- 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. Functional Plane ofGSM MS BTS BSC MSC/VLR HLR GMSC CC MM RR Trans MS BTS BSC MSC/ HLR GMSC VLR 60
- 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. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 62
- 63. Channels : differentiating betweenPhysical and Logical channels Physical channels : The combination of an ARFCN and a time slot defines a physical channel. Logical channels : These are channels specified by GSM which are mapped on physical channels. 63
- 64. Channel concept Physical channel: Onetimeslot of a TDMA-frame on one carrier is referred to as a physical channel. There are 8 physical channels per carrier in GSM,channel 0-7(timeslot 0-7) Logical channel: A great variety of information must be transmitted between BTS and the MS,for e.g. user data and control signaling.Depending on the kind of information transmitted we refer to different logical channels.These logical channels are mapped on physical 64 channel.
- 65. Logical Channels onAir 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. Logical channels Logical channels Control channels Traffic channels Half Full CCCH DCCH BCH rate rate FCCHSCH BCCH CBCH PCH AGCH RACH SDCCH SACCH FACCH 66
- 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. 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. Common Control Channels CCCH •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. Common Control Channels CCCH.. • 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. 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. 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. Traffic Channels-TCH • TCHcarries 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. GSM Channels GSM Channels Traffic 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 SACCH Traffic Multiframing Signaling Multiframing Traffic Multiframing 74
- 75. The Logical Channelson Radio Interface TS 0123456 7 BTS MS FCCH TCH Frequency correction Traffic (speech-data) SCH FACCH Synchronization Associated Signaling BCCH Broadcast control RACH Radio Measurement + SMS SACCH Access request SDCCH Dedicated Signaling PCH Subscriber paging CBCH Broadcast info AGCH Answer to Access request FCCH CBCH Broadcast info SCH M.S. Pre-synchronization SDCCH Dedicated Signaling BCCH SACCH Sys InFo 5, 6 + SMS RACH Access request PCH Traffic (speech data) Subscriber paging TCH AGCH Associated Signaling Answer to Access request FACCH 75
- 76. Logical Channel Description (1/2) SACCH MESSAGES TCH MESSAGES Measures: - 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. 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. GPRS Channels DL PDTCH PBCCH PACCH PPCH BSC PTCCH GPRS PAGCH PCUSN PNCH CORE NETWORK PDTCH PRACH Packet PACCH Common PTCCH Control UL CHannels Packet PDCH = Packet Data Traffic CHannel CHannels PBCCH 78
- 79. Traffic and ControlMultiframing 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 7 26 traffic frames = 120 ms 0 1 2 3 4 21 22 23 24 25 0 1 2 3 4 46 47 48 49 50 1326 frames 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
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- 81.
- 82. Logical Channel Mapping 1 - Traffic Channel Combination T Full 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 ms T0 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. Logical Channel Mapping 2 - Dedicated Signaling Channel Combination A A A A Downlink 51 frames = 235 ms D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3 D0 D1 D2 D3 D4 D5 D6 D7 A4 A5 A6 A7 time Uplink 51 frames = 235 ms A5 A6 A7 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3 D0 D1 D2 D3 D4 D5 D6 D7 A4 time A : SACCH D : SDCCH : IDLE 83
- 84. Logical Channel Mapping 3 - Common Channel Combination Downlink Multiframe m Multiframe Multiframe m-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. 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 : AGCH F : FCCH S : SCH B : BCCH C /PCH R : RACH A : SACCH D : SDCCH : IDLE 85
- 86.
- 87. Why 26 and51 per Multiframe? Frames 0 1 10 20 30 40 50 0 1 FS 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. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 88
- 89. From Speech toRadio Transmission Speech Digitizing and Source Step 1 source coding decoding Channel Channel Step 2 coding decoding Interleaving De-interleaving Step 3 Burst deformatting Burst formatting Deciphering Step 4 Ciphering Demodulation Step 5 Modulation equalization Step 6 Diversity Transmission 89
- 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. 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. Why Digitizing andCoding the Speech? SPEECH TRANSMISSION BETWEEN MOBILE AND NETWORK BSS MS SPEECH MUST BE DIGITIZED AND CODED Better Quality Lower Rate 64 kbit/s
- 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 Required Excellent 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. 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 78 1. Generates 160 filter coeff 2. Find out the correlation between the 2. 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 = 456 3. Selects the sequence with most between the two sequences. 1A = Filter Coeff energy Reduces data rate = 26 kbps/2 = 13 kbps block ampl, LTP ie 260 bits in 20ms params So data rate = 104/4 = 26 kbps 1B = RPE pointers & pulses 2 = RPE pulse & filter params CHANNEL LP D/A SPEECH DECODER DECODING 94
- 95. Channel Processing inGSM Overview for Full Rate 20 ms Speech blocks 20 ms 20 ms A B C Codec 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 C4 Normal 3 57 bits 1 26 bits 1 57 bits 3 burst Tail Information CRL Training CRL Information Tail 95
- 96.
- 97. Channel Processing inGSM Overview for Half Rate 20 ms Speech blocks 20 ms 20 ms A B C Codec 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 C2 Normal 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. Interleaving: TCH FullRate 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 burst b0 b1 b56 b0 b1 b56 98
- 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 Band 3 57 1 26 1 57 3 8.25 Burst 148 bits Guard 156.25 bits duration (0.577 ms) 99
- 100. Burst Formats Frequency Correction Burst (FCCH) Guard Tail Data Tail Period 3 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 Period 3 bits 39 encrypted bits 64 synchronization bits 39 bits 3 bits 8.25 bits 156.25 bits duration (0.577 ms) 100
- 101. Burst Formats Normal Burst Tail Data Training Sequence Data Tail Guard Period 3 bits 57 encrypted bits 1 26 bits 1 57 encrypted bits 3 bits 8.25 bits 156.25 bits (0.577 ms) Dummy Burst Guard Tail Dummy Sequence Training Sequence Dummy Sequence Tail Period 3 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. Ciphering Burst to be Data S S Data transmitted Plain 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. 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 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 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. Burst • The informationformat 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. Normal Burst 156.25 bits 0.577 ms T Coded Data S T. Seq. S Coded Data T GP 3 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. 156.25 bits 0.577ms T Training Sequence Coded Data T GP 3 41 36 3 68.25 Random Access Burst 156.25 bits 0.577 ms T Fixed Bit Sequence T GP 3 142 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. 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 burst Downlink 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 BTS > MS Uplink 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 MS > BTS 107 Offset
- 108. Timing Advance MS1 0 1 2 3 4 5 6 7 MS1 0 1 2 3 4 5 6 7 near near MS2 MS2 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 far far At At BTS 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. Frames Types OnUm Interface • 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. Frames Types OnUm Interface • 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. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 111
- 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. Network Attachment • CellIdentification • 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. Network Attachment….. • PLMNSelection • 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. MS Location Update MS BTS BSC (registration) (G)MSC VLR HLR Action 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. Security - Authentication MS Ki 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. 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 data Data Ciphered Data A5 A5 Ciphering Key is Data never transmitted on air 117
- 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. Communication Management (CM) • Setupof calls between users on request • Routing function i.e. Choice of transmission segments linking users • Point to Point Short message services 119
- 120. GSM Actors NSS BSS MSC Public Switched BSC Telephone Network BTS VLR HLR AUC Fixed subscriber Mobile subscriber
- 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. PLMN Selection • Constitutionof 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. 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 PLMN Eligible 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. Cell Selection Purpose: getsynchronization with the GSM network prior establishing any communication. 1 1 BTS-5 1 BTS-4 1 H 2 FCC 1 3 BTS-3 5 SCH 4 CH BC BTS-1 This cell BTS-2
- 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 TCH OR LOCATION UPDAT. REQU. 6 SDCCH or TCH
- 126. Registration: the VeryFirst Location Update 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. Intra – VLRLocation Update 1 BSS TMSI + old LAI 2 2 MSC BSC new TMSI 3 3 BTS 4 4 2 New TMSI TMSI 3 New LAI VLR IMSI TMSI LAI IMSI not Required
- 128. Inter – VLRLocation Update 1 BSS 2 TMSI + old LAI 2 BSC 5 MSC newTMSI 5 BTS 7 7 2 TMSI New TMSI 5 New LAI Old VLR New VLR IMSI, TMSI 3 IMSI,TMSI Old LAI LAI RAND, SRES, 4 RAND, SRES, Kc Kc 6 IMSI not Required HLR subscriber 6 data new VLR id 128
- 129. IMSI Attach CHANNEL 1 REQUEST BSS IMMEDIATE 2 ASSIGNMENT 3 LOCATION UPDATING BSC 3 REQUEST (IMSI Attach) Authentication BTS 4 Procedure 4 MSC LOCATION UPDATING 5 5 ACCEPT (LAC, TMSI) 4 VLR 6 129
- 130. IMSI Detach CHANNEL 1 BSS REQUEST IMMEDIATE 2 ASSIGNMENT BSC MSC 3 IMSI DETach IMSI DETach 3 INDication INDication BTS CHANNEL 4 RELEASE VLR 130
- 131. Outgoing Call Great Britain France Germany Telephone network BSS Terminating Gateway BSC MSC BTS MSC VLR HLR FT 131
- 132. Mobile Originating Call MS BSS MSC PSTN CHANNEL REQUEST VLR Dialing 1 IMMEDIATE ASSIGNMENT 2 CM SERVICE REQUEST CM SERVICE REQUEST 2 2 3 Authentication procedure 3 Ciphering procedure Sending SETUP (basic) or SETUP 4 4 Number EMERGENCY 5 IAM CALL PROCEEDING 6 Ring CALL PROCEEDING 7 7 Ringing 7 Assignment procedure ACM ALERTING 9 8 Ringing ANM Path CONNECT 10 11 Established CONNECT ACKnowledge ACM = Address Complete Message 11 ANM = ANswer Message IAM = Initial Address Message 132
- 133. Mobile Terminating Call 1 - Paging Principle LA1 6 BSC1 4 BTS11 5 3 1 BTS12 MSC/ PSTN 6 GMSC 5 VLR BSC2 BTS21 2 BTS22 HLR LA2 BTS23 BSC3 BTS31 133
- 134. Mobile Terminating Call 2 - Detailed Procedure Visitor PLMN International Home PLMN SS7 VLR HLR Provide Roaming Number 4 (IMSI) Roaming Number 5 (MSRN) 6 9 Send 1 Send info Routing Routing PAGE to I/C PAGING Information Information MSISDN (TMSI + LA) (MSRN) REQUEST (MSRN) (MSISDN) (TMSI) 3 8 11 PAGING IAM (MSRN) REQUEST IAM 10 VMSC 7 GMSC 2 ISDN BSS (TMSI + LA) (MSISDN) PN IAM : Initial Address Message IMSI : International Mobile Subscriber Identity MSISDN : Mobile Station Integrated Services Digital GMSC : Gateway MSC network Number VMSC : Visitor MSC MSRN : Mobile Station Roaming Number TMSI : Temporary Mobile Subscriber Identity 134
- 135. Mobile Terminating Call 3 - End to End Procedure MS BSS VMSC GMSC PSTN IAM IAM 1 PAGING REQUEST 2 (MSISDN) PAGING REQUEST 3 (MSRN) 4 (TMSI or IMSI, LA) Dialing CHANNEL REQUEST 5 (LAC, Cell ID) IMMEDIATE ASSIGNMENT 6 (SDCCH or TCH) CM SERVICE REQUEST 7 PAGING RESPONSE (Paging Response) 7 (TMSI or IMSI, LA) 8 Authentication procedure 9 Ciphering procedure Ringing 10 Setup, Assignment, Alerting Address Complete Message 11 CONNECT ANswer Message 12 12 Path Established 135
- 136. Call Release 1 - Mobile Initiated MS BSS MSC PSTN 1 Call in progress DISCONNECT 2 DISCONNECT 2 RELEASE RELEASE 3 3 RELEASE COMPLETE 4 Release CHANNEL RELEASE 6 5 RELEASE INDICATION 7 RF Channel Release procedure 8 Release 9 tone 136
- 137. Call Release 2 -PSTN Initiated 1 BSS 1 1 3 3 REL MSC 2 4 BSC 4 PSTN RLC 5 6 BTS 5 1 2 Purpose: informs the mobile then releases radio and network resources. On hook 137
- 138. Mobile Originated Call • Request for Service • Authentication • Ciphering • Equipment Validation • Call Setup • Handovers • Call Release 138
- 139. Mobile Terminated Call • Paging • Authentication • Ciphering • Equipment Validation • Call Setup • Handovers • Call Release 139
- 140. Mobile Terminated Call MS Paging HLR BTSTMSI Paged Assignment CMD (=TCH) on SDCCH on PCH BSC VLR Query for Allocate tunesSDCCH * MS MS Ch. REQ SDCCH Page RESP on Connect traffic Ch.to trunk VLR info AuC overRACH CMP * Assgn ( AGCH overTMSI + LAI) frees SDCCH Query VLR GMSC BTS * Phone rings Page RES Page Reply Assgn CMP for LAC and (MSRN) Assign. REQ Paging TMSI the area (+TMSI) EIR Route to MSC Alerting Network MSC BSC PSTN BTS Land to Mobile call (MSISDN) Authentication and Ciphering procedure done as seen in Location Updation 140
- 141. TOPICS • GSM CONCEPTS • GSM SYSTEM ARCHITECTURE • IDENTITIES USED IN GSM • GSM CHANNELS • GSM RADIO LINK • MOBILITY MANAGEMENT • CALL MANAGEMENT • RADIO RESOURCE MANAGEMENT 141
- 142. Radio Resource Management •Establish maintain and release stable connections between MS and MSC • Manage Limited Radio and Terrestrial resources • Handover process is the sole responsibility of the RR Layer • Functions of RR layer are performed by MS and BSC and partly by MSC 142
- 143. Radio Resource Management • Power Control • Hand over Control • Discontinuous Transmission • Frequency Hopping 143
- 144. Power Control BTS commandsMS at different distances to use different power levels so that the power arriving at the BTS’s Rx is approximately the same for each TS - Reduce interference - Longer battery life 144
- 145. Handover Means to continuea call even a mobile crosses the border of one cell to another Procedure which made the mobile station really roam Handover causes RxLev (Signal strength , uplink or downlink) RxQual (BER on data) O & M intervention Timing Advance Traffic or Load balancing 145
- 146. Handover Types • InternalHandover (Intra-BSS) – Within same base station - intra cell – Between different base stations - inter cell • External Handover (Inter-BSS) – Within same MSC -intra MSC – Between different MSCs - inter-MSC 146
- 147. Handover Types GMSC MSC BSC BSC C-3 BSC MSC C-4 C-1 C-2 BSC 147
- 148. Intra BSC handover HO performed HO required Activate TCH(facch) with HoRef# BSC Acknowledges and alloctes TCH (facch) if 1. Check for HO passed 2. Channel avail in new BTS BTS 2 Periodic Measurement Reports (SACCH) Periodic Measurement Reports MS tunes into new frequency and TS and sends HO message to new BTS (facch) HO cmd with HoRef# Receives new BTS data(FACCH) Release TCH Cell 2 Periodic Measurement Reports (SACCH) BTS 1 Cell 1 148
- 149. Frequency plan andimportance of BCCH B5 Sectored B6 antennas B4 BPL frequency plan: Broadcast frequencies : B3 B7 15 Broadcast channels = 48-62 B1 15 Hopping channels = 32-46 B8 B2 B12 MS ( monitoring the B9 broadcast radio B1 in ‘idle B10 mode’ ) B11 F0 F1 F2 F3 F4 F5 F10 F11 F50 F S B B B B ….. F S ….. ….. I •F,S,B exist in time slot 0 of each frame 149
- 150. What information doesBroadcast Control channel (BCCH) contain? Serves as a Beacon for the Cell Country Code (CC) and the Network Code (NC) Location Area Identity (LAI) List of neighboring cells which should be monitored by MS List of frequencies used in the cell Cell identity Back 150
- 151. Location Updates LocationUpdates can be classified into two: Periodic Location Updates: This occurs as per the timer set by the network operator. If the MS does not perform this update the MSC marks the MS as ‘Detached’ on the VLR. Location Update on a handover: This occurs if during a handover the MS is moved into a new Location Area Code (LAC). 151
- 152. 1. The MS is monitoring the BCCH and has all the decoded information stored on the SIM ( including the LAC) 2. As soon as the mobile is on a TCH it sends the signal strength indication on the corresponding SACCH 3. The BSC monitors the signal strengths and on analysis sends a ‘handoff request’ on FACCH. The handoff process is completed on the FACCH. 4. After the completion of call, the MS starts monitoring the BCCH again. On finding the LAC (stored on SIM) and that decoded from the BCCH to be different , the MS requests a ‘Location Update’ through SDCCH. Back 152
- 153. Discontinuous Transmission • Discontinuous Transmission(DTX) allows the radio transmitter to be switched off most of the time during speech pauses. • A Silence Indicator Block is transmitted at 500bps, which generates a comfort noise • Down Link interference is decreased. • Up link battery is saved 153
- 154. Frequency Hopping • FrequencyHopping permits the dynamic switching of radio links from one carrier frequency to another. • Base Band Hopping – At the BTS each the timeslot is shifted to another transceiver, which is transmitting at the hop frequency. User will be connected to different Transceivers depending on hop sequence. • Synthesis Hopping – At the BTS transceiver changes the frequencies used. The user will be connected to only one transceiver. • Decreases the probability of interference • Suppresses the effect of Rayleigh fading 154
- 155. Add-on to GSMnetwork : rate for GSM Evolution Enhanced Data PCU; Packet EDGE is an enhancement of GPRS and CSD technologies. • Segmentation/re-assembly and scheduling • Radio channel accessthe current GSM technology - same TDMA frame structure, Based on control and management Universal• Mobile Telecommunication Standards Wireless Data • TransmissionService Architecture retransmission.- providing the us • Innovative error detection and : VHE Concept same bandwidth (200 kHz). • Power control and feelmodulation instead services independent of the same look 8-PSK of its personalized of GMSK. • Uses SGSN: GPRSRequires good propagation conditions. Surf the Internet while on the move • mobility network and terminal. High Speed Circuit Switched Data Data Application • Encryption Allows upto:48 kbps (EGPRS) and upto 28.8 kbps (ECSD) on every • Global Convergence Fixed/Mobile, Telecom/Datacom, public/private User Data Rate:14.5kbps • W@P Gateway : • Charging Multimedia driven market. • Mobile radio channel SMS Use multiple timeslots (max=8), GGSN : Data:EDGE helps GSM-Only( operators to compete with UMTS. of the information to the mobile Interface α-numeric characters • Adaptation • Wideband160 torate 2GHz Internet MHz per carrier), -max. 2Mbps bearers - PDN, the • Rate : 9.6kbps band 5 User Data max hence = 115.2kbps. • Compression of theUMTS data UMTS Needs a over the air interface One time slot duplexor in MS for • Buffering of the information Max user data rate : 21.4 kbps simultaneous Tx and Rx Dynamic rate adaptation to suit the radio conditions at EDGE EDGE that time ( 9.05 kbps, 13.4 kbps, 15.6 kbps 21.4 kbps) GPRS GPRS HSCSD HSCSD SIM WAP WAP SIM Circuit Switched technology Toolkit Toolkit GSM GSM Packet Switched technology DATA DATA Technology for Applications Internet W F Mobile Network Time W@P Service @ o W@P Gateway P n 98 99 2000 2001 e 155
- 156. References • Wireless andPersonal Communication Systems. Vijay.K.Garg and Wilkes • Overview of the GSM System and Protocol Architecture, IEEE Comm. Magazine, Moe Rahnema. • The GSM System for Mobile Communications- Michel Mouly & Marie-Bernadette Pautet • Overview of the GSM Comm- John Scourias. 156
- 157. Coverage or TrafficLimitations TRAFFIC- LIMITED AREA COVERAGE- (10000 LIMITED subscribers AREA per km2) (-75 dBm at cell edge) COVERAGE- LIMITED AREA (-70 dBm at cell edge) 157
- 158.
- 159. Erlang Concept Erlang isthe unit of statistical resource use Average number of busy channels during the period of observation (usually, the peak hour). Erlang B At any time, more than 1 user may request the same resource simultaneously. The use of such a resource is associated with a blocking rate. Erlang C When more than 1 user request at the same time, instead of rejecting the extra calls, there is a queuing system. 159
- 160. Different Types ofCells EXTENDED-CELL: CONCENTRIC-CELL: macro cell with system coverage macro cell with system coverage extension (≤ 120 km) for coasts... limitation inside another macro MACRO-CELL: antenna radiating ‘above’ roofs ---> Wide Coverage (≤ 35 km) • High sensitivity to interference • Requires "secured" Frequency reuse pattern PICO-CELL: MICRO-CELL: • High isolation from Antenna inside building interferences ---> Very small coverage Antenna ‘below’ the roofs • A few Frequencies ---> small coverage intensively reused 160
- 161. Cell Patterns 161
- 162. Cell Sectorization TRI OMNI BI
- 163.
- 164. Bi and TrisectorialSite Antennas
- 165. Link Budgeting Calculation of the maximum coverage range of each cell in a specific environment. Definition of planning tools parameters. Based on the path loss calculation between the MS and the BS in both ways. This calculation considers: • RF parameters of MS and BS, • system parameters (diversity gains...), • propagation parameters (shadowing), • physical installation parameters (antenna height), • environment classification.
- 166. - Beyond whichdistance the communication will cut off? - Is indoor coverage guaranteed? - What is the maximum EIRP? - Is frequency hopping used? - What are the losses in transmission and reception? - Is diversity used? - What is the minimum equivalent sensitivity? - What is the maximum equivalent output power? - What are the body losses? EIRP:Equivalent Isotropic Radiated Power
- 167. Link Budget Parameters •Overview Standard conf. DLNA conf. Propagation Parameters: - Incar, Indoor penetration factors Antenna Gain - Frequency 900, 1800, 1900 MHz Rx Sensitivity - Antenna Height - Environment Radio Link Design Parameters: Common cable Losses Overlapping margin Rx Sensitivity Specific Tx Cable Losses Antenna Gain Combiner losses Rx Sensitivity Tx PA Output Power Tx PA Output Power Rx Diversity Gain MS Base Station Duplexer Other factors for MS Combiner Body Losses Common cable losses Power Amplifier DLNA:Diversity Low Noise Amplifier
- 168. Link Budget Parameters •BTS TX Power Amplifier 2.5W PA 25W PA 35W PA 20W PA 30W PA S2000E S8000 Indoor GSM 900 S2000L S4000 Indoor S4000 Indoor S2000H S8000 Outdoor S4000 Outdoor S2000E S4000 Indoor DCS 1800 S2000L S4000 Indoor S2000H S8000 Indoor S4000 Outdoor S8000 Outdoor S2000E S2000H PCS 1900 S2000L S8000 Outdoor S4000 Indoor S4000 Outdoor
- 169. Link Budget Parameters • Combiners H2D D D 4.5 dB Loss 4.5 dB Loss 4.9 dB Loss 4.9 dB Loss Hy/2 C C C C TX TX TX TX TX TX 2-Way Hybrid Combiner with Duplexer 2-Way Hybrid Combiner with Duplexer 4-Way Cavity Combiner with 4-Way Cavity Combiner with Duplexer Duplexer allows Synthesized Frequency Hopping allows Baseband Frequency Hopping
- 170. Link Budget Parameters •Cable Losses At the BS, for a 7/8” foam dielectric coaxial cable: • 4 dB/100 m (900 MHz), • 6 dB/100 m (1800 MHz), • Common cable losses for 40 meters: 2.5 dB (900 MHz) and 3.5 dB (1800 MHz). Jumpers (up and down the feeder) • 0.5 dB (800 MHz), • 1 dB (1800 MHz).
- 171. Link Budget Parameters •BTS Antenna Gain Omnidirectional antenna Default 6.5° V with 11 dBi gain Directional antenna for trisectorial site Default 65° H / 6.5° V with 18 dBi gain
- 172. Link Budget Parameters •Mobile Station Parameters 900 MHz 1800/1900 MHz TX PA Output 33 dBm (2W) 30 dBm (1W) Power RX Sensitivity -102 dBm -100 dBm -2 dBi for Handheld Antenna Gain 2 dBi for Car Kit Common Cable 0 dB for Handheld Loss 2 dB for Car Kit 3 dB for Handheld Body Loss 0 dB for Car Kit
- 173. Link Budget Presentation Parameters Antenna Gain (65 °) 18 dBi Frequency 1800 MHz Jumper Loss Base Height 40.0 m 0.5 dB Mobile Height 1.5 m Feeder Loss Environment Urban 3 dB Penetration Factor 15 dB Sensitivity Body Loss 3 dB -110 dBm Antenna Gain Coupling system Outdoor Minimum Field -2 dB Cable Loss 95%: -80 dBm 0 dB Tx loss 4.5 dB Coverage Range RX TX 95%: 810 m Output Power RXm RXd 30 dBm Sensitivity -100 dBm Max TX Output Power Options 44.8 dBm Rx Diversity Gain: 5 dB Mobile Base Station Overlapping Margin: 0 dB 173
- 174. Link Budget Calculation Exercise1: S8000 INDOOR: OPERATING FREQUENCY 1800 MHz BTS MS 30.00 W (44.8 1.00 W (30.0 TX OUTPUT POWER dBm) dBm) BODY LOSSES 3.0 dB COMBINER LOSSES 5.0 dB None OVERLAPPING MARGIN 0.0 dB RX SENSITIVITY -110.0 dBm -102.0 dBm RX SENSITIVITY + INDOOR PENETRATION DIVERSITY -115.0 dBm None FACTOR 18.0 dB COMMON CABLE LOSSES 3.0 dB 0.0 dB ANTENNA GAIN 18.0 dBm -2.0 dBm 174
- 175. Fading Example of Field Strength Variation for GSM 1800 -10 -20 Zoom on Short Term Fading -30 Measurement Field Strength (dBm) Free Space ≅ λ/2 -40 ±2m -50 -60 Long Term Fading -70 -80 -90 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 -100 Distance (m)
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- 178. Mobile Station (MS) •Hand portable unit • Contains Mobile Equipment(ME) and Subscriber Identity Module (SIM) 178