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Basic of teleom gsm


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Basic of teleom gsm

  1. 1. 1 GSM Global System for Mobiles Communication
  3. 3. 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 3
  4. 4. BACKGROUND TO GSM  1G : Advanced Mobile Phone Service (AMPS)  Analog, Circuit Switched, FDMA  2G : Digital Advanced Mobile Phone Service (D-AMPS)  Digital, Circuit Switched, FDMA  2G : Global System for Mobile (GSM)  Digital, Circuit Switched, FDMA and TDMA  2G : Code Division Multiple Access (CDMA)  Digital, Circuit Switched, CDMA 4
  5. 5. DEVELOPMENT OF THE GSM STANDARD 5 1982: Groupe Spécial Mobile (GSM) created 1984: Description of GSM features 1985: List of recommendations settled 1987: Initial MoU (Memorandum of Understanding) aside the drafting of technical specifications was signed by network operators of 13 countries: 1988: Validation and trials, of the radio interface. 1991: First system trials are demonstrated at the Telecom 91 exhibition. 1992: Official commercial launch of GSM service in Europe. First Launch in Finland 1993: The GSM-MoU has 62 signatories in 39 countries worldwide. 1995: Specifications of GSM phase 2 are frozen. 1999: GSM MoU joins 3GPP (UMTS) GPRS Trials begins 2000: 480M GSM Network operators Worldwide First GPRS Networks roll out End 2002: 792M GSM Net work Operators Worldwide
  6. 6. INCREASING GSM DATA RATES Transmission Time GPRS = General Packet Radio Service HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution UMTS = Universal Mobile Telecommunication System 10 sec 1 min 10 min 1 hour0 UMTS E/GPRS ISDN PSTN GSM webe-mail photo web photoe-mail web photo video clipreportphoto web photoe-mail video clipreport video clipreport video clipreport video clipreport
  7. 7. WIRELESS DATA TECHNOLOGY OPTIONS 7 throughputkbps 10 k 100 k 64 k 1 M 2 M 1 k 1998 1999 2000 2001 2002 Time frame UMTS GPRS HSCSD 9.6 14.4 GPRS = General Packet Radio Service HSCSD = High Speed Circuit Switched Data EDGE = Enhanced Data rate for GSM Evolution UMTS = Universal Mobile Telecommunication System EDGE
  8. 8. CIRCUIT-SWITCHED OR PACKET-SWITCHED 8 Circuit mode Packet mode A→FD→H C→G C→G C→G C→G C→G D→H D→H A→FD→H D→H A→F A→F A→F A B C D E F G H
  9. 9. GSM CONCEPTS - CELLULAR STRUCTURE 9 Cellular Networking technology that breaks geographic area into cells shaped like honey comb Cell is the radio coverage area of one base transceiver station 1 2 3 4 5 6 7 6 7 2 1 5
  10. 10. 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) 10
  11. 11. 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 ) 11
  12. 12. 12 GSM IN COMPARISON WITH 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
  13. 13. 13 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 1 2 3 4 5 6 7 4.616 ms 0.577 ms ACCESS TECHNIQUES ...
  14. 14. 14 AuC MS MS BTS BTS BTS BSC BSC MSC MSC VLR VLR GMSC HLR PSTN EIR Um A A OMC Server Um GSM - NETWORK STRUCTURE B E E C F H AuC -Authentication Center PSTN - Public Switched Telephone Network. OMC Operation And Maintenance Center GMSC -Gateway Mobile Switching Centre
  16. 16. FROM SPEECH TO RADIO TRANSMISSION Blah… Blah… Blah...Blah... Blah... Blah... Digitizing and Source Coding Channel Coding Interleaving Ciphering Burst Formatting Modulating Demodulating Burst De-formatting Deciphering De-interleaving Channel Decoding Source Decoding
  17. 17. 17 GSM NETWORK OMC AUC HLR MSC EIRVLR BSC BTS MS External PSTN & PDN N/W SS BSS Switching System Base Station System MS Mobile Station BTS Base transceiver System BSC Base Station Controller MSC Mobile Switching Center HLR Home Location Register VLR Visitor Location Register EIR Equipment Identity Register AUC Authentication Center OMC Operation And Maintenance Center
  18. 18. 18 MOBILE STATION (MS)  Hand portable unit  Contains Mobile Equipment(ME) and Subscriber Identity Module (SIM)
  19. 19. 19 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)
  20. 20. 20 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
  21. 21. 21 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
  22. 22. 22 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
  23. 23. 23 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
  24. 24. 24 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
  25. 25. 25 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.
  26. 26. 26 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
  27. 27. 28 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
  28. 28. 29 Functional Plane of GSM MS BTS BSC MSC/ HLR GMSC VLR MS BTS BSC MSC/VLR HLR GMSC CM MM RR Trans
  29. 29. 30 SUBSCRIBER IDENTITY -MSISDN  The MSISDN is a GSM directory number which uniquely identifies a mobile subscription in the Public Switched Telephone Network (PSTN).  Calls will be routed from the PSTN and other networks based on the Mobile Subscribers’ MSISDN number.  MSISDN= CC + NDC + SN  CC= Country Code (91)  NDC= National Destination Code(98370)  SN= Subscriber Number (12345)
  30. 30. 31 INTERNATIONAL MOBILE SUBSCRIBER IDENTITY [IMSI]  Subscriber always identified within the GSM network by the IMSI  This is used for all signaling in the PLMN stored in SIM and HLR/VLR  The IMSI consists of three different parts  MCC = Mobile Country Code(3 Digits)  MNC = Mobile Network Code(2 Digits)  MSIN = Mobile Station Identification Number(Upto 10 digits)
  31. 31. 32 TEMPORARY MOBILE SUBSCRIBER IDENTITY [TMSI]  The TMSI is used for the subscriber’s confidentiality.  It should be combined with the LAI to uniquely identify a MS.  Since the TMSI has only local significance (that is, within the MSC/VLR area), the structure may be chosen by each administration.  The TMSI should not consist of more than four octets.
  32. 32. 33 INTERNATIONAL MOBILE EQUIPMENT IDENTITY [IMEI]  The IMEI is used for equipment identification. An IMEI  uniquely identifies a mobile station as a piece or assembly of equipment.  IMEI = TAC + FAC + SNR + sp  TAC= Type Approval Code (6 digits),determined by GSM body  FAC= Final Assembly Code (2 digits), identifies themanufacturer  SNR= Serial Number (6 digits), uniquely identifying all equipment within each TAC and FAC  sp = Spare for future use (1 digit)
  33. 33. 34 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.
  34. 34. 35 FRAMES TYPES ON UM 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)
  35. 35. 36 BTS commands MS 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 POWER CONTROL
  36. 36. 37 HANDOVER Means to continue a 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
  37. 37. 38 HANDOVER TYPES  Internal Handover (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
  39. 39. 40 Periodic Measurement Reports (SACCH) Periodic Measurement Reports HO required Activate TCH(facch) with HoRef# if 1. Check for HO passed 2. Channel avail in new BTS Acknowledges and alloctes TCH (facch) HO cmd with HoRef# Receives new BTS data(FACCH) MS tunes into new frequency and TS and sends HO message to new BTS (facch) Periodic Measurement Reports (SACCH) HO performed Release TCH Cell 1 Cell 2 BSC BTS 1 BTS 2 Intra BSC handover
  40. 40. 41 WIRELESS DATA 98 99 2000 2001 GSM DATA HSCSD GPRS EDGE UMTS SIM Toolkit WAP Data Application Time Circuit Switched technology Packet Switched technology Technology for Applications SMS Data: 160 -numeric characters User Data Rate : 9.6kbps One time slot over the air interface High Speed Circuit Switched Data User Data Rate:14.5kbps Use multiple timeslots (max=8), hence max rate = 115.2kbps. Needs a duplexor in MS for simultaneous Tx and Rx Add-on to GSM network : PCU; Packet Segmentation/re-assembly and scheduling • Radio channel access control and management • Transmission error detection and retransmission. • Power control SGSN: GPRS mobility • Encryption • Charging GGSN : Interface to the PDN, Internet Max user data rate : 21.4 kbps Dynamic rate adaptation to suit the radio conditions at that time ( 9.05 kbps, 13.4 kbps, 15.6 kbps 21.4 kbps) W@P Gateway W@P Service W @ P F o n e Internet Mobile Network Surf the Internet while on the move W@P Gateway : • Adaptation of the information to the mo • Compression of the data • Buffering of the information Enhanced Data rate for GSM Evolution • EDGE is an enhancement of GPRS and CSD technologies. • Based on the current GSM technology - same TDMA frame structure, same bandwidth (200 kHz). • Uses 8-PSK modulation instead of GMSK. • Requires good propagation conditions. • Allows upto 48 kbps (EGPRS) and upto 28.8 kbps (ECSD) on every radio channel • EDGE helps GSM-Only operators to compete with UMTS. Universal Mobile Telecommunication Standards • Innovative Service Architecture : VHE Concept - providing the us the same look and feel of its personalized services independent of network and terminal. • Global Convergence : Fixed/Mobile, Telecom/Datacom, public/private • Mobile Multimedia driven market. • Wideband bearers - 2GHz band ( 5 MHz per carrier), - max. 2Mbps
  42. 42. MOBILE IS IN ROAMING 2.Receiving Mobile on Roaming 3. Both Mobiles are on Roaming
  44. 44. Location Area Code Global Cell Identification Country Code 404 Network Code 49 Cell Identity BSC3BSC2BSC1 MSC B MSC A Location Area-100Location Area-089 INDIA-AP-Airtel MCC-MNC 404 -49(INA49) HANDOVER
  45. 45. 46