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Gsm architecture

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  • 1. 1. Network Subsystem includes the equipmentsand functions related to end-to-end call.2. Radio Subsystem includes the equipments andfunctions related to the management of theconnections on the radio path.3. Operations and Maintenance subsystemincludes the operation and maintenance ofGSM equipment for the radio and networkinterface.2
  • 2. 3BTSMSC VLRHLRPSTNISDNDataNetworks(Air interfaceOSSBTSBTSMSC VLRBSCBSC
  • 3.  GSM Service Area PLMN Service Area MSC Service Area Location Area Cells4
  • 4. 5VMSCMSCMSCMSCVLRVLRVLRI IIIVIIII
  • 5. 6MSCVLRLA1LA2LA3LA6LA4 LA5
  • 6. 7MSCVLRLA1LA2LA3LA6LA4 LA5C1 C2 C3C6 C5C4C=CELL
  • 7. 8Location AreaCellArea served by a BTSLocation AreaMSC Service AreaPLMN Service AreaGSM Service Area
  • 8. 9MCCLAILACMNC3 digit 3 digit 2 Octets
  • 9.  Voice and data transmission Frequency and time synchronization Monitoring of power and signal qualityof the surrounding cells Provision of location updates evenduring inactive state Equalization of multi path distortions10
  • 10.  Portable, vehicle mounted, hand held MS identified by unique IMEI Shall display at least last ten received,dialed and missed calls Minimum talk time of 1hr 30 min. andstandby time of 80 hrs 160 characters long SMS11
  • 11. 12PowerClassMax. PeakPowerTolerance (dB)Normal Extreme1 20W(43 dBm)+/- 2 +/- 2.52 8W(39 dBm)+/- 2 +/- 2.53 5W(37 dBm)+/- 2 +/- 2.54 2W(33 dBm)+/- 2 +/- 2.55 0.8W(29 dBm)+/- 2 +/- 2.5
  • 12.  SIM Module Unique Subscriber’s ID IMSI and ISDN PIN Key Ki, Kc and A3,A5 and A8algorithms SIM has CPU, ROM, RAM and EPROM13
  • 13.  IMEI MSISDN IMSI TMSI MSRN14
  • 14.  Mobile Subscriber’s ISDN Number The MSISDN is registered in the telephonedirectory and used by the calling party fordialing.15CC NDC SN1 to 3 digits Variable VariableMSISDN : not more than 15 digitsN(S)N
  • 15.  International mobile subscriber’s Identity The IMSI is an unique identity which isused internationally and used withinthe network to identify the mobilesubscribers. The IMSI is stored on the subscriberidentity module (SIM), the HLR, VLRand AC database.16
  • 16. 17MCC MNC MSIN3 digits 3 digits Not more than 9 digitsNMSIIMSI : Not more than 15 digits
  • 17.  Temporary Mobile subscriber’sIdentity The TMSI is an identity which guaranteesthe integrity of the mobile subscribers onthe radio interface. The VLR assigns a TMSI to each mobilesubscribers entering the VLR area.18
  • 18. Mobile Station RoamingNumber The MSRN is used in the GMSC to setup a connection to the visitedMSC/VLR.19
  • 19.  International Mobile Equipment Identity The IMEI is an unique code allocatedto each mobile equipment. It ischecked in the EIR. IMEI checkWhite ListGrey ListBlack List20
  • 20. 21RADIO SUB SYSTEM (RSS)n BTS n BTSBSCBSCBSCMSC/VLRRSS
  • 21.  Encodes, encrypts, multiplexes,modulates and feeds the RF signals tothe antenna Transcoding and rate adaptionFunctionality Time and frequency synchronizationsignals transmission. 11 power classes from .01 watts(Micro cell) to 320 watts (Umbrellacell)22
  • 22.  Frequency hopping Random access detection Uplink radio channel measurements BTS mainly consists of a set oftransceivers (TRX). Can accommodate1 to 7 TRX per Sector23
  • 23.  It is connected to BTS and offloads MSC Radio resource management Inter-cell handover Reallocation of frequencies Power control24
  • 24.  Time delay measurement of the receivedsignals from MS with respect to BTSclock. Performs traffic concentration to reducethe number of lines from BSC to MSC. Provide interface TCP/IP X.25 to the OMS25
  • 25.  BSC performs call processing TRAU are generally located at the site of MSC. BSC- BTS configurations as per requirement. Data from OMC and can be down loaded toBSC26
  • 26. 27BTSBTSBTSBTS BTSBTSA-bisBSCBSSConfiguration -6Multi - cell site= multi--BTSsiteMany singlecell sitesBSSMSCBTSAAASingle - cell siteConfiguration -1Multi - cell site (sector CellsConfiguration -5MCC: Mobile Switching CentreBSS: Base Station SystemBSC: Base Station ControllerBTS: Base Transceiver StationA-bis
  • 27. 28MSC(PSTN)VLRHLR AUCEIRDCSS7 SignallingTraffic PathF(BSS)AEOtherMSC
  • 28.  Manages communication between GSM &other network Call setup functions, basic switching aredone MSC takes into account the RR allocation inaddition to normal exchange functions MSC does gateway function while itscustomers roams to other network by usingHLR /VLR29
  • 29.  Paging, specifically call handling Location updation Handover management Billing for all subscribers based in its area Reallocation of frequencies to BTSs in itsarea to meet heavy demands30
  • 30.  Echo canceller operation control Signaling interface to databases like HLR, VLR. Gateway to SMS between SMS centers andsubscribers Handle interworking function while working asGMSC31
  • 31.  It controls those mobiles roaming in its area. VLR reduces the number of queries to HLR One VLR may be incharge of one or more LA. VLR is updated by HLR on entry of MS its area. VLR assigns TMSI which keeps on changing. IMSI detach and attach operation32
  • 32.  IMSI & TMSI MSISDN MSRN. Location Area Supplementary service parameters MS category Authentication Key33
  • 33.  Reference store for subscriber’s parameters,numbers, authentication & Encryption values. Current subscriber status and associated VLR. Both VLR and HLR can be implemented in thesame equipment in an MSC. one PLMN may contain one or several HLR.34
  • 34.  Permanent data in HLR Data stored is changed only by man-machine. IMSI, MS-ISDN number. Category of MS ( whether pay phone or not ) Roaming restriction ( allowed or not ). Supplementary services like call forwarding35
  • 35.  Temporary data in HLR The data changes from call to call & isdynamic MSRN RAND /SRES and Kc VLR address , MSC address. Messages waiting data used for SMS36
  • 36.  AUC is a separate entity and physicallyincluded in HLR Protect against intruders in air interface Authentication (Ki) and ciphering (Kc) key arestored in this data base. Keys change randomly with each call Keys are never transmitted to MS on air Onlycalculated response are sent.37
  • 37.  AUC38DatabaseGenerationof RandomNumberRANDRANDIMSI1IMSI3IMSI2ki1ki2ki3RANDSRESKcAlgorithm forCipheringA8AlgorithmforAuthenticationA3Kc64 bitsSRES32 bitsHLR
  • 38.  This data base stores IMEI for all registeredmobile equipments and is unique to every ME. Only one EIR per PLMN. White list : IMEI, assigned to valid ME. Black list : IMEI reported stolen Gray list : IMEI having problems like faultysoftware, wrong make of equipment etc.39
  • 39. 40The centralized operation of the variousunits in the system and functions needed tomaintain the subsystems.Dynamic monitoring and controlling of thenetworkSeparate OMC-S and OMC-R for NSS andRSSOperations and MaintenanceCentre OMC
  • 40. 41functions-O&M data function-Configuration management--Fault report and alarm handling-Performance supervision/management-Storage of system software and data-Support GUI for operation andMaintenanceFunctions Of OMC
  • 41.  Four basic security services providedby GSM Anonymity : TMSI Assignment Authentication Encryption: PIN42
  • 42. 43EncryptionProcessKEYPlain TextCipher-text
  • 43. 44A3 A3Ki KiRANDRANDCompareSRESSRESResponseIMSIIMSIYes/NoRadio Path
  • 44.  AUC45DatabaseGenerationof RandomNumberRANDRANDIMSI1IMSI3IMSI2ki1ki2ki3RANDSRESKcAlgorithm forCipheringA8AlgorithmforAuthenticationA3Kc64 bitsSRES32 bitsHLR
  • 45. 46ARCHLRSRES=SREScA3SimCardKey PadA8StoreKcAccessGrantedRANDYesMSC/VLRRAND KiSRESc(128)SRES(32)KcCipherKey Transfer Kc toBTSno
  • 46. 47

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