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GSM Architecture. 2 Network Components Switching System(SS) Base Station System(BSS)

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Presentation on theme: "GSM Architecture. 2 Network Components Switching System(SS) Base Station System(BSS)"— Presentation transcript:

1 GSM Architecture

2 2 Network Components Switching System(SS) Base Station System(BSS)

3 3 BTSBTS MSC VLR HLR PSTN ISDN Data Networks Air interface OSS BTSBTS BTSBTS MSC VLR BSC A Interface A-bis interface


5 5 TRC BSC RBS Base Station System

6 6 Basic or Additiona l Abbrev.SystemFull component namePlatfor m Basic Additional MSC/VLR GMSC HLR ILR AUC EIR DTI TRC BSC BTS OMC NMC MC SSP SCP SDP SOG BGW SS BSS OSS SS Mobile service Switching Center/Visitor Location Register Gateway MSC Home Location Register Interworking Location Register Authentication Center Equipment Identity Register Data Transmission Interface TRanscoder Controller Base Station Controller Base Transceiver Station Operation and Maintenance Center Network Management Center Message Center Service Switching Point Service Control Point Service Data Point Service Order Gateway Billing Gateway AXE Unix/AXE Unix AXE RBS TMOS MXE AXE Unix

7 7 Network Structure Cell A cell is the basic unit of a cellular system and is defined as the radio coverage given by one BS antenna system. Each cell is assigned a unique CGI.

8 8 LOCATION AREA A LA is defined as a group of cells.Within the network, a subsribers location is known by the LA which they are in. The identity of the LA in which an MS is currently located is stored in the VLR. (LAI) Network Structure

9 9 Cells & LA MSC VLR LA1 LA2 LA3 LA6 LA4 LA5 C1 C2 C3 C6 C5 C4 C=CELL

10 10 Network Structure MSC Service Area An MSC Service Area is made up of LAs and represents the geographical part of the network controlled by one MSC.

11 11 MSC Service Area MSC VLR LA1 LA2 LA3 LA6 LA4 LA5

12 12 Network Structure PLMN SERVICE AREA A PLMN service area is the entire set of cells served by one network operator and is defined as the area in which an operator offers radio coverage and access to its network.

13 13 PLMN Service Area V MSC VLR I II IV III I

14 14 Network Structure GSM SERVICE AREA The GSM service area is the entire geographical area in which a subscriber can gain access to a GSM network.

15 15 Relation between areas in GSM Location Area Cell Location Area MSC Service Area PLMN Service Area GSM Service Area

16 16 Mobile Station GSM MSs consist of: Mobile Equipment Subscriber Identity Module

17 17 Functions of Mobile Station Voice and data transmission& receipt Frequency and time synchronization Monitoring of power and signal quality of the surrounding cells Provision of location updates even during inactive state

18 18 Mobile Station Discontinuous Transmission(DTX) Discontinuous reception(DRX) MS identified by unique IMEI STAR#06#

19 19 SIM Fixed data stored for the subscription: IMSI, Authentication Key, Ki Security Algorithms:kc,A3,A8 PIN&PUK

20 20 SIM Temporary network data: Location area of subscriber and forbidden PLMNs Service data: language preference, advice of charge

21 21 KEY TERMS An MS can have one of the following states : Idle: the MS is ON but a call is not in progress. Active: the MS is ON and a call is in progress. Detached: the MS is OFF.

22 22 The following table defined the key terms used to describe GSM mobile traffic cases (there are no traffic cases in detached mode): ModeTermDescription IdleRegistration Roaming International Roaming This is the process in which an MS informs a network that it is attached. When an MS moves around a network in idle mode, it is referred to as roaming. When an MS moves into a network which is not its home network, it is referred to as international roaming. MSs can only roam into networks with which the home network has a roaming agreement.

23 23 ModeTermDescription Active Location Updating Paging Handover An MS roaming around the network must inform the network when it enters a new LA. This is called location updating. This is the process whereby a network attempts to contact a particular MS. This is achieved by broadcasting a paging message containing the identity of that MS. This is the process in which control of a call is passed from one cell to another while the MS moves between cells.

24 24 Network Identities MSISDN IMSI TMSI MSRN IMEI

25 25 MSISDN Mobile Station ISDN Number The MSISDN is registered in the telephone directory and used by the calling party for dialing. MSISDN shall not exceed 15 digits. NDC--National Destination Code SN--Subscriber Number CCNDCSN 1 to 3 digitsVariable MSISDN : not more than 15 digits

26 26 IMSI International mobile subscriber Identity The IMSI is an unique identity which is used internationally and used within the network to identify the mobile subscribers. The IMSI is stored in the subscriber identity module (SIM), the HLR, VLR database.

27 27 IMSI 3 digits MCCMNC MSIN 3 digitsNot more than 9 digits NMSI IMSI : Max. 15 digits MCC--Mobile Country Code, MNC--Mobile N/W Code, MSIN--Mobile Station Identification Number NMSI--National Mobile Station Identity,assigned by Individual Administration. Mobile station Identification Number. It identifies the subs. In a PLMN. First 3 digit identifies the Logical HLR-id of Mobile subs.

28 28 Temporary Mobile subscriber Identity TMSI is a temporary IMSI no. made known to an MS at registration. The VLR assigns a TMSI to each mobile subscribers entering the VLR area. Assigned only after successful authentication. TMSI has only local significance i.e. within VLR area & controlled by the VLR. TMSI changes on location updation. TMSI is less than 8 digit.

29 29 MSRN Mobile Station Roaming Number The MSRN is used in the GMSC to set up a connection to the visited MSC/VLR. MSRN--is a temporary identity which is assigned during the establishment of a call to a roaming subs. CC NDC SN CC--Country Code, NDC--National Destination Code, SN– Servicing Node

30 30 IMEI International Mobile Equipment Identity The IMEI is an unique code allocated to each mobile equipment. It is checked in the EIR. IMEI check List White List Grey List Black List


32 32 FUNCTIONS OF BTS Radio resources Signal Processing Signaling link management Synchronization Local maintenance handling Functional supervision and Testing

33 33 FUNCTIONS OF BSC Radio Network management RBS Management TRC Handling Tx. Network Management Internal BSC O&M Handling of MS connections

34 34 MSC-BSS Configurations BTS A-bis BSC BSS MSC A A-bis

35 35 Transcoder Configurations BSCTRAU BTS MSC To MS To fixed networks TRAUMSC BTSBSC To MS To fixed networks RF Air Interface A-bis Interface A Interface 16 kbps transmission 64 kbps transmission Transcoder (XC) configurations 64Kbps 16 Kbps

36 36 Switching System (SS) MSC (PSTN) VLR HLRAUC EIR D C SS7 Signalling Traffic Path F (BSS) A E Other MSC

37 37 MSC Functions Switcing and call routing Charging Service provisioning Communication with HLR Communication with VLR Communication with other MSCs Control of connected BSCs

38 38 MSC Functions Echo canceller operation control Signaling interface to databases like HLR, VLR. Gateway to SMS between SMS centers and subscribers Handle interworking function while working as GMSC

39 39 VISITOR LOCATION REGISTER (VLR) 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 operation

40 40 Data in VLR IMSI & TMSI MSISDN MSRN. Location Area Supplementary service parameters MS category Authentication Key

41 41 Home Location Register(HLR) Reference store for subscribers parameters, numbers, authentication & Encryption values. Current subscriber status and associated VLR. Both VLR and HLR can be implemented in the same equipment in an MSC. one PLMN may contain one or several HLR.

42 42 Home Location Register(HLR) Permanent data in HLR Data stored is changed only by commands. IMSI, MS-ISDN number. Category of MS ( whether pay phone or not ) Roaming restriction ( allowed or not ). Supplementary services like call forwarding

43 43 Home Location Register(HLR) Temporary data in HLR The data changes from call to call & is dynamic MSRN RAND /SRES and Kc VLR address, MSC address. Messages waiting data used for SMS

44 44 EQUIPMENT IDENTITY REGISTER ( EIR ) This data base stores IMEI for all registered mobile 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 faulty software, wrong make of equipment etc.

45 45 AUthentication Center (AUC) To authenticate the subs. attempting to use a network. AUC is connected to HLR which provides it with authentication parameters and ciphering keys used to ensure network security.

46 46 AUC Functions To perform subscriber authentication and to establish ciphering procedures on the radio link between the network and MS.

47 47 Information provided is called a TRIPLET consists of: 1.RAND (non predictable random number) 2.SRES (Signed response ) 3.Kc (ciphering key ) AUC Functions

48 48 The centralized operation of the various units in the system and functions needed to maintain the subsystems. Dynamic monitoring and controlling of the network Operations and Maintenance Centre OMC Operations and Maintenance Centre OMC

49 49 - O&M data function -Configuration management --Fault report and alarm handling -Performance supervision/management -Storage of system software and data Functions Of OMC Functions Of OMC

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