GSM SYSTEM OVERVIEW. Important Principles and Technologies of GSM

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2 GSM SYSTEM OVERVIEW Important Principles and Technologies of GSM

3 INTRODUCTION TO GSM WHAT IS GSM? GROUPE SPECIALE MOBILE GLOBAL SYSTEM for MOBILE COMMUNICATIONS

4 OBJECTIVES To be aware of the developments of cellular mobile technology To understand the entities that made up GSM Mobile System To know the principles and services that make up GSM

5 MAIN FEATURES OF GSM 1. Spectrum Efficiency 2. Capacity 3. Strong Anti-Interference Capability 4. Open Interfaces 5. Security 6. Interconnection with other networks 7. Roaming

6 GSM SYSTEM ARCHITECTURE

7 GSM SYSTEM NETWORK DIAGRAM MS MS (Mobile Station) BTS BSS (Base Station System) BSC PSTN, ISDN... Voic Server MSC NSS (Network Switching Subsystem) SM-SC VLR HLR AuC EIR OMC NMC OMC GSM interfaces X.25 links OMM (Operations & Maintenance Management)

8 GSM SYSTEM LOGICAL NETWORK CONFIGURATION Um Abis BTS BSC TRAU MSC/VLR/GMSC A HLR/AUC BTS Qx OMC EIR SMC PSTN / PLMN / PSPDN / ISDN BTS NSMU FSMU TRAU BTS BSC Ater A MSC/VLR/GMSC

9 GSM SYSTEM GSM NETWORK ENTITIES BSS: Base Station Subsystem BSC: Base Station Controller BTS: Base Transceiver Station MSC:Mobile Services Switching Center OMC:Operation and Maintenance Center AUC:Authentication Center EIR:Equipment Identification Register

10 GSM SYSTEM GSM NETWORK ENTITIES HLR:Home Location Register VLR:Visitor Location Register MS:Mobile Station ISDN:Integrated Services Digital Network PSTN:Public Switched Telephone Network

11 GSM SYSTEM 1- MOBILE STATION (MS) MS comprises of the following: 1. Mobile Equipment Mobile Equipment 2. Subscriber Identity Module (SIM) SIM

12 Mobile Station Modes 12 7/31/2018

13 Mobile Equipment ME IMEI: 15 digit number First 6 digits type approval code. Next 2 digits assemble code. Next 6 digits S/N. Last digit spare. 13 7/31/2018

14 Subscribe Identity ModuleSIM SIM : an electronic microchip for storinginformation. Contains: CPU, Memories (RAM, ROM and EPROM). 14 7/31/2018

15 Identitynumbers IMEI Mobile Station ISDN number (MSISDN): 15digit International Mobile Subscriber Identity (IMSI): 15 7/31/2018

16 Identitynumbers Temporary Mobile Subscriber Identity (TMSI): use instead of IMSI Mobile Station Roaming Number (MSRN) 16 7/31/2018

17 GSM SYSTEM NETWORK SWITCHING SUBSYSTEM (NSS) Performs the following main functions: Switching functions Database functions Mobility Management Safety Management Manages communication among GSM Mobile subscribers and other communication network subscribers

18 GSM SYSTEM NETWORK SWITCHING SUBSYSTEM (NSS) A MSC Network Switching Subsystem F C B VLR D EIR BSC/ TRC E G HLR/ AUC MSC B C F VLR D

19 GSM SYSTEM NSS ARCHITECTURE SIX FUNCTIONAL UNITS 1. Mobile Service Switching Center (MSC) 2. Home location Register (HLR) 3. Visitor Location Register (VLR) 4. Authentification Center (AUC) 5. Equipment Identification Register (EIR) 6. Operation and Maintenance Center (OMC)

20 GSM SYSTEM NSS ARCHITECTURE MOBILE SERVICES SWITCHING CENTER (MSC) The core of GSM Network which provides switching functions Connects mobile subscribers with fixed network subscribers or with other mobile subscribers Provides interfaces to other communication networks and interconnection with other MSCs

21 GSM SYSTEM OTHER FUNCTIONS OF MSC MSC obtains all the data for processing subscriber call requests from 3 types of databases (HLR, VLR and AUC). Series of services provided by MSC: 1. TELECOM SERVICES eg. Telephony, fax, emergency call, etc 2. SUPPLEMENTARY SERVICES eg. Call forwarding, etc. 3. BEARER SERVICES eg. Security and authentication, etc.

22 GSM SYSTEM NSS ARCHITECTURE VISITOR LOCATION REGISTER (VLR) Dynamic subscriber database Stores all related information of mobile subscribers entering the MSC Service Area Obtains and stores necessary data from the HLR of a mobile subscriber

23 GSM SYSTEM NSS ARCHITECTURE HOME LOCATION REGISTER (HLR) Central Database of GSM System Stores all related data of a mobile subscribers controlled by the same HLR Important Static Data: IMSI, Access capability, subscriber type, and Supplementary services HLR also stores and provides MSC(A) with (dynamic) information of the MSC(B) area into which a mobile station has roamed, so that any incoming call is immediately sent to the called subscriber on a selected path.

24 GSM SYSTEM NSS ARCHITECTURE AUTHENTICATION CENTER (AUC) Functional unit of HLR which is especially used for security management of the GSM System Stores authentication information and encryption keys for: Subscriber authentication Encryption of voice, data, signaling messages on radio interfaces

25 GSM SYSTEM NSS ARCHITECTURE EQUIPMENT IDENTIFCATION REGISTER (EIR) Stores International Mobile Equipment Identifier (IMEI) of mobile equipment 3 Types of List: 1. WHITE Authorized Mobile Equipment 2. GRAY MEs that should be monitored in case of faults 3. BLACK Unauthorized Mobile equipment Mobile operators used EIR information the location of reported stolen MS and block it

26 GSM SYSTEM WIRELESS COVERAGE STRUCTURE GSM Service Area PLMN Service Area MSC Service Area Location Area Cell CELL LOCATION AREA MSC SERVICE AREA PLMN SERVICE AREA GSM SERVICE AREA

27 BSS SYSTEM ARCHITECTURE

28 GSM SYSTEM ZXG-10 BSS ARCHITECTURE Um Interface Abis Interface Q3 Interface MS BTS B I E B I E BSC OMC-R BTS SM SM TC MSC BS Interface Ater Interface A Interface TC: TransCoder SM: SubMultiplexing BIE: Base station Interface Equipment

29 GSM SYSTEM BASE TRANCEIVER STATION (BTS) Radio transmission part of the Base Station Subsystem Controlled by the Base Station Controller Serves cell radio tranceiver equipment Handles conversation between BSC and radio channels Performs radio transmission and control function between BTS and MS via Um interface

30 GSM SYSTEM BASE STATION CONTROLLER (BSC) Performs the switching function of BSS Network Connections Several BTSs MSC (if Transcoder is included in BSC) OMC-R

31 GSM SYSTEM BSC FUNCTIONS Manages radio network and resources Supervises and manages BTSs Controls the establishment, connection and disconnection of radio links in MS and BTS Location updating Handover Paging of Mobile Stations Operations and Maintenance functions

32 FUNCTIONAL LAYERS OF GSM Service Carrier OAM Subscriber CM MM RR TRANSMISSION

33 Frequency FREQUENCY CONCEPTS TIME SLOT IN TIME-DOMAIN AND FREQUENCY- DOMAIN 200 khz Timeslot BP 15/26 ms Interval

34 Air Interface CHANNELS CHANNEL TYPES Channels are divided into physical and logical channels: 1. Physical Channels the path used to carry information between an MS and a BTS 2. Logical Channels different information carried on the physical channels a. Control Channels b. Traffic Channels

35 Air Interface CHANNELS Logical Channels Control Channels Traffic Channels Broadcast Channels Common Control Channels Dedicated Control Channels FCCH SCH BCCH RACH AGCH PCH SDCCH SACCH FACCH

36 Air Interface CHANNELS TRAFFIC CHANNELS (TCH) Traffic channel carries encoded speech or subscriber data, including full-rate traffic channel and half-rate traffic channel: Full-rate traffic channel (TCH/F): total rate is 22.8 kbit/s Half-rate traffic channel (TCH/H): total rate is 11.4 kbit/s 1) Speech channel TCH/FS: full-rate speech traffic channel TCH/HS: half-rate speech traffic channel 2) Data channel TCH/F9.6: 9.6kbit/s full-rate data traffic channel

37 Air Interface CHANNELS CONTROL CHANNELS Control channels carry signaling information used by the MS to locate a BTS, synchronize itself with the BTS, and receive information required to perform call setup. There are three categories of control channels: 1. Broadcast Channel (BCH) 2. Dedicated Control Channel (DCCH) 3. Common Control Channel (CCCH)

38 Air Interface CHANNELS CONTROL CHANNEL BROADCASTING CHANNEL (BCH) They are used only as downward channels, i.e., one-way transmission from the base station to mobile stations. They can be divided into three types of channels: a. FCCH: frequency correction channel, carrying information used in MS frequency calibration. b. SCH: synchronization channel, carrying information of MS frame synchronization and base Transceiver station (BTS) identification. c. BCCH: broadcasting control channel; this channel broadcasts general BTS information. Among transceivers at each base station, there is always one transceiver that contains such a channel, so as to broadcast system information to mobile stations

39 Air Interface CHANNELS CONTROL CHANNEL COMMON CONTROL CHANNEL (CCCH) CCCH are shared by all mobile stations in the network. There are 3 types of such channels: a. PCH: paging channels, used by a base station to page mobile stations (downward). b. RACH: random access channel, used by mobile stations for random access network application, i.e., requesting the allocation of SDCCH channels (upward). c. AGCH: access granted channel, used by a base station to respond to random access requests of mobile stations, i.e., to assign one SDCCH or directly assign one TCH (downward).

40 Air Interface CHANNELS CONTROL CHANNEL DEDICATED CONTROL CHANNEL (DCCH) In application, the base station will assign it to a mobile station, so as to make point-to-point transmission between the base station and the mobile station. a. SDCCH: a stand-alone dedicated control channel, used to transmit such information as channel assignment. b. SACCH: slow-speed associated control channel, used in combination with one traffic channel or one SDCCH, to send some specific subscriber information, e.g.,power and frame adjustment control information, measurement data, etc.

41 Air Interface CHANNELS CONTROL CHANNEL DEDICATED CONTROL CHANNEL (DCCH) c. FACCH: fast associated control channel, combining with one traffic channel to carry the same signals as SDCCH, but it is assigned only when SDCCH has not been assigned. Call connection is realized via frames borrowed from traffic channels to transmit such commands as hand-over

42 Air Interface CHANNELS CHANNEL COMBINATION Item Configuration Combination 1 TCHFull TCH/F + FACCH/F + SACCH/TF 2 TCHHalf TCH/H)+FACCH/H+ SACCH/TH 3 TCHHalf2 TCH/H + FACCH/H+ SACCH/TH+ TCH/H 4 MainBCCH FCCH + SCH + BCCH + CCCH FCCH+SCH+BCCH+CCCH+SDCCH/4+ BCCHCombined 5 SACCH/C4 6 BCH BCCH + CCCH 7 SDCCH SDCCH/8+ SACCH/C8 FCCH+SCH+BCCH+CCCH+ SDCCH/4+ BCCHwithCBCH 8 SACCH/C4 + CBCH 9 SDCCHwithCBCH SDCCH/8+SACCH/C8+CBCH

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