Communication Protocol Engineering Lab. Hyoung Joo. Nam. 1 GSM System Overview Wireless and Mobile Network Architecture Nam Hyoung-Joo Communication Protocol Engineering Lab.

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 2 Contents  Introduction  GSM Architecture  Location Tracking and Call Setup  Security  Data services  Unstructured Supplementary Service Data

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 3 Introduction  GSM(Global System for Mobile Communications) is digital wireless network standard  Major European telecommunications operators and manufacturers  The basic requirements of GSM –Service –Quality of services and security –Radio frequency utilization –Network –Cost

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 4 GSM architecture  MS : Mobile Station  BSS : Base Station System  NSS : Network and Switching System  MSC : Mobile Switching Center

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 5 Mobile station  Composition –SIM (Subscriber Identity Module)  A smart card, usually the size of a credit card  A smaller-sized “plug-in SIM”  Protected by a PIN (Personal Identity Number)  Modified by subscriber  Updated over the air though SIM Toolkit –ME (Mobile equipment)  Contains the noncustomer-related hardware and software specific to the radio interface  Property of the subscriber –TE (Terminal Equipment) –ME and SIM are called the MT (Mobile Terminal)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 6 BSS  Composition –BTS (Base Transceiver Station)  Contains transmitter, receiver, signaling equipment  TRAU (Transcoder/Rate Adapter Unit)  Speech encoding/decoding and rate adaption in data trasmission –BSC (Base Station Controller)  Responsible for the switching function in the BSS  Supports radio channel allocation/release and handoff management  Communicates with the BTSs using ISDN protocol via the A-bis interface

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 7 NSS  Supports the switching functions, subscriber profiles, and mobile management  Interface –Signaling protocol used in the telephone network  Current location of a MS –Maintained by HLR and VLR  AuC (Authentication Center) – security data management for the authentication of subscriber  MSC –GMSC (Gateway MSC)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 8 Radio interface  Radio link –FDMA and TDMA technologies  Frequency band –Downlink signal : 935 ~ 960 MHz –Uplink signal : 890 ~ 915 MHz –200 KHz carrier frequency : 124 pairs of frequency duplex channel  The frame is divided into eight bursts (time slots) –GSM burst structure

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 9 Logical channel(1/2)  Two types –TCHs (Traffic Channels) –CCHs (Control Channels)  TCH –TCH/F (Full-rate TCH)  For speech : 13 Kbps  For data : 9.6, 4.8, or 2.4 Kbps –TCH/H (Half-rate TCH)  For speech : 6.5 Kbps  For data : 4.8 or 2.4 Kbps  CCH –Carry signaling information –Three type  CCCHs (Common control channels)  DCCHs (Dedicated control channels)  BCHs (Broadcast channels)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 10 Logical channel(2/2)  CCCH –PCH (paging channel) –AGCH (Access grant channel) –RACH (Random access channel)  DCCH –SDCCH (Standard dedicated control channel) –SACCH (Slow associated control channel) –FACCH (Fast associated control channel) –CBCH (Cell broadcast channel)  BCH –FCCH (Frequency correction channel) –BCCH (Broadcast control channel)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 11 Origination and termination

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 12 Location tracking and call setup(1/2)  Registration

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 13 Location tracking and call setup(2/2)  Termination

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 14 Security  Two aspects –Authentication –Encryption

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 15 Data services  GSM phase 2 supports two data service groups –Short message services –Bearer services  Short message services –Part of the basic subscription package  Bearer services –Similar to the ISDN services –Data rate : 9.6 Kbps –Circuit-switched connection –Channel resources are reserved : call setup time is too long  GSM phase 2+ standard –HSCSD (High speed Circuit-Switched Data) –GPRS (General Packet Radio Service)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 16 HSCSD(1/2)  HSCSD architecture –TE (Terminal Equipment) –IWF (Interworking Function) –TAF (Terminal Adaption Function) –PSDN (Public Switched Data Network) –PSTN (Public Switched Telephone Network)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 17 HSCSD(2/2)  Circuit-switched protocol for large file transfer and multimedia applications  Using multiple TDMA time slot and data compression techniques  Radio interface –Multiple, independent time slot –RLP (Radio Link Protocol)  Disadvantage of multiple time-slot –Blocking rate of the system will be increased –Solution  Flexible resource assignment

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 18 GPRS(1/2)  GPRS architecture –SGSN (Serving GPRS Support Node) –GGSN (Gateway GPRS Support Node)

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 19 GPRS(2/2)  Packet-switched protocol  Requires its own transport network  Two new entities –SGSN : receives and transmits packets between the MS and PSDN –GGSN : interworks with the PSDN  Cache –Containing location information to speed up the routing procedure  Radio link –MAC (Media Access Control) for packet switching  GPRS supports –Up to 100 users with one to eight channels –Broadcast and multisessions

Communication Protocol Engineering Lab. Hyoung Joo. Nam. 20  USSD (Unstructured Supplementary Service Data) –Supports new services in old MS –GSM 02.90, 03.90, –Used as a GSM transparent bearer for old MS  Flexible message length –Plus the asterisk (*) and pound (#) keys –For example  Command code 159 for call forwarding *159* #  USSD architecture