Mobile Technology

GSM is 2nd Generation mobile technology which provides circuit switched networks, wap access was available but it was circuit switched.

GSM Sub-sytems on infrastructure:

Public Land Mobile Network (PLMN) – consists of the whole GSM subsystem.

Mobile Station (MS) – a PLMN contains as many MSs as possible. Available in various styles and power classes. MS are the cellular devices.

Subscriber Identity Module (SIM) – stores identity of Subscriber. The SIM is a chip, and communicates directly with VLR and indirectly with HLR

Base Tranciever Station (BTS) - large no. of BTSs take care of the radio related tasks and provide connectivity using Air-interface between n/w and MS.

Base Station Controller (BSC) – BTSs of an area are connected to the BSC via an Abis-interface. BSC takes care of central functions and control of the subsystem, BSS.

BSS comprises of BSC and connected BTSs.

Transcoding Rate and Adaptation Unit (TRAU) – data compression for better bandwidth management. TRAU is part of the BSS

GPRS provides circuit switched netwoek for Speech Calls etc and Packet Switched Network for DATA, but there is fallback mechanism if in case the GPRS service is temporarily unavailable Data calls are routed through the circuit switched system.

Basically the main difference henceforth with each new technology is access method and transfer rates

GPRS Transfer rate is a

GPRS Sub-systems on infrastructure:

these are add-ons to the GSM subsystem.

SGSN - GSM Serving GPRS Support Node (SGSN) performs mobility and data session management for GPRS mobiles.

A node in a GPRS infrastructure that is responsible for the delivery of data packets from and to the mobile stations within its service area.

Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN stores location information and user profiles of all GPRS users registered with this SGSN.

GGSN - (Gateway GPRS Service Node)

A system that acts as a data gateway between 2.5G and 3G mobile networks and an IP network such as the Internet.

A node in a GPRS infrastructure that acts as an interface between the GPRS backbone network and the external packet data networks.

It converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format and sends them out on the corresponding packet data network.

In the other direction, PDP addresses of incoming data packets are converted to the GSM address of the destination user. The readdressed packets are sent to the responsible SGSN. For this purpose, the GGSN stores the current SGSN address of the user and his or her profile in its location register.

The GGSN also performs authentication and charging functions.