GPRS – General Packet Radio Service
General Packet Radio Service (GPRS) is a data service designed for second generation GSM and PCS networks. It uses a packet radio principle to carry end user’s packet data protocol like IP or X.25 information from mobiles to external packet data networks and visa versa. GPRS optimises the use of radio and network resources. Separation between the base station subsystem and network subsystem is maintained and the network subsystem can be reused with other services. GPRS radio channel reservation and allocation is done flexible from 1 to 8 radio interface timeslots per TDMA frame and timeslots are shared by all the active users. Up and downlink are allocated separately. The radio interface resources are shared dynamically between data and speech services according to operator’s preference and base station load.
Several radio channel coding schemes are specified to allow data rates from 9 kbits/s up to 171 kbits/s and eventually 384 kbits/s per user. The available bandwidth per channel depends upon which coding scheme is used. CS1 provides connectivity under “all conditions” and delivers a user throughput of up to 9.05 kbits/s, While CS4 requires excellent radio signal (Carrier to Interference ration of 27 dB) and delivers a user throughput of up to 21.4 kbits/s.
GPRS is designed to support intermittent and bursty data transfers and occasional transmission of large volumes of data, and point-to-point and point-to-multipoint services are also supported. GSM network requires two new network elements for GPRS. The Serving GPRS Support Node (SGSN), which performs security functions, mobility management and access control. Frame Relay connects the SGSN the base station system. The Gateway GSN (GGSN) is used for interworking with external packet-switched networks. GPRS is standardised in ETSI (European Telecommunications Standards Institute).