General Packet Radio Service(GPRS) is a data service of mobiles  which is available to GSM users.  It may be described as “2.5G”, that is, a technology between the second (2G) and third (3G) generations of mobile phones.  GSM standard is only kind of network where GPRS is in use.

 GPRS is packet switched which means that multiple users share the same transmission channel, only transmiting when they have data to send.  change to the radio part of GPRS called EDGE (sometimes called EGPRS or Enhanced GPRS however it actually stands for Enhanced Data rates for GSM Evolution) allows higher bit rates of between 160 and 236.8 kbit/s.

The GPRS TYPES

 TYPE 1
ItCan be connected to GPRS service and GSM service (voice, SMS), using both at the same time. Such devices are known to be available today.

TYPE 2
ItCan be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GPRS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B.

TYPE 3
It can be connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service.

A true TYPE 1 device may be required to transmit on two different frequencies at the same time, and thus will need two radios. To get around this expensive requirement, a GPRS mobile may implement the dual transfer mode (DTM) feature. A DTM capable mobile may use simultaneous voice and packet data, with the network coordinating to ensure that it is not required to transmit on two different frequencies at the same time. Such mobiles are considered to be pseudo-TYPE 1. Some networks are expected to support DTM in 2007.