Mobile Handset Design

11

Introduction to GPRS and EDGE (2.5G) Supported Mobile Phones

11.1 Introduction

The wireless data services offered by GSM are based on the circuit switched radio transmission. In this instance, at the air interface, a complete traffic channel is allocated for a single user for the entire call duration. Hence with bursty traffic (for example, Internet traffic) this results in highly inefficient resource utilization. It is obvious that for bursty traffic, packet switched bearer services will result in much better utilization of the traffic channels, because a channel will only be allocated whenever it is needed and will be released immediately after the transmission of the packets. Using this principle, multiple users can share one physical channel, for example, one physical channel can be multiplexed among several simultaneous users as required.

In order to address the inefficiencies of circuit switched radio transmission, two cellular packet data technologies have been developed: cellular digital packet data (CDPD) (for AMPS, IS-95, and IS-136) and the general packet radio service (GPRS). Here we will focus only on GPRS. This was originally developed in 1990 for GSM to support data, but later was also integrated within IS-136. We treat GPRS as an evolution from GSM to support packet based services.

Basically GPRS is based on the packet radio principle. Packets can be directly routed from the GPRS mobile (MS) to packet switch networks. Networks based on the Internet protocol (IP) ...