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Windows XP Unwired by Wei-Meng Lee

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GPRS

General Packet Radio Service (GPRS) is a data service that supplements other data services such as Circuit Switched Data (CSD, used for data and fax calls on GSM networks) and Short Message Service (SMS). The design of GPRS was informed by the fact that wireless data communications are bursty in nature. That is, the data is not sent in one long stream, but rather in short bursts. Traditional use of CSD such as the Wireless Application Protocol (WAP) for data transfer requires establishing connections between two communicating parties, which occupies bandwidth even when not transmitting data. With GPRS, data is sent as packets as and when required. This feature allows devices to stay connected all the time, and eliminates the need to establish a connection and stay connected within the entire duration. This allows service providers to bill customers based on the data transferred and not the connection time.

In this section, I take a closer look at how GPRS works, as well as some of the devices that you can use on the road.

GSM Networks and GPRS

GPRS is a packet-switched service built on the existing Global System for Mobile (GSM) communication voice network. GSM was primarily designed for voice services.

A GSM channel contains eight timeslots (a portion of time allocated to transmit data), with each timeslot dedicated to each circuit-switched call. Traditionally, when using Circuit Switched Data (CSD) — which is explained in more detail in What Is CSD/HSCSD? later in this ...

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