A CNET tutorial: What is GPRS?

GPRS, not to be confused with GPS (Global Positioning System), stands for General Packet Radio Service. Why should you care? For one thing, this could perhaps be the technology that allows us to really start using the mobile Internet. Often touted as 2.5G, GPRS is considered one step ahead of HSCSD (High Speed Circuit Switched Data), and a step towards third-generation (3G) networks.

Instant, always-on connection
GPRS is a packet-switching technology for GSM networks. Information sent on a GPRS network is split into separate "packets" before it is transmitted and reassembled at the receiving end. Simply put, packet switching is like a jigsaw puzzle. A complete image is divided into several pieces and placed in the box. When you buy the puzzle, you reassemble the puzzle to form the original image.

One of the advantages of GPRS is its ability to provide instant connection where information can be sent and received immediately. Unlike the current GSM network where you have to "dial up" and wait for a connection to be established, GPRS allows users to be "always connected" to the network.

According to the specifications provided by the European Telecommunications Standards Institute (ETSI), the highest speed for a single user session (or time slot) is the coding scheme CS4, which allows 21.4Kbps per time slot. Thus, theoretically, a GPRS connection can provide a data transmission speed of up to 171.2Kbps (approximately three times that of a fixed-line 56K dial-up) if all eight slots are used. GPRS's rival, HSCSD, can achieve up to 57.6Kbps.

However, it is unlikely that network operators will let a single user use up all the time slots. Even Nokia admitted that realistically GPRS can achieve only about 43Kbps while Ericsson thinks 56Kbps is achievable.

What is GPRS?

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Why GPRS?