General Packet Radio System (GPRS)

Chapter 24: General Packet Radio System (GPRS)



Introduction

Wireless communications lets people live and work in ways never before possible. With over two hundred million cellular subscribers worldwide, users have overwhelmingly embraced the concept of having a telephone that is always with them. And now business users also want a data connection with the office wherever they go, so that they can have access to e-mail, the Internet, their files, faxes and other data wherever and whenever it is needed, giving them a competitive advantage and more flexible lifestyles. A number of wireless data services are available today, but none are as exciting as a forthcoming data service for GSM networks called General Packet Radio Service (GPRS).

GPRS refers to a high-speed packet data technology, which is expected to be deployed in the next two years. It is expected to profoundly alter and improve the end-user experience of mobile data computing, by making it possible and cost-effective to remain constantly connected, as well as to send and receive data at much higher speeds than today. Its main innovations are that it is packet based, that it will increase data transmission speeds from the current 9.6 Kbps to over 100 Kbps, and that it will extend the Internet connection all the way to the mobile PC -- the user will no longer need to dial up a separate ISP. GPRS will complement rather than replace the current data services available through today’s GSM digital cellular networks, such as circuit-switched data and Short Message Service. It will also provide the type of data capabilities planned for "third generation" cellular networks, but years ahead of them.

Why is GPRS important?

The most important aspects of GPRS are that it allows data transmission speeds to over 100 Kbps, that it is packet based, and that it supports the world's leading Internet communications protocols, Internet Protocol (IP) and X. 25. 

The fact that GPRS will operate at much higher speeds than current networks should provide a huge advantage from a software perspective. Today, wireless middleware is often required to allow slow speed mobile clients to work with fast networks for applications such as e-mail, databases, groupware or Internet access. With GPRS, wireless middleware will often be unnecessary, and thus it should be easier to deploy wireless solutions than ever before.
Whereas today’s wireless applications tend to be text oriented, the high throughput offered by GPRS will finally make multimedia content, including graphics, voice and video practical. Imagine participating in a video conference while waiting for your flight at the airport, something completely out of the question with today’s data networks.
Why is packet data technology important? Because packet provides a seamless and immediate connection from a mobile PC to the Internet or corporate intranet allowing all existing Internet applications such as e-mail and Web browsing to operate smoothly without even needing to dial into an Internet service provider. The advantage of a packet-based approach is that GPRS only uses the medium, in this case the precious radio link, for the duration of time that data is being sent or received. This means that multiple users can share the same radio channel very efficiently. In contrast, with current circuit-switched connections, users have dedicated connections during their entire call, whether or not they are sending data. Many applications have idle periods during a session. With packet data, users will only pay for the amount of data they actually communicate, and not the idle time. In fact, with GPRS, users could be "virtually" connected for hours at a time and only incur modest connect charges. For detailed information about how GPRS works, see "For Network Managers" below.
While packet-based communications works well with all types of communications applications, it is especially well suited for frequent transmission of small amounts of data, what some call short and bursty, such as "real time" e-mail and dispatch. But packet is equally well suited for large batch operations, and other applications involving large file transfers.
GPRS will support the widely used Internet Protocol (IP) as well as the X.25 protocol. IP support is becoming increasingly important as companies are now looking to the Internet as a way for their remote workers to access corporate intranets. For further discussion about remote access, see "GPRS and Remote Access" below.
The IP protocol is ubiquitous and familiar, but what is X.25, and why is support for it important? X.25 defines a set of communications protocols that prior to the Internet constituted the basis of the world’s largest packet data networks. These X.25 networks are still widely used, especially in Europe, and so wireless access to these networks will benefit many organizations. But what does this really mean? Quite simply it means that any existing IP or X.25 application will now be able to operate over a GSM cellular connection. You can think of cellular networks with GPRS service as wireless extensions of the Internet and existing X.25 networks, as shown in figure one.