As mobile phone technology became more widely used, it became obvious that data services would become the next major generator of revenue. Although many second-generation systems were able to carry data, it was only at very low data rates. For GSM, the maximum rate was 14.4 kbps.

As a result of this, developments were made to enable higher speed data to be carried over the networks. The first was known as High Speed Circuit Switched Data (HSCSD). Although this was never widely deployed, it enabled data rates of up to about 64 kbps to be achieved by combining time slots. Although this enabled higher-speed data to be transferred, the concept was not widely taken up because it did not make efficient use of the resources of the network.

Most data transfer occurs in what is often termed a bursty fashion. The transfer occurs in short peaks, and then remains quiescent for a while. This means that the channel remains dormant, even though this capacity could be used to transfer data for other users. To overcome this problem, a system called the General Packet Radio Service (GPRS) was devised. Rather than using a circuit switched scheme, where a complete circuit is devoted to a user, this scheme uses packet data and enables a far greater level of efficiency to be obtained.

In addition to this, the data world is now very focused on the Internet and the protocols that it has adopted. The...