This chapter describes the techniques that are used for radio transmission and reception between the mobile and the radio access network. The first section reviews the use of wideband code division multiple access for transmission and reception in release 99. It concentrates on the air interface's physical layer, which is where most of the important processes take place, but it also notes the procedures used in higher layers. We then describe a technique known as high speed packet access, which has been progressively introduced from release 5 with the aim of increasing the rate at which data can be transferred. Finally, we discuss the performance of UMTS, by noting the peak and average data rates that can be achieved, and the advantages and disadvantages that CDMA has compared with other multiple access techniques.

The material in this chapter is more technical than that in later chapters of the book. However, it is unnecessary to take it all in on a first reading, as most of the chapter is self-contained. Instead, a basic understanding of Section 3.1 will be enough for Chapters 4, 5 and 6.

Radio transmission and reception in release 99

In this first section, we will describe the techniques used for radio transmission and reception in release 99. This is probably the most important part of the system: it is crucial for the delivery of high data rates to the user, and it is the part that has changed the most since the days of GSM.

The action takes place in the air interface's transport protocols, which are illustrated in Figure 3.1.