2.1 Introduction

Evaluating the various design choices of different smart antennas architectures, algorithms, and performance trade-offs when applied to modern mobile cellular communications systems requires knowledge and understanding of core access technologies as well as the impairments facing different systems. This chapter presents the concepts of FDMA, TDMA, and CDMA and describes the main differences between these access technologies. An overview of the frequency reuse concept and cochannel interference, critical to the network design of some second generation mobile communications systems, is provided. Since all 3G technologies are based on CDMA, there will be greater emphasis on this technology. When evaluating performance issues, two main components are usually considered, the link level performance and system level performance. In link level performance, we are mainly concerned with a single link between a mobile station and the base station; this link is typically based on the physical layer structure of the air interface. The physical layer is the layer that carries the actual RF transmissions. On the other hand, in system level performance the impact of the upper layers and their interactions with the physical layer has to be taken into consideration. Functions performed by the upper layers include radio resource management, admission control, and so on.

This chapter has been divided as follows. First, in Section 2.2 we discuss the concepts of FDMA and TDMA systems and how frequency reuse is applied in the design of mobile networks also briefly cover cochannel interference. The fundamentals of CDMA technologies are discussed in...