TABLE OF CONTENTS In this chapter, we present the characteristics of the cellular system and discuss the channel impairments that affect the design of a mobile cellular system. In section 3.2, we introduce the cellular concept which involves dividing the coverage area into small cells and reusing the same frequency in cells that are separated by a large enough distance. As the mobile terminal moves from one cell to the next, the telephone call is handed-off from one base station to the next. The handoff concept is also introduced in section 3.2. The channel impairments that influence the propagation of radio waves are presented in section 3.3. Large scale fading models that are used to determine the average received power are presented in section 3.4. The motion of the mobile terminal relative to the base station leads to a deviation in the frequency received by the mobile terminal (base station) relative to that transmitted by the base station (mobile terminal). This is known as the Doppler Shift, which is presented in section 3.5. Small scale fading manifests itself in large variations in the received signal strength over short distances. In section 3.6, we present the different types of small scale fading due to multi-path propagation and the time variant nature of the channel. Finally, in section 3.7, we talk about the diversity techniques used to enhance the performance of wireless communication systems.
A simple mobile telephone system that covers an entire metropolitan area would consist of a...
