TABLE OF CONTENTS The waves incident on a mobile receiving antenna sometimes arrive via a line of sight from the transmitter, but in a general case they emanate mostly from scatterers. The scatterers can be viewed as electromagnetic sources. The scenario comprises these sources and their geometric relation to the receiving antenna.
Precise scenarios are unique to a physical environment and the location of the receiver; however, it is useful if scenarios can be modelled simplistically. Such models are developed in order to help understand the basic processes of the channel, and ultimately to help define the design requirements of the antennas and signal processing required for a communications link.
For fixed pattern antenna design, the receiving pattern should be matched as well as practicable to a time (or location ) averaged scenario. For diversity antenna design, a similar match is required for the composite pattern, or field of view, of the available patterns of an adaptive antenna. In digital communications, this match is not necessarily based solely on gathering the maximum signal power, but rather on achieving the lowest bit error rate in the context of existing system constraints. There are few experimental data on average scenarios, but models can be postulated based on the propagation and scattering principles. Some parameters can be estimated from measurements.
In this chapter, scenario and propagation channel models are developed. The deterministic two path model is used extensively as a model since it offers a simple tutorial and can produce representations of most of the behaviour from real world channels.
