Random Linear Time-Variant Channels: A Survey Of Characterization, Physical Examples, Simulation, And Measurement Techniques

摘要

A survey of the engineering literature associated with random time-variant channels is presented. It is demonstrated that linear time-variant channels may be characterized in a symmetrical manner in terms of time and frequency variables by arranging system functions in (time-frequency) dual pairs. The correlation functions and power spectral densities of these various system functions give a statistical characterization of the channel. All real-life channels and signals have a finite number of degrees of freedom due to restrictions on time duration and bandwidth. This fact is used to derive useful channel models with the aid of sampling theorems and power series expansions. A large number of physical channels exhibit time-variant behavior. Examples of the many physical time-variant channels are discussed and theoretical and experimental results of multipath and Doppler spread are given. (Author)