Simulating a Time-Varying Communications Channel

In this extended tutorial, we study the motion of a transmitter and receiver and moving reflectors in a channel and the artifacts this motion introduces into a received signal, including Doppler frequency shifts and change in pulse durations. For continuous-time signals we consider these artifacts from a variety of perspectives, including simple linear motion, and arbitrary positioning of transmitter, reflectors, and receiver. The development is from a signals perspective, rather than a physics-based perspective. We consider sampled bandlimited signals in time-varying channels. An efficient way of performing the computations is presented. These results may be useful, for example, in determining the performance of a communication signal in a time-varying channel.