A discrete model for the efficient analysis of time-varying narrowband communication channels

We derive an efficient numerical algorithm for the analysis of certain classes of Hilbert-Schmidt operators that naturally occur in models of wireless radio and sonar communications channels. We show that many narrowband finite lifelength systems such as wireless radio communications can be well modelled by smooth and compactly supported spreading functions. Further, we exploit this fact to derive a fast algorithm for computing the matrix representation of such operators with respect to well time-frequency localized Gabor bases (such as pulseshaped OFDM bases). Hereby we use a minimum of approximations, simplifications, and assumptions on the channel. Moreover, we use a multivariate setting to allow for applications to, for example, antenna arrays. The derived algorithm and software can be used, for example, for comparing how different system settings and pulse shapes affect the diagonalization properties of an OFDM system acting on a given channel.