Practical implementation of jointly designed transmit-receive space-time IIR filters

The study of joint transmit-receive design over multi-input multi-output (MIMO) channels representing a wireless channel with spatial diversity at both ends is nowadays receiving a significant attention. The theoretical closed-form solutions obtained so far are given in the continuous-frequency domain corresponding in general to IIR filters. When those filters are to be implemented in a discrete-time domain, FIR filters are highly desired for many reasons. In a realistic implementation, the filter order is generally constrained to a few taps for computational reasons. In this paper, we propose practical approximations of the IIR filters using FIR filters constrained to a few taps by efficiently utilizing the degrees of freedom inherent to the filter solutions, i.e., the possibility of freely choosing arbitrary phases appearing in the structure of the filters.