Filter bank based frequency-domain equalizers with diversity combining

In earlier studies, we have considered filter bank based frequency domain processing for channel equalization both in multicarrier and single-carrier transmission. With mildly frequency selective subband processing and modest number of subbands, these approaches are able to provide better performance than the conventional FFT-based multicarrier technique OFDM, on one hand, and FFT-based frequency-domain equalizer in single-carrier transmission, on the other. The benefits in transmission link efficiency are due to the lack of guard-interval overhead and, in the multicarrier case, also due to reduced guard-band. Another significant advantage of this approach is that the same filter bank can be utilized to implement significant part of the receiver selectivity, in a very flexible way. In this paper, we extend the filter bank approach to cover also multi-antenna reception schemes. We show that the subband equalizer structure of the basic single-input scheme can be used for the different antennas of a multi-antenna receiver while introducing frequency domain combining of the diversity branches. We also show how to extend the frequency-sampling based techniques for channel equalizer design to the multi-antenna case. Performance evaluation of a simple receiver antenna diversity scheme in single-carrier transmission with maximum ratio combining is included to verify the ideas.