Transmit Antenna Subset Selection for Single and Multiuser Spatial Modulation Systems Operating in Frequency Selective Channels

The extensive study of transmit antenna (TA) subset selection (TAS) in the context of spatial modulation (SM) has recently revealed that significant performance gains are attainable compared to SM systems operating without TAS. However, the existing TAS techniques conceived for SM were studied by considering a frequency-flat channel, which does not represent practical frequency-selective channels. In this paper, we address this open problem by designing TAS schemes for zero-padded single-carrier SM systems. Specifically, we employ a partial successive interference cancellation (SIC) receiver and invoke Euclidean distance based TA subset selection (ED-TAS) for each of the subchannels. Furthermore, we show using a theoretical analysis that the parallel subchannels obtained are nearly identical, which enables us to employ majority logic decision to obtain a single TA subset to he used in all the subchannels. The computational burden is additionally reduced by restricting the number of subchannels over which the ED-TAS technique is invoked. Furthermore, the proposed TAS schemes are extended to the multiuser scenario. The theoretical insights developed are validated using simulation results. Specifically, a signal-to-noise ratio gain as high as 3 dB is observed in the single user scenario and about 1 dB in case of a two-user scenario upon employing our TAS.