On the SER of Distributed TAS/MRC in MIMO Multiuser Relay Networks

Distributed transmit antenna selection with maximal-ratio combining (TAS/MRC) is proposed for use in multiple-input multiple-output (MIMO) multiuser relay networks (MRN), where N_S, N_R, and N_D antennas are equipped at the source, the relay, and each of the K destinations, respectively. For such networks, the destination with the highest instantaneous end-to-end signal-to-noise ratio (SNR) is scheduled for transmission. In each hop, a single transmit antenna that maximizes the post-processing SNR is selected, while all the receive antennas are MRC combined. New exact closed-form expressions are derived for the cumulative distribution function (CDF), the probability density function (PDF), and the moment generating function (MGF) of the highest instantaneous end-to-end SNR. Based on these, we determine the symbol error rate with M-ary phase-shift keying. Our derived results apply to general operating scenarios with arbitrary number of antennas, arbitrary number of destinations, and distinct average SNRs.