Diversity-Multiplexing Tradeoff of simplified receivers for frequency-selective MIMO channels

Since the introduction of the Diversity-Multiplexing Tradeoff (DMT) by Zheng and Tse forML reception in frequency-flat MIMO channels, some results have been obtained also for the DMT of frequency-selective MIMO channels and for the DMT of suboptimal receivers such as linear (LEs) and decision-feedback equalizers (DFEs) for frequency-selective SIMO channels or frequency-flat MIMO channels. In this paper we extend these results to the case of linear receivers for frequency-selective MIMO channels. We consider infinite-length and FIR equalizers in standard single-carrier systems, and unconstrained equalizers in cyclic prefix systems. For linear equalizers, the diversity gain suffers significantly in the absence of any Channel State Information at the Transmitter (CSIT), since only a part of the receive spatial diversity gets exploited (the transmit spatial and frequency-selectivity diversities are lost). It is shown that some improvement can be obtained by varying the number of streams transmitted. However, the introduction of simple antenna subset selection CSIT is shown to provide for substantial boosts in the resulting DMT (partial recovery of transmit spatial diversity).