Throughput performance of low complexity MIMO extensions to OFDM-based WLANs

The paper considers two low complexity MIMO extensions for OFDM-based wireless local area networks (WLANs). The first is a spatial multiplexing (SM) approach employing a linear zero forcing (ZF) receiver; the second is based on space-time block codes (STBC). The throughput performance is demonstrated within the context of IEEE 802.11a. Low complexity channel estimation is employed using orthogonal STBC training matrices. We show that, at low SNRs, the STBC approach yields the best performance, whereas for higher SNRs, and for channels exhibiting significant delay spread, the SM-ZF scheme offers the better solution. Furthermore, the SM-ZF scheme is shown to perform close to SM-ML. Based on the results, a low complexity hybrid scheme is proposed which switches between SM-ZF and STBC to achieve high throughputs over the entire range of SNRs.