Multi-stage low complexity maximum likelihood detection for OFDM/SDMA wireless LANs

Space Division Multiple Access (SDMA) is a promising solution for the significant increase of system capacity and spectral efficiency in Wireless LANs. To make the system more robust against the detrimental effects of frequency selective fading channels, a combined OFDM/SDMA based WLAN has been recently proposed. In particular, it has been shown that MLD (Maximum Likelihood Detection) has the best SNR performance compared with other detection schemes such as LMMSE and SIC (Successive Interference Cancellation) based ones. However, the complexity of MLD increases exponentially in the number of users and constellation size. In this paper, a new multi-stage low complexity MLD scheme using sensitive bits algorithm (SB-MLD) is proposed. It is shown that it can greatly reduce the computational complexity with a minimal penalty in performance compared with the exhaustive MLD scheme.