Approximate ML detection for MIMO systems with very low complexity

Recently many space-time coding schemes for multiple antenna systems (MIMO) have been proposed in order to achieve high data rates when transmitting over wireless channels. However, most of such schemes rely on maximum likelihood (ML) detection, which can become quite complex when many antennas are involved and higher modulation schemes are utilized. On the other hand, the high diversity gains of MIMO channels are easily lost when low-complexity receivers like ZF or MMSE are applied. It is thus of utmost importance to look for low-complexity receivers which achieve almost ML performance. In this paper, a new scheme for approximate ML detection for typical flat Rayleigh fading channels is proposed, achieving ML performance in the area of bit error ratio between 10^-4 and 0.1 as it is of interest in wireless communications. The proposed scheme allows the transmission of 64QAM schemes on 4×4 antenna schemes with a detection complexity of only 1% of a brute force ML receiver.