Low Complexity BICM MIMO OFDM Demodulator

In this paper, we consider low-complexity detection of coded spatial data streams with uniform power and non-uniform rate distribution in a single-user MIMO system. The receiver decodes these different streams as if facing a multiple access channel (MAC). Conventional receiver solutions for such schemes are based on successive interference cancellation (SIC) by employing a linear minimum mean square error (MMSE) successive stripping detector, where the optimality is nonetheless constrained to Gaussian codebooks. As a remedy, this paper introduces a novel near-optimal low-complexity max-log-MAP demodulator for a 2×n_r system (n_r is the number of receive antennas) which reduces the complexity of detection from O(|χ|²) to O(|χ|¹), where |χ| indicates the size of the signal set. In the sequel, we extend the proposed low-complexity demodulation scheme to higher-dimensional MIMO systems via a hybrid detector, where significant complexity saving is realized at the expense of slight performance degradation.