Enhanced M-algorithm-based maximum likelihood detectors for spatial modulation

M-algorithm to maximum likelihood (MML) detector has been considered as an excellent choice for the detection of spatial modulation (SM) signals with lower computational complexity but satisfactory detection performance compared with the optimal maximum likelihood (ML) detector. However, MML algorithm requires a delicate tuning of the “M” values in order to achieve the optimal detection performance. Unfortunately, these values can only be retrieved via off-line experiments in general. Meanwhile, the detection order of MML algorithm is restricted to the ascending order of the receive antenna indices which neglects its huge impact on the bit-to-error-rate (BER) performance. In this paper, we propose three enhanced MML-based SM detectors with online “M” selection and strategic adjustment on the detection orders of MML algorithm: (1) hMML detector rearranges the detection order of MML algorithm with respect to the status of channel conditions; (2) yMML detector performs SM signal detection with a descending order of the received signal strength; (3) hyMML detector jointly considers the detection order of both hMML and yMML algorithms. Experimental results show that all proposed detectors outperform the MML detector in terms of reception BER performance.