A Low-Complexity Soft-Output Detector for Differential Spatial Modulation

Differential spatial modulation (DSM) can avoid pilot overhead and transmit additional data bits without increasing the number of radio frequency chains. If DSM is concatenated with a channel code, which can improve DSM's error performance, the detector's output for DSM ought to be soft-decision. The complexity of the MAP (maximum a posteriori) and Max-Log-MAP detectors increases exponentially with the number of transmit antennas, and the only existing reduced-complexity soft-output detector for DSM is derived from the Max-Log-MAP detector. In this letter, we propose a new low-complexity soft-output detector, which simplifies the MAP detector. The complexity of the proposed detector increases only linearly with the number of transmit antennas. Simulation results show that the error performance of the proposed detector is close to that of the MAP detector. Besides, the proposed detector outperforms the Max-Log-MAP detector and the existing detector with respect to both complexity and error performances.