Low-Complexity Maximum-Likelihood Detectors Incorporating Pre-Calculated Symbol Metrics for Differential Spatial Modulation

Differential spatial modulation (DSM) eliminates channel estimation and enables the transmission of additional data bits without requiring more radio frequency chains. Space-time block coded DSM (STBC-DSM) employs STBC to improve transmit diversity. However, the complexity of the original maximum-likelihood (ML) detector for either DSM or STBC-DSM grows exponentially with the number of transmit antennas. In our earlier papers, we proposed low-complexity ML detectors, but the same symbol metrics of these detectors are calculated repeatedly. In this letter, we further decrease the complexity of these ML detectors. Symbol metrics are pre-calculated, and DSM metrics are derived by incorporating these symbol metrics. For DSM, the proposed ML detectors are simpler than all existing detectors.