Transmit Antenna Combination Optimization and Detection Algorithm for Joint-Mapping-Based Variable Active Antenna Spatial Modulation System

In this paper, transmit antenna combination (TAC) optimization and detection are investigated for joint-mapping-based variable active antenna spatial modulation (JM-VSM) systems. The number of the TACs must be a power of two, hence legitimate TACs should be selected to transmit the symbols. The exhaustive search method can achieve optimal performance but may cause prohibitively high computational complexity. To address these issues, in this paper, a TAC optimization scheme for JM-VSM systems is proposed with the aid of the channel state in-formation (CSI) by maximizing the minimum Euclidean distance (MED). Secondly, to reduce the decode complexity, a partitioning and sorting based sphere decoding (PS-SD) detector is proposed. The detector first partitions the transmission vectors and sorts the partitions according to the number of active antennas, and then sorts the transmission vectors inside the partitions based on the probability of antenna being activated, finally uses the sphere decoding (SD) algorithm to detect the sorted transmission vectors. Simulation results demonstrate that the proposed PS-SD detector can achieve nearly the same performance as the maximum likelihood (ML) detector but require significantly low complexity.