Low-Complexity Signal Detection For Quadrature Spatial Modulation

Quadrature spatial modulation (QSM) is a new digital multiple-input multiple-output (MIMO) transmission technique to further increase the spectral efficiency of spatial modulation (SM). Although the maximum likelihood (ML) detection algorithm is capable of achieving the optimal performance, it necessitates exhaustive search with excessive computational complexity. In this paper, we show that the SD is applicable to QSM. Therefore, an improved SD algorithm for QSM, termed based sorting sphere decoding (BS-SD), is proposed. On one hand, an ordering algorithm is applied to sort the possible transmit antenna combinations (TACs). On the other hand, the possible symbol vectors for each TAC are detected in sequence by using sphere decoding detector algorithm. Simulation results show that SD aided by ordering schemes provides a substantial reduction in the computational complexity while maintaining the optimum bit-error-ratio (BER) performance.