Low-complexity sphere decoding for generalised spatial modulation

Generalised Spatial Modulation (GSM) is a relatively new modulation scheme for multi-antenna wireless communications to further increase the spectral efficiency of Spatial Modulation (SM). There are two well-known Sphere Decoding (SD) algorithms tailored to SM: Receiver-centric SD (SM-Rx) and Transmit-centric SD (SM-Tx). In this paper, we show that the SM-Rx is applicable to GSM while SM-Tx is not. Therefore, an improved Transmit-centric SD algorithm for GSM (GSM-Tx) is proposed. The GSM-Tx provides a more efficient and accurate computation of the searching points that lie inside a sphere without triangular factorization. Simulation results show that the proposed GSM-Tx can reduce complexity dramatically while maintaining the optimum bit-error-ratio (BER) performance, especially for high spectral efficiency GSM/SM.