Offset Spatial Modulation: An Efficient Solution For Single-Rf Mimo

Spatial Modulation (SM) has the unique advantage of its single-radio frequency (RF) structure compared to conventional multiple-input multiple-output (MIMO) techniques. However, the transmission rate of SM-MIMO is decided by the maximal switching frequency when it switches between the RF chain and transmit antennas, which has been a bottleneck for its applications in future broadband wireless communications. For alleviating this problem, in this paper, a class of novel offset spatial modulation (OSM) schemes are proposed with the aid of channel state information (CSI) at the transmitter. Compared to conventional SM, the proposed OSM scheme is capable of reducing the switching frequency of the RF chain, by introducing an offset between the connected RF chain and the index of the activated antenna. Furthermore, in some extreme conditions, OSM can even work without RF switching while maintaining the single-RF advantage of conventional SM-MIMO. Through theoretical analysis, we also develop a bit-error rate (BER) performance bound for the proposed OSM system. Finally, our simulation results demonstrate that OSM outperforms its counterparts including conventional SM and CSI-aided SM, while offering a simplified RF-switching structure.