Source-Difference-Based Mapping Improves Spatial Modulation

A new multi-antenna transmission scheme, referred to as difference-based spatial modulation (DBSM), is proposed to enhance the reliability of spatial modulation (SM). With the DBSM, a pair of amplitude/phase-shift keying (APSK) symbols are conveyed by each channel-use, but only one of them is radiated from a single transmit antenna. In contrast to conventional SM, DBSM selects the active transmit antenna based on the difference between the two symbols of a channel-use, rather than one of them. The design principle of the APSK constellation in the DBSM is detailed, which guarantees that the mean Euclidean distance between any two DBSM signals mapped by a pair of complementary bit-sequences is the largest possible among all the candidates. In this way, DBSM improves the error performance of conventional SM, even though they have the same achievable data rate given the same system configuration. We demonstrate that channel coding techniques, e.g., convolutional and turbo codes, will enhance the performance gain achieved by DBSM over conventional SM. Both theoretical analysis and simulation results are provided to substantiate the advantages of our proposed DBSM scheme.