Cosine similarity based bit to symbol-and-antenna mapping in spatial modulation system

In spatial modulation (SM) system, the information bits can be transmitted through two ways, the selection of both the transmit antenna and the constellation symbol. However, conventional bit-to-symbol mapping scheme in SM system only selects the transmit antenna or the constellation symbol independently. With the consideration of the similarity among the transmit antennas and the joint selection of the transmit antenna and the constellation symbol, cosine similarity based bit to symbol-and-antenna mapping scheme is proposed in this paper to reduce the hamming distance between adjacent symbols and achieve better system performance. Simulation results and performance analysis show that the proposed scheme can improve the system average bit error rate (BER) effectively compared with the conventional bit-to-symbol mapping scheme.