Design of Differential Spatial Modulation Cooperative System Based on Complementary Code

The traditional differential spatial modulation (DSM) cooperative system overcomes the interference between the antennas by the orthogonality of direct sequence-code division multiple access spreading code. But the spreading sequences they used have the following undesirable properties: the non-zero sidelobes of auto-correlation functions will result in severe multi-path interference, and the non-zero values of cross-correlation functions will result in serious multiple access interference. In this paper, we propose a novel DSM cooperative system scheme to overcome this limitation. In our proposed scheme, the anti-interference characteristic of the system is improved by replacing the traditional spreading codes with complementary codes (CCs) at the transmitter. The DSM signal system constructed by using a multi-symbol dispersion matrix at the transmission relay end can improve the system transmission efficiency and avoid the channel interference. At the receiver, in order to reduce the high computational complexity of traditional maximum likelihood detection algorithm, a low-complexity detection algorithm based on the column search is proposed. The simulation results show that the bit error rate performance of DSM cooperative system based on the CC is superior to the traditional DSM cooperative system based on spreading codes. Meanwhile, the system performance with complete CCs is superior to that with the other CCs, and its implementation complexity is lower.