Design and Analysis of Quadrature Spatial Modulation with Multiple Decode-and-Forward Relays.

A multi-relay cooperative quadrature spatial modulation (QSM) system with decode-and-forward (DF) scheme is proposed in this paper, which improves the system spectral efficiency via the transmission of the extra information bits to select the relay node. The source jointly selects the relay node, the transmit antennas, and the signal constellation symbol. For the proposed scheme, only one relay with DF protocol can be activated during one communication process and the optimal maximum likelihood (ML) detection is employed without direct link. Simulation results verify that the cooperative QSM system with multiple DF relays can effectively increase the system spectral efficiency and improve the system average bit error probability (ABEP) performance compared with the non-cooperative QSM scheme and the traditional cooperative spatial modulation (SM) system with multiple DF relays.