Dual-Hop Spatial Modulation With a Relay Transmitting its Own Information

In this paper, a novel dual-hop spatial modulation (SM) relay network is proposed, in which the relay is enabled to transmit its own information while forwarding the SM signal from the source over the same frequency band. Both decode-and-forward (DF) and amplify-and-forward (AF) relaying protocols are studied. For DF relaying, the relay embeds its own information into one out of two spatial dimensions of quadrature SM. For AF relaying, the relay activates only one transmit antenna to forward the received signal, and encodes its own information by the index of the active antenna. Under both relaying protocols, the throughput of the network is increased without consuming extra power. The bit error rate (BER) performance is analyzed, and tight upper bounds on the BERs are derived in closed form for the source and relay over Rayleigh fading channels for both DF and AF relaying. The performance analysis is verified by Monte Carlo simulations, showing that the proposed scheme provides a simple yet effective solution to the implementation of SM relay networks in which the relay has its own information to be transmitted.