Secrecy-enhanced cooperation scheme with multiuser diversity in wireless relay networks

From the secrecy perspective, conventional cooperation communication is not always positive since it improves the link qualities of both the legitimate receiver and the eavesdropper node. To overcome this drawback, we propose an adaptive cooperation scheme, which activates the relay only when it has better secrecy capability than the source. This adaptive scheme is combined with secure user scheduling strategy to harvest the multiuser diversity (MUD) gain in the relay networks serving multiple sources. The results show that our scheme achieves a much higher secrecy capacity than alternatives. Meanwhile, the relay becomes less beneficial for a large number of sources.