Study of Opportunistic Relaying and Jamming Based on Secrecy-Rate Maximization for Buffer-Aided Relay Systems

In this paper, we investigate opportunistic relaying and jamming techniques and develop relay selection algorithms that maximize the secrecy rate for multiuser buffer-aided relay networks. We develop an approach to maximize the secrecy rate of relay systems that does not require the channel state information (CSI) of the eavesdroppers. We also devise relaying and jamming function selection (RJFS) algorithms to select multiple relay nodes as well as multiple jamming nodes to assist the transmission. In the proposed RJFS algorithms inter-relay interference cancellation (IC) is taken into account. IC is first performed to improve the transmission rate to legitimate users and then inter-relay IC is applied to amplify the jamming signal to the eavesdroppers and enhance the secrecy rate. With the buffer-aided relays the jamming signal can be stored at the relay nodes and a buffer-aided RJFS (BF-RJFS) algorithm is proposed. Greedy RJFS and BF-RJFS algorithms are then developed for relay selection with reduced complexity. Simulation results show that the proposed RJFS and BF-RJFS algorithms can achieve a higher secrecy rate performance than previously reported techniques even in the absence of CSI of the eavesdroppers.