Research On The Secure Performance Of Relay Network With Cooperative Jamming Over Rayleigh Fading Channels

Different from the traditional communication networks, wireless ad-hoc network, whose construction is flexible and fast, is a kind of multiple-hop and peer-to-peer network, but it suffers from eavesdropping easily. The traditional key mechanism is difficult to be applied in the network, which hinders its wide application. Physical layer security related technologies bring new ways to resolve the problem. In addition, cooperative jamming can improve the physical layer security in wireless communication system. In the Rayleigh fading environment, this work foces on cooperative jamming, analyzes the secure performance of relay systems with cooperative jamming and proposes schemes to better the secure performance of wireless communication systems.Firstly, for the situation that the relay nodes are unauthenticated, this work presents the analysis expressions of intercept probability in relay system with an external cooperative jammer and relay system with the destination performing cooperative jamming. Simulation results to verify the expressions and, in terms of intercept probably, secrecy ergodic capacity and the emitting path of the jamming signal, the comparison of the two systems are given.Secondly, for the situation that the relay nodes are believeable, this work provides the secrecy outage probability expressions for relay systems with cooperative jamming in closed-form. Simulation results to verify the analysis expressions and to compare relay systems with cooperative jamming with relay systems without cooperative jamming are presented. Simulation results show that the secure performances of amplify-and-forword systems outperform that of decode-and-forward systems at the low SNR region and are worse than that of decode-and-forward systems at the high SNR region. Simulation results also indicate that cooperative jamming technique can improve the secure performance of cooperative relay system in some scenarios.Thirdly, to better the secure performance, when multiple relay nodes are located in the relay system, the channel state information of the source node to the eavesdropper is assumed to be unavailable and optimal relay selection methods are proposed for different systems based on the instantaneous channel state information of the source node to the relay nodes and the relay nodes to the destination node by minimizing the secrecy outage probability. After that, the closed-form secrecy outage probability expressions of different systems are analyzed after applying these optimal relay selection methods. Simulation results to validate the analysis expressions and the comparison of different schemes in terms of secrecy outage probability and secrecy ergodic capacity are provided. Simulation results demonstrate that cooperative jamming technique can improve the secure performance of cooperative relay network and the secure performance of a cooperative relay network remains to be at high level when the eavesdropper is located near the relay set.