Relay Selection For Cooperative Communication System Based On Secrecy Capacity

Cooperative communication could improve the performance of wireless communication system under multi-path fading conditions with the help of relay nodes.The performance of the wireless communication can be improved by choosing the optimal relay node reasonably, and the secrecy capacity can also be improved by sending artificial noise. Therefore, the schemes combining relay selection with artificial noise for amplify-and-forward cooperative communication system in the presence of an eavesdropper are designed. The main work is as follows:Both the optimal and the sub-optimal relay selection schemes are proposed according to the transmission characteristics of wireless communication system. The location of the optimal relay node is obtained by the scheme. If there is a relay node at the optimal location, then the relay node is the optimal relay to help the source node to forward the signal; otherwise, the optimal relay node can be selected by the sub-optimal relay selection scheme. As for the system with eavesdroppers, artificial noise is introduced to reduce the signal-to-noise ratio of the eavesdropper while to keep the legitimate node undisturbed. Theoretical analysis and simulation results show the signal receiving and forwarding by the reasonably chosen relay node could enhance the signal-to-noise ratio effectively, It not only could save the transmit power of wireless communication system, but also enhance the secrecy capacity. The performance of the wireless communication system with artificial noise is better than that of the wireless system without artificial noise.A relay selection scheme of the system with multiple relay nodes and multiple users is investigated, which aims to maximize the signal-to-noise ratio of the destination node by selecting the most suitable relay node to forward the signal sent by the source node. This scheme could improve the security and the reliability of the wireless communication system. The relationship between the signal-to-noise ratio and the transmit power has been investigated with simulations, and the effectiveness of the scheme is verified.