Research And Application On Physical Layer Security Of Decode-and-Forward Cognitive Relay Network

Cognitive relay network is a brand new network,which is a combination of the cooperative network and the cognitive radio,and it can not only share spectrum to improve the spectrum utilization,but also broaden the coverage area of wireless,realize the diversity order.Decode-and-forward protocol is one of the relaying transmission in cooperative communication.In addition,physical layer provides the passages for the data terminals to transmit information,and it can guarantee the reliable communication.However,because of the openness of wireless communication,it is very easy to be wiretapped and interfered.It is very meaningful to study the secrecy performance of the physical layer of DF cognitive relay network.In this paper,it was studied the secrecy performance of three different system models,and analyze the application of the network model in the reality.Some contribution are list as follows:Firstly,considering a two-hop multi-relay DF cognitive relay network system,it was researched the secrecy performance of the maximum relay selection scheme.Specifically,the selection combing technique is employed in the receive nodes with the existence of direct links.In addition,all transmit power of the transmitters are limited by the primary user's interference over the information transmission.The information will be wiretapped when the data are delivered.All channels experience the Rayleigh fading,and the secrecy outage probability and the probability of none zero capacity are derived to evaluate the system performance.Moreover,the asymptotic expressions of secrecy outage probability are also obtained in high signal-to-noise ratio.Numerical and simulation results verify the veracity of the theoretical analysis,which will make contributions to the research of relay selections in the cognitive relay network.Secondly,considering a dual-hop multi-relay DF cognitive relay network with multiple antenna,and there also exists an eavesdropper,it was researched the secrecy performance of the system.Specifically,the transmit power of transmit is limited by the primary user interference,and the selection combining technique is employed at the multiple receive antennas of relay and the destination.In addition,the eavesdropper could wiretap the information at every hop.It will be outage of the system,when any hop is outage.All channels experience Nakagami-m fading,and all main links,wiretap links,interference links are all i.i.d..The secrecy outage probability and the probability of nonzero secrecy capacity are derived,and the influence of the numbers of relay and antenna,the Nakagami-m.fading parameters are also presented.Numerical and simulation results verify the veracity of the theoretical analysis,which will make contributions to the research of dual hop in the cognitive relay network.Finally,considering relay and multiple users are affected by the co-channel interference in the DF cognitive relay network,it was researched the secrecy performance of the system.Specifically,opportunistic user selection is employed to select the ideal user,and all transmit nodes are equipped with signal antenna.The transmit power of transmitter is limited by the primary user receiver.All channels experience the Rayleigh fading,and the closed form expressions of the secrecy outage probability are derived to evaluate the system performance.Numerical and simulation results verify the veracity of the theoretical analysis,which will make contributions to the research of cognitive relay network which exists the co-channel interference.