Security Performance Research For Relay Eavesdropper Channel

The broadcast nature of the wireless medium makes the communication vulnerable toeavesdropping. Information theoretic security of wireless communication has attracted wideattention recently, various wire-tap models and their security performance have been extensivelystudied. The purpose of security communication is to ensure the messages can be transmitted tolegitimate recipient without being eavesdropped. In this paper, the author studies the securityperformance of relay wiretap channel from the perspective of information theoretic security.Firstly, we consider a single-user OFDM wire-tap channel with an external relay, whichtransmitting noise to degrade the eavesdropper without affecting the legitimate recipient. Thus, theachievable secrecy rate of the model is derived. With a set total system power constraint, byoptimizing the allocation of the source power and relay power over all sub-carriers, the overallsecrecy rate of the system can be maximized. We compare the security performances achievedthrough optimal resource allocation schemes with and without relay via implementing simulation.The simulation results indicate that the single-user OFDM wire-tap model with an external relayusing optimal resource allocation scheme can improve the security performance remarkably.Secondly, we consider a wire-tap channel model with multiple relays which can confound theeavesdropper and improve the secrecy rate. Two artificial noise schemes are listed, i.e. the nullingartificial noise and the structured artificial noise. For the nulling scheme, each relay completelyeliminates its interference at the destination node, using only local information of its link to thedestination node. For the structured noise scheme, information of all links is required, and thesecrecy rate can be maximized by general optimization. The simulation results show that thesecrecy rate achieved through the nulling solution is close to that through the structured solution.However, the algorithm of structured solution requires more information and thus is more complex,so the nulling solution is more practical in light of its convenience.