Physical Layer Security In Untrusted Relaying Network

In untrusted relay networks,the relay node is regarded as a node with lower cred-ibility,which the transmitted data needs to be kept the secret,and the physical layer security from the information theory perspective can effectively achieve the coopera-tion while the relay node is confidential.In this paper,we investigate the physical layer security performance of untrusted relay networks and provide two protocols which in-clude decode-and-forward(DF)relay networks allowing intra-link errors(DF-IE)and DF-IE with cooperative jamming(DF-IE-CJ).Different from traditional DF relaying protocol,the decoded message at the relay will always be forwarded to the destination node in decode-and-forward relaying allowing intra-link errors(DF-IE),which can be leveraged to enhance the security of relay networks with untrusted relays.To further improve the security performance of DF-IE,we allow the destination node to send jam-ming signals to impair the signal reception at the relay node,which is referred to as DF-IE with cooperative jamming(DF-IE-CJ).Reliable-and-secure probability(RSP)is used to evaluate the performance of the untrusted relay networks,which represents the probability that the destination node can successfully decode the original message sent from the source node while the relay node cannot.First,the RSP of DF-IE and DF-IE-CJ are derived in a fading scenario where all the channels between the nodes suffer from block Rayleigh fading.Next,we propose two power allocation schemes to maximize the RSP with different signal-to-noise ratios(SNRs),one of that depends on the global channel information but has better performance and the other one only needs statistic channel information which makes relay networks remain high RSP with large transmit power.To verify the effectiveness of DF-IE and DF-IE-CJ in improving the physical layer security of the untrusted relay networks,we compare the RSP performance of DF-IE and DF-IE-CJ with that of two widely used schemes,amplify-and-forward(AF)and cooperative jamming(CJ).A series of numerical simulations verified the accuracy of the theoretical analysis,and the superiority of DF-IE and DF-IE-CJ over AF and CJ,respectively.