Physical Layer Security in Untrusted Decode-and-Forward Relay Networks Allowing Intra-link Errors

In this paper, we investigate the physical layer security performance of untrusted decode-and-forward (DF) relay networks allowing intra-link errors with cooperative jamming. 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 jamming signals to impair the signal reception at the relay node, which is referred to as DF-IE with cooperative jamming (DF-IECJ). 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 can not decode the original message. First, the RSP of DFIE-CJ is derived from a fading scenario where all the channels between the nodes suffer from block Rayleigh fading. Next, we propose a power allocation scheme to maximize the RSP with different signal-to-noise ratios (SNRs). To verify the effectiveness of DF-IE-CJ, we compare the RSP performance of DF-IE-CJ with that of a widely used schemes, cooperative jamming (CJ). A series of numerical simulations verified the accuracy of the theoretical analysis, and the superiority of DF-IE-CJ over CJ about 5% in RSP.