Information-theoretic analysis of the communication system performances is of practical and theoretical importance. The discrete memoryless wiretap channel with relay and its extension to the continuous alphabet Gaussian version with uncorrelated noises have been studied previously. In this paper, based on Noise-Forwarding (NF) strategy, where the relay node sends codewords independent of the source message to confuse the eavesdropper, the impact of the relay on physical layer security in a Rayleigh fading wiretap channel is studied and closed-form expressions for the probability of positive secrecy rate (PSR), average secrecy rate (ASR), and secrecy outage probability (SOP) are derived. The results, while including previous works as its special cases, show that the relay has positive effects over the PSR, ASR and SOP, as expected intuitively. To support the claims, numerical evaluations are provided.

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