Physical Layer Secrecy Performance Analysis Over Gamma-Shadowed Two-Wave With Diffuse Power Composite Fading Channels

In this paper, the physical layer secrecy performance of the classical Wyner wiretap channel with gamma-shadowed two-wave with diffuse power (GS-TWDP) composite fading is investigated. A closed-form expression for the average secrecy capacity (ASC) is derived, assuming that the transmitter dynamically adapts its transmission rate based on the available channel state information (CSI) of both the legitimate receiver and the eavesdropper. The derived expression is validated through Monte Carlo simulations and used to conduct a detailed analysis of the impact of shadowing and multipath severity on ASC. To further enhance secrecy performance in GS-TWDP fading environments, an optimal power allocation strategy is also designed and integrated with rate adaptation. The resulting secrecy performance is compared to that achieved using only rate adaptation, providing insight into the effectiveness of the joint power/rate adaptation strategy under varying composite fading conditions.