Secrecy Capacity of Two-Hop Relay Assisted Wiretap Channels

TL;DR

This paper derives the secrecy capacity of a two-hop relay-assisted wiretap channel with an Amplify and Forward relay, providing a theoretical foundation for secure communication in the presence of eavesdroppers.

Contribution

It introduces a new derivation of the secrecy capacity for AF relay channels under power constraints and compares it with the Decode and Forward strategy.

Findings

Secrecy capacity is characterized by solving a non-convex optimization problem.

The derived upper bound matches the achievable secrecy rate with Gaussian input.

Comparison shows the proposed AF strategy's effectiveness against benchmarks.

Abstract

Incorporating the physical layer characteristics to secure communications has received considerable attention in recent years. Moreover, cooperation with some nodes of network can give benefits of multiple-antenna systems, increasing the secrecy capacity of such channels. In this paper, we consider cooperative wiretap channel with the help of an Amplify and Forward (AF) relay to transmit confidential messages from source to legitimate receiver in the presence of an eavesdropper. In this regard, the secrecy capacity of AF relying is derived, assuming the relay is subject to a peak power constraint. To this end, an achievable secrecy rate for Gaussian input is evaluated through solving a non-convex optimization problem. Then, it is proved that any rates greater than this secrecy rate is not achievable. To do this, the capacity of a genie-aided channel as an upper bound for the secrecy capacity of the underlying channel is derived, showing this upper bound is equal to the computed achievable secrecy rate with Gaussian input. Accordingly, the corresponding secrecy capacity is compared to the Decode and Forward (DF) strategy which is served as the benchmark in the current work.