Secure Transmission in Amplify-and-Forward Diamond Networks with a Single Eavesdropper

TL;DR

This paper develops efficient algorithms to optimize secure communication rates in amplify-and-forward relay networks with a single eavesdropper, providing polynomial-time solutions and closed-form expressions for specific network models.

Contribution

It introduces a novel convex transformation enabling optimal secure rate computation in AF relay networks with real-valued channels, improving upon previous iterative methods.

Findings

Polynomial-time algorithm for two network models

Closed-form expression for the third model

Enhanced secure transmission performance guarantees

Abstract

Unicast communication over a network of $M$-parallel relays in the presence of an eavesdropper is considered. The relay nodes, operating under individual power constraints, amplify and forward the signals received at their inputs. The problem of the maximum secrecy rate achievable with AF relaying is addressed. Previous work on this problem provides iterative algorithms based on semidefinite relaxation. However, those algorithms result in suboptimal performance without any performance and convergence guarantees. We address this problem for three specific network models, with real-valued channel gains. We propose a novel transformation that leads to convex optimization problems. Our analysis leads to (i)a polynomial-time algorithm to compute the optimal secure AF rate for two of the models and (ii) a closed-form expression for the optimal secure rate for the other.