Secure SWIPT for Directional Modulation Aided AF Relaying Networks

TL;DR

This paper proposes new optimization schemes for secure wireless information and power transfer in directional modulation aided AF relaying networks, achieving high secrecy rates with reduced computational complexity.

Contribution

It introduces a novel SCA-based scheme that approximates optimal solutions efficiently, outperforming traditional methods like ZF and reducing search complexity.

Findings

SCA scheme achieves near-optimal secrecy rate and BER performance.

Proposed methods outperform zero forcing scheme.

Relaxation techniques are proven to be tight under KKT conditions.

Abstract

Secure wireless information and power transfer based on directional modulation is conceived for amplify-and-forward (AF) relaying networks. Explicitly, we first formulate a secrecy rate maximization (SRM) problem, which can be decomposed into a twin-level optimization problem and solved by a one-dimensional (1D) search and semidefinite relaxation (SDR) technique. Then in order to reduce the search complexity, we formulate an optimization problem based on maximizing the signal-to-leakage-AN-noise-ratio (Max-SLANR) criterion, and transform it into a SDR problem. Additionally, the relaxation is proved to be tight according to the classic Karush-Kuhn-Tucker (KKT) conditions. Finally, to reduce the computational complexity, a successive convex approximation (SCA) scheme is proposed to find a near-optimal solution. The complexity of the SCA scheme is much lower than that of the SRM and the Max-SLANR schemes. Simulation results demonstrate that the performance of the SCA scheme is very close to that of the SRM scheme in terms of its secrecy rate and bit error rate (BER), but much better than that of the zero forcing (ZF) scheme.