Collaborative Relay Beamforming for Secrecy

TL;DR

This paper explores collaborative relay beamforming techniques to enhance physical-layer security, proposing optimal and suboptimal designs under various power constraints and considering imperfect channel information.

Contribution

It introduces new beamforming strategies for relay networks that maximize secrecy rates with analytical solutions and efficient algorithms, including robustness to channel uncertainties.

Findings

Closed-form solutions for DF beamforming at certain SNR regimes

Efficient algorithms for individual relay power constraints

Robust beamforming designs under imperfect CSI

Abstract

In this paper, collaborative use of relays to form a beamforming system and provide physical-layer security is investigated. In particular, decode-and-forward (DF) and amplify-and-forward (AF) relay beamforming designs under total and individual relay power constraints are studied with the goal of maximizing the secrecy rates when perfect channel state information (CSI) is available. In the DF scheme, the total power constraint leads to a closed-form solution, and in this case, the optimal beamforming structure is identified in the low and high signal-to-noise ratio (SNR) regimes. The beamforming design under individual relay power constraints is formulated as an optimization problem which is shown to be easily solved using two different approaches, namely semidefinite programming and second-order cone programming. A simplified and suboptimal technique which reduces the computation complexity under individual power constraints is also presented. In the AF scheme, not having analytical solutions for the optimal beamforming design under both total and individual power constraints, an iterative algorithm is proposed to numerically obtain the optimal beamforming structure and maximize the secrecy rates. Finally, robust beamforming designs in the presence of imperfect CSI are investigated for DF-based relay beamforming, and optimization frameworks are provided