Cooperative Jamming for Secure Communications in MIMO Relay Networks

TL;DR

This paper introduces cooperative jamming strategies in MIMO relay networks to enhance physical layer security against eavesdroppers, utilizing inactive nodes as jammers and optimizing beamforming and power allocation.

Contribution

It proposes novel cooperative jamming schemes with closed-form solutions and GSVD-based methods, improving secrecy rates in relay networks with known and unknown eavesdropper CSI.

Findings

Secrecy rate significantly increases with cooperative jamming.

Closed-form beamformers and optimal power allocations are derived.

GSVD-based schemes outperform non-jamming approaches.

Abstract

Secure communications can be impeded by eavesdroppers in conventional relay systems. This paper proposes cooperative jamming strategies for two-hop relay networks where the eavesdropper can wiretap the relay channels in both hops. In these approaches, the normally inactive nodes in the relay network can be used as cooperative jamming sources to confuse the eavesdropper. Linear precoding schemes are investigated for two scenarios where single or multiple data streams are transmitted via a decode-and-forward (DF) relay, under the assumption that global channel state information (CSI) is available. For the case of single data stream transmission, we derive closed-form jamming beamformers and the corresponding optimal power allocation. Generalized singular value decomposition (GSVD)-based secure relaying schemes are proposed for the transmission of multiple data streams. The optimal power allocation is found for the GSVD relaying scheme via geometric programming. Based on this result, a GSVD-based cooperative jamming scheme is proposed that shows significant improvement in terms of secrecy rate compared to the approach without jamming. Furthermore, the case involving an eavesdropper with unknown CSI is also investigated in this paper. Simulation results show that the secrecy rate is dramatically increased when inactive nodes in the relay network participate in cooperative jamming.