Robust Beamforming for Security in MIMO Wiretap Channels with Imperfect CSI

TL;DR

This paper develops robust beamforming strategies for MIMO wiretap channels that do not rely on knowledge of the eavesdropper's channel, aiming to maximize jamming power while maintaining desired SINR at the legitimate receiver, even with imperfect CSI.

Contribution

It introduces robust beamforming schemes that mitigate the impact of imperfect CSI, enhancing physical layer security without prior eavesdropper channel information.

Findings

Robust schemes significantly improve secrecy performance under CSI uncertainty.

Performance degradation due to imperfect CSI can be effectively mitigated.

Simulations confirm the effectiveness of the proposed robust beamforming methods.

Abstract

In this paper, we investigate methods for reducing the likelihood that a message transmitted between two multiantenna nodes is intercepted by an undetected eavesdropper. In particular, we focus on the judicious transmission of artificial interference to mask the desired signal at the time it is broadcast. Unlike previous work that assumes some prior knowledge of the eavesdropper's channel and focuses on maximizing secrecy capacity, we consider the case where no information regarding the eavesdropper is available, and we use signal-to-interference-plus-noise-ratio (SINR) as our performance metric. Specifically, we focus on the problem of maximizing the amount of power available to broadcast a jamming signal intended to hide the desired signal from a potential eavesdropper, while maintaining a prespecified SINR at the desired receiver. The jamming signal is designed to be orthogonal to the information signal when it reaches the desired receiver, assuming both the receiver and the eavesdropper employ optimal beamformers and possess exact channel state information (CSI). In practice, the assumption of perfect CSI at the transmitter is often difficult to justify. Therefore, we also study the resulting performance degradation due to the presence of imperfect CSI, and we present robust beamforming schemes that recover a large fraction of the performance in the perfect CSI case. Numerical simulations verify our analytical performance predictions, and illustrate the benefit of the robust beamforming schemes.