Artificial-noise-aided Secure Multicast Precoding for Directional Modulation Systems

TL;DR

This paper proposes two secure multicast precoding schemes for directional modulation systems, enhancing secrecy and BER performance by optimizing power and interference management against eavesdroppers.

Contribution

It introduces two novel secure multicast precoding schemes, Max-GRP plus NSP and leakage, that improve secrecy and performance without requiring channel statistical parameters.

Findings

Both schemes outperform conventional methods in BER and secrecy sum-rate.

Leakage scheme is more robust to direction measurement errors.

Leakage scheme is simpler due to no need for channel statistical parameters.

Abstract

In multi-cast scenario, all desired users are divided into $K$ groups. Each group receives its own individual confidential message stream. Eavesdropper group aims to intercept $K$ confidential-message streams. To achieve a secure transmission, two secure schemes are proposed: maximum group receive power plus null-space (NS) projection (Max-GRP plus NSP) and leakage. The former obtains its precoding vector per group by maximizing its own group receive power subject to the orthogonal constraint, and its AN projection matrix consist of all bases of NS of all desired steering vectors from all groups. The latter attains its desired precoding vector per group by driving the current confidential message power to its group steering space and reducing its power leakage to eavesdropper group and other $K-1$ desired ones by maximizing signal to leakage and noise ratio (Max-SLNR). And its AN projection matrix is designed by forcing AN power into the eavesdropper steering space by viewing AN as a useful signal for eavesdropper group and maximizing AN to leakage-and-noise ratio (Max-ANLNR). Simulation results show that the proposed two methods are better than conventional method in terms of both bit-error-rate (BER) and secrecy sum-rate per group. Also, the leakage scheme performs better than Max-GRP-NSP , especially in the presence of direction measurement errors. However, the latter requires no channel statistical parameters and thus is simpler compared to the former.