Secure Multigroup Multicast Communication Systems via Intelligent Reflecting Surface

TL;DR

This paper proposes a novel approach to enhance secure multigroup multicast MISO systems using IRS, optimizing beamforming, AN, and IRS phase shifts to reduce transmit power while maintaining secrecy constraints.

Contribution

It introduces a joint optimization framework for beamforming, AN, and IRS phase shifts, employing SDR and SOCP techniques to improve power efficiency in secure multicast communications.

Findings

Proposed schemes halve the transmit power compared to non-IRS systems.

SDR and SOCP methods effectively optimize IRS-assisted secure multicast.

IRS significantly enhances system security and power efficiency.

Abstract

This paper considers a secure multigroup multicast multiple-input single-output (MISO) communication system aided by an intelligent reflecting surface (IRS). Specifically, we aim to minimize the transmit power at the Alice via jointly optimizing the transmit beamformer, AN vector and phase shifts at the IRS subject to the secrecy rate constraints as well as the unit modulus constraints of IRS phase shifts. However, the optimization problem is non-convex and directly solving it is intractable. To tackle the optimization problem, we first transform it into a semidefinite relaxation (SDR) problem, and then alternately update the transmit beamformer and AN matrix as well as the phase shifts at the IRS. In order to reduce the high computational complexity, we further propose a low-complexity algorithm based on second-order cone programming (SOCP). We decouple the optimization problem into two sub-problems and optimize the transmit beamformer, AN vector and the phase shifts alternately by solving two corresponding SOCP sub-problem. Simulation results show that the proposed SDR and SOCP schemes require half or less transmit power than the scheme without IRS, which demonstrates the advantages of introducing IRS and the effectiveness of the proposed methods.