Secure MIMO Communication Systems Aided by Simultaneous Transmission and Reflection Reconfigurable Intelligent Surface

Core Concepts

The core message of this article is to maximize the secrecy rate of STAR-RIS assisted secure MIMO communication networks by jointly optimizing the active beamforming at the base station and passive beamforming at the STAR-RIS.

Abstract

The article investigates a STAR-RIS aided physical layer security (PLS) in multiple-input multiple-output (MIMO) systems, where the base station (BS) transmits secrecy information with the aid of STAR-RIS against multiple eavesdroppers equipped with multiple antennas.
The key highlights and insights are:

The authors aim to maximize the secrecy rate by jointly optimizing the active beamforming at the BS and passive beamforming at the STAR-RIS, subject to the hardware constraint for STAR-RIS.

To handle the coupling variables, a minimum mean-square error (MMSE) based alternating optimization (AO) algorithm is applied. The amplitudes and phases of STAR-RIS are divided into two blocks to simplify the algorithm design.

By applying the Majorization-Minimization (MM) method, a closed-form expression of the STAR-RIS's phase shifts is derived.

Numerical results show that the proposed scheme significantly outperforms various benchmark schemes, especially as the number of STAR-RIS elements increases.

Stats

The article presents the following key figures and metrics:
"The 3D coordinates of STAR-RIS, BS, Bob R, Eve R, Bob T, and Eve T are [0, 0, 30]m, [100, 0, 30]m, [120, 20, 0]m, [150, 150, 0]m, [-120, 0, 30]m, [-120, 50, 60]m."
"The path loss exponents of all the links are set as α = 2.2, the Rician factor is set as K = 3, and the path loss at the reference distance of 1 meter is set as ρ0 = −30 dB."
"The distance between two adjacent elements/antennas d = λ/2. The noise power is σ2k,b = σ2k,e = −90 dBm."

Quotes

"Through changing the phase shifts and/or amplitudes of incident signals, RIS has the capacity to intelligently modify wireless propagation environment."
"To address the limitation of conventional RIS, simultaneous transmitting and reflecting RIS (STAR-RIS) has been introduced as a supplement."
"Motivated by the challenge of the increased risk of eavesdropping due to the full coverage character of STAR-RIS in this MIMO case, we propose a novel secrecy joint active and passive beamforming framework to handle the eavesdropping in STAR-RIS aided MIMO secrecy communication systems."

Key Insights Distilled From

STAR-RIS Aided Secure MIMO Communication Systems

by Xiequn Dong,... at arxiv.org 04-02-2024

https://arxiv.org/pdf/2404.01059.pdf

Deeper Inquiries

How can the proposed STAR-RIS aided secure MIMO communication system be extended to scenarios with multiple legitimate users and eavesdroppers

The proposed STAR-RIS aided secure MIMO communication system can be extended to scenarios with multiple legitimate users and eavesdroppers by adapting the optimization framework to handle the increased complexity. In scenarios with multiple users and eavesdroppers, the algorithm needs to consider the additional channels and interference introduced by the multiple entities. The optimization process would involve jointly optimizing the active beamforming at the base station, passive beamforming at the STAR-RIS, and the phase shifts and amplitudes for each user and eavesdropper. By incorporating the additional channels and interference constraints into the optimization problem, the algorithm can be extended to address scenarios with multiple legitimate users and eavesdroppers effectively.

What are the potential tradeoffs between secrecy performance and system complexity in STAR-RIS aided secure MIMO communication systems

In STAR-RIS aided secure MIMO communication systems, there exist potential tradeoffs between secrecy performance and system complexity. One tradeoff is between the level of security achieved and the computational complexity of the optimization algorithms. As the system aims to maximize secrecy rates by jointly optimizing active and passive beamforming, phase shifts, and amplitudes, the complexity of the optimization process increases. This tradeoff requires balancing the computational resources required for achieving higher secrecy performance against the practical implementation constraints of the system. Additionally, there may be tradeoffs between secrecy performance and hardware complexity, as implementing a large number of elements in the STAR-RIS for enhanced security may introduce challenges in hardware design and deployment.

How can the proposed framework be adapted to incorporate other physical layer security techniques, such as artificial noise, to further enhance the secrecy performance

To incorporate other physical layer security techniques, such as artificial noise, into the proposed framework to enhance secrecy performance, the optimization algorithm can be modified to include the generation and allocation of artificial noise in the transmission process. By introducing artificial noise into the signals transmitted by the base station, the system can intentionally degrade the eavesdroppers' reception quality, thereby enhancing the secrecy performance. The algorithm can be adapted to jointly optimize the power allocation for information signals and artificial noise, considering the impact on the legitimate users and eavesdroppers. By integrating artificial noise generation and allocation into the optimization framework, the system can exploit this technique to further improve the secrecy performance while maintaining system efficiency and complexity within acceptable limits.