Mode Switching-based STAR-RIS with Discrete Phase Shifters

TL;DR

This paper proposes a joint optimization framework for mode-switching STAR-RIS with discrete phase shifters in 6G IoT networks, enhancing spectral efficiency and hardware simplicity.

Contribution

It introduces a mixed-integer nonlinear optimization model and solution methods for joint beamforming, power allocation, and phase shift design in STAR-RIS systems.

Findings

Achieves higher sum rate than partial optimization methods.

Demonstrates effectiveness of the joint optimization approach.

Validates hardware efficiency and scalability for 6G IoT applications.

Abstract

The increasing demand for cost-effective, high-speed Internet of Things (IoT) applications in the coming sixth-generation (6G) networks has driven research toward maximizing spectral efficiency and simplifying hardware designs. In this context, we investigate the sum rate maximization problem for a mode-switching discrete-phase shifters simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-aided multi-antenna access point network, emphasizing hardware efficiency and reduced cost. A mixed-integer nonlinear optimization framework is formulated for joint optimization of the active beamforming matrix, user power allocation, and STAR-RIS phase shift vectors, including binary transmission/reflection amplitudes and discrete phase shifters. To solve the formulated problem, we employ a block coordinate descent method, dividing it into three subproblems tackled using difference-of-concave programming and combinatorial optimization techniques. Numerical results validate the effectiveness of the proposed joint optimization approach, consistently achieving superior sum rate performance compared to partial optimization methods, thereby underscoring its potential for efficient and scalable 6G IoT systems.