Coupled Phase-Shift STAR-RISs: A General Optimization Framework

TL;DR

This paper introduces a comprehensive optimization framework for coupled phase-shift STAR-RISs, enabling efficient transmission and reflection with proven convergence to optimal solutions, demonstrated through throughput maximization case studies.

Contribution

It presents a novel general optimization framework for coupled phase-shift STAR-RISs that converges to the KKT optimal solution, with closed-form updates for amplitude and phase-shift coefficients.

Findings

The framework effectively maximizes throughput in STAR-RIS systems.

Numerical results show significant performance improvements over baseline schemes.

The method guarantees convergence to the KKT optimal solution.

Abstract

A general optimization framework is proposed for simultaneously transmitting and reflecting reconfigurable surfaces (STAR-RISs) with coupled phase shifts, which converges to the Karush-Kuhn-Tucker (KKT) optimal solution under some mild conditions. More particularly, the amplitude and phase-shift coefficients of STAR-RISs are optimized alternatively in closed form. To demonstrate the effectiveness of the proposed optimization framework, the throughput maximization problem is considered in a case study. It is rigorously proved that the KKT optimal solution is obtained. Numerical results confirm the effectiveness of the proposed optimization framework compared to baseline schemes.