Resource Optimization with Interference Coupling in Multi-RIS-assisted Multi-cell Systems

TL;DR

This paper proposes a resource optimization framework for multi-RIS-assisted multi-cell systems, addressing interference coupling and non-convexity to improve wireless transmission efficiency.

Contribution

It introduces a novel load coupling model and algorithms for optimizing reflection coefficients, enabling efficient resource use in complex multi-cell RIS systems.

Findings

RIS improves resource utilization in multi-cell systems

Proposed algorithms converge to locally optimal solutions

Simulation shows significant performance gains

Abstract

Deploying reconfigurable intelligent surface (RIS) to enhance wireless transmission is a promising approach. In this paper, we investigate large-scale multi-RIS-assisted multi-cell systems, where multiple RISs are deployed in each cell. Different from the full-buffer scenario, the mutual interference in our system is not known a priori, and for this reason we apply the load coupling model to analyze this system. The objective is to minimize the total resource consumption subject to user demand requirement by optimizing the reflection coefficients in the cells. The cells are highly coupled and the overall problem is non-convex. To tackle this, we first investigate the single-cell case with given interference, and propose a low-complexity algorithm based on the Majorization-Minimization method to obtain a locally optimal solution. Then, we embed this algorithm into an algorithmic framework for the overall multi-cell problem, and prove its feasibility and convergence to a solution that is at least locally optimal. Simulation results demonstrate the benefit of RIS in time-frequency resource utilization in the multi-cell system.