Towards TMA-Based Transmissive RIS Transceiver Enabled Downlink Communication Networks: A Consensus-ADMM Approach

TL;DR

This paper introduces a novel downlink communication system using transmissive RIS transceivers with TMA technology, optimizing beamforming via a consensus-ADMM algorithm to enhance signal quality and user fairness.

Contribution

It proposes a new multi-stream downlink scheme with TMA-based transmissive RIS and develops a low-complexity, convergent ADMM algorithm for optimized beamforming.

Findings

The proposed algorithm converges reliably in simulations.

System performance improves with optimized parameters.

The method achieves high signal-to-interference ratios.

Abstract

This paper presents a novel multi-stream downlink communication system that utilizes a transmissive reconfigurable intelligent surface (RIS) transceiver. Specifically, we elaborate the downlink communication scheme using time-modulated array (TMA) technology, which enables high order modulation and multi-stream beamforming. Then, an optimization problem is formulated to maximize the minimum signal-to-interference-plusnoise ratio (SINR) with user fairness, which takes into account the constraint of the maximum available power for each transmissive element. Due to the non-convex nature of the formulated problem,finding optimal solution is challenging. To mitigate the complexity,we propose a linear-complexity beamforming algorithm based on consensus alternating direction method of multipliers (ADMM).Specifically, by introducing a set of auxiliary variables, the problem can be decomposed into multiple sub-problems that are amenable to parallel computation, where the each sub-problem can yield closed-form expressions, bringing a significant reduction in the computational complexity. The overall problem achieves convergence by iteratively addressing these sub-problems in an alternating manner. Finally, the convergence of the proposed algorithm and the impact of various parameter configurations on the system performance are validated through numerical simulations.