A Review of Multiple Access Techniques for Intelligent Reflecting Surface-Assisted Systems
Wei Jiang, Hans Schotten
TL;DR
The paper addresses the challenge of enabling efficient multi-user access in intelligent reflecting surface (IRS) aided wireless networks, where non-frequency-selective IRS reflections and joint active/passive beamforming complicate conventional MA schemes. It surveys and unifies multiple access strategies—TDMA, FDMA/OFDMA, NOMA, SDMA, and opportunistic approaches—under a common IRS system model, deriving closed-form spectral-efficiency and sum-rate expressions. Key contributions include a unified system framework, detailed comparative analysis of each MA technique, and practical optimization strategies (e.g., alternating optimization, SDR) for passive/active beamforming. The work provides actionable insights for designing scalable, power- and cost-efficient IRS-aided networks in 6G and beyond, highlighting when orthogonal versus non-orthogonal or opportunistic schemes offer the best trade-offs.
Abstract
Intelligent Reflecting Surface (IRS) is envisioned to be a technical enabler for the sixth-generation (6G) wireless system. Its potential lies in delivering high performance while maintaining both power efficiency and cost-effectiveness. Previous studies have primarily focused on point-to-point IRS communications involving a single user. Nevertheless, a practical system must serve multiple users simultaneously. The unique characteristics of IRS, such as non-frequency-selective reflection and the necessity for joint active/passive beamforming, create obstacles to the use of conventional multiple access (MA) techniques. This motivates us to review various MA techniques to make clear their functionalities in the presence of IRS. Through this paper, our aim is to provide researchers with a comprehensive understanding of challenges and available solutions, offering insights to foster their design of efficient multiple access for IRS-aided systems.