Reconfigurable intelligent surfaces (RISs) bring great potential to the advancement of 6G and beyond wireless communication technologies. RISs introduce a great degree of flexibility, allowing some sort of virtual control over the wireless channel. Exploiting the flexibility introduced by RISs, we propose a novel RIS-enabled downlink (DL) non-orthogonal multiple access (NOMA) scheme where NOMA is enabled over-the-air rather than at the base station (BS) or the receiver (Rx). Here, the RIS is partitioned into distinctive groups where each part of the RIS serves a different user equipment (UE) to perform multiple accessing. The BS transmits an unmodulated signal to the RIS, and each partition modulates the impinging signal over-the-air by introducing a phase shift according to the incoming information bits to serve the corresponding UE. First, the end-to-end system model for the proposed system is presented. Furthermore, outage probability calculations, theoretical error probability analysis, and bit error rate (BER) derivations are discussed and reinforced with comprehensive computer simulation results.

翻译：可重构智能表面（RIS）为6G及未来无线通信技术的发展带来了巨大潜力。RIS引入高度灵活性，实现了对无线信道的某种虚拟控制。利用RIS带来的灵活性，本文提出一种新颖的RIS赋能下行（DL）非正交多址接入（NOMA）方案，其中NOMA在空中实现，而非在基站（BS）或接收端（Rx）完成。在此方案中，RIS被划分为不同的组，每个RIS部分服务不同的用户设备（UE）以执行多址接入。BS向RIS发射未调制信号，每个分区通过根据输入信息比特引入相移，对入射信号进行空中调制，以服务对应UE。首先，给出了所提系统的端到端系统模型。此外，讨论了中断概率计算、理论误码概率分析以及误码率（BER）推导，并通过全面的计算机仿真结果加以验证。