Reconfigurable Intelligent Surface-Enabled Downlink NOMA

Reconfigurable intelligent surfaces (RISs) bring great potential to theadvancement of 6G and beyond wireless communication technologies. RISsintroduce a great degree of flexibility, allowing some sort of virtual controlover the wireless channel. Exploiting the flexibility introduced by RISs, wepropose 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 groupswhere each part of the RIS serves a different user equipment (UE) to performmultiple accessing. The BS transmits an unmodulated signal to the RIS, and eachpartition modulates the impinging signal over-the-air by introducing a phaseshift 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 probabilityanalysis, and bit error rate (BER) derivations are discussed and reinforcedwith comprehensive computer simulation results.