Enhancing RIS-Aided OTFS-NOMA Communications through Phase Shift Optimization

Non-orthogonal multiple access (NOMA) and orthogonal time frequency space (OTFS) are two important technologies of the sixth generation mobile communication (6G) networks for the sake of enhancing spectral efficiency, and a much more reliable and low-latency integration system is developed, namely OTFS-NOMA networks. In this paper, the reconfigurable intelligent surfaces (RIS) aided OTFS-NOMA networks are concived, and the comperhensive collbrative optimization problem of the transmission rate and phase configurations is established. In order to resolve this objective function, a heuristic phase reconstruction arrangment (HPRA) algorithm is proposed, aim to maximize the overall system's transmission rate while satisfy the minimum rate requirement as well as phase constraints.In addition to phase optimization, we have integrated a power optimization approach into the HPRA algorithm, which further optimizes system performance by optimizing the power coefficient first and then putting the resulting coefficient into the HPRA algorithm. The HPRA algorithm utilizes penalty function techniques to effectively handle minimum rate constraints. Through an iterative search, the algorithm determines the approximate optimal phase configuration that maximizes the transmission rate.Based on the simulation experiments, the effectiveness of the proposed algorithm is verified. Furthermore, by comparing with the conventional methods, our HPRA algorithm could significantly improve the overall transmission rate while ensuring the constraints.