paper_authors: Omar Maraqa, Sylvester Aboagye, Telex M. N. Ngatched for: This paper aims to study the performance of optical simultaneous transmission and reflection reconfigurable intelligent surface (OSTAR-RIS) in a multi-user indoor visible light communication (VLC) system.methods: The proposed system uses a novel multi-user indoor VLC system assisted by OSTAR-RIS, which employs both power-domain non-orthogonal multiple access (NOMA) and rate splitting multiple access (RSMA) to improve the sum rate performance. The roll and yaw angles of the reflector elements, as well as the refractive index of the refractor elements in OSTAR-RIS, are jointly optimized using a sum rate maximization problem.results: The simulation results show that the proposed OSTAR-RIS RSMA-aided VLC system outperforms the OSTAR-RIS NOMA-based VLC system in terms of both the sum rate and the sum energy efficiency.Abstract
A critical concern within the realm of visible light communications (VLC) pertains to enhancing system data rate, particularly in scenarios where the direct line-of-sight (LoS) connection is obstructed by obstacles. The deployment of meta-surface-based simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS) has emerged to combat challenging LoS blockage scenarios and to provide 360 coverage in radio-frequency wireless systems. Recently, the concept of optical simultaneous transmission and reflection reconfigurable intelligent surface (OSTAR-RIS) has been promoted for VLC systems. This work is dedicated to studying the performance of OSTAR-RIS in detail and unveiling the VLC system performance gain under such technology. Specifically, we propose a novel multi-user indoor VLC system that is assisted by OSTAR-RIS. To improve the sum rate performance of the proposed system, both power-domain non-orthogonal multiple access (NOMA) and rate splitting multiple access (RSMA) are investigated in this work. To realize this, a sum rate maximization problem that jointly optimizes the roll and yaw angles of the reflector elements as well as the refractive index of the refractor elements in OSTAR-RIS is formulated, solved, and evaluated. The maximization problem takes into account practical considerations, such as the presence of non-users (i.e., blockers) and the orientation of the recipient's device. The sine-cosine meta-heuristic algorithm is employed to get the optimal solution of the formulated non-convex optimization problem. Moreover, the study delves into the sum energy efficiency optimization of the proposed system. Simulation results indicate that the proposed OSTAR-RIS RSMA-aided VLC system outperforms the OSTAR-RIS NOMA-based VLC system in terms of both the sum rate and the sum energy efficiency.
摘要
Visible light communication (VLC) 的一个关键问题是提高系统数据率，特别是在直线视线 (LoS) 连接被障碍物阻挡时。Meta-surface-based simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS) 的部署已经在这些场景中提供了一种解决方案，并提供了360度的覆盖。在这些系统中，optical simultaneous transmission and reflection reconfigurable intelligent surface (OSTAR-RIS) 的概念也在提出。本研究的目的是研究OSTAR-RIS的性能，探讨VLC系统在这种技术下的性能提升。我们提出了一种基于OSTAR-RIS的多用户indoor VLC系统，并使用了power-domain non-orthogonal multiple access (NOMA) 和 rate splitting multiple access (RSMA) 来提高系统的总率性能。为此，我们提出了一个总率最大化问题，该问题jointly优化了OSTAR-RIS中 reflector元素的扭积角和折射率，以及recipient的设备方向。该问题考虑了实际因素，例如阻挡物 (i.e., 堵塞) 和recipient的设备方向。我们使用了sine-cosine meta-heuristic algorithm来获得优化问题的解。此外，我们还研究了系统的总能效率优化。实验结果表明，我们的OSTAR-RIS RSMA-aided VLC系统在总率和总能效率方面都超过了OSTAR-RIS NOMA-based VLC系统。