Joint NOMA for Improved SER of Cell-Edge Users in Multi-Cell Indoor VLC

Uday, T.; Kumar, Abhinav; Natarajan, Lakshmi

doi:10.1109/lwc.2021.3117923

Cited by 7 publications

(1 citation statement)

References 15 publications

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“…The joint optimization of user pairing, link selection, and power allocation to maximize the sum-rate of a hybrid VLC and RF communication system was investigated in [146], [203]. NOMA-based modulation schemes for single cell and multi-cell VLC systems where users located at the edge of the cells are served by multiple APs were examined in [204] and [205], respectively. A user pairing scheme for a 3D VLC-NOMA systems was proposed in [206].…”

Section: Noma and Rismentioning

confidence: 99%

RIS-Assisted Visible Light Communication Systems: A Tutorial

Aboagye¹,

Ndjiongue²,

Ngatched³

et al. 2022

Preprint

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Recent intensive and extensive development of the fifth-generation (5G) of cellular networks has led to their deployment throughout much of the world. As part of this implementation, one of the challenges that must be addressed is the skip-zone problem, which occurs when objects such as trees, people, animals, and vehicles obstruct the transmission of signals.In free-space optical (FSO) and radio frequency (RF) systems, dead zones are most often caused by buildings and trees, while in visible light communications (VLC), obstructions are caused by individuals moving around a room or objects placed in the room. A signal obstruction can significantly reduce the signal-to-noise ratio in RF and indoor VLC systems, whereas in FSO systems, where the transmitted signals are directional, the obstruction can completely disrupt data transmission. Therefore, the skipzone dilemma must be resolved to ensure the smooth and efficient operation of 5G and beyond networks. By placing a relay between a transmitter and a receiver, the effects of obstacles can be mitigated. As a result, the signal from the transmitter will reach the receiver. In recent years, reconfigurable intelligent surfaces (RISs) that are more efficient than relays have become widely accepted as a method of mitigating skip-zones and providing reconfigurable radio environments. However, there have been limited studies on RISs for optical wireless communication (OWC) systems. Through the RIS technology, OWC and RF communication channels can be reconfigured. This paper aims to provide a comprehensive tutorial on indoor VLC systems utilizing RIS technology. The article discusses the basics of VLC and RISs and reintroduces RISs for OWC systems, focusing on RIS-assisted indoor VLC systems. We also provide a comprehensive overview of optical RISs and examine the differences between optical RISs, RF-RISs, and optical relays. Furthermore, we discuss in detail how RISs can be used to overcome line-of-sight blockages and the device orientation issue in VLC systems while revealing key challenges such as RIS element orientation design, RIS elements to access point/user assignment design, and RIS array positioning design problems that need to be studied. Moreover, we discuss and propose several research problems on integrating optical RISs with other emerging technologies, including non-orthogonal multiple access, multiple-input multiple-output systems, physical layer security, and simultaneous lightwave and power transfer in VLC systems. Finally, we highlight other important research directions that can further improve the performance of RISassisted VLC systems.

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