Fairness Enhancement of Non-Orthogonal Multiple Access in VLC-Based IoT Networks for Intravehicular Applications

Visible light communication (VLC) is being envisioned as an enabling technology for the physical layer of the sixth generation (6G) of communication networks which promises to support the massive connectivity requirements of the Internet of things (IoT). Due to its ability to safely function in areas that are otherwise susceptible to electromagnetic interference (e.g., aircraft, hospitals, etc.), VLC is a popular candidate for intravehicular communication systems in flights, ambulances, etc. However, the achievable data rate in VLC systems is severely limited by the low modulation bandwidth of the light sources. This limitation is ameliorated by using non-orthogonal multiple access (NOMA) to multiplex users in the power domain. In this paper, we propose to enhance the fairness among users in terms of their error performance and the achievable data rate in a NOMA-VLC system. Based on numerical and simulation results, we show that the fair power allocation (FPA) scheme not only provides significantly higher fairness but it also entails better error performance, improved energy efficiency, and enhanced system throughput as compared to the existing power allocation schemes. We also demonstrate that the FPA scheme exhibits superior performance even when the system parameters, like the number of users, transmitter semi-angle, and detector field-of-view, are changed. We conclude that the FPA scheme is a promising technique for the efficient implementation of NOMA in 6G-VLC broadcasting systems.