Enhancement in power stratification efficiency of NOMA-MIMO-aided downlink indoor visible light communication networks

Abstract

Non-orthogonal multiple access (NOMA)-aided visible light communication (VLC) network is deemed a potential alternative for data access and offers superior spectral efficiency, primarily for indoor communication systems. Despite its apparent advantages, the NOMA technique suffers from residual interference in multi-user multiple-input multiple-output (MIMO)-based VLC networks when users attempt to reconstruct their signals from the superimposed received signal. To combat such difficulties, developing an optimal and adaptive power splitting algorithm is crucial. In this paper, a novel power stratification strategy termed as sigmoid gain ratio power allocation (SGRPA) is proposed to alleviate the power allocation constraints of MIMO-NOMA-based downlink VLC networks through sigmoid function transformation. A comparative study between conventional power allocation approaches for a $2\times 2$ MIMO-based VLC network is conducted in multi-user indoor environment. We also illustrate the impact of tuning the field of views (FoVs) of receivers and the transmission angles of light-emitting diodes (LEDs) to find the optimal position of the VLC access point (AP) and the user FoV. The proposed SGRPA scheme exhibits a significant data rate enhancement when compared to gain ratio power allocation (GRPA), normalized gain difference power allocation (NGDPA), and normalized logarithmic gain ratio power allocation (NLGRPA) methods with a multi-user scenario.