An Improved Power Allocation Scheme for Downlink NOMA-Based MIMO Visible Light Communication Systems

Abstract

Non-orthogonal multiple access (NOMA), as a multiple access scheme, is foreseen as an emerging technology in enhancing the achievable sum rate of indoor downlink multiple-input multiple-output (MIMO) visible light communication (VLC) networks. Also, power allocation scheme plays a vital role in achieving these enhanced achievable sum rates. In literature, there are multiple power allocation schemes available such as gain ratio power allocation (GRPA), normalized gain difference power allocation (NGDPA), normalized logarithmic gain ratio power allocation (NLGRPA), and so forth. In this paper, an improved power allocation scheme has been proposed, which is based on the ratio of logarithmic sum channel gains of users as well as on the user index in the decoding order. In the proposed power allocation scheme, multiple transmitting light emitting diodes (LEDs) and multiple users are considered along with their optical channel information required for data communication. The transmitting LEDs are fixed on the room ceiling at optimal positions. The optimal positions of LEDs are selected by using particle swarm optimization (PSO) algorithm. The simulation results depict that the proposed power allocation scheme with optimal LED positions can achieve a performance gain of 5% or higher in the achievable sum rate over NLGRPA scheme when the number of users present in the room is more than five, and even when the user location is far from the LED. Thus, the proposed power allocation scheme with optimal LED positions achieves significant performance improvement when compared with existing power allocation schemes for NOMA-based MIMO-VLC networks for randomly located users in indoor scenario.