Strategy-Based Gain Ratio Power Allocation in Non-Orthogonal Multiple Access for Indoor Visible light Communication Networks

Visible light communication (VLC) is an evolving green communication technology for indoor wireless communication networks. VLC utilizes light-emitting diodes (LEDs) for both illumination and communication. To achieve economic and energy-efficient communications, non-orthogonal multiple access (NOMA) improves the system throughput by enhancing spectral efficiency. In indoor VLC networks, the gain ratio power allocation (GRPA) of NOMA allocates greater signal power to the users of poor channels to achieve both fairness and high data rate. However, current GRPA strategies developed for radio frequency channels are not necessarily effective in all VLC channel and illumination cases. This study makes the following contributions. First, a GRPA strategy based on VLC channels is proposed that modifies the power counting and channel proportions enhance the NOMA-VLC throughput. Second, owing to difficulties of directly analyzing NOMA-VLC throughput, an alternative lower bound based on a VLC channel model to facilitate throughput comparisons is proposed. It is proved that the proposed alternative lower bound is asymptotic and compact with respect to NOMA-VLC throughput. Third, for the case of LED heights greater than 1 m, a local extremum solution using the proposed strategy is analytically demonstrated based on the alternative bound of VLC network throughput. Then, for the case of LED heights smaller than 1 m, the necessary but not sufficient condition under which the proposed strategy outperforms previous strategies is provided in VLC scenarios. Finally, the experimental results demonstrate the compactness of the proposed alternate lower bound and the advantages of the proposed strategy.