Design of MAC-layer Protocols for Distributed NOMA-based VLC Networks

In this paper, a visible light communication (VLC) cellular network that utilizes non-orthogonal multiple access (NOMA) is investigated. To deal with the high inter-cell interference attributed to the high-density of VLC network nodes, a medium access control (MAC) scheduler is designed based on a distributed NOMA approach that aims at increasing the performance of cell-edge users, while securing the high data rate requirements of cell-center users in the VLC network. To this end, two practical protocols are proposed to guarantee the increased spectral efficiency and interference mitigation through distributed NOMA. In each protocol, the decoding strategy and power allocation of the users is investigated through a low complexity algorithm that ensures user fairness in the network. The presented analysis is validated through simulations, where the proposed schemes notably outperform the benchmark scheme in which the cell-edge user does not perform successive interference cancellation. Finally, the results showcase valuable insights, mainly on the fact that the decoding strategy in such networks is not as obvious as in conventional downlink NOMA.