A Novel Relay-Assisted DCO-OFDM Green VLC System Based on NOMA

In recent years, relaying technique and non-orthogonal multiple access (NOMA) are introduced to visible light communication (VLC) system to improve the system performance. Relay-assisted VLC system can boost link reliability and extend effective communication coverage compared with the traditional VLC system. Besides, the adoption of NOMA can significantly improve the system throughput, enhance the spectral efficiency and support massive connectivity. A novel relay-assisted VLC system based on NOMA is proposed in this paper. All the source-to-relay and relay-to-destination links in the proposed system use DCO-OFDM scheme to transmit information. The relay terminal serves two destination terminals at the same time. The signals in these two relay-to-destination links are superposed in the power domain based on NOMA. The total throughput with different parameters such as power allocation factors and DC bias is modeled and deduced in this paper. By simulations, the optimal values of DC bias and power allocation factors that maximize the system throughput are obtained. Moreover, the simulation results also show superiority of the NOMA-based VLC system over the OMA-based VLC system.