A Superimposed Relaying Strategy and Power Allocation for Outdoor Visible Light Communications

In this paper, we consider an outdoor visible light communications relaying system in which the relay node needs to transmit both its own information and the information from a source node simultaneously. A superimposed relaying (SR) strategy and the corresponding constellation design are presented. We derive the closed-form dominant term of average bit error rate (BER) for the system, and obtain an optimal power allocation to minimize the average BER. Simulation results demonstrate that SR can improve the error performance of the system significantly.