Modeling and Throughput Analysis of an ADO-OFDM Based Relay-Assisted VLC System for 5G Networks

Visible light communication (VLC) is a powerful supplement to the fifth generation (5G) mobile communications. In VLC system, the adoption of orthogonal frequency division multiplexing (OFDM) and relaying technique can greatly improve system performance. In this paper, we proposed a novel relay-assisted VLC system based on asymmetrically clipped direct current biased optical OFDM (ADO-OFDM) for 5G networks. An amplify-and-forward relay is used in the proposed system to forward the signals from source terminal and transmit its own signals simultaneously. The signals from source terminal are allocated to even subcarriers, while the signals from relay terminal are allocated to odd subcarriers. Then, these two parts of signals are combined to constitute ADO-OFDM signals. The signals on odd subcarriers don't interfere with the signals on even subcarriers, while the interference of the signals on even subcarriers to the signals on odd subcarriers can be eliminated by the noise estimation in ADO-OFDM system. Finally, both signals can be recovered at the receiver. We derive the formula of system throughput and investigate the impacts of two power allocation factors on system throughput. Simulation results show that the proposed system makes full use of the relay terminal and improves system throughput. In addition, simulation results also demonstrate that there are optimal power allocation factors to achieve maximum throughput.