A Bi-Directional Visible Light Communication System Based on DTMB-A

Abstract

In this paper, we propose a new method to realize bidirectional visible light communication (VLC). We implement the bi-directional VLC system based on digital television terrestrial multimedia broadcasting-advanced (DTMB-A) and apply timedomain synchronous OFDM (TDS-OFDM) in the physical layer. A new type of APSK constellation with Gray mapping is used to provide a considerable shaping gain in both the independent demapping and the iterative demapping. Our system realizes the goal of bi- directional transmission between the station and the train, by which we could download driving data conveniently instead of getting on the vehicle. We also measure the output spectrum of photodetector and present our analysis. Through the experiment testing, the download rate of this bi-directional VLC system can achieve 63.67 Mb/s and the physical layer rate can reach 180Mb/s when two computers are connected through our system within the distance of 0.1m. With transmission distance exceeding 0.1m, the signal using 256APSK constellation mapping and 1/2 code rate can still be normally demodulated.