Optimum Spread Code Applied in Indoor Visible Light Data Transmission for Optical Multipath Dispersion Reduction

In an indoor visible light communication (VLC) system, diffuse channels are very easily caused by numerous reflections of the optical signals from the obstacle surface, resulting in optical multipath dispersion which can further reduce the bit error rate (BER) performance of wireless communication system. In this paper, we investigated non-directed LOS links and optimized the design of this short-range communication model using white light-emitting diodes illumination. In our VLC system, we proposed spreading scheme to combat the severe effects of multipath dispersion. We compared the BER performances of four spread codes on the diffuse channel: pseudo random code, Walsh code, m-sequence code, and gold code. Through the analysis and comparison of simulation results, we obtained the optimum spread code, namely Walsh code, which can alleviate the serious effects of multipath dispersion.