The performance of optical wireless OOK, 2-PPM and spread spectrum under the effects of multipath dispersion and artificial light interference

Indoor wireless infrared transmission systems are mainly affected by ambient light-induced shot noise, multipath dispersion and the interference produced by artificial light sources. In this paper, spread spectrum techniques are proposed to combat multipath dispersion and artificial light interference. The bit error rate performance of the spread spectrum technique under the combination of these detrimental effects are studied and compared with that of OOK and 2-PPM. A novel analysis is derived to provide a simplified common analytical platform to facilitate the comparison among the three modulation schemes. Bit error rate analyses for OOK, PPM and spread spectrum taking into account the combined effects of multipath dispersion and artificial light interference are derived for the first time. Analytical, simulation and experimental results of bit error rate versus optical signal-to-noise ratio are then presented. The results show that spread spectrum techniques are very robust to multipath dispersion and artificial light interference.