Infrared wireless communication using spread spectrum techniques

Abstract

The performance of nondirected line-of-sight indoor wireless infrared communication systems is mainly affected by ambient light-induced shot noise, multipath dispersion and interference produced by artificial light sources. Application of spread spectrum techniques to combat multipath dispersion and artificial light interference is presented, with bit error rate analysis considering these two effects. Experiments were carried out to verify the bit error rate analysis and to demonstrate the practical performance of a spread spectrum system. For the line-of-sight link investigated, both experimental and analytical results show that a spread spectrum system operating at 2 Mbit/s and with spreading factor 31 suffers a power penalty of less than 0.5 optical dB due to multipath dispersion, and less than one optical dB penalty is incurred under the influence of 10 dB artificial light interference.