Performance of wireless infrared transmission systems considering both ambient light interference and inter-symbol interference due to multipath dispersion

The performance of optical wireless transmission systems is mainly impaired by the shot noise induced by ambient light, interference produced by artificial light sources, transmitted optical power limitations due to high path losses and channel bandwidth limitations due to inter-symbol interference (ISI) produced by the multipath dispersion of the optical signal. The contribution of these factors to the performance evaluation of infrared links have only been addressed independently and the combined effect of these channel impairments was not presented yet. The work presented in this paper extends the previous analysis by taking into account the combined effects of both optical noise (shot noise and interference) and channel impulse response. A simulation package was used to determine the indoor optical channel impulse response due to the propagation losses and multipath dispersion under various room geometries and emitter/receiver parameters. The contribution of the interference produced by incandescent and fluorescent tamps was done through the utilisation of analytical models. The penalty introduced by these channel characteristics was quantified considering the modulation schemes usually considered for optical wireless communication systems: 2-, 4- and 16-PPM (pulse position modulation) at bit rates from 1 to 10 Mbps.