Statistical impulse response models for indoor optical wireless channels

Abstract

The indoor optical wireless channel is significantly different than the radio channel. Statistical propagation models developed for the radio channel, which characterize path loss, shadowing, and multipath fading, do not apply. In this paper, we investigate statistical modelling for the indoor optical wireless channel through the examination of the characteristics of a large set of channel impulse responses. The channel responses are generated using an estimation method based on geometrical modelling of indoor environments together with an iterative technique for calculating multiple reflections. We confirm prior studies showing that channels with line-of-sight paths must be modelled separately from those fully diffuse channels with no such path. We show that the distribution of the channel gain in dB for the LOS component follows a modified gamma distribution, and the channel gain in dB for LOS channels including all reflections follows a modified Rayleigh distribution for most transmitter-receiver distances. Similar results are described for distributions of channel gains of diffuse channels and for distributions of rms delay spreads. Finally, we describe a method for generating a statistically realistic impulse response given any transmitter-receiver separation in an indoor environment. Copyright © 2005 John Wiley & Sons, Ltd.