The Impact of Configuration on Channel Characteristics in Visible Light Communication

A featured research topic, Visible Light Communication (VLC), is the idea of using Light Emitting Diodes (LEDs), that are used for illumination, for data communication. Reliable communication in VLC systems, as well as in other communication systems, necessitates accurate knowledge of the channel. In this paper we are interested in the characteristics of indoor VLC channels under various configurations. The channel model used in simulations is based on modified Monte Carlo ray tracing algorithm, which is capable of obtaining channel impulse responses. As case studies, we consider a number of room environments with different dimensions and surface materials. We further consider scenarios with different transmitter numbers placed in various layouts. For these circumstances, we obtain channel impulse and frequency responses and present a channel characterization study where channel root mean square (rms) delay spread, maximum bit rate and coherence bandwidth parameters are evaluated. It is shown that, although the contribution of reflections increases if the room size is decreased or the reflectivity of the walls is increased, the frequency selectivity of the channel does not changed considerably. But as the receiver moves away from the source, an appreciable attenuation is noticed. Multiple transmitter is the most forceful factor that has impact on the channel frequency characteristics. Thus, multiple sources cause a fluctuation in the frequency band, and the shape of the fluctuation is related to the configuration of sources.