Characterizing channel fading in vehicular visible light communications with video data

There is no prior work in characterizing fading caused by vehicle mobility in vehicular visible light communications (V2LC). Different from a radio frequency (RF) communication link, the path loss of a V2LC link is dictated by not only the transmitter-receiver (T-R) distance, but also the irradiance angle and the incidence angle, which have large variation when the vehicles are in motion. In this paper, we took a novel approach to take a first look at the problem. Utilizing the video data obtained from a dashboard camera and computer vision techniques, we are able to estimate the relative location and angle parameters of neighboring vehicles with great level of detail. These parameters are then used to derive a time function of path loss, with which the autocorrelation and the channel coherence time are calculated. Our results show that V2LC links have much slower channel time variation compared to RF V2V links: the coherence time is at least an order larger.