Transmitter Half Distribution Angle Optimization in Non-Line of Sight Visible Light Communication

Abstract

Visible light communication is a subset of wireless optical communication that uses white light-emitting diode-based illumination infrastructure for data transmission. Visible light communication (VLC) for indoor communication has recently received much attention to meet the ever-increasing data demands. In VLC, line-of-sight (LOS) connections can provide massive bandwidth while ensuring low path loss if there is an unobstructed path between the transmitter and the receiver, but they are prone to blocking. Non-line of sight (NLOS) links can provide significant blocking resilience and ease of usage by relying on light reflections from the walls, ceiling, and other diffusely reflecting surfaces. Non-line-of-sight optimization is required in VLC to improve receiver optical power and, as a result, system performance. Various studies have been conducted to optimize receiver setups to improve the optical power at the receiver end. In a non-line of sight (NLOS) scenario, however, transmitter configurations significantly impact the received optical power at the detector. The received optical power is spatially non-uniform owing to the scattered trait of white LEDs. This reduces the NLOS link performance. While employing LEDs with a larger half distribution angle minimizes these spatial power fluctuations, it also intensifies reflections from the walls. The more the reflections the more the signal attenuation. In consequence, to improve the receiver optical power in NLOS, this research provides a Transmitter half distribution angle optimization technique, in which the spatial power heterogeneity and the receiver’s mean power gain are recursively estimated for different reflections. The optimization results in a higher mean power gain and reduced spatial power heterogeneity, improving VLC link performance when transmitter and receiver are not in-line.