Outage Probability Improvement Through Optimal LED Placement for Visible Light Communications

We address optimal light-emitting diode (LED) placement on ceiling for indoor visible light communications (VLC) with the aim of minimizing the outage (blockage) probability at the location of the mobile receiver. More precisely, in the considered scenario, several LEDs (transmitters) are placed on the ceiling and a mobile user device (receiver) with random position is distributed over the width and height of a corridor where the instantaneous received signal-to-noise ratio (SNR) is random. First, we derive the expression for instantaneous received SNR of the underlying non-directed line-of-sight (NLOS) channel. Second, we propose an algorithm to determine the optimal position of the transmitters by minimizing the
outage
probability
at the position of the mobile receiver. Finally, we characterize the interactions between number and height of LEDs and the total optical power at their optimum location. Our results show that by increasing the height of ceiling-mounted LEDs or by decreasing the total emission power (leading to a decrease of the instantaneous received SNR), the optimal location is tilted toward the center of the ceiling.