About Digital Communication Methods for Visible Light Communication

The visible light communication (VLC) by LED is one of the important methods because can work as high speed and VLC sends information flushing LED. We use pulse wave modulation for with be controlled easily microcontroller, which has digital output pins. At modulation, deciding low voltage middle when receiving signal level amplified equal to it threshold without amplification. In this paper, we proposed two that adjust value using counting slot number measuring level. slots constant per symbol Pulse Position Modulation (PPM). If received time less than theoretical value, means higher optimal value. more lower. So, slots. second method, average not there a ratio between calculate from ratio. Unfortunately, first method adjusts after data, once distance sender receiver changed, then performance becomes worse. And adjusting threshold, better. Therefore, should used in stable environments. change during received. That very quickly. show good wide range. these performances real experiments.