A novel demodulation algorithm for CMOS camera-based VLC using adjacent pixel threshold

Abstract

Using rolling shutter effect of the CMOS camera can increase the data rate of camera-based visible light communication (VLC) system. However, when fewer pixel columns represent one bit, the grayscale value fluctuation becomes serious, which leads to data logic not being correctly defined by the threshold, and therefore degrades the demodulation performance. In this paper, a thresholding scheme based on adjacent pixel grayscale value to reduce the influence of grayscale value fluctuation is proposed, which sets threshold using the grayscale values of the forward and backward pixels adjacent to the current pixel. And combining with segment downsampling, experimental results show that the proposed demodulation algorithm can achieve a bit-error-rate (BER) performance well below the forward error correction (FEC) limit of 3.8×10-3 with the bit resolution of 2.962 pixel/bit, and the net data rate can reach 10.56 kbit/s.