Development of low-complexity MLE method for image-sensor-based visible light communication

In this paper, we focus on the visible light communication (VLC) using an LED (transmitter) and a high-speed image sensor (receiver) for an intelligent transport system (ITS). The receiver of this system suffers from an inability to detect the correct luminance values of each LED since the image captured by the receiver blurs owing to defocusing. To overcome this problem, our previous study proposed a data demodulation method from blurred images by using the maximum likelihood estimation (MLE) method. However, this method requires high complexity as the number of LEDs increases. In this paper, we propose a demodulation method whose performance approaches the MLE method with significantly reduced complexity. The proposed method first apply the MMSE estimation to discern each LED's condition. According to the results of the estimation, we divide symbols from each LED into high reliability symbols and low reliability symbols. If the symbol is categorized as high reliability symbol, we demodulate data based on the result. On the other hand, if the symbol is categorized as low reliability symbol, we apply the MLE method to the LEDs who have low reliability symbols to demodulate data. We conduct computer simulation and compare the performance of the proposed method with the previous (MLE) one.