Optical-Camera Communication

Optical-camera communication (OCC), a rapidly developing and emerging optical wireless imaging communication technology, has broad application prospects, owing to its low cost and highly popular optical-camera receivers. However, the received images have problems, such as perspective distortion, tilt distortion, halo effects, and optical noise, making threshold detection in image processing difficult. Implementing an OCC system that improves the data rate and transmission distance remains a problem. An image-optimization demodulation scheme is proposed. In the decoding process, the region of interest (ROI) is first used to extract the image matrix to reduce the impact of halo effects. Distortions in the image must be detected and corrected. We designed an improved center/surround retinex image-enhancement scheme, based on fast-scale adaptive bilateral texture filtering, which can efficiently eliminate the fluctuation of grayscale values both globally and locally. Subsequently, a simple threshold assessment is performed. The stripe width of the received pixel is used for symbol judgment to complete subsequent demodulation and decoding; then, the original transmission data are obtained. In an experimental analysis, the improved center/surround retinex algorithm proposed in this study solved the problem of fluctuating grayscale values. Compared with other algorithms, it had the highest decoding efficiency, whether with an increase in communication rate from 3.5 kbps to 6.5 kbps or a change in communication distance. It had an average decrease in bit-error rate of about one order of magnitude and the best decoding performance.