Time Span of an Image Frame Using a CMOS Sensor in Rolling Shutter-Based Optical Camera Communications

In this paper, a rolling shutter optical camera communication system is investigated by analysing the internal working principle of a receiver based on complementary metal oxide semiconductor image sensors. Based on the thorough analysis of system parameters such as the clock signal, integration and read-out times at the sensor level, and the calculation of the bandwidth and the time span of the image frame containing the information signal, it was demonstrated that the communication functionalities can be enhanced. A new model was proposed and validated by developing an experimental testbed and demonstrating matching between the data packet duration and the predicted time span. This enables the optimisation of the samples obtained by the image postprocessing, using different sensor clock signals and evaluating the bit error rate performances. The experimental results demonstrated that the internal design of the camera and its packet structures have impacts on the read-out times. For camera settings of pixel clock frequency and exposure time of 300 MHz and 61 $\mu$s, respectively, a data rate of 14.5 kbps at a bit error rate below the forward error correction limit has been achieved.