Undersampled differential phase shift on-off keying for optical camera communications with phase error detection

This paper introduces the design and implementation of an optical camera communication (OCC) system. Phase uncertainty and phase slipping caused by camera sampling are the two major challenges for OCC. In this paper, we propose a novel modulation scheme to overcome these problems. The undersampled differential phase shift on-off keying is capable of encoding binary data bits without exhibiting any flicker to human eyes. The phase difference between two consecutive samples conveys one-bit information which can be decoded by a low frame rate camera receiver. Error detection techniques are also introduced to enhance the reliability of the system. Furthermore, we present the hardware and software design of the proposed system. This low-cost communication system has been implemented with a Xilinx FPGA and a Logitech commercial camera. Experimental results demonstrate that a bit-error rate of 10
^-5
can be achieved with 7.15 microwatts received signal power over a link distance of 15 centimeters.