Multilevel Intensity-Modulation for Rolling Shutter-Based Optical Camera Communication

High data transmission rates are desirable in an optical camera communication (OCC) system. In order to achieve this, a novel multilevel-intensity modulation (m-IM) scheme for a rolling-shutter (RS)-based OCC is introduced in this letter. The proposed multilevel intensity signal is obtained by transmitting the signal pulse time faster than the camera shutter speed, where the shutter speed is highly dependent on the camera exposure time and the RS-effect of CMOS-image sensor of the camera. In addition, pulse width modulation is also used on the transmitter side to control the output intensity (signal pulse) of the LED transmitter. As the optical signal is received wirelessly by the camera, we further propose a novel smartphone-based digital demodulation algorithm for our RS-based OCC system. In this letter, we compare the performance of the proposed system to a typical modulation scheme for OCC system, such as ON-OFF keying. Moreover, an intensive performance test is conducted for different symbol times to determine their relationship to bit error rate and achieved data rate. A data transmission rate >10 kbps over a range of up to 2 m by using a 30 fps smartphone camera can be achieved by using our proposed 4-IM in our proposed scheme.