Multi-coded variable PPM with level cutting for high data rate visible light communications

In this paper, we propose an improved modulation scheme called multi-coded variable pulse position modulation (MC-VPPM) with level cutting for Visible Light Communications. Similar to conventional MC-VPPM scheme [ 9], two groups of signals (Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) group) are multi-coded by orthogonal codes for transmitting data simultaneously. Then, multi-coded signals which have larger value than cutting threshold is mapped to small value via level cutting. By limiting the level of multi-coded signals, we can increase the data rate even decreasing the error performance, either. In addition, we can greatly reduce the computational complexity in receiver end by reducing the required correlation metric for demodulation. Through simulation, we confirm that the proposed MC-VPPM with level cutting shows a comparable BER curve and much greater achievable data rate than the conventional variable-pulse position modulation (VPPM) and MC-VPPM scheme under the VLC channel environment.