M-Point Combinatory for Parallel Transmission Image Sensor-Based Visible Light Communications

M-point combinatory (MC) modulation is proposed for parallel transmission (PT) image sensor (IS)-based visible light communication (VLC). In the conventional PT system, M_{0} discrete signals which incorporate N=(M_{0}-1)/2 spatial frequencies are transmitted in parallel with M_{0} transmitting regions of liquid crystal display (LCD). When each of spatial frequencies is modulated with P-ary phase shift keying (P-PSK), the number of bits transmitted in one frame is given by k=N \log _{2} P bits. k increases when the number of spatial frequencies N increases with M_{0}, but at the same time, the peak-to-average power ratio (PAPR) becomes high because the signal of the PT system is essentially orthogonal frequency modulation, thus remaining at a very low number of spatial frequencies N that the system accommodates without any error. In this paper, we propose MC modulation, which is combined with the PT system to increase the number of bits per frame that the system carries without any error. In the MC PT system, M out of the M_{0} transmitting regions are used for transmitting M discrete signals related to M-point DFT, where M \leq M_{0}. Since there are \binom{M_{0}}{M} ways in choosing M out of the