Variable multi-pulse PPM using new dimming control method for visible light communications

In this paper, we propose a variable multi-pulse pulse-position-modulation (VMPPM) system with a dimming control that combines the use of pseudo-orthogonal codes and MPPM. In VMPPM, r slots are selected from n MPPM slots and codes for data are generated in each selected r slot according to source data equation [bit/frame]. Therefore, VMPPM can achieve higher data-transmission rate than the conventional variable PPM (VPPM). Additionally, VMPPM can represent the dimming level of n-r+1 stages by using the empty n-r slots. Moreover, the symbol error rate (SER) of VMPPM is evaluated through theoretical analysis. Also, we compare both the SER performance and the spectral efficiency of VMPPM with those of VPPM. Consequently, the data-transmission rate, the error rate performance and the spectral efficiency of VMPPM are better than those of VPPM.