Simplified and accelerated PPM receivers for VLC systems

Abstract

This study presents two receivers for visible light communication (VLC) systems. First, modified pulse position modulation (PPM) (MPPMD) and variable pulse position modulation (VPPM) (MVPPMD) demodulators are considered for MPPM and traditional VPPM schemes. The aim of this study is to minimise complexity at the receiver. On the basis of the derived mathematical framework, the multiplication stage is removed from the coherent detector architecture. Moreover, the generation of mask signals is unnecessary for the proposed receiver because they would be multiplied by the modulated signal for the traditional coherent detector. The simulation results show that MPPMD has the same bit error rate (BER) performance compared with the traditional coherent demodulators. Additionally, the resource utilisation of MPPM and VPPM receivers is dramatically reduced with removing the multiplication stage and the mask generator. Second, an accelerated VPPM (A-VPPM) algorithm is proposed to achieve a fast demodulation of the VPPM signal under the unknown dimming-level condition. Compared with the earlier VPPM receivers, the A-VPPM receiver can also demodulate the VPPM signal without any iteration stage and the mask generator. The BER performance of A-VPPM receiver is close to that of the traditional VPPM demodulator at 30 and 70% dimming levels.