Improved BER for offset pulse position modulation using priority decoding over VLC system

Offset pulse position modulation (OPPM) the signal modulation scheme offers key advantages compared to other existing pulse position modulation (PPM) schemes, namely greater sensitivity and reduced bandwidth expansion. Most error correction schemes result in bandwidth reduction of the system. This work shows that the bit-error rate (BER) of the OPPM scheme can be further improved using a priority decoding method, without additional expansion in bandwidth. An experimental link incorporating visible light communication (VLC) system based on 'cool' 30 W LED was used. This study also addresses the difference of using cool and warm white LEDs for a VLC system. The experimental results show cool white LED achieves improved performance compared to previously studied warm white LED. The OPPM scheme, along with priority decoding, was implemented on FPGA, using VHDL. This study compares the BER results between original and improved OPPM, showing significant improvement in BER of priority decoding OPPM. The analysis has also been made on how the priority decoding operates and limitations of the system.