A visible-light communication system using optical CDMA with inverted MPSC

Visible-light communication systems are suitable to realize secure indoor networks. In this paper, an optical CDMA scheme employing EWO signaling with inverted sequences of MPSC or GMPSC is proposed for visible-light communication systems. The proposed scheme has the property of canceling MUI as well as the conventional EWO-MPSC scheme. Average light intensity and normalized intensity fluctuation of multiplexed optical signals are investigated by computer simulation. It is shown that the proposed scheme is more suitable for visible light communication, since it has lower intensity fluctuation and higher average light intensity, in comparison with the conventional scheme which adopts non-inverted sequences. Then, the authors implemented a visible-light CDM system with several LEDs. It has four channels on each of which 31.25KHz MIDI data, coded with a generalized MPSC with a length of 64, is transmitted. It is confirmed that the system can correctly decode every MIDI data transmitted simultaneously.