A modified a-law companding scheme for indoor visible light communication

Visible light communication (VLC) has been received much attention because it simultaneously provides data transmission and illumination without electromagnetic wave interference. However, the modulation using discrete multi-tone (DMT) is possible to suffer from harmful effect of human eye. To solve this problem, this paper introduces the manner of applying constant envelope orthogonal frequency division multiplexing (CE-OFDM) to VLC and then proposes optimal companding scheme. The basic idea is to deliberately convert statistical distribution of phase modulator input signal into quasi-uniform distribution using modified A-law companding (MA-law companding). The proposed scheme can bring enhancement of system performance regardless of the scaling constant. Simulation results show that bit error rate (BER) performance of the proposed MA-law companding is superior to original CE-OFDM and conventional companding schemes.