Optimum Assignment of Variable Code Length and Modulation Index for VLC-OFDM

Abstract

Over the last few years, wireless communication technology has been developed rapidly, and high-speed and high-capacity communications are expected to become possible. On the other hand, the available frequency band is limited, and the issue of frequency band exhaustion becomes more serious. Visible Light Communication (VLC) is attracting attention as a solution to these problems. VLC is a technology that transmits signals by means of flicker or obscuration of visible light. The advantage of this technology is that it does not impose restrictions on the frequency band because lighting can be used as communication. Another advantage is that it is safe for the human body and does not impact other wireless devices [1] . In a VLC system based on orthogonal frequency division multiplexing (OFDM), Intensity Modulation - Direct Detection (IM/DD) is applied as a cost effective design [2] . The intensity modulated optical signal is transmitted, which is directly detected by the photodiode on the receiving side. Although the system is quite simple, it is susceptible to noise [1] . Therefore, it is important to improve the performance in a low SNR situation.