Multi-level Optical On-Off Line Code For Outdoors Visible Light Communications

This paper investigates a multi-level optical line code using the On-Off technique for visible light outdoors communications. The technique consists of assigning to each symbol, through a Miller coding combined with a correlative level technique, an elementary signal within the same signaling bit duration. The resulting asymmetric signals are differentiated by (M-1)-time transition levels to produce M-ary On-Off Keying (OOK) signals. An analytical investigation conducted on the 4-ary (quaternary) OOK (4-OOK) using duo-binary technique and Miller's coding technique over an OOC difference family pattern has resulted in a better data rate and an increase at an acceptable level of the signal-to-noise ratio (SNR), which is then compared to the ordinary binary OOK NRZ signaling.