Experimental validation of a three‐dimensional modulation format for data transmission in RGB visible light communication systems

Transmission of three‐dimensional (3D) orthogonal frequency division multiplexing (OFDM) signals over red, green and blue (RGB) visible light communication (VLC) systems is proposed and experimentally validated. The novel 3D modulation format aims to overcome the different luminous response of RGB light‐emitting diodes at the same driving current levels, that generates a correlation among the three RGB analog signals instead of considering each channel as independent from each other, as is in classical uniform wavelength division multiplexing transmissions. In the proposed scheme, real and imaginary parts of OFDM signals are sent through the red and blue channels of the VLC transmitter, respectively, while the third dimension of the OFDM symbol is transmitted through the green channel, according to a procedure that allows the maximisation of the Euclidean distance among the 3D constellation symbols. For the OFDM signal reconstruction and decoding at the receiver side, advanced digital signal processing for frame synchronisation and reconstruction of the 3D constellation diagram are implemented. Experimental results are included to validate the transmission of a 27.3 Mbps system through a VLC link of 1.5 m.