A Novel Orthogonal Transmission Scheme for Visible Light Communication

The spatially-incoherent radiators in visible light communication (VLC) constrain the optical carrier to be only driven by a real electrical sub-carrier, which cannot be quadrature modulated as in classic RF-based communication systems. This, in turn, severely limits the transmission throughput of VLC systems. To overcome this technical challenge, a novel coherent transmission is proposed. As such, the optical carrier is only treated as a purely amplitude- modulated carrier capable of transmitting the quadrature modulated symbols. The ability of our novel coherent transmission to fully reconstruct the in-phase and quadrature parts is validated through analytical symbol error rate and Matlab simulations. Results also show that the proposed scheme, while remarkable in its simplicity, can improve both the spectral and energy efficiency of VLC systems, i.e. double the spectral efficiency and achieve more than 45% energy efficiency improvement, when compared to its existing counterpart.