Comparation of Nonlinear Trellis-Coded-Modulation, Duobinary and QAM Modulation Formats in Visible Light Communication System

Improving the spectral efficiency of light-emitting diodes (LEDs) based visible light communication (VLC) system has become a hot topic. Duobinary (DB) and nonlinear trellis-coded PAM (NLTCP) are two typical schemes for improving spectral efficiency. In this paper, we compare the performance of QAM, DB and NLTCP modulations. An experimental comparation is conducted in the VLC system utilizing silicon substrate blue LED over 1-m indoor free space transmission with different signal peak-to-peak voltage (Vpp) and data rate. The experimental results clearly display the NLTCP outperforms the QAM and DB when the system operates at highly nonlinear status. And a data rate of 2 Gbps is achieved. To the best of our knowledge, this is the first time comparing the above coding methods, choosing the most suitable coding scheme for different working situations in the VLC system is worth considering.