Energy-Spectral Efficiency Tradeoff of Visible Light Communication Systems

In this paper, we propose a new definition of the energy efficiency (EE) for indoor visible light communication (VLC) systems and further investigate the tradeoff between the EE and spectral efficiency (SE). Different from the conventional concept of the EE in wireless communication systems, the newly defined EE in VLC systems utilizes the optical communication power instead of radio frequency power to evaluate the consumed energy. Some key parameters (e.g., horizontal distance and vertical distance) in optical transmission circumstances are included when calculating the SE. The nonlinearity of light-emitting diode (LED) is also considered in the EE-SE tradeoff and such nonlinearity can be eliminated by pre-distortion. In particular, the relation between the electrical power and optical power can be derived based on the LED nonlinearity. Numerical results verify the presented EE-SE tradeoff. It is shown that the geometric parameters and the LED turn-on voltage (TOV) can significantly affect the relationship of the EE and SE.