Energy Efficiency of SISO and MISO in Visible Light Communication Systems

In this paper, we focus on maximizing energy efficiency problems for visible light communication (VLC) systems. Specifically, for single-input-single-output (SISO) VLC systems, we first systematically analyze the power consumption along the signal processing path and propose an explicit energy efficiency expression, which is a quasi-concave function of the power consumption at the power amplifier (PA). Then, we investigate the energy efficiency maximization problem under both the power constraint and rate requirement. By exploiting Dinkelbach's algorithm and Lagrangian method, the optimal power consumption of PA is obtained in a closed form. Numerical results are presented to evaluate the performance of the proposed optimal solution. Moreover, we analyze the power consumption of multi-LED and study the energy efficiency maximization problem for the multi-input-single-output (MISO) VLC system, under both per LED's power constraint and rate constraint. This problem is shown to be nonconvex. With leveraging Dinkelbach's algorithm, the original problem can be reformulated as a convex problem, and the optimal solution can be efficiently obtained by the interior point algorithm. Meanwhile, numerical results are presented to show the performance of the proposed optimal solutions. In particular, it is shown that the power is preferentially allocated to the subchannels with higher channel gain in the MISO VLC system.