Energy Efficient Optimization of Base Station Intensities for Hybrid RF/VLC Networks

This paper focuses on the development of energy efficient hybrid networks consisting of radio frequency (RF) base stations (BSs) and visible light communication (VLC) BSs. More specifically, since the quality-of-service and energy cost are key parameters in designing energy efficient networks, this paper optimizes the RF BS and VLC BS intensities to minimize the area power consumption (APC) under an outage probability constraint. Using stochastic geometry, approximations of the outage probability of VLC networks, which are applicable to an arbitrary field-of-view at photodiodes and present low computational complexities, are first introduced. Leveraging the derived analytical results, a low complexity algorithm to find the VLC BS intensity that minimizes the APC of VLC networks is then proposed. Furthermore, algorithms to identify the intensities of RF BSs and VLC BSs for energy efficient hybrid RF/VLC networks via one-dimensional search methods are also developed. The numerical simulations corroborate the tightness of the approximations on the outage probability and confirm that the proposed algorithms exhibit almost identical performances as the algorithms that exhaustively search the optimal BS intensities. Finally, it is shown that the hybrid RF/VLC networks achieve a lower outage probability with a reduced APC compared to the RF-only networks and VLC-only networks.