  This paper investigates a hybrid radio frequency (RF)/visible light
communication (VLC) ultra-small cell network consisting of multiple optical
angle-diversity transmitters, one multi-antenna RF access point (AP), and
multiple terminal devices. In the network, the optical transmitters play the
primary role and are responsible for delivering information and power over the
visible light, while the RF AP acts as a complementary power transfer system.
Thus, we propose a novel collaborative RF and lightwave resource allocation
scheme for hybrid RF/VLC ultra-small cell networks. The proposed scheme aims to
maximize the communication quality-of-service provided by the VLC under a
constraint of total RF and light energy harvesting performance, while keeping
illumination constant and ensuring health safety. This scheme leads to the
formulation of two optimization problems that correspond to the resource
allocation at the optical transmitters and the RF AP. Both problems are
optimally solved by appropriate algorithms. Moreover, we propose a closed-form
suboptimal solution with high accuracy to tackle the optical transmitters'
resource allocation problem, as well as an efficient semi-decentralized method.
Finally, simulation results illustrate the achievable performance of the
investigated system and the effectiveness of the proposed solutions.
