Visible light communications heterogeneous network (VLC-HetNet): new model and protocols for mobile scenario

In order to resolve the crowded radio spectrum of wireless communication systems, visible light communications (VLC), which uses a vast unregulated and free light spectrum, has emerged to be a viable solution. However, duplex communication, user mobility, multi-user access and transmission mechanisms are becoming challenging tasks in VLC network. In this article, we propose a new VLC heterogeneous network (VLC-HetNet) model which merges VLC and radio frequency (RF) network. VLC channel is only used for downlink transmission, while RF channels are served for uplinks in any situation, or for downlinks only without VLC hotspots coverage. New VLC frame, multi-user access mechanism, horizontal and vertical handover protocols are presented to support the VLC-HetNet model, especially for solving the problems at multi-user mobility scenario. Simulation results show improvements in capacity performance of the VLC-HetNet, when compared to RF system. Besides, the average vertical handover number and VLC downlink dwelling time ratio have been analysed.