Dynamic load balancing with handover in hybrid Li-Fi and Wi-Fi networks

In this paper, a hybrid network combining light fidelity (Li-Fi) with a radio frequency (RF) wireless fidelity (Wi-Fi) network is considered. An additional tier of very small Li-Fi attocells which utilize the visible light spectrum, offers a significant increase in the wireless data throughput in an indoor environment, while at the same time providing room illumination. Importantly, there is no interference between Li-Fi and Wi-Fi. A Li-Fi attocell covers a significantly smaller area than a Wi-Fi access point (AP). This means that even with a moderate user movement a large number of handover between Li-Fi attocells can occur, and this compromises the system throughput. Dynamic load balancing (LB) can mitigate this issue so that the quasi-static users are served by Li-Fi attocells, while moving users are served by a Wi-Fi AP. However, due to the user movement, local overload situations may occur which prevent handover, leading to a lower throughput. This research studies LB in a hybrid Li-Fi/Wi-Fi network by taking into account user mobility and handover signalling overheads. Furthermore, a dynamic LB scheme is proposed, where the utility function considers system throughput and fairness. In order to better understand the handover effect on the LB, the service areas of different APs are studied, and the throughput of each AP by employing the proposed LB scheme is analyzed.