Joint Optimisation of Load Balancing and Handover for Hybrid LiFi and WiFi Networks

Recently a promising concept of hybrid networks based on light fidelity (LiFi) and wireless fidelity (WiFi) emerged. The idea is to combine ultra-small cell LiFi networks with ubiquitous coverage radio frequency (RF) communication systems. In such a hybrid network, WiFi access points (APs) serve a relatively large coverage area with limited bandwidth, and are thus susceptible to traffic overload. This issue is magnified with an increasing number of users because of the inefficient medium access control (MAC) in WiFi systems. LiFi can alleviate this issue by providing additional capacity. LiFi cells, however, have a limited coverage and this could result in significant handover overhead. A conventional load balancing (LB) method optimises the network throughput when the signal-to-noise ratio (SNR) of each user is known and fixed. Although this method delivers maximum throughput at a given time instance, it fails to consider the throughput loss due to handover, especially in an indoor scenario where users may frequently switch between APs. Taking the handover overhead into account, in this paper we propose a novel LB method that focuses on optimising the network throughput over a period of time. Simulation results show that the proposed method can increase the system throughput by up to 70% compared to existing LB methods.