A Wireless Backhaul Solution Using Visible Light Communication for Indoor Li-Fi Attocell Networks

Light-fidelity (Li-Fi) is an emerging technology for wireless optical networking using the principle of visible light communication (VLC). Li-Fi attocells are smaller in size than the radio frequency (RF) femtocells, suitable for deploying ultra-dense cellular networks. In this paper, a novel wireless backhaul solution is proposed for indoor Li-Fi attocell networks using VLC, which is already embedded in the Li-Fi base station (BS) units. Since the backhaul links operate in the visible light spectrum, two methods are proposed for bandwidth allocation between the access and backhaul links, namely, full frequency reuse (FR) and in-band (IB). In order to realize dual-hop transmission over the backhaul and access links, both amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols are analyzed. Considering a direct current optical orthogonal frequency division multiplexing (DCO-OFDM)-based multiple access system, novel signal-to-interference-plus-noise ratio (SINR) and spectral efficiency expressions are then derived for user equipment (UE) randomly distributed in each attocell. Downlink performance of the optical attocell network is assessed in terms of the average spectral efficiency using Monte Carlo simulations. Guidelines are given for the design of the proposed wireless backhaul system.