Interference Characterization in Downlink Li-Fi Optical Attocell Networks

Wireless access to data using visible light, popularly known as light-fidelity (Li-Fi), is one of the key emerging technologies that promises huge bandwidths and data rates. In Li-Fi, the data are modulated on optical intensities and transmitted and detected using light-emitting diodes (LEDs) and photodiodes, respectively. A network of such LED access points illuminates a given region in the form of attocells. Akin, to wireless networks, co-channel interference or simply interference is a major impediment in Li-Fi attocell networks. Also, when in such networks, the field of view (FOV) of a photodiode is limited, and the network interference distribution gets affected significantly. So, for any given network scenario, interference characterization is critical for a good system design. Currently, there are no good closed-form approximations to interference in Li-Fi attocell networks that can be used for the analysis of signal-to-interference-plus-noise ratio (or coverage), particularly for the case of limited FOVs. In this paper, using a technique from Fourier analysis, we provide a very close approximation to interference in one- and two-dimensional Li-Fi attocell networks for any given finite inter-LED separation. We validate the interference approximation by providing theoretical error bounds using asymptotics and by performing numerical simulations. We show that our method of approximation can be extended to characterize interference in limited FOV scenarios as well.