  Wireless access to data using visible light, popularly known as
light-fidelity (Li-Fi), is one of the key emerging technologies which promises
huge bandwidths and data rates. In Li-Fi, the data is modulated on optical
intensities and transmitted and detected using light-emitting-diodes (LED) 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, the network interference distribution gets affected significantly.
So, for any given network scenario, interference characterization is critical
for 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 dimension
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.
