  Interference between cells or users can have a significant impact on the
quality of optical wireless communication (OWC) links. This paper studies the
co-existence of infrared based Micro cells with Visible light communication
based Pico and Atto Cells for downlink communication. The signal to noise ratio
(SNR) of each cell and the signal to interference and noise ratio (SINR)
between cells are evaluated when an angle diversity receiver and an imaging
receiver are used. The results show that Atto cell systems provide higher SNR
and data rates compared to the Pico cell systems which provide higher SNR and
data rates compared to Micro cell systems. The Micro cell systems however
provide mobility as they provide a larger coverage area, followed by the Pico
cell systems.
