Coverage Improvement of Visible Light Communications using an Engineered Diffuser

Due to the Lambertian radiation profile of lighting grade of light emitting diodes (LEDs), the visible light communication (VLC) performance is not uniform and varies dramatically for a small change in the receiver’s position. A practical VLC system demands uniform performance over a significant coverage area to allow users’ movement. In this paper, a top-hat engineered diffuser is used to distribute the optical signal equally over a large area. The signal to noise ratio (SNR) varies a little over a large coverage area. Due to a sharp fall in the diffuser’s intensity distribution, the interference from neighbouring transmitters is reduced and as a result, the coverage area is further improved. In a 5m ×5m ×3m room, employing four LED transmitters with the proposed top-hat diffuser, the coverage probability has been improved from 31.91% to 67.55% when compared to the situation without the diffusers.