Abstract
The emergence of visible light communication (VLC) as a subset of optical wireless communication (OWC) in the early 2000s has turned any light-emitting diode (LED) source into a potential data transmitter. The design process for any VLC or OWC system typically involves a link budget analysis performed by studying the signal-to-noise ratio (SNR) at the receiver. Since this SNR strongly depends on the radiant flux collected by the receiver, an accurate model for this parameter is required. The point-source model has been widely used since 1979 and generally provides a good approximation of the received radiant flux. However, it might be less accurate for typical extended lighting sources like LED panels or large-area organic LEDs. In this paper, the radiant flux distribution of flat Lambertian rectangular or circular sources is derived from a vector analysis of their irradiance. It is then validated through actual measurements in the case of a circular source. The resulting extended-source models thus better capture the light beam pattern of such transmitters to enable a more accurate link budget. It provides at the same time almost identical results to the point-source model for small sources and can, therefore, be seen as a natural extension of this already widely used model. INDEX TERMS LED pattern, irradiance pattern, light power pattern, non-imaging optics, link budget, optical wireless communication, visible light communication.
Highlights
O PTICAL wireless communications (OWC) have been investigated since the 1960s for various applications ranging from high-speed point-to-point communication over long distances to optical camera communication or indoor networking [1]–[4]
This research has increased significantly since the 2000s, following the market introduction of white light-emitting diodes (LED) that can turn any lighting into a potential visible light communication (VLC) system [5], [6]
WORKS This paper presents a model of the irradiance of one or several extended and tilted light sources at the level of a tilted photoreceiver
Summary
O PTICAL wireless communications (OWC) have been investigated since the 1960s for various applications ranging from high-speed point-to-point communication over long distances to optical camera communication or indoor networking [1]–[4]. Note that the radiant flux is often called optical power, especially in the OWC community In their 1979 article [1], Gfeller and Bapst proposed a model of the optical wireless channel that allows the average radiant flux collected by the receiver to be evaluated from the average radiant flux radiated by the light source. We propose to extend this model to the case of multiple light sources and receivers tilted independently of each other, as illustrated by Fig. 1 For this purpose, we use a vector analysis of the irradiance of a transmitter that is initially not tilted and introduce a change of the Cartesian coordinate system to take into account the tilt angle. The rest of the notations and variable definitions are listed in Appendix A
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