Angle-of-arrival reception for optical wireless location technology.

An optical wireless location (OWL) system is introduced for indoor positioning. The OWL system makes use of a mobile photoreceiver that facilitates triangulation by measuring angle-of-arrival (AOA) bearings from LEDs in an optical beacon grid. The photoreceiver has three photodiodes (PDs), arranged in a corner-cube, to facilitate differential photocurrent sensing of the incident light AOA, by way of azimuthal ϕ and polar θ angles. The AOA error for indoor positioning is characterized empirically. Optical AOA positioning is shown to have a fundamental advantage over known optical received signal strength (RSS) positioning, as AOA estimation is insensitive to power and alignment imbalances of the optical beacon grid. The OWL system is built, and a performance comparison is carried out between optical AOA and RSS positioning. It is shown that optical AOA positioning can achieve a mean 3-D positioning error of only 5 cm. Experimental design and future prospects of optical AOA positioning are discussed.