S. Cincotta, C. He, A. Neild and J. Armstrong, "Indoor Visible Light Positioning: Overcoming the Practical Limitations of the Quadrant Angular Diversity Aperture Receiver (QADA) by Using the Two-Stage QADA-Plus Receiver," Sensors, Vol.19, PP. 956, 2019
Abstract: Visible light positioning (VLP), using LED luminaires as beacons, is a promising solution to the growing demand for accurate indoor positioning. In this paper, we introduce a two-stage receiver that has been specifically designed for VLP. This receiver exploits the advantages of two different VLP receiver types: photodiodes and imaging sensors. In this new receiver design a quadrant angular diversity aperture (QADA) receiver is combined with an off-the-shelf camera to form a robust new receiver called QADA-plus. Results are presented for QADA that show the impact of noise and luminaire geometry on angle of arrival estimation accuracy and positioning accuracy. Detailed discussions highlight other potential sources of error for the QADA receiver and explain how the two-stage QADA-plus can overcome these issues.
S. Cincotta, C. He, A. Neild and J. Armstrong, “High angular resolution visible light positioning using a quadrant photodiode angular diversity aperture receiver (QADA),” Optics express, Vol. 26, PP. 9230-9242, 2018
Abstract: The increasing use of white LEDs for indoor illumination provides a significant opportunity for Visible Light Positioning (VLP). The challenge is to design a small, unobtrusive sensor that can be incorporated into mobile devices to provide accurate measurements for triangulation. We present experimental results for a novel angle of arrival (AOA) detector that has been designed for use in a VLP system. The detector is composed of a transparent aperture in an opaque screen that is located above a quadrant photodiode (PD), separated by a known vertical distance. Light passing through the aperture from an LED casts a light spot onto the quadrant PD. The position of this spot, coupled with knowledge of the height of the aperture above the quadrant PD, provides sufficient information to determine both the incident and polar angles of the light. Experiments, using a prototype detector, show that detector is capable of accurate estimation of AOA. The root mean square errors (rMSE) were less than 0.11° for all the measured positions on the test bed, with 90% of positions having an rMSE of less than 0.07°.
J. Armstrong, Y. A. Sekercioglu and A. Neild, "Visible Light Positioning: A Roadmap for International Standardisation," IEEE Communications Magazine, December 2013.
Abstract— The widespread introduction of white LEDs for illumination provides a unique opportunity to create an indoor positioning system that is flexible, accurate, and ubiquitous. Signals transmitted by the LEDs are used to determine the position of a person or object within a room. To take full advantage of this new opportunity, it is essential that comprehensive and robust international standards are developed before a plethora of incompatible proprietary systems flood the market. In this article, we discuss the very diverse range of potential applications of these future systems and their implications for the design of a new standard. Another consideration is that the transmission of positioning signals must not compromise the primary function of the LEDs, which is energy-efficient illumination, so visible flicker must be avoided. Position information can be derived from a range of properties of the received signal, such as the power of the received signal or the angle at which the signal reaches the receiver. The suitability of different techniques for an indoor positioning system is considered.Finally, we discuss the implications each of these aspects has for the design of an effective standard.
T. Q. Wang, Y. A. Sekercioglu, A. Neild, and J. Armstrong, "Position Accuracy of Time-of-Arrival Based Ranging Using Visible Light With Application in Indoor Localization Systems," Journal of Lightwave Technology, vol. 31, pp. 3302-3308, 2013. Download
Abstract— This paper analyzes an indoor positioning system that uses white lighting LEDs. Modulated signals transmitted by the LEDs are used as the basis of time-of-arrival based distance estimation. The theoretical limits on the accuracy of estimation are calculated by deriving the Cramer-Rao bound for intensity modulated windowed sinusoidal signals. Calculations for a typical indoor scenario, assuming perfect synchronization between transmitter and receiver, but using realistic values for other parameters show that very accurate distance estimates are achievable, with typical errors being in the order of centimeters depending on the frequency and power of the sinusoidal signals, the distance from the LED and the properties of the LED and the photoreceiver.
K. Panta and J. Armstrong, "Indoor localisation using white LEDs," Electronics Letters, vol. 48, pp. 228-230, 2012
Abstract— Energy efficient white LEDs are increasingly being used for indoor lighting but unlike conventional lighting, the intensity of the light emitted by white LEDs can be modulated at high frequencies. This paper describes a novel positioning technique based on transmitting signals with known sinusoidal components from a number of LEDs. The receiver uses the resultant optical signal at the receiver photodiode to calculate the receiver position. Proof of concept experiments show that white LEDs designed for indoor lighting can be used as the transmitters. The modulation bandwidth of white LEDs is large enough to give a range of localisation that is compatible with typical indoor applications.