Light-emitting diode (LED) based visible light positioning (VLP) has been widely studied to provide high-accuracy and low-cost localization services. Existing single-LED VLP systems suffer from severe energy attenuation when the receiver is far from the LED. Even though multiple LEDs could be deployed, the fusion of their positioning information remains an open problem. In this paper, we propose a multi-LED indoor VLP system with LED signal selection or combining. The receiver contains several differently-oriented photodiodes (PDs) working cooperatively as an angle-of-arrival estimator, and each LED individually provides the receiver with a localization result. With these single-LED positioning results, we select the results with the minimum localization error, or combine the results according to their distributions. Closed-form positioning error expressions are derived for the proposed methods. Moreover, increasing the LED number is shown to reduce the positioning error, but the reduction is negligible when the LED number is sufficiently large. Finally, an experimental testbench is built to verify the feasibility of the proposed methods, and a millimeter-level accuracy has been achieved, which is better than that of the classic trilateration method.

Visible light positioning (VLP) is endowed with high accuracy in indoor scenarios. However, the positioning algorithms require plenty of beacon light-emitting diode (LED) coordinates stored in databases, which are expensive to obtain by manual measurements. To circumvent such laborious efforts, we propose a two-step automatic scheme for simultaneous VLP and LED database construction. Specifically, in the first step, a receiver with a photodiode (PD) array samples the optical signals from few benchmark LEDs to locate itself. In the second step, the receiver estimates the unknown beacon LED coordinates through its own locations and the beacon LED signals. For the proposed two-step scheme, we derive closed-form error expressions for the beacon LED coordinates to evaluate the benchmark LEDs’ arrangement and the sampling places. Simulation results agree with the analytical error expressions and reveal that the proposed scheme can achieve centimeter-level accuracy with reasonable transmit powers. Experimental results from the hardware platform verify the feasibility of the scheme. The proposed scheme can circumvent laborious manual measurements and allow the LED database to “grow” while the receivers wander and more receivers enter.

Visible light positioning is a promising indoor positioning technique for its high accuracy and immunity to radio-frequency interferences. However, it is expensive and time-consuming to manually measure the coordinates of the massive beacon light-emitting diodes (LEDs). We propose a two-step scheme to locate the LEDs automatically. Firstly, the mobile receiver estimates its own coordinates based on the signals of few LEDs with known coordinates; secondly, the receiver samples the signals of the other unknown LEDs, and estimates their coordinates. The signals are all sampled by a photodiode (PD) array, which outputs the angles of arrival of the LED signals. Explicit positioning error expression is derived as a function of the noise terms and the locations of sampling. Simulation results show that the positioning scheme for the LEDs has centimeter-level accuracy with practical transmit powers. The proposed method can construct the database of the massive LED coordinates based on few beacon LEDs, significantly reducing the cost of manual measurements. Both analytical and simulation results show that the accuracy can be improved by properly choosing the transmit powers and the sampling places.