Visible light positioning (VLP) is playing a critical role in delivering better location-based services. However, traditional VLP systems rely on line-of-sight (LOS) paths and have a requirement for large numbers of light-emitting diodes (LEDs) and sensors, making them unprepared for various scenarios. This article proposes a 3-D non-line-of-sight (NLOS) VLP system using a single LED and an image sensor (IS) to address the problem of obstructed LOS paths. On the one hand, an optical camera communication (OCC) subsystem is designed to receive the transmitter’s position based on NLOS links. In contrast, two highlights are visible in the picture when the IS captures the reflected light from the floor. Using the proposed luminance distribution model (LDM), it can be demonstrated that the two highlights can be regarded as the projections formed by two virtual LEDs. Based on the projection equations of the two virtual LEDs, an image sensing algorithm can estimate the receiver’s position. Experimental results show that the proposed system can achieve a 90th percentile accuracy of < 22 cm for 3-D positioning. To the best of author’s knowledge, this is the first work to demonstrate 3-D NLOS VLP using just a single LED and an IS. Additionally, the proposed LDM is the first physically based model for the first reflected light to estimate the channel gain of an NLOS link.

Three-Dimensional NLOS VLP Based on a Luminance Distribution Model for Image Sensor

Camera based visible light positioning (VLP) can be promising for indoor positioning applications powered by the widespread use of light emitting diodes (LEDs) in lighting applications. Most of the VLP works in the literature have either implemented two-dimensional (2D) indoor positioning or assumed that the height of the ceiling is either fixed or known. In this paper, the real-time height of the ceiling from the receiver is taken into consideration to make the three-dimensional (3D) positioning possible in practical use case scenarios. A low cost light detection and ranging (LIDAR) sensor has been used to measure the height of the ceiling in real time to estimate the location in 3D space using a single LED transmitter. Additionally, though camera based indoor positioning using the rolling shutter effect, offers high accuracy, its reliability at long distances and robustness against the line of sight (LOS) blockage are still questionable. In this paper, a low resolution, high frame rate camera is proposed for an indoor positioning system with centimeter-scale accuracy. Direct detection has been utilized instead of the rolling shutter effect thus making the system more robust and reliable. A gravity virtual sensor has been used to compensate for the error caused by the tilt of the smartphone. The average 3D positioning error in the proposed VLP system is 6.8 cm. The positioning latency of the proposed system is 54 ms. To the best of the Authors’ knowledge, this is the first reported truly 3D VLP system that works without any prior knowledge of the ceiling height and irrespective of LED shape, size, and arrangement using a single LED. The proposed system is also robust against any partial light blockage by the user’s body and it can also provide coarse location information without any direct LOS between the LED and the camera using reflected lights from the surroundings.

A Truly 3D Visible Light Positioning System using Low Resolution High Speed Camera, LIDAR, and IMU Sensors

Recent advancements in visible light positioning (VLP) systems have continuously improved positioning accuracy, extending the application fields in Internet-of-things and factory automation technologies. However, their multiplexing and modulation methods still limit the applicability of VLP systems. Multi-level driving and sensing techniques that use orthogonal frequencies increase the design complexity and are strictly constrained by the bandwidths of the illuminators and sensor devices. Existing binary modulations require additional amendments to the code synchronization. In addition, real-time VLP is fundamentally affected by the distorted signal after orthogonal demultiplexing. Herein, we present a low-cost expansion of VLP that employs binary demodulation in code-division multiplexing. The proposed method utilizes DC-biased binary sequences using the palindromic variant of the Hadamard matrix, which provides perfectly orthogonal sequences while maintaining robustness to signal changes. The proposed demodulation regroups the signal collections of orthogonal sequences in an interleaved manner and determines the source signals via re-modulation. Compared with existing methods, it does not require extra-synchronizing structures and naturally compensates for dynamic sensor signals solely via binary operations. Following its implementation in an FPGA using commercial LEDs and a PIN-PD, we validated that the method achieved 48 dB SNR at a source-to-sensor distance of 10 m. The experiments showed that the proposed method eliminates 45–66% of signal errors and 33–43% of positional displacement during the sensor movements at 800 mm/s. Combined with trilateration, the static positioning error is 0.0158 m on average in 1.31, 0.91, 2.36 m, whereas the standard deviation of the raw position is limited to 0.0016 m. 

Interleaved Binary Demodulation Technique for Low-cost and Fast-response Visible Light Positioning Using Palindromic Sequences

Abstract With the increasing demand for indoor positioning, visible light positioning (VLP) systems have become an optics technologies research hotspot due to their high accuracy and avoidance of electromagnetic interference. However, current photodiode (PD)-based and image sensor (IS)-based VLP systems still suffer from high costs at the receiver, and the problem of the trade-off between field of view (FoV) and positioning accuracy. Therefore, we propose a smartphone-based low-cost, and high-precision VLP system, Acpro. The system combines the smartphone’s embedded ambient light sensor and IS as the receiver for the positioning. First, for the low sampling rate of the ambient light sensor, we use the frequency aliasing characteristic to identify the LED’s beacon through the dynamic undersampling principle. Then, to increase the FoV and positioning accuracy, we use the standard distance information corrected by the IS to improve the noise distance calculated by the ambient light sensor. Further, the corrected distance information is used for positioning. Extensive results show that our system can achieve sub-meter positioning accuracy. 

Acpro: fusion of embedded ambient light sensor and image sensor for visible light positioning

: A cooperative positioning flamework of human and robots based on visible light communication (VLC) is proposed. Based on the experiment system, we demonstrated it has high accuracy and real-time performance.

A Cooperative Positioning Flamework for Robot and Smart Phone Based on Visible Light Communication

Benefiting from the development of image sensors and the popularity of light-emitting diode (LED) lighting technology, visible light positioning (VLP) technology based on image sensors has ushered in vigorous development and broad prospects, which can provide low-cost and high-accuracy position service. However, the existing approaches require dense LEDs or sensors such as gyroscopes to assist positioning, which limits the area and lower the accuracy of positioning because of the errors from imperfect sensors. In this article, we propose a simultaneous localization and calibration VLP method based on double coplanar circular LED lights aiming to get rid of the dependence on additional sensors and dense LED transmitters. By the pinhole camera model and the perspective projection of circle, our proposed method extends the available position area and relaxes the required quantity of LED to two. The experiment result showed that our system has a mean 3D positioning accuracy of 7.91cm, a mean angle error of less than 1.6°, and an average latency of 182ms on mobile devices.

https://figshare.com/articles/preprint/High_Accuracy_6-DoF_Simultaneous_Localization_and_Calibration_using_Visible_Light_Positioning/21082069/1/files/37414540.pdf

High Accuracy, 6-DoF Simultaneous Localization and Calibration Using Visible Light Positioning

pdf/bridging-knowledge-gap-between-image-inpainting-and-large-9tg9h9qj4df3.pdf

Bridging Knowledge Gap Between Image Inpainting and Large-Area Visible Watermark Removal

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High Accuracy, 6-DoF Simultaneous Localization and Calibration Using Visible Light Positioning

A Cooperative Positioning Flamework for Robot and Smart Phone Based on Visible Light Communication

Bridging Knowledge Gap Between Image Inpainting and Large-Area Visible Watermark Removal