# A Novel Ranging Technique Based on Optical Camera Communications and Time Difference of Arrival
## 2 Brief Literature Review
### Photodiode-Based Visible Light Positioning
The authors obtained accuracies around 10 cm in a 100 cm-height scenario[PERSON] The authors did not comment on whether they used a lens distortion compensation algorithm. Fisheye lenses introduce significant errors at relatively small deviations from the optical axis and for positioning purposes this errors should be compensated. Camera-based position detection aided with accelerometer information was proposed by [PERSON] et al. [42]. They included the rotation matrices resulting from the gravity vector estimation in the distance calculation equations. Accuracies below 5 cm are claimed within a 1.95-m-height scenario. The camera resolution is 1296 \(\times\) 964 but no focal length or FOV is provided in the paper. The lamps used as reference are 0.5 m in diameter, do not transmit information, and each one is assigned a different color as ID. [PERSON] et al. [43] proposed a system that estimates position in the XY-plane using a single luminaire. It uses the typical configuration subject to the upwards-pointing restriction. The authors used a geometrical approximation without taking into account lens distortion. The experimental results claim an accuracy of around 2.5 cm. Nonetheless, the link range is not mentioned and relative error could not be extracted. In [9], an IPS based on OCC using Undersampled Phase Shift Keying (UPSK) is experimentally evaluated. The approach followed in this work is the same as in the majority of related literature. The only contribution is the experimental evaluation of UPSK to transmit each lamp's ID. The positioning error reported is 5 cm at 120 cm. [PERSON] and [PERSON] described their Epsilon system [44]. In this camera-based VLP system, each LED bulb broadcasts location beacons to the receivers. The proposed beacons use Binary Frequency Shift Keying (BFSK). However, the authors only provided the theoretical framework. [PERSON] et al. proposed a camera-based visible light IPS with specular reflection cancellation [45]. The positioning algorithm is addressed and the geometrical relationship of LED beacons is used to identify and cancel the specular reflection. A mirror deployed close to a smartphone camera at a determined angle is used to create the specular reflection. The authors claimed that, using this method, more than 90% of the positioning error can be avoided, improving the robustness of the positioning system. The average error is 48.25 cm before cancellation and 1.53 cm after cancellation. [PERSON] et al. [46] proposed a modification of the Single Value Decomposition (SVD) positioning algorithm in camera-based VLP. Generally, positioning algorithms estimate the orientation using homography when at least three LED emitters are located within the captured frame, and then solve the positioning algorithm as an optimization problem. The authors proposed a closed-form equation and compared their with the traditional iterative Levenberg-Marquardt algorithm, improving accuracy and convergence time. Regarding surveys, some can be found in the literature. Concretely, in [47; 48], some interesting issues are highlighted regarding VLP. In proximity positioning, an RF-based interface is yet needed to fulfill the location procedure. It is hoped that, in the future, VLC-based uplink can be used for this purpose. Outdoor VLC-based positioning is still a big challenge using traditional photo-receivers, and camera-based systems will be a hot research topic in the future. Finally, lens distortion is generally not addressed in the literature, and its capital to improve the positioning performance in OCC-based systems. Furthermore, motion blur in rolling-shutter cameras is generally neglected, but this highly affects both positioning and tracking, and must be studied more profoundly. As can be observed from the presented state-of-the-art analysis, OCC-based positioning systems are based on the combination of lamp identification and geometrical relationships between the located emitters. In this work, a novel ranging technique based on the Rolling Shutter (RS) effect is presented.