## 1 Introduction
First, for positioning accuracy, a circle projection-based single LED system was proposed in Reference [21], whose positioning accuracy was only 25.12 cm. In Reference [22], the positioning error was reduced to less than 10 cm; however, the performance remained unsatisfactory. These works did not give satisfactory accuracy. In Reference [23], a novel method was proposed utilizing the electronic compass and gyroscope to calculate the yaw angle of the positioning terminal. The stimulated results showed the error was within 2 cm. However, the real-time ability was not considered in the article. Additionally, few studies could maintain a good balance between real-time ability and positioning accuracy. The author used a minimax filter to estimate the trajectory of the terminal in Reference [24], whose average velocity simulated by MATLAB simulator was 1 m/s (3.6 km/h), unable to fit higher motion speed. Finally, the VLP method proposed in Reference [25] considers the system's real-time ability, whose maximum allowable motion speed of the positioning terminal was 18 km/h, with a positioning accuracy of 7.5 cm. Though it maintained a relatively good balance between accuracy and real-time ability, the blur effect, caused by high relative speed between IS and LED, was ignored. When the target moves at such a speed, the image of the LED will blur. Because the IS-based positioning method in Reference [25] is based on pixel intensity detection, when the LED is blurred in the image, the LED-ID recognition process through pixel intensity detection becomes tough, which may lead to failure of location. The ignorance of robustness is crippling in the field of VLP, which can make research outputs have little practical value, and this reference article is no exception. Moreover, few papers have considered the general circumstance that the transmitter (i.e., LED) is shielded or broken. When the light links are blocked between LEDs and positioning terminal,the positioning would fail because most of the positioning algorithms are based on two or more LEDs, the absence of even one LED in the image can lead to failure of the whole algorithm. The shielded effect is a fatal problem in the field of VLP. No one has yet solved the problem except our previous work [9], where a relatively perfect method is proposed. Based on optical flow and Bayesian forecast, the algorithm possesses the ability to address all the difficulties of VLP systems mentioned above, whose positioning accuracy is 0.86 cm and the maximum allowable speed of positioning terminal is up to 48 km/h. Also, the algorithm can locate the target even if half of the LED is shielded. However, the computational cost of the optical flow method is very large. Furthermore, optical flow algorithms alone cannot track the LED under shielded effect. Therefore, Bayesian forecast is introduced to solve the problem of shielded effect. Finally, the outcomes of the Bayesian forecast algorithm and the optical flow algorithm was combined by Kalman filter to obtain the final output. Though our previous work [9] seems powerful enough to address all the knotty problems in the field of VLP, it also raised some problems that cannot be ignored. First, the optical flow method used in Reference [9] greatly increases the computational cost and the running time of the whole system, which reduces the real-time ability of the algorithm, whose utility is inversely proportional to the computational cost. Because the function of the optical flow method is to track the LED, in this article, to improve the real-time ability of our visible light positioning method, it was replaced by the mean shift algorithm, which greatly reduces the computational cost. Moreover, the mean shift algorithm possesses wonderful robustness, which can reduce the influence of the shielded effect exists in the VLP situations to a great degree. Furthermore, in the simple background of VLP, the precision of the mean shift algorithm does not lose to any other target tracking algorithm.