## 1 Introduction  
In business centers [1], large public buildings (subways, airports, libraries, etc. ), high-risk industrial parks, hospitals, nursing homes [2], and other indoor places where Global Positioning System (GPS) helps little but where navigation and location services are urgently needed, indoor positioning technology has broad application prospects [3, 4]. Common optional techniques for indoor positioning include infrared ray (IR), ultrasonic wave, radio-frequency identification (RFID), wireless local area network (WLAN), Bluetooth, ultra-wideband (UWB), etc. Based on these technologies, different implementation schemes have been developed. However, each has obvious drawbacks considering positioning accuracy [5] or the ability to resist electromagnetic interference [6], or the high cost of hardware devices [7], which makes them difficult to become popularized. Compared with these indoor positioning technologies mentioned above, visible light positioning (VLP) technology has outstanding advantages because of its abundant bandwidth resources [8],strong ability to resist electromagnetic interference, higher positioning accuracy and illumination ability. Additionally, the cost of hardware devices supporting VLP systems is relatively small, because complex facilities conducting precise measurement are not necessary. A simple VLP system even can be structured with an image sensor, some LEDs and a processor. Therefore, VLP technology has a promising prospect in the field of indoor positioning. There exist two modes of indoor positioning systems based on VLP: The photodiode-based (PD-based) positioning, and the image-sensor-based (IS-based) positioning [9; 10]. The PD-based VLP systems have been deeply studied by researchers before. A series of research projects on VLP systems based on PD have been completed in our previous works [11; 12; 13; 14; 15; 16] through which we found that the mobility of the positioning terminal has been severely limited because of PD's sensibility to the direction of the light beam. To deal with the orientations of the PDs, the authors of Reference [17] designed a pyramid receiver (PR) and hemispheric receiver (HR), which improved the channel capacity and bit-error-rate (BER) performance under various settings and reduced the space usage. However, another significant drawback of PD-based VLP systems is the doubtful robustness. Even at the same location, repeated measurements will yield a fluctuating value of light intensity. Also, PD-based VLP systems are easily disturbed by ambient light and reflected light [15]. Meanwhile, the angular and signal strength received need to be precisely measured. Otherwise the positioning results will have noticeable error. In addition, precise instruments must be exploited because the received signal strength and signal's time difference of arrival should be measured to calculate the distance between the reference point and target [2]. In contrast, IS-based VLP methods are unaffected by these problems mentioned above. What is more, smart phones are nowadays equipped with high-resolution complementary metal-oxide-semiconductor (CMOS) sensor cameras, which can be combined with IS-based VLP methods easily, where huge commercial value lies. Furthermore, the position would fail if the LED is shielded in PD-based VLP systems. In comparison, our previous work [9] based on image sensor solved the problem effectively. Therefore, image sensors are better than PDs as the receiving terminal for VLP systems [18; 19]. Finally, few research projects on PD-based VLP have explored the field of dynamic positioning, which has significance for real-time indoor navigation, but restricts the application to low-speed motion or static positioning [20]. Theoretically, IS has better performance than PD regarding the field of VLP, but existing studies have not yet yielded satisfactory results in terms of positioning accuracy, real-time ability, and robustness, which are three vital elements for VLP systems. There is still much room for improvement.