# A Survey of Visible-Light-Communication-Based Indoor Positioning Systems
## 1 Introduction  
Mobile devices have become essential tools for communication in our daily lives, and the utilization of positioning systems is becoming increasingly common. These systems facilitate the precise localization of mobile devices, thereby supporting a range of applications, including tracking [1], navigation [2], social networking [3], and augmented reality [4]. In addition, positioning systems also play a crucial role in ubiquitous computing [5], as well as emergency services [6]. In general, positioning systems can be classified into two categories: indoor and outdoor systems. In outdoor scenarios, the Global Positioning System (GPS) [7] is the most widely used and well-developed technology. It leverages a worldwide satellite network to offer precise user location information and turn-by-turn navigation. However, in indoor environments, the various obstacles, like roofs, walls, and equipment, significantly weaken and scatter satellite signals. Additionally, the effects of multipath interference and other sources of interference can lead to positioning errors of several meters [8]. Despite efforts to enhance accuracy through the introduction of high-sensitivity GPSs, achieving satisfactory results in indoor settings remains a challenge [9]. Undoubtedly, a wide range of applications significantly benefit from indoor location services. In our daily lives, the presence of large buildings with complex interiors, such as hospitals, airports, supermarkets, university campuses, and the like, often poses a formidable challenge to visitors who invest a great deal of time and effort in navigating them. An indoor positioning system (IPS) emerges as a vital ally in such circumstances, affording invaluable assistance and introducing an added layer of value. A typical example is the application for museums, where an IPS utilizes the visitor's position to offer advice and guidance, enabling them to immerse themselves in the exhibits and enhance their overall experience [10]. In addition to the indispensable role of an IPS in navigation, it also serves as a desirable tool for tracking purposes, particularly for monitoring the whereabouts of portable mobile devices, such as wheelchairs in hospitals. This duality of functionality provides multiple benefits. On the one hand, patients can promptly access enhanced services exactly when needed, fostering a sense of immediacy and efficacy. On the other hand, the IPS effectively enhances the traceability of expensive devices, improving their security and reducing the risk of loss. It is worth noting that the availability of high-precision positioning information is of paramount importance in areas such as robotics and the Internet of Things (IoT) [11; 12], in accordance with the extensive references provided therein. Because of the growing potential and evolving applications of indoor positioning, there has been extensive discussion in recent years. An exemplary initiative in this area is the In-Location Alliance (ILA) [13], an organization founded by leading companies in the mobile communications industry. Its primary goal is to drive innovation and cultivate cutting-edge indoor positioning services characterized by exceptional accuracy and minimal power consumption, even when users move. Notable companies such as Google, Apple, and Microsoft [14] have embarked on the development of novel indoor positioning solutions. This has further fueled the discourse in this area. Numerous technologies have been the subject of intense discussion, including VLC, infrared (IR), radio frequency identification (RFID), ultrasound, wireless local area network (WLAN), Bluetooth, sensor networks, ultra-wideband communication (UWB), magnetic signals, and others. In Section 3, we will delve into a comprehensive exploration of these technologies. In this article, we focus on VLC-based IPSs. Our primary goal is to summarize the latest breakthroughs and significant findings in this emerging field of research. The overall organization of this paper is summarized as follows.