Survey on CSI-based Indoor Positioning Systems and Recent Advances

With the popularization of mobile devices, location based services (LBS) have received significant attention. Global Navigation Satellite System (GNSS) that widely used outdoors is unable to achieve high-precision positioning indoors, thus various indoor positioning methods are proposed for precise positioning. Wi-Fi based indoor positioning is widely used to provide accurate and efficient location services due to the convenience of hardware facilities. Channel state information (CSI) is an essential feature provided by Wi-Fi signals, which depicts the fine-grained features of channels, and attracts great attention in recent years. This paper comprehensively reviews the positioning technology based on CSI, and compares the primary positioning systems that makes great progress. This paper are mainly represented from two aspects: geometry-based positioning method and fingerprint-based positioning method. The former introduces angle-based method, range-based method, and the combination of both. The later mines the development process from traditional machine learning method to deep learning method. At the same time, this article also gives a brief overview of CSI's multi-source fusion technologies. Finally, this paper summarizes the challenges and points out the trends in this rapidly developing field.