Widor: Resolving Practical Challenges in WiFi-Based Corridor Localization

Abstract

WiFi-based indoor localization, a fundamental technology for numerous real-world applications, including indoor navigation and emergency evacuation, has garnered significant attention over the past decade. While existing works have already achieved remarkable performance under various practical scenarios, they simply take corridor as a test scenario, and attribute performance degradation to complex multipath. To further release the functionality of corridor as bridges connecting different physical spaces, in this paper, we propose Widor, the first WiFi indoor localization system that designed specifically for corridor. We first explore the neglected elevation angle dimension information in WiFi positioning and creatively place AP vertically to avoid the large-angle effect, which is caused by the unique slender structure of the corridor. To eliminate the impact of complex multipath introduced by the narrow environment, we make full use of the Toeplitz structure of the covariance matrix to further improve the spatial resolution of existing commercial WiFi AP without increasing the additional hardware cost. Furthermore, we design a tailored multi-APs joint height compensation algorithm to bridge the gap between 2-D and 3-D localization, which iteratively optimize the height difference between the AP and the client through an alternating optimization method. Both the time dimensional information and map constraint can be used to further improve localization accuracy. We evaluate Widor under various complex corridors in an $ 82\,\text{m} \times 65\,\text{m}$ building, and extensive experimental results show that Widor can achieve $5.2^\circ$ median angle estimation error and 58 cm localization median error. We also highlight that the proposed Widor system has little impact on the communication performance of existing commercial APs, and can be easily extended to any slender building scenarios, such as mines and tunnels, further broadening the application boundaries of WiFi indoor localization.