Indoor Positioning With Smartphone by Using Doppler Observations From Asynchronous Pseudolite System

Smartphones provide good outdoor positioning services through the global navigation satellite system (GNSS), playing an important role in various fields, such as the Internet of Things (IoT) and smart logistics. However, since GNSS are blocked by buildings in indoor environments, there is currently no general technology or solution for indoor positioning in outdoor environments like GNSS. As a supplement to GNSS, it has been verified that pseudolite systems can make full use of the GNSS chips embedded in smartphones to provide raw observations for indoor positioning services. Aiming at the problem of indoor positioning of smartphones, a low-cost distributed asynchronous pseudolite system and an indoor positioning method based on Doppler observations are proposed. The asynchronous pseudolite system consists of multiple dual-channel transmitters and uses Doppler raw observations to reduce the need for precise synchronization of signal transmission time. To evaluate the feasibility and positioning accuracy of the method, static and dynamic experiments were carried out in a large underground garage of an building using commercial smartphones. The field experiment shows that the indoor pseudolite positioning method proposed in this article achieves static decimeter-level and dynamic meter-level positioning accuracy for smartphones. Compared with the indoor positioning technology of smartphones based on radio frequency (RF) signals, such as Wi-Fi and Bluetooth, this study explores a new indoor positioning system for smartphones, enriches the observation information, and brings more possibilities for smartphones indoor positioning. Moreover, this study discusses an on-the-fly solution for initialization without known points using only Doppler observations and motion diversity.