Device-Free Multi-Person Indoor Localization Using the Change of ToF

Indoor position information, which is difficult to obtain by GPS, can be used for various services and applications, thus indoor localization methods have been widely researched. Among them, device-free indoor localization does not require the target persons to possess a localization device, such as a smartphone, which can support the localization of all persons in the environment. Many methods using RSSI and Wi-Fi CSI have been proposed as device-free indoor localization using radio waves. However, RSSI is easily affected by environmental factors, such as multipath propagation. Wi-Fi CSI also has the disadvantage that there is no standard, so it relies on special hardware and software. Therefore, we propose device-free multi-person indoor localization using ToF information, which is less susceptible to noise. ToF information in indoor localization has mainly been used for highly accurate estimation of the receiver position, while this paper proposes a new application. In addition, distance measurements using ToF of Wi-Fi and UWB have been standardized and can be implemented with commercial equipment, which is highly practical. In this research, we considered the change in the distance measurement due to radio wave occlusion by a human body and built a device-free indoor localization system that can estimate multi-person position even if the model is trained on the data of only one person.