基于LoRa信号的行走距离和方向估计

Human walking tracking is widely used in many real applications, such as security monitoring, elderly care and indoor navigation. In recent years, RF based contactless human walking tracking has attracted much attention from researchers, including Wi-Fi based or RFID based human walking tracking system. However, existing sensing systems face some serious problem, such as short sensing range, dense device deployment and weak through-wall sensing capability. In this paper, we are the first to explore LoRa, originally used for low-power and long-distance communication in Internet of Things (IoT), to track human walking at a long distance in a contactless way. This new sensing method can significantly increase the sensing range of the system. Particularly, we exploit the multiple antennas equipped on LoRa gateway, and propose to utilize ratio of the received signals from multiple antennas. This proposed division operation can effectively remove the signal noise and cancel out the random phase offsets, and further increase the sensing range. Then, the phase change of the dynamic component in the original signal is calculated accurately by calculating the phase change of the tangent vector to estimate the walking distance and direction. Thus, we propose the LoRa based contactless sensing system, which can accurately determine the motion status of the human target and segment the walking activity in the continuous signal. Then, the distance and direction of walking can be accurately calculated to achieve the human walking tracking. Experimental results demonstrate the accuracy and robustness of the system. Our system achieves an average error of 3.8% in walking distance estimation and can reliably detect walking direction with 100% accuracy for a latency of 0.7s.