Effects of Body Shadowing in LoRa Localization Systems

Abstract

Applications where a person carries environmental sensors benefit from knowing the position of the individual. Researchers can locate the device by analyzing the radio signals used for sending information. However, it is necessary to know the impact of body obstruction on communication links and, therefore, on the localization system. The paper studies this impact by using field tests employing one LoRa node with an omnidirectional antenna in an outdoor parking lot with vegetation. The tests use four LoRa gateways located in the corners of the area to measure the signals with and without body obstruction. The node was located on the subject’s chest to maximize signal obstruction. Results show that signal strength decreases by an average of 3 dB on links with body shadowing. Additionally, the study uses these signals with machine learning and Kalman filter localization algorithms. Finally, the results show that body shadowing affects location accuracy in most methods. These results are useful for IoT researchers that need to locate people carrying LoRaWAN devices but cannot use GPS/GNSS due to energy constraints.