Channel Emulation for the Characterization of Wearable RFID Systems

Wearable sensors with RFID (Radio Frequency Identification) tags are considered to be an integral part of the upcoming revolution in the IoT (Internet of Things) sector. As with many deployed IoT sensor systems, dynamic environment conditions present challenges in reliably measuring system performance; this difficulty is enhanced due to proprietary details about the sensors, such as an RFID chip embedded within a novel knitted antenna acting as a passive sensor. A repeatable and scalable platform is necessary to evaluate the performance of the entire system in the pre-deployment stage in order to compare the predicted effects of varying components, design, and integration of sensors in an integrated IoT device. This paper demonstrates the development of an RFID channel emulation testbed in the United States ISM band (902-928 MHz). The testbed includes a commercial RFID interrogator, a custom-built circuit board housing a commercial passive RFID chip, and a dynamic spectrum environment emulator (DYSE) for wireless channel emulation. A single link scenario was considered where the DYSE emulates the antenna gain fluctuation due to the sensing of breathing with a fabric-based RFID. Two regular and one irregular breathing scenarios were emulated, and breathing rate or anomaly was detected from post-processed RSSI (Received Signal Strength Indicator) data received by the RFID interrogator.