Backscatter RFID Sensor System for Remote Health Monitoring

Since the concept of modulating backscatter for communication was proposed in 1948, considerable research and development has been invested in the area of backscatter radio-frequency (RF) systems and devices, or rather backscatter radio frequency identification (RFID) systems and devices. Backscatter RFID in the ultra-high frequency (UHF) and microwave frequency ranges is a promising communication technology for wireless sensing applications. In particular, the operation in the unlicensed frequency bands around 900 MHz and 2.45 GHz is attractive for many wireless sensor systems because of relatively large communication distances, comparatively small devices, and potentially high data rates. Backscatter RFID in wireless sensor networks relies on the radio communication between an RFID reader, acting as a control unit, and a multitude of passive or semi-passive RFID tag, acting as sensor nodes. The principle of communication for transmitting information from the tag to the reader relies on a modulated backscatter signal. All power for the transmission of the sensor data is drawn from the electromagnetic field radiated by the reader. Hence, their low-power consumption makes backscatter tag appropriate for sensing applications that require small, light-weight, and low-maintenance nodes. In backscatter RFID systems, it is vital to ensure a reliable wireless power transfer to the backscatter tag and to realize a robust wireless communication between the reader and tag. Thus, the proper design of backscatter RFID devices, which are included in sensor tag, and the investigation of backscatter radio channels are key study areas. This work revisits the use of backscatter RFID systems in remote health monitoring applications at 900 MHz and 2.45 GHz. Particular attention is paid to the performance analysis of an on-body RFID system for a specific WBAN.