A method developed at NASA Johnson Space Center uses Radio Frequency Identification (RFID) interrogators for use with wearable active RFID sensor tags that can operate on ultra-low power. The technique uses a store-and-forward approach to manage the collection of data from RFID active tags even when they are not in range of an individual interrogator, as they move from the coverage area of one interrogator to the next. This allows the use of RFID active tags to transport sensor data in a highly complex environment where instantaneous access to an RFID interrogator cannot be guaranteed. Using this technique, an RFID active tag battery operational lifetime can be extended.
The technology exploits the inherently passive nature of RFID to approximate the services provided by traditional active Internet of Things (IoT) protocols like ZigBee and Bluetooth. A novel store-and-forward overlay on COTS RFID protocols allows an RFID active tags to transit through an ecosystem of RFID interrogators, exploiting contact opportunities as they arise and quietly transfers sensor readings at nearly no power cost to the RFID active tag.
Specific intelligence built into both the interrogator and the tag leverages the RFID tag user memory (UM) as a stand-in IoT interface. The tag operates by sampling data into timestamped packets and loads them into tag memory. When an interrogator in the ecosystem realizes that a tag is in view and that there is unrecovered data on the tag, it takes custody of the sensor data packet and offloads the data into a database. A smart scheduler reads from the population of interrogators and schedules data transfers for specific tags when an interrogator can seed the custody transfer process for the data packets.
NASA has produced working prototypes of wearables, worn by the crew aboard the International Space Station, that reports humidity, temperature, and CO2 readings. In one estimate, the battery life is on pace to last an estimated nine years.
The technology has potential for applications including wearable sensors for air quality monitoring; wearable geo-location and biometric sensors for staff and patients moving throughout medical facilities; telehealth/medical monitoring of home-bound patients; monitoring space habitats for astronauts; as well as applications for wearable sensors where battery charging or replacement is not practical.