Jun 01, 2011Passive RFID transponders are great for identifying objects, but they've never been able to do complex computations because the power they gather, or harvest, from readers is often interrupted. When that happens, even for a microsecond, memory is lost and the computation stops. It's like pulling the plug on your desktop computer while the computer is performing a task. But now, researchers at University of Massachusetts Amherst have developed a software program called Mementos that could solve the problem.
Mementos runs on a passive ultrahigh-frequency transponder with a microprocessor that can do more than just store a serial number and some user data. The software is designed to run on the Wireless Identification and Sensing Platform, developed by Intel Labs Seattle. (The software name is based on the Oscar-nominated 2000 movie Memento, in which a man suffering short-term memory loss uses notes and tattoos to hunt for the man he believes killed his wife.)
The software running on the prototype tag monitors the amount of energy being havested from the RFID reader, evaluates the state of the microprocessor prior to the energy loss, and then restarts the computation from where it left off when the tag lost power. "It's hard to keep up with energy demands with energy harvesting," says Kevin Fu, an assistant professor in the computer science department at UMass Amherst. "Mementos provides robustness against power loss when you are running these devices."
One application Mementos could support is running sophisticated cryptography on the chip. Today, most secure RFID tags use very limited cryptography, because the computation will fail if it takes too long and the tag loses energy before the computation is completed. Mementos would allow a transponder to run cryptography comparable to that found on more powerful devices, such as laptops.
Beyond that, Mementos could enable RFID transponders to authenticate readers (so no one without authorization could use a standard reader to capture data from a tag) or perform more complex statistical processing of sensed data. For instance, an engineer checking the structural integrity of a steel bridge might be able to use a lightweight reader and have the tag calculate the average vibration over a period of time, rather than lugging a reader and a laptop to do the calculation.
Benjamin Ransford, a Ph.D. candidate at UMass and the principal researcher on the project, says the next step is to integrate the Mementos software more tightly with prototype devices the team is building. The software is open-source. "Our goal is to plant the seeds of innovation," Fu says.