A team of Researchers at Carnegie Mellon University’s Future Interfaces Group have developed self-powered radio tags called Sozu, which enables building-scale activity sensing, without the need for line-of-sight and at a very low cost. They claim a 99 percent detection rate and “almost no false positives.”
The team of researchers includes Yang Zhang, Yasha Iravantchi, Haojian Jin, Swarun Kumar, and Chris Harrison. Sozu is built to enable wide-area sensing of activity in a human-populated environment at a low cost. To actualize that, the team came up with the ides of dropping the idea of having a battery or mains power connection for the nodes themselves. They say :
Sozu tags convert energy from activities that they sense into RF broadcasts.
In the team’s paper, they say the Sozu acts like a miniature self-powered radio station. Sozu’s deployment includes one antenna that can be placed in a concealed location, like a basement. Users can then attach Sozu ‘tags’ to items and infrastructure of interest. For low cost, the tags are constructed from ultra-low-cost analog components, and thus cost only a few dollars each (i.e., no digital components, nor digital communication like Wi-Fi or Bluetooth).
Even though it is similar in concept to radio-frequency ID (RFID) tags that harvest energy from a nearby transmitter to power a reply, Sozu harvest energy from a different source i.e the activities they monitor itself. The paper says