The home of the future, we are assured, will be swarming with tiny sensors: security cameras, carbon monoxide detectors, speakers and everything else. Few need to be running all the time — but how do you wake them up when they’re needed if they’re off in the first place? Ultrasound.
That’s the idea being pursued by Angad Rekhi and Amin Arbabian at Stanford, anyway. Their approach to the problem of devices that can’t stay on, yet can’t be all the way off, is to minimize the amount of energy necessary to send and receive a “wake” signal. That way the Internet of Things really only consumes power when they’re actively in use.
Radio, which of course all these tiny sensors use to transmit and receive information, is actually pretty expensive in terms of power and space….