Imagine that you are looking at a poster from a pop group at a bus stop – and that this poster then sends you a sound byte from this group to your smartphone, or a link to cheap tickets? Or that your T-shirt measures how much you perspire while you are jogging and sends this directly to your mobile phone. A new technique, conceived by researchers from the University of Washington, makes these 'clever' posters and clothes possible.
The biggest challenge with this, is that conventional radio technologies (WiFi, Bluetooth, FM) won't even 'stay on the air' for a day when powered from a button cell. That is why a new communication method has been developed in which information is sent by reflecting the omnipresent FM radio signals. This requires almost no energy.
The research team have demonstrated how a technique, which is called backscattering, can be applied outdoors. The new system sends messages by coding audio and data in these reflected signals – without disturbing the original broadcast. A 'singing poster' can be received from up to 4 meters using a smartphone (or up to 20 meters using a car radio).
The total energy consumption of the demonstration project amounts to only 11 microwatts – so that a button cell or a couple of small solar panels will be more than sufficient for the power supply.