Engineers at the University of Washington (UW) have pioneered a technique which allows common city features like billboards and street signs to send digital content to a smartphone or car radio.
In a first, the team at UW has shown how to apply a technique called backscattering to outdoor FM radio signals. The new system transmits messages by reflecting and encoding audio and data in these signals that are ubiquitous in urban environments, without affecting the original radio transmissions.
Within the ‘smart’ city landscape it could have a number of applications, for example billboards at a bus stop could send information about local attractions to a smartphone.
The results of the UW study are published in a paper to be presented in Boston at the 14th USENIX Symposium on Networked Systems Design and Implementation in March.
“What we want to do is enable smart cities and fabrics where everyday objects in outdoor environments — whether it’s posters or street signs or even the shirt you’re wearing — can ‘talk’ to you by sending information to your phone or car,” said lead faculty and UW assistant professor of computer science and engineering Shyam Gollakota.
The team demonstrated that a ‘singing poster’ for the band Simply Three placed at a bus stop could transmit a snippet of the band’s music, as well as an advertisement for the band, to a smartphone at a distance of 12 feet or to a car over 60 feet away. They overlaid the audio and data on top of ambient news signals from a local NPR radio station.
Co-author and UW electrical engineering doctoral student Vikram Iyer added: “The challenge is that radio technologies like WiFi, Bluetooth and conventional FM radios would last less than half a day with a coin cell battery when transmitting. So we developed a new way of communication where we send information by reflecting ambient FM radio signals that are already in the air, which consumes close to zero power.”
The system works by taking an everyday FM radio signal broadcast from an urban radio tower. The ‘smart’ poster or T-shirt uses a low-power reflector to manipulate the signal in a way that encodes the desired audio or data on top of the FM broadcast to send a “message” to the smartphone receiver on an unoccupied frequency in the FM radio band.