A novel method introduced by University of Washington engineers makes these ‘smart’ posers and clothing a reality by enabling them to communicate directly with your car’s radio or your smartphone. For example, bus stop billboards could send digital content about local attractions. A street sign could broadcast the name of an intersection or notice that it is safe to cross a street, enhancing accessibility for the disabled. In addition, clothing with integrated sensors could monitor important signs and send them to a phone.
“What we intend to do is allow smart cities and fabrics where everyday objects in outdoor environments, whether it’s posters or street signs or even the shirt you are wearing, can talk to you by sending data to your car or phone,” says lead faculty and UW assistant lecturer of computer science and engineering Shyam Gollakota.
“The challenge is that radio technologies such as Bluetooth, Wi-Fi and traditional FM radios would last less than half a day with a coin cell battery when transferring,’ says co-author and UW electrical engineering doctoral student Vikram Iyer. “So we introduce a novel method of communication where we transmit data by reflecting ambient FM radio signals that are already in the air that consumes close to zero power.”
“FM radio signals are everywhere. We can listen to music or news in car and it is common way for us to get our data,” says co-author and UW computer science and engineering doctoral student Anran Wang. “So what we do is usually make each of such everyday objects into a small FM radio station at almost zero power.” Such ubiquitous low-power connectivity can also allow smart fabric applications like clothing integrated with sensors to monitor a runner’s gait and important signs that transfers the information directly to a user’s phone.
The group illustrated three distinct techniques for sending audio signals and data using FM backscatter – one simply audio signal and information on top of existing signals, another takes benefit of unused portions of a stereo FM broadcast, and the third uses cooperation between two smartphones to decode the message. “Because of its unique structure of FM radio signals, multiplying the original signal with the backscattered signal actually produces an additive frequency change,” says co-author VamsiTalla, UW postdoctoral scientist in computer science and engineering. “Such frequency changes can be decoded as audio on the normal FM receivers built into smartphones and cars.”
In the illustration presented by the team, the total power consumption of the backscatter system was 11 microwatts, which could be conveniently supplied by a small coin-cell battery for a couple of years, or powered employing small solar cells.
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