New technology may 'de power from within provl( the building envelope

A s coNnecrED DEVICES continue to Apermeate our world. one disruptive technology may be changing the game all together-one that communicates without batteries or wires at all. By harnessing the power of existing radio waves, ambient backscatter technology may present an entirely new way of developing for the smart environment.

This emerging communication sYstem is being developed at the University of Washington in Seattle. It essentially enables tiny devices to use existing TV and cellular transmissions as their only source of power, eliminating the need for wires to communicate progressively extended distances and in previously inaccessible places. "If you think about conventional radio like Bluetooth or Wi-Fi, energy is taken from the mobile device's battery, turned into radio signals and actively emitted by the device. But in ambient backscatter, we don't actively emit any energy," says Aaron Parks, a PhD student at the UniversitY of Washington who is on the develoPment team and works under Prof. Shyam Gollakota and Prof. Josh Smith. "We use existing radio energy, and we reflect that existing energy towards nearby peer devices. It's kind of like using a signal mirror to communicate with someone, so you can select whether you're shining the sun's light at them or not, and you can communicate with someone on a distant hilltop without actively emitting any energy."

Parks says that ambient backscatter far exceeds similar technologY in terms of power consumption: "We're two to three orders of magnitude better than conventional active radio, because we don't emit signals; we use existing signals. In the context of mobile devices, a pretty significant amount of energy goes to Wi-Fi or mobile communication, so we can essentially augment that with ambient backscatter technology."

Parks' team is most excited about the potential the technology creates for battery-free communication devices. While the team says it is a ways off from making this commercially available to developers and manufacturers, it certainly has identified an abundance of use cases. In addition to the obvious applications like extending or augmenting battery life, are the possibilities of sensor networks that work within structures and environments with no power requirements.

"We've done a lot in our lab with RFID sensors, which are battery-free and communicate with RFID readers, and I think ambient backscatter technology lends itself to sensing networks as well," Parks says. "Imagine outfitting every tree in an orchard with moisture and humidity sensors that relay information on the tree's health."

Ambient backscatter devices, dubbed "tags," can be embedded within smart buildings as well. He explains: "One of the things that people have been excited about with

Siding And Trim Specifications And Coverage

RFID sensors is putting strain gauges on big structures. Ambient backscatter tags can be embedded in concrete within a skyscraper, and since they don't need power, they would be relatively maintenance-free. They could , theoretically monitor strains and stresses and provide an estimate of structural health. For instance, after an f earthquake, these sensors could quick- lV report if the building is safe for reentrv."

J.R. Babineau, building scientist with Johns Manville, Denver, Co., ... says he can see the potential for multi-

" pl. uses for ambient backscatter with- in the building envelope. "I could envision a builder wanting to include sensors with these devices installed as pur, of the roof. Maybe that even means their roofing guarantee costs less, because you would know well in advance if there were a problem. I could also envision us encouraging architects and builders to use this kind of technology, especially in key areas like simple sensors to detect moisture. I could even see this being used by the

Department of Energy as a way to collect data easily that doesn't involve stringing a bunch of wires, because today it's kind of a big deal to try to instrument a building. If it would be possible to do it much less expensively, that would be a big improvement."

Parks says his team's technology could be manufactured inexpensively. "There's nothing about these tags that couldn't be made the same way as a five-cent RFID tag. You don't need a battery, you don't need a solar panel," he says. "So we can make these using a roll-to-roll process very cheaply and with tiny integrated circuits. We can maybe even make smart wallpaper that shares some sort of data throughout a room, for example. Sensing nodes that are built into walls is technically possible."

Babineau considers the technology unique and promising since it is both wireless and battery-less. "Today, in terms of instrumenting a building, I do not know of anything that you can do that is completely wireless," he says. "Avoiding wires lends a huge amount of durability to this, because when you add sensors and wires there is a lot more opportunity for things to break (during construction). If you can bury something in a system, then maybe just one trade needs to know about it but everyone else can avoid it, then you're good and you can move on."

Charles Cottrell, v.p. of technical

services for the North American Insulation Manufacturers Association, also believes the technology looks interesting. "It looks like a very beneficial tool for building scientists to embed sensors that could transmit data out of walls, although (running wires) is not that difficult for most construction, but it certainly makes it tougher to bury things inside of walls," he says. "This technology looks fairly similar to the key cards you use to get in and out of a parking galrage."

So, will ambient backscatter technology get us one step closer to mass adoption of the connected building? Perhaps, and Babineau is confident that commercial construction will be first to integrate such a technology.

"Commercial buildings are ahead of residential in terms of the smart building," he says. "Commercial buildings have more margin for cost to implement systems, whereas on the residential side it's so driven by cost with rare exceptions. Also, the smarter the structure, the smarter the people operating the building need to be and that's also where a commercial building has the benefit of dedicated facilities managers that can be educated on how to properly run whatever the smart systems are, whereas with residential, it's the general public."

Parks explains that another key differentiator for his team's technology is the opportunity to reprogram the tags. "In conventional RFID tags, those are single purpose and they don't have much in the way of smarts," he says. "All they say is 'here is my ID,' kind of like an IP address. With ambienr backscatter tags, I think the most exciting version of that would be a wirelessly reprogrammable tag. In other words, a single chip that you could reprogram wirelessly from a nearby laptop or mobile phone that has an access point attached."

He says they're currently working with computer science students on developing a platform and APL "We're identifying where this would have the most benefit, whether that would be consumer electronics or commercial electronics," Parks says. "We currently have research prototypes, so it's difficult to say when this would be commercially available and what hurdles we'll have to cross prior to commercialization. We're developing a new radio communication standard and there are some hurdles there. Maybe by this time next year we'll have something to talk with manufacturers about."

The future of ambient backscatter is not clear, but the University of Washington team establishes one thing. It isn't designed to replace conventional Wi-Fi or Bluetooth, but it does have the potential to augment and extend devices that also rely on battery life.

- Brandy Alexander-Wimberly is an independent writer and part of the Interrupt team, a strategic marketing agency devoted to the building materials and home improvement space. To view the University of Washington team's paper published last year, visit abc.cs.washingto n.e du/fi le s/ comm I 5 3 - liu pdf