91ΧΤΕΔ 91ΧΤΕΔers have demonstrated for the first time that devices that run on almost zero power can transmit data across distances of up to 2.8 kilometers β breaking a long-held barrier and potentially enabling a vast array of interconnected devices.
For example, flexible electronics β from knee patches that capture range of motion in arthritic patients to patches that use sweat to detect fatigue in athletes or soldiers β hold great promise for collecting medically relevant data.
But todayβs flexible electronics and other sensors that canβt employ bulky batteries and need to operate with very low power typically canβt communicate with other devices more than a few feet or meters away. This limits their practical use in applications ranging from medical monitoring and home sensing to smart cities and precision agriculture.
By contrast, the UWβs , which uses reflected radio signals to transmit data at extremely low power and low cost, achieved reliable coverage throughout 4800-square-foot house, an office area covering 41 rooms and a one-acre vegetable farm. The system is detailed in a to be presented Sept. 13 at .
βUntil now, devices that can communicate over long distances have consumed a lot of power. The tradeoff in a low-power device that consumes microwatts of power is that its communication range is short,β said , lead faculty and associate professor in the Paul G. Allen School of Computer Science & Engineering. βNow weβve shown that we can offer both, which will be pretty game-changing for a lot of different industries and applications.β
The teamβs latest long-range backscatter system provides reliable long-range communication with sensors that consume 1000 times less power than existing technologies capable of transmitting data over similar distances. Itβs an important and necessary breakthrough toward embedding connectivity into billions of everyday objects.
The long-range backscatter system will be commercialized by , a spin-out company founded by the UW team of computer scientists and electrical engineers, which expects to begin selling it within six months.
The sensors are so cheap β with an expected bulk cost of 10 to 20 cents each β that farmers looking to measure soil temperature or moisture could affordably blanket an entire field to determine how to efficiently plant seeds or water. Other potential applications range from sensor arrays that could monitor pollution, noise or traffic in βsmartβ cities or medical devices that could wirelessly transmit information about a heart patientβs condition around the clock.
βPeople have been talking about embedding connectivity into everyday objects such as laundry detergent, paper towels and coffee cups for years, but the problem is the cost and power consumption to achieve this,β said , CTO of Jeeva Wireless, who was an Allen School postdoctoral 91ΧΤΕΔer and received a doctorate in electrical engineering from the UW. βThis is the first wireless system that can inject connectivity into any device with very minimal cost.β
The 91ΧΤΕΔ team, for instance, built a contact lens prototype and a flexible epidermal patch that attaches to human skin, which successfully used long-range backscatter to transmit information across a 3300-square-foot atrium. Thatβs orders of magnitude larger than the 3-foot range achieved by prior smart contact lens designs.
The system has three components: a source that emits a radio signal, sensors that encode information in reflections of that signal and an inexpensive off-the-shelf receiver that decodes the information. When the sensor is placed between the source and receiver, the system can transmit data at distances up to 475 meters. When the sensor is placed next to the signal source, the receiver can decode information from as far as 2.8 kilometers away.
The advantage to using reflected, or βbackscattered,β radio signals to convey information is a sensor can run on extremely low power that can be provided by thin cheap flexible printed batteries or can be harvested from ambient sources β eliminating the need for bulky batteries. The disadvantage is that itβs difficult for a receiver to distinguish these extremely weak reflections from the original signal and other noise.
βItβs like trying to listen to a conversation happening on the other side of a thick wall β you might hear some faint voices but you canβt quite make out the words,β said , an Allen School doctoral student. βWith our new technology we can essentially decode those words even when the conversation itself is hard to hear.β
To overcome the problem, the UW team introduced a new type of modulation β called β into its backscatter design. Spreading the reflected signals across multiple frequencies allowed the team to achieve much greater sensitivities and decode backscattered signals across greater distances even when itβs below the noise.
βWe basically started with a clean slate and said if what we really need to enable smart applications is long-range communication, how could we design the system from the ground up to achieve that goal?β said , a co-founder at Jeeva Wireless who was a UW electrical engineering student.
The 91ΧΤΕΔ was funded by the National Science Foundation.
Co-authors include , professor in the Allen School and the UW Department of Electrical Engineering, and UW electrical engineering doctoral student .
For more information, contact the 91ΧΤΕΔ team at longrange@cs.washington.edu.