The researchers at UW have demonstrated devices transmitting data across distances of up to 2.8 km using RF energy harvested from WiFi networks and other reflected radio sources.
The long-range backscatter system achieved reliable coverage throughout 4800-square-foot house, an office area covering 41 rooms and a one-acre vegetable farm using a dedicated radio source.
“Until 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,” said Shyam Gollakota, lead faculty and associate professor in the Paul G. Allen School of Computer Science & Engineering. “Now we’ve shown that we can offer both, which will be pretty game-changing for a lot of different industries and applications.”
The long-range backscatter system will be commercialized by Jeeva Wireless, a spin-out company founded by the UW team of computer scientists and electrical engineers, which expects to begin selling it within six months.
Using the backscatter approach means the sensors can be as low cost as 10 to 20 cents each in volume, allowing applications for farmers looking to measure soil temperature or moisture could who 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 “smart” cities or medical devices that could wirelessly transmit information about a heart patient’s condition around the clock.
“People 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,” said Vamsi Talla, CTO of Jeeva Wireless, who was an Allen School postdoctoral researcher and received a doctorate in electrical engineering from the UW. “This is the first wireless system that can inject connectivity into any device with very minimal cost.”
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.
It uses a new type of modulation — called chirp spread spectrum – where spreading the reflected signals across multiple frequencies allowed the team to achieve much greater sensitivities and decode backscattered signals across greater distances even when it’s below the noise.
“We 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?” said Bryce Kellogg, a co-founder at Jeeva Wireless who was also a UW electrical engineering student.