Long range communication barriers broken

Researchers in the US have successfully demonstrated that devices running on nearly no power can transmit data across almost three kilometres.

Flexible electronics, such as patches that can capture motion range or monitor sweat to detect fatigue levels have great potential to collect medically relevant data. However they are limited by the fact that they cannot use bulky batteries, and as such, cannot communicate with devices more than a few metres away.

Game changer

Shyam Gollakota, associate professor at the University of Washington and co-author of the paper, said: “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. Now we've shown that we can offer both, which will be pretty game-changing for a lot of different industries and applications."

The researchers’ communication system – a long-range backscatter system – provides reliable long-range communication with sensors that consume 1000 times less power than existing technologies. It is hoped the system can empower connectivity into billions of everyday objects as the sensors are expected to have an expected bulk cost of 7 to 15p. This could enable farmers interested in measuring soil temperature or moisture to cover an entire field with sensors to best decide how to plant seeds or water crops. Other uses could include noise or traffic pollution monitoring or medical devices that transmit information about patients.

Vamsi Talla, CTO of Jeeva Wireless, a spin out formed as a result of this research, said: “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. This is the first wireless system that can inject connectivity into any device with very minimal cost."

The research team have, so far, built a contact lens prototype as well as a flexible epidermal patch that attaches to human skin, capable of transmitting information across a 3300 sq ft atrium. Previous smart contact lens designs could achieve a range of three feet. The system consists of three components, a source that emits a radio signal, sensors that encode information in reflections of that signal and a receiver to decode this information.

By using backscattered – or reflected – radio signals to transmit information a sensor is able to run, drawing very little power. This can either be provided by thin cheap flexible printed batteries or harvested from ambient sources, eliminating the need for bulky batteries. A disadvantage of this, however, is that it is difficult for a receiver to distinguish these very weak reflections from the original signal and noise. The researchers solved this by introducing a new type of modulation – called chirp spread spectrum – into its backscatter design. Spreading reflected signals across multiple frequencies allowed the team to achieve greater sensitives and decode backscattered signals across greater distances.

The research seen in this paper, was presented at UbiComp 2017.