The team has developed a new way of communicating that allows devices like brain implants, contact lenses, credit cards or small wearable electronics to interact with everyday devices such as smartphones and watches.
The new method is called "interscatter communication,” and it works by converting Bluetooth signals into Wi-Fi transmissions over the air. An interscatter device, such as a smart contact lens, can convert Bluetooth signals from other devices—like a smartwatch—into Wi-Fi transmissions that can be picked up by a smartphone—using only reflections.
"Wireless connectivity for implanted devices can transform how we manage chronic diseases," said Vikram Iyer, a UW electrical engineering doctoral student. "For example, a contact lens could monitor a diabetic's blood sugar level in tears and send notifications to the phone when the blood sugar level goes down."
Technologies like smart contact lenses and brain implants are at a disadvantage when it comes to sending data via traditional wireless transmission due to their size and location within the body.
But what the UW electrical engineers and computer scientists demonstrated was that these types of power-limited devices can actually “talk” to other devices using standard Wi-Fi communication. The system does not require any specialized equipment, and instead relies solely on mobile devices to generate Wi-Fi signals using 10,000 times less energy than ordinary methods.
"Instead of generating Wi-Fi signals on your own, our technology creates Wi-Fi by using Bluetooth transmissions from nearby mobile devices such as smartwatches," said Vamsi Talla, a recent UW doctoral graduate in electrical engineering, who is now a research associate in the Department of Computer Science and Engineering.
The process depends on a technique called backscatter, which allows devices to exchange information by reflecting existing signals, and which is how the team came up with the name “Interscatter.”
Interscatter communication uses the Bluetooth, Wi-Fi or ZigBee radios embedded in common mobile devices (smartphones, watches, laptops, tablets and headsets) to act as both sources and receivers for these reflected signals.
The team demonstrated how a smartwatch transmits a Bluetooth signal to a smart contact lens equipped with an antenna.
"Bluetooth devices randomize data transmissions using a process called scrambling," said Shyam Gollakota, assistant professor of computer science and engineering, who led the research. "We figured out a way to reverse-engineer this scrambling process to send out a single tone signal from Bluetooth-enabled devices, such as smartphones and watches, using a software app."
When it comes to backscattering, though, the process creates an unwanted mirror-image copy of the signal, which consumes more bandwidth and interferes with networks on the mirror-copy Wi-Fi channel. The UW team came up with a technique called "single sideband backscatter" to eliminate this.
"That means that we can use just as much bandwidth as a Wi-Fi network, and you can still have other Wi-Fi networks operate without interference," said co-author and electrical engineering doctoral student Bryce Kellogg.
In addition to the smart contact lens, the engineers created an implantable neural recording device that can communicate directly with smartphones and watches.
Not only does Interscatter enable Wi-Fi for these implanted devices, but it does so while only consuming tens of microwatts of power.
According to the researchers, the technology has other potential applications, such as smart credit cards. They developed credit card prototypes that communicate directly with each other by reflecting Bluetooth signals from a smartphone, paving the way for a future in which users can split a bill by just tapping their credit cards together.
"Providing the ability for these everyday objects like credit cards—in addition to implanted devices—to communicate with mobile devices can unleash the power of ubiquitous connectivity," said Gollakota.