Researchers working at the University of Massachusetts Amherst (UMass Amhurst) have created a new type of radio technology that has the potential to dramatically extend battery life up to many hundreds of times in mobile devices by allowing them to automatically share battery power loads with other devices when communicating.

To create this new technology, researchers in the UMass Amhurst College of Information and Computer Sciences modified aspects of Bluetooth technology to allow it to operate as if the unit with the larger capacity battery was a radio-frequency identification (RFID) reader and the lower-powered device was a RFID tag. In other words, an asymmetrical form of communication where the reading device expends the most energy, while a tag merely responds when prompted, making the whole system very power-efficient.

Dubbed "Braidio" (for "Braid of radios", referring to their intertwined behavior), the new technology behaves like a standard Bluetooth radio and both devices operate at ordinary power levels when enough battery energy is available. However when energy levels are low, the smaller device operates like an RFID tag, effectively offloading energy use to the device with a larger battery. As such, when devices such as a smartwatch and a smartphone are fitted with Braidios, they are able to cooperatively proportion their energy share during communications.

"We take for granted the ability to offload storage and computation from our relatively limited personal computers to the resource-rich cloud," said professor Deepak Ganesan of UMass Amherst. "In the same vein, it makes sense that devices should also be able to offload how much power they consume for communication to devices that have more energy."

Professor Ganesan explains that, as the battery dimensions in portable devices is generally proportional to the size of the device, then the larger the device, the larger the battery. As such, a laptop battery is something like ten times bigger than that used in a smartphone, a hundred times greater in size than that used in a smartwatch, and around a thousand times bigger than the battery in a fitness tracker. The problem with all of this though, according to professor Ganesan, is that "the battery on your smart watch cannot survive longer by taking advantage of the higher battery level on your smartphone."

The new Bradio device, makes that ability possible by allowing smaller devices to transfer their communication energy requirements to larger devices nearby, effectively meaning that the system makes device size and battery consumption proportional to the size of all batteries in the loop.

According to UMass Amhurst graduate student Pan Hu, test results have shown that when a a small battery-powered device is communicating with a larger battery device, the Braidio technology allows approximately 400 times longer battery life than when using standard Bluetooth.

"To be clear, our results only cover the cost of communication or transmitting data," said Pan Hu. "If a radio is transmitting from a camera that consumes hundreds of milliwatts while using its sensor, clearly the sensors may dominate total power consumption and reduce the benefits of optimizing the radio."

Built using simple, readily-available components, the UMass AMhurst team designed the radio frequency front end of its Bradios to operate in various transmission and reception modes while only using power similar to the levels consumed by Bluetooth radio. To achieve power-proportional communication without sacrificing data transmission throughput, the researchers also devised a set of algorithms to oversee the energy levels at the transmitter and receiver and switch between high and low power modes on the fly.

Professor Ganesan believes that Braidio technology may influence new approaches in the design of mobile devices and wearables. "Wearable devices are often bulky due to large batteries needed for adequate battery life," said professor Ganesan. "Perhaps such energy offload techniques can reverse this trend and enable thinner and lighter devices."

Still in the prototype stage, the UMass Amhurst researchers believe that further optimization will make Braidio smaller and more efficient so that it would be much more suitable to mass-market needs and commercial production.

The results of this research were recently presented at the Association for Computing Machinery's special interest group on data communication (SIGCOMM) conference in Florianópolis, Brazil.