Researchers eliminate need for external power in Wi-Fi connectivity system
August 5, 2014
One of the advantages of the "connected world" is that myriad different devices can interact with each other over Wi-Fi to exchange data, control equipment, and generally lay the foundations of the Internet of Things of the not-too-distant future. Unfortunately, on the downside, all of the Wi-Fi connections need power to operate, and this severely restricts the pervasiveness of this technology. However, researchers at the University of Washington have developed a system that they say eliminates the need for power supplies for these connections by using what is known as radio frequency (RF) backscatter technology.
The researchers claim that their prototype technology uses radio signals as a source of power and incorporates this in existing Wi-Fi infrastructure to deliver connections to the internet for devices. The power is sourced via RF Wi-Fi backscatter that exists as reflected energy whenever a wireless router or other radio frequency device transmits (similar to the technology found in RF ID tags, where the circuit remains dormant until radio signals on the device’s antenna create an induced voltage in the circuit to power the device).
In effect, the system scavenges power from the wireless transmitting devices around it to power battery-free devices and connect them to the Internet. Previous technological challenges in providing such Wi-Fi connectivity was that even low-power Wi-Fi consumes three to four times more power than can generally be wrought from Wi-Fi backscatter signals.
To solve this problem, the team claims to have developed its own RF tag prototypes that have ultra-low power consumption. With in-built antennas and circuits that are able to communicate with Wi-Fi-enabled devices such as laptops or smartphones, the team says that they are able to maintain this connection with minimal power.
"If [the] Internet of Things devices are going to take off, we must provide connectivity to the potentially billions of battery-free devices that will be embedded in everyday objects," said Shyam Gollakota, a UW assistant professor of computer science and engineering. "We now have the ability to enable Wi-Fi connectivity for devices while consuming orders of magnitude less power than what Wi-Fi typically requires."
In essence, to save power and maximize efficiency, the UW team's tags operate by receiving Wi-Fi signals transmitted between the router and a connected device, such as a laptop. By either reflecting or not reflecting the Wi-Fi router transmitted RF energy, the tags then encode data accordingly, to minutely change the wireless signal. Other Wi-Fi-enabled devices then detect these minute changes and receive data from the tag.
"You might think, how could this possibly work when you have a low-power device making such a tiny change in the wireless signal?" co-author and UW associate professor Joshua Smith said. "But the point is, if you’re looking for specific patterns, you can find it among all the other Wi-Fi reflections in an environment."
The UW team’s work is premised upon previous investigations on ambient backscatter that demonstrated how low-energy requirement devices such as wearable technology could be powered by scavenging energy from the all-pervasive radio signals from TV transmitters, radio towers, and other RF sources that exist all around us. According to the UW engineers, this research enhances that capability to connect individual devices to the internet, which the team claims was not possible previously.
According to the UW team, the Wi-Fi backscatter tag it has developed has achieved a data communication rate of 1 kbps with a Wi-Fi device about 2 m (6.5 ft) distant. The researchers assert that they will attempt to increase the range tenfold and plan to launch a company based on their proprietary technology, with patents being filed to protect their intellectual property.
The team intends to publish the results at the SIGCOMM (Special Interest Group on Data Communication) annual conference this month in Chicago.
The short video below shows the technology being demonstrated in the lab.
Source: University of Washington