The system combines a router with custom sensors that harvest electricity from radio waves.
“The second piece, the access point, there we actually developed a custom solution on it, just a software modification that would enable the access point to act both as a good power delivery source and, simultaneously, also as a good Wi-Fi router.”
In other words, it achieves power over Wi-Fi in a way that both works with pre-existing hardware, and doesn’t interfere with your Internet connection.
As for Wi-Fi interference, there’s a hard cap on how much output of any kind your router can manage at once, sort of like how putting more ketchup on a hot dog leaves less room for mustard. But the UW team came up with a clever workaround to make sure neither charging nor connectivity goes sideways.
“If we wanted to just blast as much power as we possibly can, that would kill your Wi-Fi, because you’d have power on the channel all the time,” explains Bryce Kellogg, another researcher on the project. “We optimized the router so that we can deliver what seems like, to the sensor, constant power without impacting your Wi-Fi too much. Instead of having continuous power on one of your Wi-Fi channels, we split it among your three non-overlapping Wi-Fi channels. That allows us to deliver about the same amount of power without impacting any one channel very much.”
I very much look forward to the day when you go to a wifi hotspot both to charge your device and browse the web.
The UW team has already installed functional systems in six Seattle-area homes, using Asus RT-AC68U routers outfitted with custom code. It’s worth noting both that the router model they used is several years old, and ultimately inconsequential. It could just as easily be the router in your office right now.
“The work we’ve published, you could think of it as the first proof of concept,” says Talla. “But it’s by no means the optimal solution. We’re actively working to make it better.”