Looks like a great proof of concept, but I wonder whether the off-the-shelf WiFi devices will need to support some sort of protocol to enable this to work? I didn't see anything in the video about how they specifically integrate with WiFi, but I'm assuming there will need to be some sort of broadcast and then response read. Either way, very interesting project from both a software and electronics point of view.
This particular work, requires forcing transmission of CTS-to- self to avoid transmission by nearby stations. The effect of the tag on the signal strength/ CSI can be measured at software level. Both enforcing the CT-to-Self and measuring the impact on CSI should be doable in software level and on the off the shelf APs. The downside of this method is low range, and low data rates, at Wavelite, we are leveraging the same backscattering concept, where we use off the shelf routers with no software modification, and using a separate device (a cellphone or laptop or router)as the receiver. Here is a link to a demo video: https://drive.google.com/file/d/1wprRR7LhPNwy07JjDlB0Hv804D7...
This is interesting. I wonder whether in the domestic apartment, the wifi signal carries most energy density (Watt/volume) or whether there are more fruitful bands to explore, such as
- 50Hz radiating power cables (especially heavy current like for the oven or water heater)
- socket transformators (the old ones, not thinking of switching power supplies as your smartphone charger has it)
- cellular networks (especially the waves emitted by mobile phones in the same room)
In principle, exploiting these signals is like operating solar cells but optimized for other frequencies in the electro-magnetic spectrum.
IIRC backscatter works by frequency pulling to a free channel, so for mains frequency the inductor would have to be huge.
DARPA was working on some low frequency tech which might be of aid though.
Wouldn’t this only work if the receiver has a low strength from the router, and so the backscatter device can use its antenna to “reflect” more signal to the receiver? What happens if the receiver already sees 100% signal strength from the router?
The backscatter node is not necessarily used for hopping purpose, since it is ultra low power in operation, it can be used for data transmission where life time is a bottleneck.
The authors of this original paper have been leading this work on backscatter and even have a long range backscatter system that gives ranges of a kilometer. They also have a startup commercializing backscatter.
