2 ms·
A good solution to that problem are UWB radios with timestamping (like the Decawave DW1000), which let you measure the time it takes for the signal to travel. Y
by jwr 8y ago
A good solution to that problem are UWB radios with timestamping (like the Decawave DW1000), which let you measure the time it takes for the signal to travel. You can then place physical limits on the proximity, rather than assuming that a strong radio signal means proximity.
Coupled with a cryptographic authentication protocol these solve the issue quite nicely.
- ghaff 8y agoIt looks like the chips are about $10 each. That's quantity 1 but it's also just the radio IC. It's not immediately obvious what the power draw would look like in an application like this as the sleep mode draws far less power than when it's operating. There is an open source project based on the chip. https://github.com/lab11/polypoint https://github.com/lab11/polypoint What I'd really like to be able to do is to wirelessly tether a Tile-like small long battery life device to a band (or watch) I wear with user configurable distance settings but it doesn't look like the tech is quite there today. UWB does seem to be the current approach you'd take though.