Bluetooth Detection Range

The BBC has an article on Coronavirus: Why are there doubts over contact-tracing apps? It says:

But critics warn this kind of system would be imprecise since some phones detect signals from up to 30m (98ft) away without being able to determine the distance.

The BBC took this from information in a Wired article that says:

… but with Bluetooth being able to ping other phones within a 30-metre range, without precision, there’s an increased chance of the app alerting you to false positives of people who have never even come into contact with you

This isn’t correct and misunderstands how the Bluetooth signal is being used. Receiving devices, such as smartphones, don’t just see the beacon signal but also have a received signal strength (RSSI) that can be used to infer distance. Our post on testing if a beacon is working explains and shows this value in the nRF Connect app running on Android.

While not fake news, the BBC and Wired are providing incorrect information. In these times, in the rush and panic, too many things are being written that aren’t thoroughly researched.