measure relative distance between devices through wifi or bluetooth (COVID19 application)

[aleskeyfedorovich]

In order to help my company restarting its production I'm thinking of making wearable devices that checks if there is any other device within say 1.5 meters: in that case devices produce an alarm sound.

Constraints are:
* easy and fast to develop and produce some hundreds devices
* assess if any other device is within say 1.5 meters with 0.25 uncertainty
* indoor usage
* many other devices in the same room
* wearable form factor (on ankle or wrist)

My idea is to use a plain esp32 with a battery.
I plan to measure distances through Bluetooth or Wifi: my idea is actually not to measure exactly the distance between devices (from my googling this is not easy) but to reduce power and if need isolate devices till Bluetooth or wifi range drops to the desired distance (approx 1.5 meters). Then checking if any other device is within that distance is as easy as performing a scan.

Anyone ever tried something similar or think this is feasible or not? Any better solution possibily with micropython?

[danielm]

Distance estimation can be done using RSSI of received BLE advertisments from other devices.

I think there are some hackable smart-watch or smart-bands available on the market which are based on nRF52. This platform can run MicroPython as well. In that case you would not need to develop custom hardware.

Your use-case would require simultaneous BLE advertising and scanning - not sure if this is possible. Also you should consider power consumption aspects of continuous scanning.

[rcolistete]

Distance estimation from RSSI depends on the external environment (geometry, obstacles, type of materials of the surfaces, etc), so the same RSSI can indicate 2 m or 20 m :

THE INVENTORS OF BLUETOOTH SAY THERE COULD BE PROBLEMS USING THEIR TECH FOR CORONAVIRUS CONTACT TRACING
Sam Biddle - May 5 2020, 7:00 a.m.
https://theintercept.com/2020/05/05/cor ... t-tracing/