[g_p]

Interestingly, and purely anecdotally (so not designed to replace the study itself), I've been experimenting with the RSSI being reported by the NHSx app through the debug menu. At least based on what I've seen so far on my devices (and noting the NHSx model considers device model ID to allow for antenna variations going forwards), there was a ~25 dBm change in signal strength (from -32 to around -57) between phones being sat together, and through a wall yet still close.

Clearly this is going to vary depending on building construction, but I suspect the most relevant factor will be determining whether a contact event takes place through a wall or not. The real question is whether or not this can be modelled into the app and it proves reproducible.

My understanding is there's no claimed intention to measure the 2m distance, and this is accepted as a known factor, at least for now. I suspect in an indoor setting the initial challenge will be preventing spurious triggers from indoor use (although arguably if people are that close they might live in an apartment block, and they could have been exposed through contact with door handles or lift buttons etc). But once people are outside more and returning to normality, all bets seem to be off - I imagine a lot of false positives.

My instinct would be that contact exposure duration will become more of a factor than the RSSI, or that a min/max/median/standard deviation might be captured in addition to a "raw" RSSI, to perhaps get a better idea. If the RSSI never goes "above" -60 (noting it's a negative number) then that's not likely to be a hugely close contact event.

[crushthecurve]

It would be interesting to model two humans standing close to each other, and each phone on the closest side of the pairing, then on the opposite side, with the phones rotated at every angle.

Having to traverse two human bodies will create significant variation, and antenna angle will also add to that.

As mentioned in the video [1] this can make people look much further away, making it rather useless at estimating real distance.

[1] https://www.youtube.com/watch?v=KgKbllhgESc&feature=youtu.be...

[7952]

I wonder if WiFi connection information could help. Being on different networks would suggest greater social distance.

[g_p]

During current "distance under all circumstances, stay at home", that is likely going to be true (modulo people using multi-AP setups that aren't meshed under one SSID, assuming you use SSID, or who use 2.4 and 5 GHz SSIDs).

Going forward though, I imagine that as restrictions loosen, the usefulness of WiFI connections would drop significantly, as people aren't always at home. It would also not really help in the workplace, assuming a large campus WiFi setup, since everyone would probably be joined to the same network anyway.

The challenge would be privacy - you'd have to send some kind of information (or unique derivative) of the BSSID/SSID, which would introduce some privacy impact too. At that point, assuming you got access to the hashed SSID/BSSIDs, someone like Google with a street view dataset of AP MAC addresses could "enrich" the anonymised dataset with "ordinary location".