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Bluetooth Low Energy is unsuitable for COVID-19 contact tracing, say inventors
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Marco:
How about using BLE for a conservative estimate and then using 20-22 kHz audio for ranging when people are near?

Or maybe even just use audio period. Autocorrelation of a chirp signal don't care about multipathing.
jogri:

--- Quote from: Marco on May 12, 2020, 09:09:37 pm ---How about using BLE for a conservative estimate and then using 20-22 kHz audio for ranging when people are near?

Or maybe even just use audio period. Autocorrelation of a chirp signal don't care about multipathing.

--- End quote ---

The "RSSI" would be absolutely terrible as soon as you put your phone into your pocket. Plus, having a microphone that is listening all the time is actually worse than having GPS running 24/7 when it comes to privacy. You need at least 60% of the population to use this app, if you have to admit that you (the government) have basically created a bug that is spying on people when they use the app no one will use it.
Marco:

--- Quote from: jogri on May 12, 2020, 09:21:13 pm ---The "RSSI" would be absolutely terrible as soon as you put your phone into your pocket.

--- End quote ---
Autocorrelation with a chirp doesn't get you RSSI, it gets you multipath insensitive time of flight for the closest path. As for SNR, repetition, repetition, repetition. (Ping-pong ranging makes it a little more complex than that, but it's just audio ... almost nothing in audio is processor intensive any more by today's standards.)

--- Quote ---Plus, having a microphone that is listening all the time is actually worse than having GPS running 24/7 when it comes to privacy.
--- End quote ---
No it's not.

With an open source app and tons of researchers verifying the integrity of the appstore version you can be certain it doesn't do anything with the data except ranging and identification and that that data does not leave the phone.

With GPS data in a central database however no such verification is possible, you're reliant on trust of the database maintainers.
Zero999:

--- Quote from: Buriedcode on May 12, 2020, 08:51:32 pm ---
--- Quote from: cdev on May 12, 2020, 08:18:07 pm ---Accuracy matters a great deal. IMHO.

If they are using a technology that cannot be accurate enough according to its own developers, maybe its not the right technology!

--- End quote ---

The only alternative would be to use absolute location - GPS - which, as pointed out raises obvious privacy concerns.  Also, I don't believe Apple allow for continuous location tracking on any app.  I'm sure there will be a version that uses location tracking, but users would have to opt in, and I'm sure the powers-that-be are pretty hesitant because of an inevitable backlash.

The phrase "accurate enough" implies there is a known level of accuracy desired.  There isn't.  Even if somehow current smart phones had the ability to measure proximity to other phones with mm accuracy - at what point would it flag up "possible contagion contact" ?  Would it be a sliding scale?  Would that only be inside enclosed spaces?  All the app really needs to do (for now) is to know whether or not the phones owner has been tested, and the result, and how often they have come into reasonably close proximity to other users that aren't in their household.  I'm sure the devs working on this aren't making any kind of claims about efficacy - right now they're busy ironing out bugs and it will be an on-going experiment.

--- End quote ---
Yes and I doubt the developers themselves are epidemiologists. Any small degree of accuracy is better than the current situation. Even if it errs on the side of caution, generating some false positives, it will still mean fewer people, than now, will need to be isolated to control the spread.
jogri:
When i said "RSSI" i meant loudness of the recieved signal (that's why it is in quotation marks). Fabric dampens the volume quite a bit, and combined with the fact that the microphones were never designed to be used at this frequency range the SNR will be abysmal.

Btw, good luck telling the general pulic that an app that is developed by the government and will most likely be verified by researcher that are working for the government (universities etc) can be trusted... You just need one guy telling everyone that said app is used to spy on people via the microphones. And you have to confirm that "yes, the app is constantly listening via the microphone BUT...". I don't think it would matter what comes after the "but", as soon as you say it the damage is done.
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