Author Topic: Bluetooth Low Energy is unsuitable for COVID-19 contact tracing, say inventors  (Read 9146 times)

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Offline cdevTopic starter

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There is a whole body of new technology that is attempting to make it easy for autonomous vehicles and robots to navigate inside of buildings. Its not something that a cell phone can do reliably yet. (although they are working on it quite a bit) The CPUs and GPUs on small computers arent powerful enough. If they used a combination of inddor beacons and visual cues and GPS and inertial sensors and maybe autio becons in phones - they might be able to do it but that would (if it worked) eat up battery like crazy.


Actually, its my understanding that the risk of catching coronavirus outdoors is very very much reduced from indoors. Most buildings are not well ventilated this is the real cause of their being dangerous when people in them have infectious respiratory diseases.

I think universal healthcare and sick leave (so people dont go to work when they get sick, and then seek treatment) and other comon sense things, are what they should be concentrating on.
Adequate ventilation, especially if they intend to switch people to electric heating (from natural gas) will mean much higher energy costs in the winter, although they could reduce a lot of that cost with heat exchangers, a good retrofit. They might recoup costs on savings on air conditioning.

They should also install UVC fixtures in places like classrooms where people congregate during the day, and then turn them on at night to disinfect surfaces. Also some surfaces can retain viable virus for extended periods of time. (more than a week is conservative estimate, they tested a suite of rooms on one of those cruise ships17 days after all the crew and passengers had left and there was still lots of detectable COVID-19 on surfaces) The best surface for antiviral activity is copper, plastic is very bad and viruses can last for many days, perhaps even as long as two weeks on plastics. So, it might be smart to analyze what objects people touched the most and transmitted viruses (dorknobs would be up there) and replaced them with copper sheathed versions.

Unfortunately, plastic is all around us.

« Last Edit: May 12, 2020, 10:45:36 pm by cdev »
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Offline SilverSolder

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The best solution has to be some kind of biotech - a vaccine or a treatment that works reliably without unacceptable side effects.

 

Offline cdevTopic starter

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Thats what we're all hoping for.


The best solution has to be some kind of biotech - a vaccine or a treatment that works reliably without unacceptable side effects.
"What the large print giveth, the small print taketh away."
 

Offline cdevTopic starter

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Fabric dampens the volume quite a bit,

If they coated particularly problematic elements in indoor environments with RF damping foam, they might be able to get significantly better accuracy with the RF location. At least it might mitigate the false positives somewhat, maybe.

There are some cool visualizations out there of 2400 MHz RF bouncing around showing how its possible, sort of, to use wifi signals in a sort of passive radar to "look through walls"  That seems to me to be a big potential source of problems. Suppose you are separated from somebody with COVID-19 by a wall. They may be just a meter away from you but there is little risk of contagion because there is a wall presumably with no vents through it.

A dumb BTLE and GPS system even if perfectly accurate is never going to realize that you're safe and is going to flag you as a potential sickie for the "contact" that never occurred. The only way around that will be to draw a line slightly less than two meters away from every exterior wall in your space and never go into that "border zone".

Note that this kind of data is also going to be used to price health insurance. Thats probably one of the real reasons they want it.

No doubt this research is paid for with DOD/MOD funding.

Well at least they arent implanting hidden microphones into cats any more.
« Last Edit: May 12, 2020, 11:01:40 pm by cdev »
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Offline Someone

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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.
You might have missed the circus going on at the moment with the apps already rolled out.. the messaging has been very carefully curated/controlled to say happy things but carefully framed to avoid denying the privacy issues. Political doublespeak is working on most of the population and they just don't notice.
 

Offline cdevTopic starter

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The places where accuracy matters the most will be impossible to get GPS signals into If there is a so called leaky coax system (used for cell phone operation) they tend to create strange anomalies on GPS tracks. (I know because I often carry a GPS logger when I am in the city just so I can see visually later where Ive been.)

 Sometimes when I go into a tunnel it does pick up signal for quite a ways. But the location during that section of trace is never right, its bizarrely wrong.

I have never been on the London Tube but it appears to be exactly like NYC subways in terms of people being close together.  The kind of places where "social distancing" is impossible. The worst areas are the ones where people are moving very fast in both directions. (curious, do people in London obey UK traffic rules, "driving" on the left hand instead of the right, when walking??) Here the lanes for walking mimic the cars, so youre always walking on the right and the opposite dirction is on your left.

Anyway, in Manhattan, especially in major subway transit points, there are huge numbers of people all walking through the same spaces, where its impossible to stay two meters apart.. (See "Koyaanisqatsi" by Godfrey Reggio, a film from 1982 of fast motion photography for some great scenes taken in NYC.) During the morning or evening rush hour (both of which are actually two or three hours long) there are lots of people in places like multilevel stairways (some people out of breath and breathing deeply) and six way intersections, and long two way escalators underground. You cant adjust your position once you get on the escalator if somebody starts coughing, during rush hour there are people very close together. They have a small space in the middle between the up and down escalatators and each side's stairway is narrow, maybe 1M wide. These escalators are very long and whatever ventilation they have is of the "air blows in one end and out the other" variety. Thats no longer adequate.

That is a problem. they need more fresh ventilation in the middle of those long stairways and similar spaces. Instead of focusing their efforts on half-baked schemes that dont seem destined to work for their intended purpose, they should concentrate on the actual problem, the epidemic and mundane seeming problems like ventilation. Also they should stagger arrival times for workers. To spread the commute hours out so the density is reduced.

Specifically, making being in tight spaces and public transit, particularly, safer.

Because the main reason cities like New York and London work as well as they do is GREAT public transit.

People all getting private cars is a non starter, its just plainly impossible. Also many people dont like cell phones, and either dont have one or if they do, don't use it as these people who seem glued to cell phones do. I personally prefer reading when I am away from computers, things like physical newspapers and books. And I'm sure I am not the only one.


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!

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.
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.

Its technically impossible to get what they say they are trying to do, isnt that what the code comments seem to be saying?

GPS does not work in subways - at all. Not at al, nor does it work in most city buildings, at all. Outdoors, relative to indoors, there is practically no danger, maybe not no danger, but it is much much reduced. Even under the best of conditions, the only place GPS is going to be accurate is outdoors.   Indoors, because the GPS antenna in a phone (typically a chip antenna on the PCB) is never going to be oriented as it should be, its always going to be next to this big thing that easts up most of the signals. (your body) So the location it calculates jumps around a lot unless you take care to make ot accurate. (I put my little tracking box in the "cd" pocket in my backpack and go to great lengths to check it that it hasnt shifted so the top is facing the sky. And when I go down in the subway I know from experience the GPS trace is going to be useless and vanish so I turn it off so as not to create a big jag between when I go into the subway and come out. Instead I get individual GPX files. (cheap non-RTK GPS logging produces various kinds of files, mine produces a "GPX file" the way its set up now. I use a program called GPSBabel to turn those traces into KML files.
« Last Edit: May 13, 2020, 05:26:47 pm by cdev »
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Offline Red Squirrel

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Not a fan at all of this surveillance but it's inevitable.  They'll do it "for our safety" but once the tech is there they'll just keep using it. 

In Toronto  they are getting people to install a tracking app if they want to use the transit and such.  (just saw a quick blurb on news so don't know the full details, maybe it has not happened yet and it's just a suggestion)

I mean, I kinda get it, and on the surface it does seem like a good idea, especially if it can also be used to quickly alert anyone that has been in close contact with someone who tested positive, but it still gives me really bad vibes.  Almost "mark of the beast" style.   

What really needs to happen is to move towards work from home being the standard instead of a niche thing.  That would greatly reduce the amount of traffic.  Not only would it be better for the environment it would be better for us too.   Especially in big cities where people have like a 1 hour commute.  You could not pay me enough for that.  I sometimes take it for granted that I live in a small city and work is like 10 minutes away from my house. 
 
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Offline cdevTopic starter

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It depends on the employer. Sometimes being at work is really fun.

I think the general plan/trend is one where there are a lot fewer jobs and a lot of them are outsourced or automated. The outsourced jobs will probably eventually be on the other side of the world. Quite possibly being done at night by the people there. (India is "The Back Office of the World" now, you know)  But the surveillance will remain because people wont have anyplace else to go but they still will be expected to move elsewhere if they have no money. .

This is what happens when you have a big problem with groupthink and nobody has the common sense to call them out on it. "hey, this doesn't make sense" Like should have occurred in the Challenger disaster. 

Not a fan at all of this surveillance but it's inevitable.  They'll do it "for our safety" but once the tech is there they'll just keep using it. 

In Toronto  they are getting people to install a tracking app if they want to use the transit and such.

What about people who dont have cell phones or whose cell phones dont support this "app"?
(Which it seems is unlikely to actually work)
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Offline Red Squirrel

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What really needs to happen is to move towards work from home being the standard instead of a niche thing.

Think twice. If WFH becomes the new norm, not only manufacturing, but engineering will also be virtually 100% taken by Chinese and Indians.

If a job can be done by more potent engineers at home at half the price with zero benefits, and they payment can be in bitcoin or other untraceable, untaxable means, then literally "you" are in big trouble.

Yeah that's a good point, and even now might be too late.  All these people working from home temporarily might light a bulb over the CEOs' heads.  "If this job can be done from anywhere..."    What really needs to be stopped is this whole globalization thing.  Companies should be required to keep at least a certain percentage like say, 80% of work work within the country.   That's never going to happen though.
 

Offline Electro Detective

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Don't people already look ridiculous enough walking about with their heads stuck in phone apps 24/7

without another app that will waste their time till they realize it's not their phone at fault, but a dud app  :palm:

 

Offline Syntax Error

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For those playing at home, here is how the British boffins simulated a 'real world' BLE environment at R.A.F. Leeming this April.

(uk) NHS COVID App Closed Beta Test Data Gathering Plan

https://github.com/nhsx/COVID-19-app-Documentation-BETA/blob/master/Beta%20Test%20Staged%20Exercise.pdf

Not so sure this is a real world scenario for a public transit system, supermarket or campus, but at least they were  using some kind of scientific method.

Battlefield tested: https://www.raf.mod.uk/news/articles/rafs-digital-airbase-tests-covid-19-tracking-app/
« Last Edit: May 13, 2020, 09:39:20 am by Syntax Error »
 

Offline SilverSolder

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[...]
 Companies should be required to keep at least a certain percentage like say, 80% of work work within the country.   That's never going to happen though.

We are all divided into groups called "countries" because it is human nature to think of our "country" as a kind of extended family, that we want to take care of and that we expect to take care of us too. 

It becomes increasingly difficult make the emotional connection, beginning with your own actual family (high divorce rates etc.)...  your neighbourhood...  town... state/province... country...  continent...  planet.  Arguably, the higher up you make it in that pyramid, the better person you become?
 

Online tszaboo

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I did a test before for RSSI distance estimation. There was two dev boards, fixed location, fixed environment, pinging each other for hours, 2.4GHz. The RSSI values went anywhere from -52dBm to -40dBm, average is -45dBm (1.2m distance), bell curve distribution. And that with simple, unobstructed, well defined antennas, custom firmware, kept in place during the test, no humans around, no large metal surfaces. 6dB means double the distance.
Different phone manufacturers will used different bluetooth implementation, with different gain on the antenna, different margin to the +10dBm legal limit, different algorithm to save battery power. The phone antenna has directionality. This doesnt work, even in the best scenario.
« Last Edit: May 13, 2020, 12:51:27 pm by NANDBlog »
 
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Offline Marco

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Someone already had the ultrasonic idea and applied it.

https://www.novid.org/

They make a good point that it also solves another false positive problem with RF, sound doesn't go through barriers as easily.
 

Offline SiliconWizard

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Someone already had the ultrasonic idea and applied it.

https://www.novid.org/

They make a good point that it also solves another false positive problem with RF, sound doesn't go through barriers as easily.

Uh huh, but I always  find it interesting when people claim to reliably emit AND record ultrasounds on most mobile phones just using the existing hardware.
 

Offline Marco

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Near ultrasound is actually part of android compatibility test suite.

Knowing that should make it less interesting and more self evident.
 

Offline Syntax Error

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How about good old fashioned 1990's style IRD? We wear an IR transceiver on our facemasks.

Seriously though, BLE contact tracing apps are reliant on data exchange after a BLE connection has been made between two devices. In practical terms, kein problem in a low density environment with few people, but what about walking through a high density (high risk) place like a crowded metro station? Is there enough time for devices to advertise, connect, exchange, hang up and repeat, when you're walking as quick as you can through the 'danger zone'? How many devices get missed?

btw I came across this informative primer on BLE Advertising, which is the core technology for most contact tracing apps. https://www.argenox.com/library/bluetooth-low-energy/ble-advertising-primer/
« Last Edit: May 13, 2020, 04:49:56 pm by Syntax Error »
 
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Offline cdevTopic starter

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How about a system where people are totally in control that doesnt connect up to anybody or anything else that merely warns them when somebody else is too close with an audio alarm.

No surveillance state anything. Dumb electronics only. using sound TDOA and with no means of offloading data.
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Offline SparkyFX

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(Near) Ultrasound/Sonar would circumvent the problems with EM-reception field strength indication vs. physical contact, but most people carry their phone in pockets, introducing lots of noise and dampening, making a distance measurement hard. And all this effort is thwarted by someone sneezing into his hand and touching a doorknob, or not for elderly or young kids.

This is why I think the approach to trace contacts and possible infections via smartphone is ill-fated, i doubt there is an advantage over the regional physical distancing rules indicated by test/amount of newly infected people. It would take time to crunch the data, make the decision and will probably affect as many people as to locally check by infection rate if measures for a whole area are needed. Both methods just follow what this virus is doing, but given the long incubation time only preventative methods could make an impact.

Psychologically i think rules work best when everyone is required to e.g. wear face masks, keep distance and such, not singling out subgroups.
« Last Edit: May 13, 2020, 07:25:39 pm by SparkyFX »
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Offline cdevTopic starter

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Quotas like that are being disputed as we speak, and indeed,  if India wins its case against the US the changes are binding on the entire world. Many businesses may lay off their old expensive employees and rush to get the newer cheaper ones. This may be why governments are suddenly so keen to keep track on people? 

the new arrangements are not being fair to anybody when they make the wages so low. (Even if now they are 'legal')

Companies should be required to keep at least a certain percentage like say, 80% of work work within the country.

Said from an old fashioned Westerner who failed to compete in, or should I say, with, the brave new world.

« Last Edit: May 13, 2020, 08:43:16 pm by cdev »
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Offline cdevTopic starter

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How about good old fashioned 1990's style IRD? We wear an IR transceiver on our facemasks.

Seriously though, BLE contact tracing apps are reliant on data exchange after a BLE connection has been made between two devices. In practical terms, kein problem in a low density environment with few people, but what about walking through a high density (high risk) place like a crowded metro station? Is there enough time for devices to advertise, connect, exchange, hang up and repeat, when you're walking as quick as you can through the 'danger zone'? How many devices get missed?

btw I came across this informative primer on BLE Advertising, which is the core technology for most contact tracing apps. https://www.argenox.com/library/bluetooth-low-energy/ble-advertising-primer/

It looks like battery life may become an issue. How much, its hard to say.
"What the large print giveth, the small print taketh away."
 

Offline SiliconWizard

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(Near) Ultrasound/Sonar would circumvent the problems with EM-reception field strength indication vs. physical contact, but most people carry their phone in pockets, introducing lots of noise and dampening, making a distance measurement hard

I would personally not expect it to really be of any use outside of ideal conditions indeed.
 

Offline Syntax Error

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It looks like battery life may become an issue. How much, its hard to say.

Maybe a moot point for many Android smart phone owners as the Covid tracking apps only run on the latest edition of the operating system. Globally ~60% of Android phones are not up to version 6.0, me included. 6.0 is baseline for the Australian and the UK Beta apps. On the other hand, Apple iOS offerings at 10.0 would only exclude some 5% of users. However, iOS does BLE in it's own unique 'designed in California' way.

We should also take note of the success of South Korea at fighting the spread of the virus as their contact tracking is a mix of GPS, cell tower triangulation and bank transaction analysis. Basically, throw away your electronics and pay cash.
 

Offline Someone

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(Near) Ultrasound/Sonar would circumvent the problems with EM-reception field strength indication vs. physical contact, but most people carry their phone in pockets, introducing lots of noise and dampening, making a distance measurement hard.
There are a non-trivial number of people who carry their phones in a bag. Pocket locations/sizes/availability don't always match phones. Bluetooth was the best of the options already in place and ready to use.

This is why I think the approach to trace contacts and possible infections via smartphone is ill-fated, i doubt there is an advantage over the regional physical distancing rules indicated by test/amount of newly infected people. It would take time to crunch the data, make the decision and will probably affect as many people as to locally check by infection rate if measures for a whole area are needed. Both methods just follow what this virus is doing, but given the long incubation time only preventative methods could make an impact.
There are good motivations for digitally enhanced contact tracing, partly that peoples memory is really unreliable. Being able to reliably know where someone was during the period they might have been infectious is valuable alone. But when that location information is then cross-referenced against other people a so they are notified with little effort on their part, its a possible game changer.

The main justification for such an automated system is that you can reduce broad "sledgehammer" measures like arbitrary travel constraints (border straddling towns for instance. Instead focus on just the people who have higher likelihood of having caught the virus. We've already seen this sort of thing by applying additional restrictions to travellers coming across borders. That has its problems, trying to convince a subset of the community that they need to undertake an individual quarantine/isolation while 99% of people continue with their daily lives has been a hard sell already:
https://www.abc.net.au/news/2020-04-15/man-jailed-for-breaching-coronavirus-quarantine-by-leaving-hotel/12149908

Imagine instead of being arbitrarily quarantined, travellers were only segregated if they were within [arbitrary measure of infectious distance/trave] of confirmed cases. And such restrictions could be applied to individuals retroactively, after discovering new applicable cases. That could be a big win for the vast majority of the population. Keep up the physical distancing etc, and people who do that will be less likely to have restrictions placed on them individually. Its handing back control to the individuals, but both sides need to have a trusted system in the middle to mediate it.
 

Offline cdevTopic starter

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But when people are outside, there is virtually no chance of infection, and as I was trying to explain, when people are indoors the locations reported and saved to logs are invariably wrong. They are not accurate indoors. Most dangerous encounters are not in RF transparent buildings. They are in big buildings (work) or underground, neither of which is a good environment for location capture. Dont believe me? Look into "SLAM" on github.
« Last Edit: May 14, 2020, 12:01:18 am by cdev »
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