Apple Inc.’s AirTag

Klaus · wrote on 21 Apr 2021, 11:51

@klaus said in Apple Inc.’s AirTag:

How do they know the direction from which the signal came?

My understanding is that it's the U1 chip in the iPhone 11 and 12.

Maybe, but if you have just an antenna and you receive a signal, you have no clue where the signal comes from. One would need a directional antenna and a rotation mechanism, somewhat similar to radar.

mark · 21 Apr 2021, 13:05

I predict failure in the marketplace for this POS.

Axtremus · 21 Apr 2021, 13:45

Don’t know how Apple does this exactly, but maybe you can get some idea about what is possible from a paper like this: https://www.mdpi.com/1424-8220/19/20/4466

Assuming you have access to large troves of academic research publications, search for “single channel ultra wide band direction finding.”

I kind of zeroed in on “single channel” because I don’t know how many UWB antennae Apple puts in an iPhone. So for the worst case I assume one antenna.

I further speculate that in spaces where there are multiple Apple devices present (iPhones, iPads, Macs, HomePods, etc.), when there are multiple such devices are UWB capable, Apple can treat them as a distributed antenna array and deploy location/directional finding algorithms that take advantage of multiple antennae. This can also partially answer the question of why using a centralized server.

George K · 21 Apr 2021, 13:27

@mark said in Apple Inc.’s AirTag:

I predict failure in the marketplace for this POS.

Tell that to the folks at Tile.

Axtremus · 21 Apr 2021, 13:08

@mark said in Apple Inc.’s AirTag:

I predict failure in the marketplace for this POS.

Entirely possible ... don’t know how well something like this will perform in real life yet. Might turn out like the Apple Watch’s EKG function where medical professionals like George would look at it and laugh.

George K · wrote on 21 Apr 2021, 13:08

@axtremus said in Apple Inc.’s AirTag:

EKG function where medical professionals like George would look at it and laugh

Actually, it's very good for what it does. Detect rhythm and nothing else. It's functionally the same as the KardiaMobile device you see advertised. Probably (but perhaps could) won't detect a heart attack, but it'll detect all kinds of nasty arrhythmias.

mark · 21 Apr 2021, 13:39

@george-k said in Apple Inc.’s AirTag:

@mark said in Apple Inc.’s AirTag:

I predict failure in the marketplace for this POS.

Tell that to the folks at Tile.

Do you own a Tile? Do you know people who do?

George K · M mark 21 Apr 2021, 13:27

@mark said in Apple Inc.’s AirTag:

Do you own a Tile?

Nope. I tend to not lose things.

Do you know people who do?

D3 has about 5 of them. She loves them.

D3 and D4 have Apple watches as well. When you have a 2 year old running around, and you put your phone down, the ability to "ping" your phone from the watch is very useful.

Klaus · wrote on 21 Apr 2021, 13:45

@axtremus said in Apple Inc.’s AirTag:

Don’t know how Apple does this exactly, but maybe you can get some idea about what is possible from a paper like this: https://www.mdpi.com/1424-8220/19/20/4466

Assuming you have access to large troves of academic research publications, search for “single channel ultra wide band direction finding.”

I kind of zeroed in on “single channel” because I don’t know how many UWB antennae Apple puts in an iPhone. So for the worst case I assume one antenna.

I further speculate that in spaces where there are multiple Apple devices present (iPhones, iPads, Macs, HomePods, etc.), when there are multiple such devices are UWB capable, Apple can treat them as a distributed antenna array and deploy location/directional finding algorithms that take advantage of multiple antennae. This can also partially answer the question of why using a centralized server.

That's interesting.

The way I understand it is that the device, such as the AirTag, sends an impulse and then the receiver receives the impulse multiple times - once from the straight line path, then from reflections. The angle can then somehow be estimated from the strength and delays between the received signals? But I completely fail to understand how the "somehow" can work. How can you ever get a direction vector out of this?

In that particular paper, they seem to require measurements within a room (by robots or something) to get a kind of profile, that they can feed into a neural network for predicting direction from impulse responses.

But that's not how the AirTag can work, because obviously you won't use robots to get a profile of all the rooms you work in.

But the report mentions that other methods include the usage of multiple antennas and, according to the report, it seems to be standard to have more than one antenna in a device. I can see how that works with two antennas. Maybe that's how AirTag works?

George K · 21 Apr 2021, 15:09

Accessory:

https://www.apple.com/shop/product/MX8A2AM/A/airtag-hermès-luggage-tag

Mik · M mark 21 Apr 2021, 13:27

@mark said in Apple Inc.’s AirTag:

@george-k said in Apple Inc.’s AirTag:

@mark said in Apple Inc.’s AirTag:

I predict failure in the marketplace for this POS.

Tell that to the folks at Tile.

Do you own a Tile? Do you know people who do?

Ayup. I bought them for MFR who was continually misplacing her keys. She never really got the hang of using it. Technophobia.

Mik · 25 Apr 2021, 12:39

@george-k said in Apple Inc.’s AirTag:

Accessory:

https://www.apple.com/shop/product/MX8A2AM/A/airtag-hermès-luggage-tag

$449?!?!?! I could buy the luggage and everything in it for less!

Klaus · wrote on 21 Apr 2021, 15:10

@george-k said in Apple Inc.’s AirTag:

Accessory:

https://www.apple.com/shop/product/MX8A2AM/A/airtag-hermès-luggage-tag

If ever there was a proper usage for the term "lolwut", this is it.

Horace · wrote on 21 Apr 2021, 15:45

Looks like a fantastic product, thanks for posting about it, Ax. I'll get some for my mom and my wife and myself. But they're selling like hotcakes and not currently available from apple's website. Apparently the word is out about this extraordinarily useful product.

George K · wrote on 23 Apr 2021, 12:24

https://www.engadget.com/apple-airtags-trackers-first-look-hands-on-130036848.html

kluurs · wrote on 23 Apr 2021, 14:36

I ordered one. Sounds like it takes a while. Clearly, they could give away the tag as they make their profit on the little holder.

Axtremus · 27 Apr 2021, 11:45

One thing I want to use it for is to put one in each car so I can find my own car in a big parking lot after I shop. Not all sure if that will work, though. Apple, Inc. seems to have goofy rules about precision/directional finding not working unless you (your iPhone?) are "close enough "to a tag, and that if you (your iPhone?) move "far enough" away from the tag it might beep to help others be aware of unwanted tags. Apple so far has not tell you the thresholds for what constitute "close enough" or "far enough," and even then I am not sure those thresholds would work for the parking lot at a shopping mall/plaza use case.

Take Costco for example, the parking lot and the store itself are HUGE, so it's very likely I have to walk pretty far away from the store entrance and walk pretty far away from the car. Will the Apple AirTag work well in that scenario? For now, I am not confident that it will.

Hey @Horace, go do some user experience testing with AirTags in some big box store's parking lot and tell us how well the AirTag can help you find your car in the parking lot. Thanks!