The coolest hack in here is definitely the way that the 4G base station can be (mostly uniquely) identified after the RF signal for a packet is run through an envelope detector through a low-pass filter, as opposed to the normal (and higher-power) method of using a high-frequency oscillator and a demodulation chain.
Ultra-low-power localization tag uses cellular signals [pdf]
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Re: Ultra-low-power localization tag uses cellular signals [pdf]
#12How are they able to achieve sub-100 meter accuracy? I might be missing something, but In my experience, collecting the cellular parameters is the easy part. The challenge is knowing where the cells actually are. You can ask Google's geolocation API, but that typically returns a fix with ~1000 meter accuracy if it returns a fix at all. These databases are curated based on GPS+cellular information from millions of pho…
FTA: Our localization approach combines open-source databases (OpenCellID [47], Mozilla Location Services [66], and CellMapper [12]) for PCI-to-coordinate mapping of cell towers with a trilateration technique based on relative signal strengths.
Interesting.
CellMapper, at least, is not even a little bit open source. It doesn't even have an API.
This leads me to wonder what other details that FA provides which might have been fabricated from thin air.
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#13Earlier quoted context omitted.
FTA: Our localization approach combines open-source databases (OpenCellID [47], Mozilla Location Services [66], and CellMapper [12]) for PCI-to-coordinate mapping of cell towers with a trilateration technique based on relative signal strengths.
Interesting. CellMapper, at least, is not even a little bit open source. It doesn't even have an API. This leads me to wonder what other details that FA provides which might have been fabricated from thin air.
If someone is focusing on extracting data for a small area, they can manually browse the CellMapper data. An API isn’t required for that—it’s a matter of accessing and analyzing what’s already available through the platform.
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#14How are they able to achieve sub-100 meter accuracy? I might be missing something, but In my experience, collecting the cellular parameters is the easy part. The challenge is knowing where the cells actually are. You can ask Google's geolocation API, but that typically returns a fix with ~1000 meter accuracy if it returns a fix at all. These databases are curated based on GPS+cellular information from millions of pho…
FTA: Our localization approach combines open-source databases (OpenCellID [47], Mozilla Location Services [66], and CellMapper [12]) for PCI-to-coordinate mapping of cell towers with a trilateration technique based on relative signal strengths.
That doesn't really answer the question. Those services basically work the same way as Google's geolocation API, but they're somehow able to magically get better accuracy.
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#15Cool. I want this for my cats, my kids, my keys and everything else. But I wonder: if millions of this are deployed, would this weaken cellular signals (by drawing power from it)?
Do you currently have tracker tags on those things? If not, why not? Multi-year lifetimes are already available with Tile (3 years), AirTag (>1 year), and Samsung's SmartTag 2 (700 days), using BLE detection instead of 4G detection. Millions of these would not degrade signal. A random bit of metal (like a quarter, as shown for scale) in between you an a 4G tower should have the same effect as one of these devices. Th…
> Do you currently have tracker tags on those things?
Yes. I have AirTags on my fur babbies, but if I were to need to use them I'd be hoping they came within range of a device to pick them up. Then, in FindMy app, I could see where the had been, but not where they are now to go get them. I would hope a system like this could give me a much more current location. Hopefully, I'll never need any of this.
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#16Earlier quoted context omitted.
Do you currently have tracker tags on those things? If not, why not? Multi-year lifetimes are already available with Tile (3 years), AirTag (>1 year), and Samsung's SmartTag 2 (700 days), using BLE detection instead of 4G detection. Millions of these would not degrade signal. A random bit of metal (like a quarter, as shown for scale) in between you an a 4G tower should have the same effect as one of these devices. Th…
Thanks. I miss-read it and thought it's energy harvesting from celular. I already have some trackers on important stuff (like keys and school bag of kids if they loose it in the bus). But for other use cases it's either too large (cats) or makes no sense to have too many because then I'd have to replace a battery every few weeks ("everything else").
> replace a battery every few weeks
make it easy on yourself and change them all on the same day like a clock reset day like the recommendation for your smoke detectors. bite the bullet and change change some early to get them on the same schedule. it's worth it for sanity
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#17Relevant Don't Get Distracted (2017) https://news.ycombinator.com/item?id=42388354
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#18Earlier quoted context omitted.
FTA: Our localization approach combines open-source databases (OpenCellID [47], Mozilla Location Services [66], and CellMapper [12]) for PCI-to-coordinate mapping of cell towers with a trilateration technique based on relative signal strengths.
That doesn't really answer the question. Those services basically work the same way as Google's geolocation API, but they're somehow able to magically get better accuracy.
Google's cellular geolocation implementation is probably unmaintained & all their focus is on WiFi+GPS+Fusion via SLAM.
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#19Cool. I want this for my cats, my kids, my keys and everything else. But I wonder: if millions of this are deployed, would this weaken cellular signals (by drawing power from it)?
The interaction of EM waves and their behavior is a long and complex topic to address here, however, keep in mind that the signal is sent out into void - what happens after emitting does not concern the emitter. Think of it as rain falling down, or water from the sprinkler. If you catch the droplets you ll cast a "shadow". Completely surrounding the emitter might create "Faraday" cage of sorts. However in reality in the droplet analogy, the EM waves curve around the buckets and leave the shadow. The reception of EM waves is a wave-cancellation process, but thats a deep rabbit hole..
Re: Ultra-low-power localization tag uses cellular signals [pdf]
#20Cute idea, works only in a very narrow range of scenarios, namely: dense urban without strong near-CW interferers: It has a sensitivity of -70dBm, so it misses >50dB of the bottom dynamic range, present typically in urban indoor and also in non-urban areas. And it get saturated by any strong signal, so it will fail near FM stations, microwave links, and any other transmitter with near-constant signal. This type of wideband non-rf-filtered design usually has too many failure modes in real-world tests to become an actual useful product.