Posted by hasley 4 days ago
This isn't exactly a new subject, the same concept powered the first radar guided missiles in the 1940s (enemy is illuminated by a ground or airborne radar, missile tracks the reflection).
I'm fairly certain I've already read an article in an IEEE magazine talking about this topic (passive radar via cell towers) a few years ago.
USML Category XI(a)(3)(xxvii):
> (xxvii) Bi-static/multi-static radar that exploits greater than 125 kHz bandwidth and is lower than 2 GHz center frequency to passively detect or track using radio frequency (RF) transmissions (e.g., commercial radio, television stations);
There are separate ITAR provisions for radio direction finding, but these come with plenty of exclusions for systems not designed for defence applications or signals intelligence etc, and otherwise not meeting certain performance requirements, such as those in 5A001.e.
They were direct sampling the RF signals and running them through a bunch of H100's to get the algorithm to operate near real time. (They were quite proud of their 20 or so H100's)
Maybe this post is about that? It really lacks any technical substance. A bunch of corpo-talk is your ask me.
They probably throw all the signals, phase information into a ML model. But likely think the model inputs are very proprietary information so they just say ~ML will solve it~.
>I'm fairly certain I've already read an article in an IEEE magazine talking about this topic (passive radar via cell towers) a few years ago.
https://www.popsci.com/military-aviation-space/article/2001-...
https://www.heraldnet.com/2001/06/20/cell-towers-can-spot-st...
One idea is to exploit the signal's structure - despite simply trying to correlate the received line-of-sight signal with its delayed copies.
Especially OFDM has a nice structure. You can estimate delays (-> distances) as frequencies along the subcarriers and Doppler shifts (-> velocities) as frequencies along consecutive OFDM symbols. Estimators like maximum likelihood, ESPRIT, MUSIC, and compressed sensing etc. are your friends here for high-resolution results.
Unfortunately OFDM has a problem with large Doppler shifts (velocities). Therefore, people are looking at other multiplexing schemes like OTFS or AFDM.
Are there people who experience positive emotions in reaction to sentences like these? I just… even in my days when I thought social good came from states/organizations downward rather than from humans upward… even then, when I thought a God’s-eye view was achievable, that more and better measurable data were the way to get there, and that the main barrier to effective social regulation was poor legibility… I feel like even then this would ring craven and avaricious to me.
That's kind of strange. What are you going to sense that the cellular network doesn't already know? Air traffic? Car traffic? Drones?
The most useful application for this is probably drone detection. We might see this rolled out in China, which is setting up traffic control for the "low altitude economy".[1] This includes drones, now, and flying cars, soon. There's also interest in tracking balloons, traditional hot-air flying lanterns, and other small sky traffic obstructions. As usual, Shenzhen leads in this area.
[1] https://eastasiaforum.org/2026/10/16/chinas-low-altitude-eco...
I run some fairly large data structures and business software platforms for clients. I'm not impervious to the urge to creatively invent ways to mine their data in ways that would help a client's bottom line and win me a gold star, provided they're data in aggregate. But there have been things I've been asked to mine that I will outright rebel against doing and refuse to touch. This is partly a moral issue, but partly something else: If I appear to be the kind of person who would do that, I'll end up misused myself. If they're the type of client who would do it, I don't want them as a client.
If you disrespect humanity, or life, you disrespect yourself. Whatever comes at you as a result, you bring upon yourself.
This lesson has been demonstrated in every generation throughout history, and never seems to be learned.
The project here itself is a technical issue, but the potential monetization of it is disrespectful to humanity. Unfortunately, at any given time, there are enough sociopaths willing to profit from the worst possible uses of any new technology.