3 ms·
I worked with mmWave radars previously, but not professionally. In my opinion, it would be quite challenging to extract enough features from the current generat
by krasin 5y ago
I worked with mmWave radars previously, but not professionally. In my opinion, it would be quite challenging to extract enough features from the current generation of mmWave radars, such as TI IWR1642 ([1]) which have around 4 receivers and 2-3 transmitters, because the incoming data, while having a lot of temporal resolution is very limited in spatial resolution.
With greater number of antennas something like what you describe is theoretically possible, but becomes cost prohibitive.
By limiting the number of transmitters / receivers, we can have an almost perfect privacy monitoring. For example, it would be possible to detect a attack / a fight in a public bathroom, while not exposing anyone.
1. https://www.mouser.ec/datasheet/2/405/1/swru521c-1954464.pdf https://www.mouser.ec/datasheet/2/405/1/swru521c-1954464.pdf
- R0b0t1 5y agoTemporal res can be turned into spatial res.
- krasin 5y agoTheoretically: yes. Practically, there are limits to that.
- jcims 5y agoTo an extent, but depending on the sampling rate and frequency and your ability to control the area being observed, there is still a lot of information available for modeling and biometric identification. In the extreme you can detect things like heartbeat, rate of breathing, etc. For example, I have a CDM324 24Ghz radar module here on my desk. I set it up to 'watch' me type this comment from across the keyboard. This is an extremely simple module that I have powered by a bench power supply and the IF routed directly to the audio input on my desktop. It was sampled with audacity and amplified a bit to help with visibility. Towards the end of the recording I'm expecting a flat spot followed by regular motion followed by 'noise' as I pause motionless for ~10 seconds or so, then take about 5-6 exaggerated breaths, then resume typing. This is with zero design, the wrong frequency for the job, and next to zero signal conditioning. (post: i've included a zoomed in image of the 'motion demonstration' to show still/breathing/typing, then zoomed in on typing to show the detail, then a spectrogram and waveform of me reaching up to scratch my ear.) https://imgur.com/a/0JmENYu https://imgur.com/a/0JmENYu Bonus: yo check out my soundcloud - This is what the doppler signal actually sounds like: Scratching my ear - https://soundcloud.com/buckrunner2/scratch https://soundcloud.com/buckrunner2/scratch Talking directly at the module - https://soundcloud.com/buckrunner2/talking https://soundcloud.com/buckrunner2/talking
- AdamH12113 5y ago“Privacy” seems to be a marketing term here; what they really mean is that you can’t take naked pictures with it.
- samatman 5y agoWhich is also nonsense of course, the pornotron of TSA fame is mm wave radar.
- krasin 5y agoThe difference is the number of transmitters / receivers. TSA uses an array of them (from top to bottom) with narrow beams and they also rotate them and ask you to not move, so that effectively their number is considerably higher (ten of thousands), when reconstructing the image. Additionally, they use a higher frequency (160-400GHz), which additionally helps with resolution. See [1] and [2]. If we limit the number of transmitters / receivers to 3/4, the image reconstruction becomes impossible, similar how you would not really make a real photo from a few color sensors stationary looking at a scene, while a linear array of them that moves around an object would make a perfect scanner. It's a non-ideal analogy, but the best I can offer. 1. http://mt-fedfiles.blogspot.com/p/tsa-frequency-updates.html http://mt-fedfiles.blogspot.com/p/tsa-frequency-updates.html 2. https://www.3dbodyscanning.org/cap/papers/2017/17263mcmakin.pdf https://www.3dbodyscanning.org/cap/papers/2017/17263mcmakin....
- visarga 5y agoYou can reconstruct the images with neural networks even if you have little signal to guide.
- akimball 5y agoThis is true in the sense that NNs offer a convenient way to estimate a distribution of hidden values conditionalized upon visible values. That is an approximation of what is usually understood by "a reconstruction". I would argue that a reconstruction per se would only include parts for which the credible interval could be systematically bounded within a suitable tolerance threshold.
- samatman 5y agoSorry, don't buy it. Gait analysis is excellent at identifying people, and that's projecting from a 2D image at a distance. Anything which can draw a moving voxel cloud around a human is going to figure out who that human is eventually.
- kjeetgill 5y agoI don't disagree but I think this version of privacy is reductive. Plenty of real world privacy exists on a spectrum. My family knowing I'm in the bathroom is a far cry form them pointing a camera at me. If stores track you "anonymously" with this ... Who cares? It's less invasive than the ubiquitous security cameras they have pointed at you.
- samatman 5y agoI have no opinion on your reply, I was discussing technical feasibility in response to someone claiming it was infeasible. The normative claims aren't germane or particularly interesting to me.
- krasin 5y agoBy not exposing anyone I meant reconstructing an image. Identification is a different story and there are multiple ways on how to achieve that (heartbeat classification is an obvious one). If you have ideas how to reconstruct an image with 4 receivers / 2-3 transmitters, please, buy a dev kit from TI (they cost <$200, https://www.mouser.com/c/?q=mmwave https://www.mouser.com/c/?q=mmwave) and show us a demo.
- ulrikrasmussen 5y agoWhat about correlation? If you have other information that can tell you who is alone in the bathroom (common area CCTV, log of RFID key usage, etc) and your radar can infer that something very private is taking place there because the person thinks they are alone, then isn't that still a huge breach of privacy?
- krasin 5y agoI really must have phrased my message more clearly. I meant reconstructing images, not identifying who is inside. The latter is quite feasible, and you're correct that extra data helps with that as well. Just like with browser pinning, we have a variety of signals, which combined together give a very high rate of correct identification.
- ulrikrasmussen 5y agoGot it, I think I read your message as defending the idea more than it was.
- yjftsjthsd-h 5y ago...so what I'm hearing is "hard today so probably trivial in 5 years"? Or is this an exception to the usual march of technological progress?