12 ms·

BPS is a GPS alternative that nobody's heard of

430 points by sksxihve 2y ago

fortran77 2y ago
A alternative, but only for timing and as GPS supplement. Unless you’re in a place where you can pick up 4 ATSC transmitters at different locations you won’t get position or navigation with it.
- chipsa 2y ago
  So if you can get more than 3 different TV stations you should be good. Most stations don’t share transmission towers, AFAIK. There are places, especially in the mountains where you don’t get the requisite number of towers, but large portions of the US will, and the required signal to noise ratio is better than to decode regular TV signals, so you have a larger area covered than for TV.
geerlingguy 2y ago
Note that this blog post (and the associated video) were a quick off-the-cuff thing while I was on the NAB show floor—I have been talking to a few of those involved in the testing at NIST, Sinclair, and Avateq (among others), and will hopefully have a lot more in a follow-up. Right now it's in the experimental stage, with only 6 towers total deployed (only 5 were operational during NAB, and only one in Nevada... so timing, not navigation yet). The ultimate plan—which is probably dependent on how well ATSC 3.0 rolls out (which has plenty of hurdles[1])—is to encourage broadcasters to add on the necessary timing equipment to their transmitter sites, to build a mesh network for timing. That would allow the system to be 100% independent of GPS (time transfer could be done via dark fiber and/or ground-satellite-ground directly to some 'master' sites). The advantages for BPS are coverage (somewhat) inside buildings, the ability to have line of sight nearly everywhere in populated areas, and resilience to jamming you can't get with GPS (a 100 kW transmitter signal 10 miles away is a lot harder to defeat than a weak GPS signal hundreds of miles away in the sky). The demo on the show floor was also using eLoran to distribute time from a site in Nevada to the transmitter facility on Black Mountain outside Vegas, showing a way to be fully GPS-independent (though the current eLoran timing was sourced from GPS). [1] ATSC 3.0, as it is being rolled out in the US, doesn't even add on 4K (just 1080p HDR), and tacks on 'features' like 'show replay' (where you tap a button and an app can stream a show you're watching on OTA TV through the Internet... amazing! /s), DRM (at stations' discretion, ugh), and 'personalized ad injection' (no doubt requiring you to connect your TV to the Internet so advertisers can get your precise location too...). Because ATSC 3.0 requires new hardware, consumers have to be motivated to buy new TVs or converter boxes—I don't see anything that motivates me to do so. I feel like it may be a lot like the (forever ongoing) HD Radio rollout.
- toast0 2y ago
  I bought an atsc 3 tuner, and the experience turned me off of OTA tv. Since then, things managed to get worse as when I was poking around, DRM wasn't in use, but now it is. I was hoping to get better fidelity between the roughly 2x bitrate per channel, and the video codec update. And probably overly optimistically was hoping the 1080p feed source was progressive so there wouldn't be a deinterlacing step. Otoh, local broadcasters use an audio codec I can't easily use, integration with mythtv is poor, and there's no sign anything is going to get better soon. Maybe if I had a tv with an atsc 3 tuner, live tv would be an option, but I'm not buying a tv for that. ATSC 1.0 took a while before gathering momentum, so maybe that's going to be the same here, and in another few years, it might make sense to consider a transition. OTOH, maybe the writing is on the wall and OTA broadcasting will die on this hill. I was an OTA enthusiast, but between ATSC 3 being terrible, and the reallocation of spectrum that means cellular base stations sometimes overwhelm my pre-amp, it's not much fun anymore. (I have a filter post-pre-amp but it'd be better if I got on the roof to put it pre-pre-amp, but roofs are scary) Maybe I'm just getting curmudgeonly though.
- The_Double 2y ago
  How does it solve for time without location? With GPS location and time are one solution to an equation with 4 unknowns (x,y,z,t). Without location you won't know the time delay between you and the transmitter.
  - fnordpiglet 2y ago
    The the transmitters are of fixed terrestrial locations.
    - namibj 2y ago
      The satellites are on known positions too, once you know the time.
    - michaelt 2y ago
      So you set your clock up by telling it its own location, so it can offset for the signal's flight time?
teleforce 2y ago
>an oscilloscope that costs 3x the value of your car on a trade show floor Typical high end microwave measurement system cost as much as a Ferrari car. Good cable and connectors can set you back by several thousand dollars. It's a very good business space prime for disruption (hint SDR - or software-defined radio). Fun facts, the grand daddy of Silicon Valley start-up is HP (then Agilent, and now Keysight) selling function signal generator.
- concrete_head 2y ago
  Interesting. Though he didn't say what kind of car he drives, it could be a real shitter
  - geerlingguy 2y ago
    2007 Toyota Camry. I looked it up, it's actually worth even less than I thought it was haha.
- mindcrime 2y ago
  Good cable and connectors can set you back by several thousand dollars. Another domain where that is true involves logic analyzers. A few years ago, on a bit of a lark, I bought a (used) fairly high-end Keysight logic analyzer. The kind of thing that cost like $20,000 or more when it was brand new. But I got a sweet deal on it, so I bought it. Only... it came with no test leads. And then I started shopping for the leads. Yikes. I forget the exact numbers now, but as best as I can recall, the leads came in 64pin sets, where the device supported up to 4 test lead sets, for 256 total channels. And just one of the 64pin test lead sets cost something like $1500. So a full set would cost another $6000 on top of the device itself. I think that was about what I paid for the analyzer itself in the first place! Now I don't regret buying it and in truth I never needed to use 256 channels anyway, so I only bought 1 of the test lead sets so far. But yeah... test leads / cables /etc. for high bandwidth / low latency / high frequency applications get pretty damn expensive.
- wildzzz 2y ago
  I've got a rack of equipment that sometimes requires a special calibration where I need to lug over a signal generator. Of course the only ones we have available that go to the necessary frequency weigh like 50lbs. I've recently been eyeing a little gadget that costs about 1/10 or 1/20 the cost of the Keysight units, interfaces using USB oe Ethernet, and is about the size of a deck of cards. The accuracy isn't perfect on its own but that's what a 10MHz ref clock is for. It's amazing how far tech has come and it's amazing how much we are still paying for these dinosaur pieces of test equipment.
RyanShook 2y ago
Slide deck of BPS (Broadcast Postioning System) https://www.gps.gov/governance/advisory/meetings/2022-11/matheny-mondal.pdf https://www.gps.gov/governance/advisory/meetings/2022-11/mat...
- louwhopley 2y ago
  Thanks for sharing this. It creates a clear picture of its use cases and roll out plans. GPS is such a critical infrastructure component to modern society- knowing that a redundancy system like this is in the works is great.
master_crab 2y ago
This sounds interesting but it most likely will only be of use in populated areas where there is enough signal overlap from broadcast towers. You’ll still need GPS in the countryside and on water.
- bri3k 2y ago
  In a lot of cities the broadcast towers are concentrated in the same place, I wonder how effective it could be.
  - lxgr 2y ago
    At least in Europe, when broadcasting went digital (DVB-T), a lot of cities started being covered by single frequency network transmission, which specifically leverages different transmitter locations transmitting the same signal to decrease dead zones. Due to how OFDM works, I suppose the idea here is to intentionally send a heterogeneous signal on a few non-overlapping subcarriers (for single-frequency networks) or on different transponders at different locations (since single frequency networks aren't as common in the US due to how broadcasting evolved there, although ATSC 3.0 apparently also allows single frequency networks).
publicola1990 2y ago
While this is is interesting, the "nobody's heard of" phrase is rather condescending and such phrases leave a bad taste in the mind.
- jen729w 2y ago
  Hmm it's just a turn of phrase. I would bet you $100 that no more than 0.001% of the population have heard of BPS. I hadn't. That's functionally "nobody".
  - jandrese 2y ago
    The title is still clickbait given the reason nobody has heard of it is that it barely exists and is not useful yet. Also, it smelled a bit like wishful thinking to assume the high precision clock would not be driven by GPS on real world deployments. I know some cell towers synchronize via PTP, but a great many others use GPS as their time source.
    - geerlingguy 2y ago
      For anyone who deploys GPS-based timing systems at scale, having more sources of precise time is a huge boon. (Some companies pay many millions for dark fiber just to have a redundant time source). Holdover can only help so much, if there's a persistent jamming effort, it can wreak havoc on many time-critical systems.
  - bmacho 2y ago
    It's worse in every way than just omitting it. 'BPS is a GPS alternative' is better as a title, on HN at least
- Calwestjobs 2y ago
  yes saying jeff geerling is the nobody who never heard of that thing is offensive to me. XD
- p_ing 2y ago
  It's a curiosity gap headline; it's a lazy form of headline that insults the intelligence of the audience. It also extends into clickbait. Poor form. Do better.
Iwan-Zotow 2y ago
GLONASS? Baidu?
- toomuchtodo 2y ago
  Controlled by other nation states.
  - LeoPanthera 2y ago
    Galileo. Controlled by the EU, and therefore a better choice than GPS, since the United States is no longer trustworthy.
    - Tabular-Iceberg 2y ago
      Honestly how trustworthy was the US before? Are we supposed to be completely fine with PRISM and XKeyscore now?
      - Calwestjobs 2y ago
        well i do not share your "enthusiasm" do not forget those systems used twitter,google,amazon,microsoft infrastructure, so those private companies build it first...
    - petesergeant 2y ago
      It's a little unclear to me from reading the Wikipedia page; is it fully functional today, and worldwide? It'd be cool if my phone showed me which systems it was using at any time, but I have chosen The One True Apple Way so I don't think that'll come any time soon
      - Flatterer3544 2y ago
        Yes it has full world coverage, see the esa navipedia for more info. No idea how it is in the US, but in EU you can't really easily choose, it will by default use GPS+Galileo combined for better accuracy. I guess you can through developer settings on android though.
Lammy 2y ago
I hope it will still be possible to receive a BPS timing signal privately and anonymously with ATSC 3 like one can with GPS. ATSC 3 has the Dedicated Return Channel because marketers “““need””” to spy on every-fucking-thing we do: https://www.atsc.org/wp-content/uploads/2024/04/A323-2024-04-Dedicated-Return-Channel.pdf https://www.atsc.org/wp-content/uploads/2024/04/A323-2024-04... “Conventional linear TV services alone (albeit ultra-high-definition) may not be sufficient to sustain the terrestrial broadcasting business which requires a large amount of highly coveted spectrum resources. Intelligent media delivery and flexible service models that maximize the network Return on Investment (ROI) is of paramount importance to the broadcasting industry in the new era.” That's a lot of fancy words to say ‘we're doing this because it makes us more money’ lol “Recent studies have shown that interactivity between media customers and service providers and between users themselves will be one of the most important features in the next-generation media service. In this document, this unique opportunity is addressed by defining a Dedicated Return Channel (DRC) system for the next-generation broadcasting system.”
- geerlingguy 2y ago
  Yeah... and that's one of the most innocuous new "features" in ATSC 3.0. Almost everything I've seen (besides BPS, and maybe HDR if you're one of the few who has a really good home theater setup) is a benefit for broadcasters and advertisers, and a bit worse for consumers (especially requiring new hardware/decoders... and sometimes persistent Internet connections!).
  - 1970-01-01 2y ago
    Same feeling here. ATSC 3.0 with DRM and persistent Internet requirements tells me this is going to be the downfall of OTA television. I can see ATSC 4.0 being a discounted ISP subscription paired with some OTA location checks via BPS.
    - Alive-in-2025 2y ago
      So atsc 3 won't work unless you have some continuous "i'm user xyz watching this channel at time x.y.z" going back to the broadcaster? Why would anyone use atsc 3? It's not free over the air, you can't spoof it?
keithwinstein 2y ago
You don't need ATSC 3.0 to do this kind of thing! The short-term stability of the oscillators they use for commercial DTV transmission is apparently good enough that just having one local reference to compare GPS vs. each TV station's phase (and distribute that data) can produce a pretty good positioning system. Rosum was doing this back in 2005: https://www.tvtechnology.com/news/tv-signals-used-for-geopositioning https://www.tvtechnology.com/news/tv-signals-used-for-geopos...
kristopolous 2y ago
https://www.nab.org/bps/ https://www.nab.org/bps/ for people who don't want to watch videos
- geerlingguy 2y ago
  The OP link is a blog post, which includes links out to the primary resources (much more in depth than the BPS landing page). The video is a byproduct of my conversations at NAB, and both are just preliminary... I've been working on a more in depth look at GPS and BPS (and other alternatives).
  - kristopolous 2y ago
    I'm fighting through a cold so granted my reading comprehension is way down but at least in my diminished state I was reading through that and was baffled ... I'm sure the average reader who deals with broadcast signal electronics knows what's going on here but I just walked away from it confused. It looks like terrestrial broadcasters sending out time codes for triangulation?
    - gblargg 2y ago
      I was amazed to not even find a Wikipedia article about BPS.
      - kristopolous 2y ago
        I'm guessing the long term vision is phones and cars will receive broadcast television because traditional TVs are usually pretty stationary objects? It sounds like a hail mary. How many people use the fm radio transceivers in their smartphone? Maybe it's a total re-imagining of what to do with high power terrestrial band broadcasting?
        geerlingguy 2y ago
        Or a way to try to preserve ownership of some spectrum. IMO it may follow the same route as HD Radio adoption.
lxgr 2y ago
High-power, and ideally authenticated, alternatives to space-based GNSS are desperately needed, given the sharp uptick in jamming and spoofing incidents in many places. In a true "end of history" moment, the US and other NATO members discontinued both of their ground-based systems (which are inherently harder to jam due to their much higher transmission power, since transmitters are not power limited) – Omega in the late 1990s and Loran-C in the early 2010s – in favor of GPS, while Russia kept their equivalent functional, and China completed an eLoran network last year. Add to that the FAA's reduction of their ground-based VOR/DME station network that lets planes navigate when GPS is unavailable... GPS jamming, and much more concerningly spoofing, will probably quickly come within reach of non-nation-states and smaller groups of all kinds, and ultimately individual actors, and that can't possibly end well for civil aviation if robust countermeasures don't become available very soon.
- mindcrime 2y ago
  GPS jamming, and much more concerningly spoofing, will probably quickly come within reach of non-nation-states and smaller groups of all kinds, and ultimately individual actors It may already be so: https://hal.science/hal-03456365v1 https://hal.science/hal-03456365v1
- jeffbee 2y ago
  A university of Texas research group demonstrated more than ten years ago that they could spoof GPS in the vicinity of an automatically navigating UAV, and force it to land at a point of their choosing. This has been within the reach of garage hackers for a long time.
  - Scoundreller 2y ago
    Now the UAV needs to track where the signal is coming from. “Hey, this isn’t coming from the sky, what gives”
    - touisteur 2y ago
      Gets trickier when you're using dGPS. And you need at least 2 antennas/receivers to know direction of arrival. Beamforming in the direction(s) of the expected satellite(s) seems to help a lot with e.g. starlink. But you'll need a phased array and a beamformer.
anonymousiam 2y ago
Nice article on HackADay from yesterday covering this: https://hackaday.com/2025/04/11/gps-broken-try-tv/ https://hackaday.com/2025/04/11/gps-broken-try-tv/
skissane 2y ago
Is there any DVB-T equivalent?
- Calwestjobs 2y ago
  Czech technical university - 2018 - https://www.radioeng.cz/fulltexts/2018/18_04_1155_1165.pdf https://www.radioeng.cz/fulltexts/2018/18_04_1155_1165.pdf But concepts are translatable to other technologies, for example mobile phone network signals (even without decrypting it) which in most populated areas can have hundreds frequencies by itself. there are literally literally thousands of radio signals around us which can be used for various unintended / non-cooperative purposes. also not only ground based signals, satellites are transmitting all kinds of signals towards earth, some for communication, some for remote sensing / earth observation. Or not only is it possible to use non-cooperative signals for timing, but also for passive radar. For example DVB-T - you receive bounces/echoes of signal from airplanes, drones and measure its characteristics. NATO public document - UAV Detection and Localization Using Passive DVB-T Radar MFN and SFN - https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/STO-MP-SET-231/MP-SET-231-18.pdf https://www.sto.nato.int/publications/STO%20Meeting%20Procee... Good community is around GNURadio, they have all kinds of enthusiast and profesional usecases, explorations, videos, ... Or just simple 30$ RTL-SDR + laptop, you can sit next to road and listen for tire pressure monitoring sensors data, they contain unique ids, so you can know when postman enters your street...
  - Calwestjobs 2y ago
    (some of those thousands signals can be dependent on GPS too...) it is possible to listen to small part of spectrum thru receivers which enthusiasts connected to internet, without buying anything for example -http://kiwisdr.com/public/ http://kiwisdr.com/public/ but "high performance signals" are not in frequency range of those radios. but it is possible to hear ham radio, aviation, military, maritime, not only voice but weather fax, other digital signals, all sorts of timing signals...
LeoPanthera 2y ago
ATSC 3.0 channels (there are some already) are encrypted. So no more free-to-air, no open standards, no more open source viewers. Watch TV using Kodi? VLC? Not anymore. It's a travesty that this was ever approved.
dust42 2y ago
tldr; BPS is Broadcast Positioning System. Same principle as GPS: a known waveform is used to triangulate position and time. Advantage: indoor available, less easy to jam/spoof due to high tx power of broadcasting stations. BPS can be added to ATSC 3.0 Next Gen TV signal which is rolled out since 2019 in the US. Current planning is public availability in 2027-2029. A good gov presentation with an overview and technical details is here [1]. [1] https://www.gps.gov/governance/advisory/meetings/2022-11/matheny-mondal.pdf https://www.gps.gov/governance/advisory/meetings/2022-11/mat...
rwg 2y ago
I want to like this — I think having ground-based alternatives to GPS and other space-based PNT systems is a very good thing! But after reading the paper at https://www.nab.org/bps/Broadcast_Positioning_System_Using_ATSC30.pdf https://www.nab.org/bps/Broadcast_Positioning_System_Using_A... and other BPS information on the NAB's website, I think the NAB is being wildly optimistic about BPS: • ATSC 3.0's physical layer can already transmit GPS time in a way that receivers could get it back out. What BPS brings to the table is a requirement and specification for accurately and consistently filling in the physical layer preamble fields containing the time data, along with a new physical layer pipe (think "low-level data stream") that contains additional information about the transmitter and, optionally, its neighboring transmitters. • BPS is capable of producing time fixes when the receiver only has a lock on one source. This isn't surprising at all — GPS receivers can do the same thing. But either type of receiver with only one source would see a clock offset proportional to the path delay, which it wouldn't be able to compute and back out without knowing its position. • BPS is only designed for 2-D position fixes. While that's a reasonable design decision (the vertical position error would be massive), it also makes BPS less useful for the NAB's "indoor positioning for first responders" use case, especially in areas with multi-story buildings. • The need to receive and process/decode multiple, most likely non-adjacent 6 MHz channels for positioning increases receiver complexity and cost. • The NAB claims that 1 kilometer of separation between two BPS transmitters is "sufficient for useful position determination." I don't buy it, especially in the face of poor transmitter geometry. • They note that 16 TV stations in the New York City area broadcast from One World Trade Center, so for the purposes of BPS, they're effectively one station. This kind of transmitter colocation is incredibly common, both in urban areas (ten TV stations broadcast from Sutro Tower in San Francisco) and in more rural areas (six TV stations in the Roanoke-Lynchburg DMA broadcast from towers within ~1 mile of each other on the ridgeline of Poor Mountain). Even if every ATSC TV station became an ATSC 3.0 w/ BPS transmitter, bad transmitter geometries would destroy BPS's position accuracy in lots of markets. • What's the business case for broadcasters? BPS won't be free for broadcasters to implement, and there doesn't seem to be a path to it generating revenue except for a hand-wavy "maybe one day televisions will be able to determine their locations without Internet connections using BPS, and then broadcasters can do location-targeted advertising with those TVs!" My uncharitable take is that BPS will never be a usable standalone PNT system. A timing system in the "rebroadcasts GPS" sense? Maybe. Standalone positioning? No way. Broadcasters implementing BPS (or ATSC 3.0 at all) without being forced to by the government? I don't see it.
dieselerator 2y ago
If planning/designing a timing system like this using existing antenna, why wouldn't you choose to use cellular base stations? The cellular network reaches most places with overlapping coverage and carries network time. The lowest cellular frequencies are adjacent the upper broadcast TV channels. Aren't modern cellular receivers what we call software defined radios? They can choose which channels to receive.
- michaelt 2y ago
  Interestingly, cellular base stations are one of the major customers for high precision timing systems. They use precise timing to coordinate timed broadcast slots between base stations with overlapping coverage.
throw84848484 2y ago
This system should be shutdown. What if enemies use it to guide their rockets?
- Calwestjobs 2y ago
  your phone ai can recognize dogs in your photos, and militaries have all kinds of aerial survey, satellit photos of your house, so do they really need to use external radio signals, or is it enough for them to use fully internal system with just cameras and khadas mind 2 ?
hwpythonner 2y ago
I’m trying to understand if this depends on something specific to FM or TV signals, or if it’s more of a protocol-level idea (i.e., any time-synced, known-location transmitters would work). If it’s not intrinsic to FM, why not use existing cellular towers to do this? They’re everywhere, and phones already receive broadcast messages (like Amber Alerts) even without a SIM (I think) — so it feels like this could be done without needing new radios. What makes this more accurate than cell tower triangulation today? Is the limitation in timing sync across towers, or something else in how cell networks are structured? And for indoor use — how does this handle multipath? Reflections from walls or even atmospheric bounce seem like they’d throw off timing accuracy, similar to what messes with GPS in dense areas.
ConteMascetti71 2y ago
Could be cheated with a retartd line?
neuroelectron 2y ago
What about RTK/PPS? Here's a module that implements them along with GPS and GGNS. https://www.sparkfun.com/sparkfun-gps-rtk2-board-zed-f9p-qwiic-gps-15136.html https://www.sparkfun.com/sparkfun-gps-rtk2-board-zed-f9p-qwi... The datasheet: https://cdn.sparkfun.com/assets/f/8/d/6/d/ZED-F9P-02B_DataSheet_UBX-21023276.pdf https://cdn.sparkfun.com/assets/f/8/d/6/d/ZED-F9P-02B_DataSh...
AndrewKemendo 2y ago
Is there a COTS component that gives you something like a GPS Sentence return from this?
cbsmith 2y ago
There are all kinds of terrestrial alternatives to GPS. The US used to have LORAN-C. The trick is to deploy them...
WhyNotHugo 2y ago
I'm surprised that broadcast TV is used as a basis for this. It's not a topic with which I'm familiar, but I would have guessed that it was only slightly more popular than Fax and that it would have faded out is most of the world.

430 points by sksxihve 2y ago

A alternative, but only for timing and as GPS supplement. Unless you’re in a place where you can pick up 4 ATSC transmitters at different locations you won’t get position or navigation with it.

chipsa 2y ago
So if you can get more than 3 different TV stations you should be good. Most stations don’t share transmission towers, AFAIK. There are places, especially in the mountains where you don’t get the requisite number of towers, but large portions of the US will, and the required signal to noise ratio is better than to decode regular TV signals, so you have a larger area covered than for TV.

geerlingguy 2y ago

Note that this blog post (and the associated video) were a quick off-the-cuff thing while I was on the NAB show floor—I have been talking to a few of those involved in the testing at NIST, Sinclair, and Avateq (among others), and will hopefully have a lot more in a follow-up. Right now it's in the experimental stage, with only 6 towers total deployed (only 5 were operational during NAB, and only one in Nevada... so timing, not navigation yet). The ultimate plan—which is probably dependent on how well ATSC 3.0 rolls out (which has plenty of hurdles[1])—is to encourage broadcasters to add on the necessary timing equipment to their transmitter sites, to build a mesh network for timing. That would allow the system to be 100% independent of GPS (time transfer could be done via dark fiber and/or ground-satellite-ground directly to some 'master' sites). The advantages for BPS are coverage (somewhat) inside buildings, the ability to have line of sight nearly everywhere in populated areas, and resilience to jamming you can't get with GPS (a 100 kW transmitter signal 10 miles away is a lot harder to defeat than a weak GPS signal hundreds of miles away in the sky). The demo on the show floor was also using eLoran to distribute time from a site in Nevada to the transmitter facility on Black Mountain outside Vegas, showing a way to be fully GPS-independent (though the current eLoran timing was sourced from GPS). [1] ATSC 3.0, as it is being rolled out in the US, doesn't even add on 4K (just 1080p HDR), and tacks on 'features' like 'show replay' (where you tap a button and an app can stream a show you're watching on OTA TV through the Internet... amazing! /s), DRM (at stations' discretion, ugh), and 'personalized ad injection' (no doubt requiring you to connect your TV to the Internet so advertisers can get your precise location too...). Because ATSC 3.0 requires new hardware, consumers have to be motivated to buy new TVs or converter boxes—I don't see anything that motivates me to do so. I feel like it may be a lot like the (forever ongoing) HD Radio rollout.

toast0 2y ago
I bought an atsc 3 tuner, and the experience turned me off of OTA tv. Since then, things managed to get worse as when I was poking around, DRM wasn't in use, but now it is. I was hoping to get better fidelity between the roughly 2x bitrate per channel, and the video codec update. And probably overly optimistically was hoping the 1080p feed source was progressive so there wouldn't be a deinterlacing step. Otoh, local broadcasters use an audio codec I can't easily use, integration with mythtv is poor, and there's no sign anything is going to get better soon. Maybe if I had a tv with an atsc 3 tuner, live tv would be an option, but I'm not buying a tv for that. ATSC 1.0 took a while before gathering momentum, so maybe that's going to be the same here, and in another few years, it might make sense to consider a transition. OTOH, maybe the writing is on the wall and OTA broadcasting will die on this hill. I was an OTA enthusiast, but between ATSC 3 being terrible, and the reallocation of spectrum that means cellular base stations sometimes overwhelm my pre-amp, it's not much fun anymore. (I have a filter post-pre-amp but it'd be better if I got on the roof to put it pre-pre-amp, but roofs are scary) Maybe I'm just getting curmudgeonly though.
The_Double 2y ago
How does it solve for time without location? With GPS location and time are one solution to an equation with 4 unknowns (x,y,z,t). Without location you won't know the time delay between you and the transmitter.
- fnordpiglet 2y ago
  The the transmitters are of fixed terrestrial locations.
  - namibj 2y ago
    The satellites are on known positions too, once you know the time.
  - michaelt 2y ago
    So you set your clock up by telling it its own location, so it can offset for the signal's flight time?

teleforce 2y ago

>an oscilloscope that costs 3x the value of your car on a trade show floor Typical high end microwave measurement system cost as much as a Ferrari car. Good cable and connectors can set you back by several thousand dollars. It's a very good business space prime for disruption (hint SDR - or software-defined radio). Fun facts, the grand daddy of Silicon Valley start-up is HP (then Agilent, and now Keysight) selling function signal generator.

concrete_head 2y ago
Interesting. Though he didn't say what kind of car he drives, it could be a real shitter
- geerlingguy 2y ago
  2007 Toyota Camry. I looked it up, it's actually worth even less than I thought it was haha.
mindcrime 2y ago
Good cable and connectors can set you back by several thousand dollars. Another domain where that is true involves logic analyzers. A few years ago, on a bit of a lark, I bought a (used) fairly high-end Keysight logic analyzer. The kind of thing that cost like $20,000 or more when it was brand new. But I got a sweet deal on it, so I bought it. Only... it came with no test leads. And then I started shopping for the leads. Yikes. I forget the exact numbers now, but as best as I can recall, the leads came in 64pin sets, where the device supported up to 4 test lead sets, for 256 total channels. And just one of the 64pin test lead sets cost something like $1500. So a full set would cost another $6000 on top of the device itself. I think that was about what I paid for the analyzer itself in the first place! Now I don't regret buying it and in truth I never needed to use 256 channels anyway, so I only bought 1 of the test lead sets so far. But yeah... test leads / cables /etc. for high bandwidth / low latency / high frequency applications get pretty damn expensive.
wildzzz 2y ago
I've got a rack of equipment that sometimes requires a special calibration where I need to lug over a signal generator. Of course the only ones we have available that go to the necessary frequency weigh like 50lbs. I've recently been eyeing a little gadget that costs about 1/10 or 1/20 the cost of the Keysight units, interfaces using USB oe Ethernet, and is about the size of a deck of cards. The accuracy isn't perfect on its own but that's what a 10MHz ref clock is for. It's amazing how far tech has come and it's amazing how much we are still paying for these dinosaur pieces of test equipment.

RyanShook 2y ago

Slide deck of BPS (Broadcast Postioning System) https://www.gps.gov/governance/advisory/meetings/2022-11/matheny-mondal.pdf https://www.gps.gov/governance/advisory/meetings/2022-11/mat...

louwhopley 2y ago
Thanks for sharing this. It creates a clear picture of its use cases and roll out plans. GPS is such a critical infrastructure component to modern society- knowing that a redundancy system like this is in the works is great.

master_crab 2y ago

This sounds interesting but it most likely will only be of use in populated areas where there is enough signal overlap from broadcast towers. You’ll still need GPS in the countryside and on water.

bri3k 2y ago
In a lot of cities the broadcast towers are concentrated in the same place, I wonder how effective it could be.
- lxgr 2y ago
  At least in Europe, when broadcasting went digital (DVB-T), a lot of cities started being covered by single frequency network transmission, which specifically leverages different transmitter locations transmitting the same signal to decrease dead zones. Due to how OFDM works, I suppose the idea here is to intentionally send a heterogeneous signal on a few non-overlapping subcarriers (for single-frequency networks) or on different transponders at different locations (since single frequency networks aren't as common in the US due to how broadcasting evolved there, although ATSC 3.0 apparently also allows single frequency networks).

publicola1990 2y ago

While this is is interesting, the "nobody's heard of" phrase is rather condescending and such phrases leave a bad taste in the mind.

jen729w 2y ago
Hmm it's just a turn of phrase. I would bet you $100 that no more than 0.001% of the population have heard of BPS. I hadn't. That's functionally "nobody".
- jandrese 2y ago
  The title is still clickbait given the reason nobody has heard of it is that it barely exists and is not useful yet. Also, it smelled a bit like wishful thinking to assume the high precision clock would not be driven by GPS on real world deployments. I know some cell towers synchronize via PTP, but a great many others use GPS as their time source.
  - geerlingguy 2y ago
    For anyone who deploys GPS-based timing systems at scale, having more sources of precise time is a huge boon. (Some companies pay many millions for dark fiber just to have a redundant time source). Holdover can only help so much, if there's a persistent jamming effort, it can wreak havoc on many time-critical systems.
- bmacho 2y ago
  It's worse in every way than just omitting it. 'BPS is a GPS alternative' is better as a title, on HN at least
Calwestjobs 2y ago
yes saying jeff geerling is the nobody who never heard of that thing is offensive to me. XD
p_ing 2y ago
It's a curiosity gap headline; it's a lazy form of headline that insults the intelligence of the audience. It also extends into clickbait. Poor form. Do better.

Iwan-Zotow 2y ago

GLONASS? Baidu?

toomuchtodo 2y ago
Controlled by other nation states.
- LeoPanthera 2y ago
  Galileo. Controlled by the EU, and therefore a better choice than GPS, since the United States is no longer trustworthy.
  - Tabular-Iceberg 2y ago
    Honestly how trustworthy was the US before? Are we supposed to be completely fine with PRISM and XKeyscore now?
    - Calwestjobs 2y ago
      well i do not share your "enthusiasm" do not forget those systems used twitter,google,amazon,microsoft infrastructure, so those private companies build it first...
  - petesergeant 2y ago
    It's a little unclear to me from reading the Wikipedia page; is it fully functional today, and worldwide? It'd be cool if my phone showed me which systems it was using at any time, but I have chosen The One True Apple Way so I don't think that'll come any time soon
    - Flatterer3544 2y ago
      Yes it has full world coverage, see the esa navipedia for more info. No idea how it is in the US, but in EU you can't really easily choose, it will by default use GPS+Galileo combined for better accuracy. I guess you can through developer settings on android though.

Lammy 2y ago

I hope it will still be possible to receive a BPS timing signal privately and anonymously with ATSC 3 like one can with GPS. ATSC 3 has the Dedicated Return Channel because marketers “““need””” to spy on every-fucking-thing we do: https://www.atsc.org/wp-content/uploads/2024/04/A323-2024-04-Dedicated-Return-Channel.pdf https://www.atsc.org/wp-content/uploads/2024/04/A323-2024-04... “Conventional linear TV services alone (albeit ultra-high-definition) may not be sufficient to sustain the terrestrial broadcasting business which requires a large amount of highly coveted spectrum resources. Intelligent media delivery and flexible service models that maximize the network Return on Investment (ROI) is of paramount importance to the broadcasting industry in the new era.” That's a lot of fancy words to say ‘we're doing this because it makes us more money’ lol “Recent studies have shown that interactivity between media customers and service providers and between users themselves will be one of the most important features in the next-generation media service. In this document, this unique opportunity is addressed by defining a Dedicated Return Channel (DRC) system for the next-generation broadcasting system.”

geerlingguy 2y ago
Yeah... and that's one of the most innocuous new "features" in ATSC 3.0. Almost everything I've seen (besides BPS, and maybe HDR if you're one of the few who has a really good home theater setup) is a benefit for broadcasters and advertisers, and a bit worse for consumers (especially requiring new hardware/decoders... and sometimes persistent Internet connections!).
- 1970-01-01 2y ago
  Same feeling here. ATSC 3.0 with DRM and persistent Internet requirements tells me this is going to be the downfall of OTA television. I can see ATSC 4.0 being a discounted ISP subscription paired with some OTA location checks via BPS.
  - Alive-in-2025 2y ago
    So atsc 3 won't work unless you have some continuous "i'm user xyz watching this channel at time x.y.z" going back to the broadcaster? Why would anyone use atsc 3? It's not free over the air, you can't spoof it?

keithwinstein 2y ago

You don't need ATSC 3.0 to do this kind of thing! The short-term stability of the oscillators they use for commercial DTV transmission is apparently good enough that just having one local reference to compare GPS vs. each TV station's phase (and distribute that data) can produce a pretty good positioning system. Rosum was doing this back in 2005: https://www.tvtechnology.com/news/tv-signals-used-for-geopositioning https://www.tvtechnology.com/news/tv-signals-used-for-geopos...

kristopolous 2y ago

https://www.nab.org/bps/ https://www.nab.org/bps/ for people who don't want to watch videos

geerlingguy 2y ago
The OP link is a blog post, which includes links out to the primary resources (much more in depth than the BPS landing page). The video is a byproduct of my conversations at NAB, and both are just preliminary... I've been working on a more in depth look at GPS and BPS (and other alternatives).
- kristopolous 2y ago
  I'm fighting through a cold so granted my reading comprehension is way down but at least in my diminished state I was reading through that and was baffled ... I'm sure the average reader who deals with broadcast signal electronics knows what's going on here but I just walked away from it confused. It looks like terrestrial broadcasters sending out time codes for triangulation?
  - gblargg 2y ago
    I was amazed to not even find a Wikipedia article about BPS.
    - kristopolous 2y ago
      I'm guessing the long term vision is phones and cars will receive broadcast television because traditional TVs are usually pretty stationary objects? It sounds like a hail mary. How many people use the fm radio transceivers in their smartphone? Maybe it's a total re-imagining of what to do with high power terrestrial band broadcasting?
      - geerlingguy 2y ago
        Or a way to try to preserve ownership of some spectrum. IMO it may follow the same route as HD Radio adoption.

lxgr 2y ago

High-power, and ideally authenticated, alternatives to space-based GNSS are desperately needed, given the sharp uptick in jamming and spoofing incidents in many places. In a true "end of history" moment, the US and other NATO members discontinued both of their ground-based systems (which are inherently harder to jam due to their much higher transmission power, since transmitters are not power limited) – Omega in the late 1990s and Loran-C in the early 2010s – in favor of GPS, while Russia kept their equivalent functional, and China completed an eLoran network last year. Add to that the FAA's reduction of their ground-based VOR/DME station network that lets planes navigate when GPS is unavailable... GPS jamming, and much more concerningly spoofing, will probably quickly come within reach of non-nation-states and smaller groups of all kinds, and ultimately individual actors, and that can't possibly end well for civil aviation if robust countermeasures don't become available very soon.

mindcrime 2y ago
GPS jamming, and much more concerningly spoofing, will probably quickly come within reach of non-nation-states and smaller groups of all kinds, and ultimately individual actors It may already be so: https://hal.science/hal-03456365v1 https://hal.science/hal-03456365v1
jeffbee 2y ago
A university of Texas research group demonstrated more than ten years ago that they could spoof GPS in the vicinity of an automatically navigating UAV, and force it to land at a point of their choosing. This has been within the reach of garage hackers for a long time.
- Scoundreller 2y ago
  Now the UAV needs to track where the signal is coming from. “Hey, this isn’t coming from the sky, what gives”
  - touisteur 2y ago
    Gets trickier when you're using dGPS. And you need at least 2 antennas/receivers to know direction of arrival. Beamforming in the direction(s) of the expected satellite(s) seems to help a lot with e.g. starlink. But you'll need a phased array and a beamformer.

anonymousiam 2y ago

Nice article on HackADay from yesterday covering this: https://hackaday.com/2025/04/11/gps-broken-try-tv/ https://hackaday.com/2025/04/11/gps-broken-try-tv/

skissane 2y ago

Is there any DVB-T equivalent?

Calwestjobs 2y ago
Czech technical university - 2018 - https://www.radioeng.cz/fulltexts/2018/18_04_1155_1165.pdf https://www.radioeng.cz/fulltexts/2018/18_04_1155_1165.pdf But concepts are translatable to other technologies, for example mobile phone network signals (even without decrypting it) which in most populated areas can have hundreds frequencies by itself. there are literally literally thousands of radio signals around us which can be used for various unintended / non-cooperative purposes. also not only ground based signals, satellites are transmitting all kinds of signals towards earth, some for communication, some for remote sensing / earth observation. Or not only is it possible to use non-cooperative signals for timing, but also for passive radar. For example DVB-T - you receive bounces/echoes of signal from airplanes, drones and measure its characteristics. NATO public document - UAV Detection and Localization Using Passive DVB-T Radar MFN and SFN - https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/STO-MP-SET-231/MP-SET-231-18.pdf https://www.sto.nato.int/publications/STO%20Meeting%20Procee... Good community is around GNURadio, they have all kinds of enthusiast and profesional usecases, explorations, videos, ... Or just simple 30$ RTL-SDR + laptop, you can sit next to road and listen for tire pressure monitoring sensors data, they contain unique ids, so you can know when postman enters your street...
- Calwestjobs 2y ago
  (some of those thousands signals can be dependent on GPS too...) it is possible to listen to small part of spectrum thru receivers which enthusiasts connected to internet, without buying anything for example -http://kiwisdr.com/public/ http://kiwisdr.com/public/ but "high performance signals" are not in frequency range of those radios. but it is possible to hear ham radio, aviation, military, maritime, not only voice but weather fax, other digital signals, all sorts of timing signals...

LeoPanthera 2y ago

ATSC 3.0 channels (there are some already) are encrypted. So no more free-to-air, no open standards, no more open source viewers. Watch TV using Kodi? VLC? Not anymore. It's a travesty that this was ever approved.

dust42 2y ago

tldr; BPS is Broadcast Positioning System. Same principle as GPS: a known waveform is used to triangulate position and time. Advantage: indoor available, less easy to jam/spoof due to high tx power of broadcasting stations. BPS can be added to ATSC 3.0 Next Gen TV signal which is rolled out since 2019 in the US. Current planning is public availability in 2027-2029. A good gov presentation with an overview and technical details is here [1]. [1] https://www.gps.gov/governance/advisory/meetings/2022-11/matheny-mondal.pdf https://www.gps.gov/governance/advisory/meetings/2022-11/mat...

rwg 2y ago

I want to like this — I think having ground-based alternatives to GPS and other space-based PNT systems is a very good thing! But after reading the paper at https://www.nab.org/bps/Broadcast_Positioning_System_Using_ATSC30.pdf https://www.nab.org/bps/Broadcast_Positioning_System_Using_A... and other BPS information on the NAB's website, I think the NAB is being wildly optimistic about BPS: • ATSC 3.0's physical layer can already transmit GPS time in a way that receivers could get it back out. What BPS brings to the table is a requirement and specification for accurately and consistently filling in the physical layer preamble fields containing the time data, along with a new physical layer pipe (think "low-level data stream") that contains additional information about the transmitter and, optionally, its neighboring transmitters. • BPS is capable of producing time fixes when the receiver only has a lock on one source. This isn't surprising at all — GPS receivers can do the same thing. But either type of receiver with only one source would see a clock offset proportional to the path delay, which it wouldn't be able to compute and back out without knowing its position. • BPS is only designed for 2-D position fixes. While that's a reasonable design decision (the vertical position error would be massive), it also makes BPS less useful for the NAB's "indoor positioning for first responders" use case, especially in areas with multi-story buildings. • The need to receive and process/decode multiple, most likely non-adjacent 6 MHz channels for positioning increases receiver complexity and cost. • The NAB claims that 1 kilometer of separation between two BPS transmitters is "sufficient for useful position determination." I don't buy it, especially in the face of poor transmitter geometry. • They note that 16 TV stations in the New York City area broadcast from One World Trade Center, so for the purposes of BPS, they're effectively one station. This kind of transmitter colocation is incredibly common, both in urban areas (ten TV stations broadcast from Sutro Tower in San Francisco) and in more rural areas (six TV stations in the Roanoke-Lynchburg DMA broadcast from towers within ~1 mile of each other on the ridgeline of Poor Mountain). Even if every ATSC TV station became an ATSC 3.0 w/ BPS transmitter, bad transmitter geometries would destroy BPS's position accuracy in lots of markets. • What's the business case for broadcasters? BPS won't be free for broadcasters to implement, and there doesn't seem to be a path to it generating revenue except for a hand-wavy "maybe one day televisions will be able to determine their locations without Internet connections using BPS, and then broadcasters can do location-targeted advertising with those TVs!" My uncharitable take is that BPS will never be a usable standalone PNT system. A timing system in the "rebroadcasts GPS" sense? Maybe. Standalone positioning? No way. Broadcasters implementing BPS (or ATSC 3.0 at all) without being forced to by the government? I don't see it.

dieselerator 2y ago

If planning/designing a timing system like this using existing antenna, why wouldn't you choose to use cellular base stations? The cellular network reaches most places with overlapping coverage and carries network time. The lowest cellular frequencies are adjacent the upper broadcast TV channels. Aren't modern cellular receivers what we call software defined radios? They can choose which channels to receive.

michaelt 2y ago
Interestingly, cellular base stations are one of the major customers for high precision timing systems. They use precise timing to coordinate timed broadcast slots between base stations with overlapping coverage.

throw84848484 2y ago

This system should be shutdown. What if enemies use it to guide their rockets?

Calwestjobs 2y ago
your phone ai can recognize dogs in your photos, and militaries have all kinds of aerial survey, satellit photos of your house, so do they really need to use external radio signals, or is it enough for them to use fully internal system with just cameras and khadas mind 2 ?

hwpythonner 2y ago

I’m trying to understand if this depends on something specific to FM or TV signals, or if it’s more of a protocol-level idea (i.e., any time-synced, known-location transmitters would work). If it’s not intrinsic to FM, why not use existing cellular towers to do this? They’re everywhere, and phones already receive broadcast messages (like Amber Alerts) even without a SIM (I think) — so it feels like this could be done without needing new radios. What makes this more accurate than cell tower triangulation today? Is the limitation in timing sync across towers, or something else in how cell networks are structured? And for indoor use — how does this handle multipath? Reflections from walls or even atmospheric bounce seem like they’d throw off timing accuracy, similar to what messes with GPS in dense areas.

ConteMascetti71 2y ago

Could be cheated with a retartd line?

neuroelectron 2y ago

What about RTK/PPS? Here's a module that implements them along with GPS and GGNS. https://www.sparkfun.com/sparkfun-gps-rtk2-board-zed-f9p-qwiic-gps-15136.html https://www.sparkfun.com/sparkfun-gps-rtk2-board-zed-f9p-qwi... The datasheet: https://cdn.sparkfun.com/assets/f/8/d/6/d/ZED-F9P-02B_DataSheet_UBX-21023276.pdf https://cdn.sparkfun.com/assets/f/8/d/6/d/ZED-F9P-02B_DataSh...

AndrewKemendo 2y ago

Is there a COTS component that gives you something like a GPS Sentence return from this?

cbsmith 2y ago

There are all kinds of terrestrial alternatives to GPS. The US used to have LORAN-C. The trick is to deploy them...

WhyNotHugo 2y ago

I'm surprised that broadcast TV is used as a basis for this. It's not a topic with which I'm familiar, but I would have guessed that it was only slightly more popular than Fax and that it would have faded out is most of the world.