Posted by sksxihve 4/13/2025
for people who don't want to watch videos
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?
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?
Every time I show someone I first have to introduce the concept of it existing. And these are technical people.
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.
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 $6000 on top of the device itself. I think that was about what I paid for the analyzer itself in the first place!
Now I don't regret buying it and in truth I never needed to use 256 channels anyway, so I only bought 1 of the test lead sets so far. But yeah... test leads / cables /etc. for high bandwidth / low latency / high frequency applications get pretty damn expensive.
https://www.sparkfun.com/sparkfun-gps-rtk2-board-zed-f9p-qwi...
The datasheet: https://cdn.sparkfun.com/assets/f/8/d/6/d/ZED-F9P-02B_DataSh...
But concepts are translatable to other technologies, for example mobile phone network signals (even without decrypting it) which in most populated areas can have hundreds frequencies by itself.
there are literally literally thousands of radio signals around us which can be used for various unintended / non-cooperative purposes. also not only ground based signals, satellites are transmitting all kinds of signals towards earth, some for communication, some for remote sensing / earth observation.
Or not only is it possible to use non-cooperative signals for timing, but also for passive radar. For example DVB-T - you receive bounces/echoes of signal from airplanes, drones and measure its characteristics.
NATO public document - UAV Detection and Localization Using Passive DVB-T Radar MFN and SFN - https://www.sto.nato.int/publications/STO%20Meeting%20Procee...
Good community is around GNURadio, they have all kinds of enthusiast and profesional usecases, explorations, videos, ...
Or just simple 30$ 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...
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/
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...
• 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.
My uneducated guess is government funding, plus becoming part of a new "essential backbone" infrastructure, thus guaranteeing incentives to stay operational for a longer period of time.
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/mat...
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.