[ajross]

I'm all for a good spy story, but this seems like a big shrug to me. Interference-sensitive satellite communication is done with directional dishes, who cares what some other satellite is transmitting? That's the kind of nonsense you already engineered around.

And of course all communication managed by modern ICs is done with some kind of spread spectrum protocol with the property that "interference" is a routine/expected thing that doesn't degrade service. You can't break a modern satellite with an accidental transmission, you have to deliberately "jam" it.

Is the ITU rule in question being violated? Probably. Is that actually impactful to real systems? Almost certainly not. Old rules are old. Our goal should be to work together to update them for the benefit of all (to be sure, not to violate them with impunity!), and not to scream about them as part of a proxy war about the CEO's political and conspiracy proclivities.

[iamnothere]

(1) Some older satellites are still in use and this may affect them, especially if it becomes more common.

(2) Defending these norms is important to prevent chaos on the radio bands. If we can do this, why not China? Russia? Europe? Erosion of norms has real consequences when you are dealing with a scarce resource like RF spectrum.

[ajross]

I really think point 1 needs an example. Again, older satellites talk to dishes, not random off-axis antennas hundreds of miles away.

> Erosion of norms has real consequences when you are dealing with a scarce resource like RF spectrum.

So... no, that's wrong. Like 99% of all wireless data transferred anywhere is squeezed into a paltry 100 MHz in the 2.4 GHz ISM band, with no effective guardrails of any kind about who can use it, or with how many devices.

Technology fixed this problem, dedicated bands have little to no value anymore[1], haven't for like two decades now, and any discussion like this needs to treat with that as a prior.

Again, we all know this story isn't about rigorous adherence to international norms. It's about Musk doing shady spy stuff.

[1] Outside some otherwise important edge cases like radio astronomy which aren't "communication" as generally understood.

[iamnothere]

> dedicated bands have little to no value anymore

Citation needed. Cellular devices are an obvious application that needs dedicated spectrum allocation. Amateur bands (including volunteer civil defense helpers) and private terrestrial radio systems count on their spectrum being clean enough for use. Emergency responders have critical radio systems with dedicated frequencies. Ships and airplanes use dedicated spectrum allocations for navigation and reporting their positions, weather satellites have dedicated bands, safety equipment like avalanche beacons have dedicated frequencies, and so on.

None of this stuff would work if there were a free-for-all competition for whoever could shout the loudest on each band. To say that these bands are not important (or even critical to life safety) just because more data goes over unlicensed spectrum is frankly ignorant.

[ajross]

> Cellular devices are an obvious application that needs dedicated spectrum allocation.

Not since the death of TDMA, it isn't. Mobile bands are regulated to be exclusive, but nothing about LTE or 5G requires exclusive access or the absence of interference. These devices step on each others toes all the time and (via the magic of OFDMA and other dark trickery) still receive their data just fine.

You could start up a transmitter right in the middle of Verizon's or TMO's exclusive band (ICE is doing so all the time at protest sites across the country!) and the phones wouldn't bat a proverbial eyelash.

[iamnothere]

Without rules around spectrum usage or interference in place, you’re saying I could just set up my own 1 MW transmitter on the cellular bands and the phones would just continue working as if nothing was happening? Fantastic, let’s get rid of the rules then. I have been wanting to build a giant spark gap in my backyard, that would finally make it legal.

[ajross]

Now you're moving the goalposts. The subject at hand is a seemingly benign use of ITU-regulated spectrum for a purpose that is not quite what it was supposed to be for (literally the direction of transmission is wrong, not the location or power level of the signals!).

I don't disagree that people shouldn't be setting up 1MW jammers on mobile bands, but neither did I argue for that, and you know it.

[kragen]

This is not correct. Low-data-rate satellite communication is generally received on the satellite with omnidirectional antennas, because if you try to do it with directional dishes, any problem with your satellite's attitude control system or position estimation leaves you with a dead satellite, because the directional dish on the satellite is pointed somewhere you don't have a transmitting antenna. Attitude control problems can be serious in any case (for a publicly known example, see Kepler), but if you can't communicate with the satellite you have no chance to fix or work around the problem, or even find out what it was so the next satellite doesn't have it.

[xyzzyz]

This is not the case with Starlink (and presumably Starlink) satellites. The ground stations use directional phased arrays. They can do it, because they keep good track of where each satellite is at any given moment, and do trajectory adjustments as needed.

[kragen]

Yes, groundstations are virtually always highly directional, except for, like, radio hams sometimes. (Even hams usually use yagis.) Possibly you didn't notice this, but I'm talking about the antennas on the satellites, which are the ones that could suffer interference (since they're the ones receiving the uplink frequencies we're discussing), not the groundstation antennas.

You always have to keep track of where each satellite is at any given moment.

What do you mean by "Starlink (and presumably Starlink)"?

[Jtsummers]

To add to this, we know what objects interfere with our satellite contacts. We keep their orbital positions (as best as possible) in mind when scheduling satellite operations to avoid communication failures (partial or total) caused by their interference.

This is often learned after the fact. A contact will fail or go badly and then you can examine what was around it at the time. Over a series of failures the offending satellite will be identified.

[xyzzyz]

Ah sorry, I misread you. I meant “presumably Starshield”, I think autocorrect replaced it with Starlink.

[kragen]

Oh, that makes sense! Thanks for explaining!