All Things Direct-To-Mobile

[JB47394]

Omnispace's report to the FCC: ECFS

I would think it would take all of about 10 minutes to turn on the SpaceX stuff and measure its influence on the claimed frequencies from the ground. The Omnispace satellite was 17,000 km away, so any emissions should be easily detected on the ground. The frequencies used are for satellite-to-ground communication, so there's no issue with them being affected by atmosphere.

What am I missing?

 

[scaesare]

I would think it would take all of about 10 minutes to turn on the SpaceX stuff and measure its influence on the claimed frequencies from the ground. The Omnispace satellite was 17,000 km away, so any emissions should be easily detected on the ground. The frequencies used are for satellite-to-ground communication, so there's no issue with them being affected by atmosphere.

What am I missing?

Yeah, I dunno..., all they really seemed to have done is say "yes we could detect radio signals". but not necessarily prove it was harmful.

 

[Electroman]

Yeah, I dunno..., all they really seemed to have done is say "yes we could detect radio signals". but not necessarily prove it was harmful.

If "we can detect it" is their line of argument, what are they going to do with CMB (Cosmic Microwave Background radiation) ?

 

[JB47394]

Yeah, I dunno..., all they really seemed to have done is say "yes we could detect radio signals". but not necessarily prove it was harmful.

They're saying that those radio signals are introducing noise to their system. As I understand it, SpaceX isn't supposed to intrude into those frequencies at all. Omniverse's assertion is that this much interference was produced by one or two Starlink satellites, and they project that hundreds of such satellites would make their service untenable. The connection to Starlink satellites is a result of timing; the interference was seen during Starlink's short period of DTC testing. They also excluded surface noise from T-mobile because Omniverse's satellite didn't have line of sight to those transmitters.

 

[mongo]

I would think it would take all of about 10 minutes to turn on the SpaceX stuff and measure its influence on the claimed frequencies from the ground. The Omnispace satellite was 17,000 km away, so any emissions should be easily detected on the ground. The frequencies used are for satellite-to-ground communication, so there's no issue with them being affected by atmosphere.

What am I missing?

They did measure on the ground simultaneously with the satellite.

 

[JB47394]

They did measure on the ground simultaneously with the satellite.

I meant to have the FCC measure it as a means of verifying Omniverse's claims. Ten minutes. Done.

 

[mongo]

I meant to have the FCC measure it as a means of verifying Omniverse's claims. Ten minutes. Done.

Ah yeah. I wonder what the selectivity of their antenna was.

 

[scaesare]

They're saying that those radio signals are introducing noise to their system. As I understand it, SpaceX isn't supposed to intrude into those frequencies at all. Omniverse's assertion is that this much interference was produced by one or two Starlink satellites, and they project that hundreds of such satellites would make their service untenable. The connection to Starlink satellites is a result of timing; the interference was seen during Starlink's short period of DTC testing. They also excluded surface noise from T-mobile because Omniverse's satellite didn't have line of sight to those transmitters.

Hmmm... if the FCC grants permission to use those frequencies, how can they not "intrude" at all, unless what that means is that it's not "harmful interference", which is what the FCC often stipulates.

As an example, many things are allowed to use the 2.4Ghz band (Wifi, wireless mics, wireless cameras, etc...) but their modulation schemed, sub-channel selection, etc... must not interfere with other stuff also using that band.

Simply detecting usage in the band the FCC allowed would seem different than it being demonstrated as "harmful".

 

[JB47394]

Simply detecting usage in the band the FCC allowed would seem different than it being demonstrated as "harmful".

Omniverse describes the harm in the document. A certain amount of noise is introduced to their signals now, and they expect much more as Starlink increases the number of DTC satellites.

 

[scaesare]

Omniverse describes the harm in the document. A certain amount of noise is introduced to their signals now, and they expect much more as Starlink increases the number of DTC satellites.

Well, they seem to describe a rise in the "noise floor":

The observations showed that when the spectrum analyzer in Brewster confirmed that SpaceX test satellites were transmitting a 5-megahertz carrier in the 1990-1995 MHz band, the spectrum analyzer in Dubai showed that the Omni-F2 satellite detected a noise rise of 2 to 5 dB across the 1990-1995 MHz band. When the spectrum analyzer in Brewster showed the 5-megahertz SpaceX test satellite transmissions had ended, the noise rise observed by Omni-F2 over Asia and recorded in Dubai also stopped, and the noise floor returned to normal levels.

That's entirely to be expected. As if you are transmitting in that band, then to anybody else, that's "noise". In the same way that multiple devices in the 2.4Ghz band see "noise" from other devices, but your WiFi access point and RF TV remote are able to work at the same time.

But I don't see where they describe the actual "harmful" interference... but rather they talk about:

...interference threat SpaceX’s experimental tests pose to primary 2 GHz MSS operations...

So it seems to me this is largely "we can see them using the 1990-1995 MHz band". That's kind of to be expected, as the FCC granted them permission to experimentally use that band... ostensibly to determine if things like filtering, modulation schemes, etc.. could allow two parties to do so simultaneously.

 

[JB47394]

So it seems to me this is largely "we can see them using the 1990-1995 MHz band". That's kind of to be expected, as the FCC granted them permission to experimentally use that band... ostensibly to determine if things like filtering, modulation schemes, etc.. could allow two parties to do so simultaneously.

I was assuming that use of that band was not authorized. If the FCC authorized it, then I too have no idea what Omniverse is going on about.

 

[scaesare]

I was assuming that use of that band was not authorized. If the FCC authorized it, then I too have no idea what Omniverse is going on about.

That seems what they are saying:

In tests of its proposed supplemental coverage from space service at 1990-1995 MHz, experimental authorization holder Space Exploration Holdings, LLC (SpaceX) is causing harmful interference to the primary, Mobile Satellite Service (MSS) operations of Omnispace, LLC (Omnispace).

They refer to the experimental authorization a few times in the doc.

 

[JB47394]

They refer to the experimental authorization a few times in the doc.

I took "experimental authorization" as a reference to the Starlink DTC test itself, but that wording seems a bit ostentatious for such a simple thing. Then again, it's a legal document. Dunno. I guess we'll eventually find out.

 

[scaesare]

I took "experimental authorization" as a reference to the Starlink DTC test itself, but that wording seems a bit ostentatious for such a simple thing. Then again, it's a legal document. Dunno. I guess we'll eventually find out.

In the slide deck at th end, they do refer to the DTC test, but specify it includes using that 1990-1995Mhz band: