C🅰️tSE Profile picture
Sep 15 8 tweets 3 min read Read on X
Constellation level aggregated out of band emmission interference is a showstopper for Starlink.

This is due to crazy big leakage in adjacent bands/channels.

So when constellation increase from 300 to 4500 (15x) they need to cut radiated power down to 15%
The system can’t scale Image
There is a term for such a system:

Non-scalable architecture. In technical contexts, this is often referred to as negative scaling or diminishing returns.

2/n
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Two. 2.

Major changes to the SCS R&O killed starlink d2c

One is that the proposition of co-primary licenses was changed to SCS being on secondary basis.

Other primary users (read terrestrial MNOs) enjoy total protection.

Starlink can use PCS on a _non_interference basis.

3/ Image
The other thing was the -120 dBW/m2/MHz interference limit.

Their bad RF equipment with an ACLR around 20 can’t make it.

A single Starlink sat can barely make it.

4500 not so much.

4/ Image
Beatings will continue until ACLR improves and the democratic lead Commission will enjoy handing out the fascia.

Yes, T-Mobile, this is decimation.

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And so the massive spamming of each new Starlink d2c into adjacent channels they aren’t supposed to emit in forces Starlink to turn down power of every satellite on orbit as they launch more.

It is a _very_ dire situation for Starlink.

They need complete redesign of modem.

6/
They would most likely need also redesign their _vulnerable_ earth moving cells. Which will cut calls if they keep it.

And they need more directivity and sidelobe control. As they also spam spatially in the physical domain, not just in the frequenzy domain.

7/ Image
Think of this as scheduling an 8th meeting in one single office day.

With the same people. They stopped listening at the 5th and got frustrated at the 6th. Two called sick on the 7th.

Additional Starlink sats beyond ~1000 are like that 8th meeting:
Destructive.

No reward.

8/
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More from @CatSE___ApeX___

Sep 14
Here are some Carrier to noise specifications of AST SpaceMobile.

In a filing today to the FCC Starlink reveals more of their d2c system.

Click link twice.

1/n licensing.fcc.gov/myibfs/downloa…



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Space-x Starlink d2c will drop from being able to do 5dB SINR (voice) to 0dB (texts)

If they were to comply with FCC rules.

We can now compare this to $ASTS.

2/n

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Interesting that Starlink squeak about first responders this and that (hint they’re on First Net so will not use this SCS at all).

They do not like AST simply reply with all their specs.

Like so:

22dB Carrier signal to interference and noise. When in compliance with FCC rules.
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Read 5 tweets
Sep 14
Scotia analysts apparenly read some of the DD shared by the SpaceMob community.

If You want Alpha or ”edge” investing in the nascent SCS market, so should You.

Previously thought by many to be the more technically advanced satcom operator Starlink is not getting approval.

1/n
🐾 ACLR. Adjacent Channel Leakage Ratio.

Recent requests by Starlink and some math (I was more kind to them than RKF engineering)

Is for Starlink ~-24.6 dBW/m2/MHz
And for AST ~-45 dBW/m2/MHz

This relates to quality of RF equipment.

A 20dB delta.

2/
It’s important to understand how AST beats Starlink by a lot in multiple different dimensions.

ACLR is focus in the frequenzy domain. How good a system is at not spamming adjacent _channels_.

And the 20dB difference is log scale.

AST is 100 times better.

3/
Read 25 tweets
Sep 2
A few aspects of a NTN system design affects the area spectral efficiency of the system.

I have touched on them and how they relate to Shannons law.

High directivity that creates narrow beams and small cells is key.
See my pinned tweet.

Then there is also interference.🧶🐈‍⬛ Image
We can think of this as the area spectral efficiency aSE as the main metric by which MNOs will choose which Satellite Network Operator Mobile to work with.

And interference is the metric by which regulators select which SNO-Ms are allowed to operate at all.

Gain affects both
/2 Image
Lets consider this image.

It shows the wide beam of smaller arrays (from 2 antennas wide) and the narrow beam of a medium sized array (up to 64 antennas wide)

Creating a beam cell we use the central strongest part of the beam marked in red and blue.

Narrow is good for aSE

/3
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Read 22 tweets
Aug 24
T-Mobile and a Freudian slip.

Decimation. What is that?

🧶🪓🐈‍⬛

Adhering to interference regulations of aggregate OOBE PFD limits would require a deficient system, such as Starlink d2c v2 mini, to use very wide guard bands and/or throttle (shrink) their power.

1/n
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PCS spectrum block that Starlink and T-Mobile intends to use is very narrow to begin with this has a large impact.

They need to maximize its use in power and in bandwidth to make the system profitable.

If they do that with deficient / sub par technolgy it affects others.

2/n Image
Decimation is a disciplinary process of the state with three distinct purposes:

1. Discipline and Order
2. Punishment for Failure or mutiny
3. Reassertion of Authority

It was in the context of the Roman army used to maintain order and

>ensure adherence to standards<

3/n Image
Read 22 tweets
Aug 17
Live view of @FCC regulatory staff watching recent Starlink and T-mobile filings asking to be exempt from new rules they helped greate and want to see imposed on others.

🧶🐈‍⬛

1/n
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In 2020 T-mobile asked FCC not to allow ASTs system w/o filings to show that they do not cause harmful interference to terrestrial networks.

$TMUS also requested new rules that FCC started.

AST showed their system doesn’t cause interference. ASTS design criteria since 2018.
2/n


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In 2022 T-Mobile and Space-X Starlink
recognixe that direct to cell will be a reality.

Essential for T-Mobile to stay competitive & much more profitable than Starlinks legacy VSAT architecture / fixed internet protocol service.
They join forces and declare d2c cooperation.

3/n Image
Read 46 tweets
Jul 26
Let’s unpack this $ASTS picture.

First and foremost 150+ heroes building revolutionary technology.

Many Thanks to the @AST_SpaceMobile staff.

🧶🐈‍⬛

1/n Image
It is the same guys as in this picture from january.

But a few things have progressed.

Notice the evolved (as in much more simple & easy) contraption to furl an array on the left.

2/n
Noteably we’ve got two of those.

So parallell workflows / stations.

Highlighted them in yellow on the recent picture.

Remember: Initial pilot of 5 is as much about a pilot to ramp up the factory production rate as it is to test flying the new birds.

(Closeups are older)

3/n

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Read 11 tweets

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