C🅰️tSE Profile picture
Jun 1, 2024 11 tweets 6 min read Read on X
There are different portions of lowband spectrum that BlueBirds block 1 and BlueWalker 3 can use.

The range has public safety and commercial cellular spectrum in it.

🧶🐈‍⬛

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Back in 2020 plan was 617-960 range. In 2024 the plan is 617-960 MHz range. Same.

Micron antenna elements are c-c 161 mm. That is optimized for ~930 MHz if You space the phased array at 1/2 wavelength.

Consistent with that range.

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In the schedule S from March 2024
the range is the same. 617–960.

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How they go about operating in that range, (and others like c-band and midband), is piece by piece.

They start with some but aim for more.

They will try to find large chunks of spectrum - a big continous bandwidth - and spectrum that covers large swaths of land and sea.

4/n
The reason they want large blocks of spectrum is that cell phones can not currently aggregate one sliver of lowband with another sliver of lowband.

They can however aggregate lowband with midband.

5/n
They also want to cover a large swath of land not just pieces of a mosaic.

For two reasons.

To offer coverage everywhere and to not have the fuzz of protecting the neighbouring towers from interference.

This is AT&T 850 MHz alone.

And the total coverage adding Verizon.

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In a 2023 amendment AST points out the commercial lowband service links in that frequenzy range they want to start operating in first, on top of other gov use cases.

”700 MHz and 850 MHz”

Specifically:

704-746 and 824-894

On top of this FirstNet is known:
758-768+788-798

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Verizon lowband spectrum fits neatly with FirstNet spectrum to allow a massive block for DoD/gov/First responder use cases.

This is the large block part. They aren’t very public about this opportunity. Yet.

Nice to make Extended Reality work everywhere and overlay AI intel

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In the 824-894 range ”850 MHz” there is band 5.

Here AT&T holds what Verizon does not and together they hold all of it.

And by pooling spectrum not only do they create wider bands for the gov use case.

They also create a total blanket coverage for the commercial use case.

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The wider story is about prime lowband spectrum being the scarce resource and how more of it will migrate from analouge / narrowband Land Mobile Radio type applications to digital 5G/6G use once the latter assures coverage.

There is more to this further down the track.

10/10 Image


Live view ^ from FCC ULS system of fronthaul / service links in cellular lowband spectrum being leased to $ASTSwireless2.fcc.gov/UlsApp/Applica…

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More from @CatSE___ApeX___

Mar 15
It is an underappreciated fact that $ASTS Bluebird constellation is capable of rendering Russian GLONASS system ineffective globally or regionally while not jamming allied GPS.

The LEO PNT-Denial military use case.
(One of many)
🧶🐈‍⬛

1/n Image
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Consider first upper L-band and Block 3 bluebirds stats, Seperately.

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Then combine the two.

Glonass 1 channel totally jammed while others are unaffected.

The entire band gone.

That’s PNT-denial. Total blackout.
Not Accuracy Degradation.

But that’s also possible.

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Read 6 tweets
Feb 16
All of it.

Per public request.

$ASTS

1/ Image
Chapter one.

MESA and the L-band duality.

The Sensor Superiority Advantage
Sensor superiority isn't just about "seeing" first; it’s about Decision Space.

2/
By integrating Identification Friend or Foe with Radar, the Wedgetail discriminates targets at standoff ranges.

If you know where every friendly / 3rd party asset is, the rest are targets.

Speeding up Detection→ Recognition→ Identification means you Decide & Act first.

3/ Image
Read 35 tweets
Jan 23
In Latin, the concept of drawing an inference from what is not shown or mentioned is most commonly expressed as:

Argumentum ex silentio

$ASTS

🧠🐈‍⬛

1/n Image
When the last BlueBirds deployed there was two patterns.

One was a spike in drag and the level of drag settling on a higher level afterwards.

The other and first sign was a delay of TLE data longer than usual.

In a way the first -inconclusive- sign was the absence of data.
/2
As back then TLEs was delayed more than 2 full days. Which is /was unusual.

/3 Image
Read 10 tweets
Jan 8
Deploying a 200 sqm array within two weeks of launch is a high-stakes move. Historically, large structures wait longer for "checkout."

Is the upcoming FM2 launch giving us a faster deployment?

There is now FM1 data.

1/ Image
Here is drag data.

/2 Image
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Here is the relative change of drag (schematically) that you’d expect from detumbling, unfolding and the reorienting back to edge on flight.

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Read 9 tweets
Jan 6
I was asked to comment on Space-x last Ex parte letter that they have filed to the FCC.

So here is the picture:

$ASTS has asked authority to launch full constellation beyond 25 satellites.

Space-x wants to delay and complicate that.

They keep filing all the way to sunshine
1/ Image
It’s extremely uncompetitive behaviour and a bit immoral as what Space-X has begged be implemented onto AST is the same type of regulations they see as an obstacle when applied to themselves.

What they ask that AST shall not be allowed to is what they themselves do.
Golden rule? Image
It’s important to grasp that the next 20 satellites and the Block1s are approved already.

So this pen-fighting is about about satellites to launched beyond Q1 2026.

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Read 20 tweets
Jan 2
_One way to increase Area spectral efficiency is lowering constellation altitude.

That way comes at two costs: The number of 🛰️satellites required on orbit increases and their orbital dwell ⏳time decreases both affecting the replenish rate 🛠️adversely as:

🛠️ = 🛰️/⏳

🧶🐈‍⬛

1/n Image
Let’s do a SpaceMob thing and look at this from first principles.

A satellite has a field of view. FoV.

That Field of View projects a footprint on earth.

The footprint increases with angle of the field of view and increases with altitude.

2/ Image
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Within this field of view the satellite creates beams.

They also have an angle called beamwidth and a footprint called beamcell.

There are many of these beams and beamcells within the satellite footprint.

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Read 31 tweets

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