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
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
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/
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/
Beatings will continue until ACLR improves and the democratic lead Commission will enjoy handing out the fascia.
Yes, T-Mobile, this is decimation.
5/
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/
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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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.🧶🐈⬛
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
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.
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.
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.
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
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.