Modeling Starlink Capacity

https://mikepuchol.com/modeling-starlink-capacity-843b2387f501

by walterbell • 4 years ago

234 82 4 years ago

mikepuchol.com

lettergram2• 4 years ago

While awesome they should really note the CPU usage upfront before linking to the site lol

My phone feels like it may catch fire

walterbell• 4 years ago

The calculations required to run a single snapshot can become massive, taking up considerable CPU resources from your computer, and locking the browser for a long time. A large country with 30k cells, served by 150 satellites, each with 48 spot beams, could require up to 216 million calculations.

lettergram2• 4 years ago

That section was after the link to the site, but sure.

jiveturkey• 4 years ago

216 million calculations

Is that a lot?

jsjohnst• 4 years ago

My phone feels like it may catch fire

Sounds like a design defect of your phone. Might consider getting something which isn’t a fire safety hazard just by visiting a random website.

NotYourLawyer• 4 years ago

I explicitly do not authorize any organization or entity to cite this article, or the results obtained by the simulation, for inclusion in filings with any regulatory body under any jurisdiction.

Interesting. I wonder if you’d actually need the author’s authorization to cite his work in such a way.

m463• 4 years ago

it seems to be on medium.com so they could do all they could probably do what they want with it.

Also, I thought the court said linking to something was ok, no matter what the content.

yokem55• 4 years ago

Sure, but an opposing party could then easily call it out as bad evidence. "Commissioner/your honor, the author themselves didn't this was any good for use in court".

wpietri• 4 years ago

I get where he's coming from. There's a maritime protocol for ship location, AIS, mainly meant so ships can all have nice radar-like displays of the ships around them. I wrote a decoder for it for an art project, the Twitter bot @sfships. I was very concerned that somebody would take it too seriously, so I wrote:

"I needed a simple AIS decoder for a small art project. I couldn’t find one, so I’m making something minimally adequate for my needs. Decoders are generated automatically from public protocol documentation, but since I use few of the fields myself, I haven’t verified much of the decoding. This code is rough and doesn’t worry much about correctness, and so shouldn’t be used for anything that matters. It especially shouldn’t be used for ship navigation." -- https://pypi.org/project/simpleais/

I can't really stop people, but at least I tried!

bombcar• 4 years ago

Similarly you see disclaimers on various softwares that they shouldn’t be used for life support or nuclear facilities.

I use them anyway wheeeeee

sangnoir• 4 years ago

If feels a lot like those YouTube uploader disclaimers to me: makes the author feel good, but probably won't mean much in a court of law - if it comes to that. IANAL

adastra225• 4 years ago

You don’t and that restriction is toothless.

icegreentea2• 4 years ago

You don't need the author's authorization. However, any regulatory body reviewing your filing and following up on your sources might find your choice questionable.

Rygian• 4 years ago

You don't need it. You can go ahead and use without authorization.

The regulator will then simply dismiss your filing for using unacceptable sources.

jxf• 4 years ago

This is some really fantastic, detailed analysis. I'm almost always impressed by the synthesis of knowledge required to be authoritative on expansive topics like this one.

sebsebmc• 4 years ago

Outstanding work, I wrote an incredibly naive simulator of Starlink coverage using H3 over a year ago before we even knew that Starlink was using H3 internally. The community over in r/Starlink wrote some other simulations too and we all stopped short of actually calculating based on gateway reachability and ISLs weren't in use yet either.

kanbara2• 4 years ago

i love H3 and got my last company to use it internally for _something_, will try to use it again now

ge96• 4 years ago

This looks great, glad there is that listen feature.

I'm interested in the subject but it's a good read.

It is amazing the coverage of just one.

cycomanic• 4 years ago

Something not covered in the article, but I have wondered about. How does Starlink do the handover? The satellites are in Leo and thus have orbit times of around 90min or so (not sure about the exact number), so every cell must be served by several satellites at the same time no? Otherwise we would see significant interruptions at the handover.

kanbara2• 4 years ago

well, some (or all?) have laser links now, so as another sat gets covisibility with a ground station and user terminal, it can just instantly pass the traffic off

without laser link, it's looks to me that most of the time in populated latitudes, there will be more than one sat's beams covering a cell, and if not then there would be interruption in coverage

the terminal should handle transmitting to multiple sats that are close by, but i dunno how omnidirectional the dishy is

wmf3• 4 years ago

I assume the satellites are synced so the handoff could be scheduled in advance and done in milliseconds. All you'd notice is some jitter.

I don't think it's any harder than driving on a highway where you'd do a cellular handoff every two minutes or so.

viczsaszbo• 4 years ago

The beam hopping (TDM) part of the article is similar to satellite handover. There's a lag before a beam returns to a location or a new beam is over a location, and the beams can't overlap (nco=1).

kidme511• 4 years ago

Funny people think Starlink is mainly a commercial enterprise. Since Teledesic in the 90s, these low earth orbit constellation projects have always been about stepping towards the real goal, which started with Strategic Defense Initiative and now embodied in the Space Development Agency

wmf3• 4 years ago

If it's not really commercial, why go to the trouble of supporting a million customers for a mere ~billion per year of revenue?

tsimionescu2• 4 years ago

To extract more value from this military operation is what they're hinting at.

bitcharmer• 4 years ago

There might be something to it. I work for a fortune 500 company and we've been trying to get in contact with them about a project we're working on for the last 12 months.

Firstly getting any contact details like a phone number or email is close to impossible. Then you just don't get any response from them anyway. It just looks strange.

seydor• 4 years ago

Judging by the valuation of Elon's companies, crowdfunding

tra3• 4 years ago

I’m not in the know…can you ELI5?

kidme511• 4 years ago

https://youtu.be/KsPLmb6gAdw?t=55m47s

But a historical prerequisite is understanding https://wikipedia.org/wiki/Strategic_Defense_Initiative unless you're old enough to remember.

Then carefully read Mike Griffin's career history: https://wikipedia.org/wiki/Michael_D._Griffin#Career

elephant81• 4 years ago

Look at Brilliant Pebbles. Starlink is just V.20 under the cover of Musk.

medion• 4 years ago

Why do they need Elon part of it and why also commercialize it?

tsimionescu2• 4 years ago

Because ballistic missile defense is an aggressive nuclear action, potentially allowing the country that has deployed such a system to launch a nuclear first strike without fear of retaliation. It would entirely destroy the "mutually-assured destruction" balance of power system, and would almost certainly be seen as an act of aggression by all other (non-allied) nuclear powers.

Also, why not also commercialize it, if it's simple? Just because you're being subsidized by tax payers doesn't mean you can't turn some extra profit.

blobbers• 4 years ago

This is an amazing simulation. It feels like the type of tool that would be used internally to monitor the entire system.

I'm truly impressed / shocked that people have the capacity and will to be build such amazing things as side projects!

comboy• 4 years ago

Mind boggling. If author is around here I'd love to know how much time did this project require. Everything seems so polished. Aesthetics alone are something that many big projects could learn from.

aimor2• 4 years ago

I'm not understanding why Starlink is limited in terms of how many cells it can serve by beam hopping. What's driving the analyst's choices for the different "TDM split" and "beam spread" values? I naively expected the system to have much more granularity than 10% TDM splits.

wmf3• 4 years ago

Beam hopping adds latency and jitter because packets have to wait for the beam to become available. For example if they use a ~1 ms superframe and they want to limit jitter to 20 ms they couldn't split more than 20:1.

Beam hopping also cuts available throughput. If they're promising 100 Mbps they can't slice things too finely.

aimor2• 4 years ago

Thanks for the explanation. It raises the next question about how small a superframe can be, which I imagine as they get smaller makes efficient scheduling a more difficult problem.

TruthWillHurt• 4 years ago

My brain melted. Amazing stuff!

vanattab• 4 years ago

I explicitly do not authorize any organization or entity to cite this article, or the results obtained by the simulation, for inclusion in filings with any regulatory body under any jurisdiction.

Would this be in anyway binding? Can you say someone is not allowed to link to my blog?

lazide• 4 years ago

Probably not, but it does make it clear to anyone following references what was intended use or not. Which can be helpful.

Modeling Starlink Capacity

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