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Fibre versus Starlink Discussion

bxr140

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Nov 18, 2014
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I'm not sure we do, unless you are pivoting... as I read your assertion you said rain fade isn't a thing, no?:

"blockage" isn't a thing either--including weather related degradation like rain fade--unless the user's antenna is improperly installed/located."

The point was that "blockage" and degradation from rain fade are not he same thing.
I can appreciate that message wasn't crystal clear.

I worked for Primestar and DirecTV for over 7 years back in the late 90s and early 2000s...That was nearly 20 years ago so maybe things have changed.

Yes, GEO satellite service in the past was materially different than current generation. To wit "electric cars are crap because they have limited range and no charging infrastructure" was once a valid statement.
 

SageBrush

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May 7, 2015
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Hi folks,
Noob with dumb question:

When a Starlink Sat beams a stream of data to Earth, what is the maximum area on Earth that can receive that stream ?
Is it a cone or a line ?
 

bxr140

Active Member
Nov 18, 2014
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When a Starlink Sat beams a stream of data to Earth, what is the maximum area on Earth that can receive that stream ?
Is it a cone or a line ?

It is more or less broadcast as a cone, and when projected onto the earth at an angle--which is the case except for the instant the cone is directly overhead the user-- the pattern becomes a sort of egg shaped ellipse, with the width and height of the egg being a function of the angle between the satellite and the region on the ground.

Edit: The user beam width is 1.5°, which translates to a ~150km^2 circle when directly overhead, and probably ~2x that (in an egg shape) at the edge of coverage.
 
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dkemme

Supporting Member
Apr 3, 2016
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Greeley, CO
It is more or less broadcast as a cone, and when projected onto the earth at an angle--which is the case except for the instant the cone is directly overhead the user-- the pattern becomes a sort of egg shaped ellipse, with the width and height of the egg being a function of the angle between the satellite and the region on the ground.

Edit: The user beam width is 1.5°, which translates to a ~150km^2 circle when directly overhead, and probably ~2x that (in an egg shape) at the edge of coverage.
So a little under 4.5 mi radius?
 

bxr140

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Nov 18, 2014
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So a little under 4.5 mi radius?

In Freedom Units, yeah. At least when a sat ~directly overhead. Then the beams stretch as the slant angle grows.

I don't know if there's an image representing starlink out there anywhere, but just for the visual, here's the beam map for the three new Viasats. You can see how the beams progressively cover more area on the ground as the angle between the user and sats grows. The stretching here is to serve extremely low user angles (like, single digit degrees). Starlink user elevations are I think in the 20's or something as a minimum (maybe even planned to be higher?), so the geometry doesn't result in quite the extreme difference in ground coverage from directly overhead to edge of coverage.

ViaSat-3-Map.png
 
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SageBrush

REJECT Fascism
May 7, 2015
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New Mexico
It is more or less broadcast as a cone, and when projected onto the earth at an angle--which is the case except for the instant the cone is directly overhead the user-- the pattern becomes a sort of egg shaped ellipse, with the width and height of the egg being a function of the angle between the satellite and the region on the ground.

Edit: The user beam width is 1.5°, which translates to a ~150km^2 circle when directly overhead, and probably ~2x that (in an egg shape) at the edge of coverage.
Interesting -- thanks !

Then if a sat is broadcasting a show in real time, does that mean that anybody with a dish in the coverage area can watch, analogous to broadcast TV ?

Fwiw, I was reading about the Starlink data capacity ( some 20 gbps per sat) and started to think that all the ways we have to compress, split and join data makes the actual data capacity much, much greater. Not to mention a moving target to innovation.
 
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bxr140

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Nov 18, 2014
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Then if a sat is broadcasting a show in real time, does that mean that anybody with a dish in the coverage area can watch, analogous to broadcast TV ?

No. Its still, in layperson terms, the internet. Its just secure data packets. To wit, the only person that knows you're streaming Bridgerton right now is you and the Netflix Mothership.
 

SageBrush

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May 7, 2015
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No. Its still, in layperson terms, the internet. Its just secure data packets. To wit, the only person that knows you're streaming Bridgerton right now is you and the Netflix Mothership.
Ahh..

If I am understanding you, every dish in the coverage area receives the packet but only one dish router opens the packet ?
 

bxr140

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If I am understanding you, every dish in the coverage area receives the packet but only one dish router opens the packet ?

Essentially, yeah. A pretty reasonable analogy would be data to/from your device relative to other devices in your same wireless coverage area. Near as I know Starlink is going to use a more proprietary waveform/protocol than whatever a mobile carrier or wifi uses, though I don't really think that changes the analogy much.
 

SageBrush

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May 7, 2015
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Essentially, yeah. A pretty reasonable analogy would be data to/from your device relative to other devices in your same wireless coverage area. Near as I know Starlink is going to use a more proprietary waveform/protocol than whatever a mobile carrier or wifi uses, though I don't really think that changes the analogy much.
Then without turning the Internet protocol on it's head, could starlink broadcast packets that were 'opened' ** by more than one router ?

** I sort of know that the actual mechanism is the IP mask, but 'opened' is hopefully a good enough albeit inaccurate description
 

hmcgregoraz

Member
Jul 16, 2014
109
187
Tucson AZ USA
Then without turning the Internet protocol on it's head, could starlink broadcast packets that were 'opened' ** by more than one router ?

** I sort of know that the actual mechanism is the IP mask, but 'opened' is hopefully a good enough albeit inaccurate description

At Layer 3 (TCP/IP) there are things such as broadcast and multicast, but I don't know if SpaceX's Layer 2 would work with this or not.

Years ago we used to try and leverage multicast for data we knew multiple systems needed (Such as pushing out a system image to a computer lab worth of computers), and there are other protocols to help with this like IGMP (IP multicast).

In reality today, it has been found that even for streaming services, unicast is generally easier to do and more practical.

Ie not everyone starts the NetFlix movie at the exact same time.

At some point SpaceX may decide that a large amount of NAND flash would be worth it to put a Content Delivery Network cache on each StarLink Satellite, but that is probably a fair ways away.

-Harry
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,387
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San Diego
At Layer 3 (TCP/IP) there are things such as broadcast and multicast, but I don't know if SpaceX's Layer 2 would work with this or not.

Years ago we used to try and leverage multicast for data we knew multiple systems needed (Such as pushing out a system image to a computer lab worth of computers), and there are other protocols to help with this like IGMP (IP multicast).

In reality today, it has been found that even for streaming services, unicast is generally easier to do and more practical.

Ie not everyone starts the NetFlix movie at the exact same time.

At some point SpaceX may decide that a large amount of NAND flash would be worth it to put a Content Delivery Network cache on each StarLink Satellite, but that is probably a fair ways away.

-Harry

Starlink uses a proprietary protocol when pushing bits up and down the satellite links to conserve bandwidth. They compress and then reconstruct the TCP/UDP and IP frames at the end points, so it looks like a single hop IP network to us. Also, I believe all Starlink satellite traffic has an encryption overlay onto all the data transmitted.

And yes, intuitively, you'd think multicast multimedia would be a huge bandwidth saver, but it has never caught on. Partially as hmcgregoraz pointed out, everyone's stream is slightly out of sync anyways due to pauses, rewinds, FF, etc. So two other things had to happen to make it work.

One is that access networks (the "last mile" from an active central office) had to get upgraded so that enough people could simultaneously grab different streams. This usually means pushing fiber deeper and deeper into the access network, the end result being an all fiber network.

The second thing is that caching content servers had to be deployed to the network's edge. Large ISPs that serve metro areas all have Netflix and other content cache servers in their distribution hubs, so they only need to grab one copy of the hottest videos that are being watched right now in each 50,000 or 200,000 population user area.
 

SageBrush

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Ie not everyone starts the NetFlix movie at the exact same time.
Multicasting.

I admit it, Netflix was the scenario I was contemplating ;)

Not starting at the same time ... but more along these lines of the same movie:

  1. Movie download started at 10:00 pm by home #1: Sat starts broadcast
  2. Movie started at 10:10 by home #2: Both homes receive movie from 10:10. Home #1 views in Sat real time, Home #3 caches. Home #3 downloads in a separate stream the first 10 minutes
And you are right -- nothing stopping us from thinking about predictive multi-cast downloads.
 
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hmcgregoraz

Member
Jul 16, 2014
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187
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Multicasting.

I admit it, Netflix was the scenario I was contemplating ;)

Not starting at the same time ... but more along these lines of the same movie:

  1. Movie download started at 10:00 pm by home #1: Sat starts broadcast
  2. Movie started at 10:10 by home #2: Both homes receive movie from 10:10. Home #1 views in Sat real time, Home #3 caches. Home #3 downloads in a separate stream the first 10 minutes
And you are right -- nothing stopping us from thinking about predictive multi-cast downloads.

The kind of edge caching that would be needed for that (ie integrated in to the CPE/Router/etc) is kinda interesting. I actually am a co-inventor on a patent that covers that kind of technology and predictive analytics tied to it.

That being said, most IP networks have just gone the "more bandwidth" route, and SpaceX really is not any different, they are doing it with more satellites....

-Harry
 

MorrisonHiker

S 100D 2021.4.15
Mar 8, 2015
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Colorado
Multicasting.

I admit it, Netflix was the scenario I was contemplating ;)

Not starting at the same time ... but more along these lines of the same movie:

  1. Movie download started at 10:00 pm by home #1: Sat starts broadcast
  2. Movie started at 10:10 by home #2: Both homes receive movie from 10:10. Home #1 views in Sat real time, Home #3 caches. Home #3 downloads in a separate stream the first 10 minutes
And you are right -- nothing stopping us from thinking about predictive multi-cast downloads.
20 years ago, Primestar, DIRECTV and DISH all had PPV offerings where they would schedule a movie to start every 30 minutes or so. You could buy it and it would enable you to view the broadcast that was already in progress or watch an upcoming broadcast of the movie. This used a lot less bandwidth than using a different stream for each viewer but it wasn't nearly as viewer-friendly as instantly streaming movies to each viewer.

Eventually, DIRECTV and DISH offered boxes with hard drives and they would automatically download a few of the most recent movies to them. This way you could start a movie whenever you liked, but the selection was pretty limited.
 
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SageBrush

REJECT Fascism
May 7, 2015
12,159
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New Mexico
The kind of edge caching that would be needed for that (ie integrated in to the CPE/Router/etc) is kinda interesting. I actually am a co-inventor on a patent that covers that kind of technology and predictive analytics tied to it.

That being said, most IP networks have just gone the "more bandwidth" route, and SpaceX really is not any different, they are doing it with more satellites....

-Harry
Unless they decide to compete in dense urban areas ...
 

SageBrush

REJECT Fascism
May 7, 2015
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These posts confirm at least the future possibility of Starlink having much more practical bandwidth than 20 gbps * viewable_sat_number would suggest

The kind of edge caching that would be needed for that (ie integrated in to the CPE/Router/etc) is kinda interesting. I actually am a co-inventor on a patent that covers that kind of technology and predictive analytics tied to it.

20 years ago, Primestar, DIRECTV and DISH all had PPV offerings where they would schedule a movie to start every 30 minutes or so. You could buy it and it would enable you to view the broadcast that was already in progress or watch an upcoming broadcast of the movie. This used a lot less bandwidth than using a different stream for each viewer

Eventually, DIRECTV and DISH offered boxes with hard drives and they would automatically download a few of the most recent movies to them. This way you could start a movie whenever you liked, but the selection was pretty limited.
 

drtimhill

Active Member
Apr 25, 2019
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Seattle
Starlink isn't a good solution for rural broadband. It's better than nothing but countries like Canada should be aiming much higher, otherwise people in rural areas will just be stuck with outdated broadband again.

Fibre is the only technology fit for the next decades, gigabit+ speeds and ultra low, consistent latency. Starlink is great and all but the speeds and latency are already on the low side and will only continue to fall behind as fibre becomes more common and the Starlink system gets more subscribers (and therefore less bandwith per user).

There is no "good" solution for rural broadband since by definition the low household density makes physical connectivity (e.g. fibre/fiber) prohibitively expensive, and any shared non-physical solution (wireless of any sort) will always eventually suffer congestion issues. A service like Starlink changes the overall balance since it can address area that are poorly serviced even by cell phone services.
 

SageBrush

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May 7, 2015
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New Mexico
I'm still on the 'is starlink capacity limited ?' angle as a matter of Sat count, or is it a fuzzy number dependent on tech solutions.

In addition to mutli-casting, Starlink can also play with LEO and MEO orbits -- LEO for low latency and MEO for JIT delivery.
 

bxr140

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Nov 18, 2014
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I'm still on the 'is starlink capacity limited ?' angle as a matter of Sat count, or is it a fuzzy number dependent on tech solutions.
So the ultimate 'capacity' cap in any local region on the globe is the amount of radiated power that can be put on the ground by the constellation (using the metric of PFD = Power Flux Density). Those are limits approved by the FCC and ITU and coordinated with agencies from the serviced countries. It is unlikely that one single Starlink sat could exceed these limits in any one cell (I don't actually know; that's just speculation based on "KISS and don't over engineer"), but it is certain that an aggregation of many starlink sats could exceed this limit in any one cell.

Note that the amount of power that can be radiated by the UTs also has an upper limit. I have no idea how close the Starlink UT's are to that limit.

The concept of multicasting would theoretically improve total data moved by the constellation (as you've postulated), but as others have stated its pretty complicated to implement to any materially useful benefit.

In addition to mutli-casting, Starlink can also play with LEO and MEO orbits -- LEO for low latency and MEO for JIT delivery.

IMHO that's the sustainable solution. A while back I did a quick cost workup on Starlink vs Viasat; they're reassembly close in bit/$. One could postulate that if someone with SpaceX's mindset approached a MEO or GEOs satellite design, that cost trade could very favorably turn toward the higher orbits. The solution would then become a LEO constellation for low latency demands and coverage of very low population density areas, then much bigger and more powerful sats with huge bandwidth persisting over high value regions (like a GEO over North America). Send the necessary low latency traffic through the LEO (video conferencing/voice, gaming, caching a streaming feed, etc.) and send the bulk of the traffic (steady state streaming, etc) through the higher sats.
 
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