Re: [Starlink] Starlink "beam spread"

[Doc Searls <doc@searls.com>]

All good points.

I'm also wondering if (and how) Starlink is improving any satellite gear in successive launches. And, if that's the case, what would be the upper limit to what's possible with the system?

I ask the first question because Starlink has been deorbiting quite a few satellites...

https://spacenews.com/spacex-launches-starlink-satellites-as-it-deorbits-original-ones/

https://www.space.com/spacex-starlink-satellite-deorbit-video

... while launching many new ones. 

For example, there will be a Falcon launch from Vandenberg, of several dozen satellites, at 10:30 (or :40) PM Pacific time on Wednesday night (though there are conflicting reports, and launches often get canceled):

https://www.edhat.com/news/spacex-starlink-launch-rescheduled-for-tuesday

https://www.spacelaunchschedule.com/category/vandenberg-sfb/

https://www.space.com/spacex-starlink-group-3-4-launch-rocket-landing

https://www.ksby.com/news/local-news/spacex-targets-tuesday-night-for-falcon-9-launch-of-starlink-satellites

A late evening launch time makes for good viewing because it's dark enough to see the launch from a distance, and the rocket hits sunlight at the edge of space, where exhaust moves outward in all directions uncontained by atmosphere, leaving a tubular trail in the sky.

Here is a collection of screen grabs from a camcorder recording of a launch in 2005: https://www.flickr.com/photos/docsearls/albums/999576 This launch will be later in the evening, but still quite visible. One big difference will be the return trip of the first stage to a platform out in the ocean. I caught one of those in this series of shots here: https://www.flickr.com/photos/docsearls/albums/72157701027229232

(Forgive my indulgence in space-freakery. I do enjoy this stuff, and I'm not here in Santa Barbara often enough. But I am here now, so I'll be shooting it again, this time with a new camera and a longer lens.)

Doc

> On Aug 30, 2022, at 9:53 AM, David P. Reed via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
> I have no clue why this matters (other than this is in color).
>  
> The phased array antennas used by Starlink are quite limited - in particular, there are 4 on each satellite and each earth-ground path is half-duplex, TDM, essentially. Limited by hardware. The problem of signal equalization and quantization limits prevent "space division multiplexing" and "frequency division multiplexing" in practice.
>  
> The 4 msec "turnaround time" at the physical level (satellite) means that time from a packet arriving at one end to be sent to the other end of the sat-dishy links gets worse the more dishys are served by one of the 4 antennas on the satellite. 
> 
> trying to increase the coverage of an individual satellite basically means serving more dishys per satellite, with less total bit rate, and much longer latency due to the half duplexness.
>  
> Now if the total bit rate of a sat-to-dishy link were, say, 1 Gigabit, like an 802.11ac AP gives you, and the turnaround time were under 1 microsecond rather than 4 msec.  maybe then you could get reasonable Internet service to dishys.
>  
> But 240 Mb/s or 172 Mb/s as proposed for getting a bit more coverage per satellite? This is nowhere near competitive with what we expect in the US. 
>  
> Sorry to rain on all the techy dreaming.
>  
> First, it's worth looking at all the problems currently in WiFi performance when you share an AP with multiple active stations using 100's of Gb/s on the average (not just occasionally).
>  
> Dave - you tried in "make-wifi-fast", and the architecture gets in the way there. (yeah you can get point to point gigabit/sec single file transfers, but to do that you invoke features that destroy latency and introduce huge variability if you share the AP at all, for these reasons).
>  
> Starlink is a good "last resort" service as constituted. But fiber and last few-hundred meters wireless is SO much better able to deliver good Internet service scalably.
> Even that assumes fixing the bufferbloat that the Starlink folks don't seem to be able to address...
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink