[Starlink] musk: 28ms median latency on starlink

[Ulrich Speidel]

Getting the satellite density up will help, but it will only improve 
things so far.

The problem on user downlink in particular is that there's a limit on 
the maximum spectral power flux density that arrives from the satellite 
in space on the ground. If you point all (mutually compatible) user 
downlink beams from a single satellite at a single cell, you all but 
reach that limit there. In fact, where SpaceX want to use two beams on 
the same frequency but with opposite polarisations to the same cell, 
they must reduce the transmit power on each beam by 3 dB (50%) in order 
to stay within the limit. More satellites would give you more beams, but 
you can't point them at cells that already have a beam on the same 
frequency in use from another satellite (unless you de-rate on the power 
front, I guess). That seriously limits what you can receive in terms of 
total capacity within a single cell to what a single satellite's 
mutually compatible beams can deliver, which appears to be about 12 Gb/s 
on V1 and V1.5 birds, and 20 Gb/s on V2 (on Ku, if you add in Ka-band 
and anticipate Dishys that can do Ka, then it's a lot more for Ka). In 
practice, we know that a cell gets served by beams from different 
satellites, but the overall constraint still applies - if you deploy 
beam X from sat A and beam Y from sat B to the same cell, this makes the 
same contribution to PFD as deploying both from the same satellite. Note 
that Starlink sats do have multiple mutually incompatible beams that 
they can only point at different cells, bringing Ku user downlink 
capacity up to 16 Gb/s on V1 and 1.5, and 48 Gb/s on V2. But that only 
ups your chances of getting a larger slice of those 12 or 20 Gb/s in 
your cell.

Your best bet for continuing good service at the moment is literally to 
tell your neighbours that Starlink is useless, so they don't sign up and 
you can have your cake all to yourself ;-)

On 3/06/2024 5:13 am, Dave Taht via Starlink wrote:
> Via elon musk:
>
> Starlink just achieved a new internal median latency record of 28ms 
> yesterday! Great work by the engineering and operations teams.
>
> - https://twitter.com/elonmusk/status/1797282250574184587
>
> I of course, am very interested in y'all´s external measurements of 
> how well starlink is doing. For me, it is fantastic - 30Mbit uploads 
> nowadays, 0
> latency on the upload (how?) 
> https://www.waveform.com/tools/bufferbloat?test-id=2a1d139b-87cb-4ba4-a829-e2167801cffe
>
> I also keep hoping that the rest of the ISP industry is now paying 
> attention and deploying stuff like fq_codel and cake and libreqos, 
> but, ah well - I will settle for starlink blowing past a lot of dsl 
> and cable and finding ways to get their density up.
>
> Anyone going to the Starship launch on the 6th?
>
>
>
> -- 
> https://www.youtube.com/watch?v=BVFWSyMp3xg&t=1098s 
> <https://www.youtube.com/watch?v=BVFWSyMp3xg&t=1098s> Waves Podcast
> Dave Täht CSO, LibreQos
>
> _______________________________________________
> Starlink mailing list
> Starlink at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink

-- 
****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel at auckland.ac.nz  
http://www.cs.auckland.ac.nz/~ulrich/
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