[Starlink] musk: 28ms median latency on starlink

[Mike Puchol]

While the terminals use focused beams, Starlink does not operate in isolation or using protected spectrum. They must comply with EPFD limits, which are the reason why they just cannot land two co-frequency beams that overlap, as they could be causing harmful interference to other users of the same spectrum.

Best,

Mike
On Jun 3, 2024 at 09:43 -0700, David Lang via Starlink <starlink at lists.bufferbloat.net>, wrote:
> If the ground stations were omnidirectional antennas, you would be correct, but
> since they are phased array directional antennas, they can steer the beam to
> receive one satellite even while a different one is transmitting on the same
> frequency to the same cell.
>
> David Lang
>
>
> On Mon, 3 Jun 2024, Ulrich Speidel via Starlink wrote:
>
> > Date: Mon, 3 Jun 2024 22:40:24 +1200
> > From: Ulrich Speidel via Starlink <starlink at lists.bufferbloat.net>
> > Reply-To: Ulrich Speidel <u.speidel at auckland.ac.nz>
> > To: starlink at lists.bufferbloat.net
> > Subject: Re: [Starlink] musk: 28ms median latency on starlink
> >
> > 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
> >
> >
> _______________________________________________
> Starlink mailing list
> Starlink at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
>
> _______________________________________________
> Starlink mailing list
> Starlink at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.bufferbloat.net/pipermail/starlink/attachments/20240603/90b2d2c0/attachment.html>