On Jun 3, 2024 at 09:43 -0700, David Lang via Starlink <starlink@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@lists.bufferbloat.net>
Reply-To: Ulrich Speidel <u.speidel@auckland.ac.nz>
To: starlink@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

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