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 > Reply-To: Ulrich Speidel > 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 >> Waves Podcast >> Dave Täht CSO, LibreQos >> >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink > >