From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp121.iad3a.emailsrvr.com (smtp121.iad3a.emailsrvr.com [173.203.187.121]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id E0AC03CB37 for ; Tue, 30 Aug 2022 13:32:12 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=searls.com; s=20200317-uaz7569a; t=1661880732; bh=uYUc6Qw4E5vXERB2oaJX6yPgicEt5p2E5G71MgxW+ZI=; h=From:To:Subject:Date:From; b=PPkQItcv3yHhRk2f6fpYyWYDODuO7cIpXLnS2kDmPy8RC+w1y9EYfz4TSPPTXOjCr kd7soWRa070TFL6AzKdm8vL/w9ea8neTBWcnefGt7xAsdETveuq6TEbv9O8kZSyBNn 2M5v6Rdjt3uKxAXkSVxDzFkvKXV4wYOeUe66xDYE= Received: from smtp192.mex09.emailsrvr.com (unknown [74.205.9.160]) by smtp16.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTPS id 6E1F043C9; Tue, 30 Aug 2022 13:32:12 -0400 (EDT) Received: from MBX20B-IAD3.mex09.mlsrvr.com (172.29.64.74) by MBX20B-IAD3.mex09.mlsrvr.com (172.29.64.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.9; Tue, 30 Aug 2022 13:32:11 -0400 Received: from MBX20B-IAD3.mex09.mlsrvr.com ([fe80::e94e:ecd0:729e:7f5c]) by MBX20B-IAD3.mex09.mlsrvr.com ([fe80::e94e:ecd0:729e:7f5c%25]) with mapi id 15.01.2507.009; Tue, 30 Aug 2022 13:32:11 -0400 From: Doc Searls To: "David P. Reed" CC: "starlink@lists.bufferbloat.net" Thread-Topic: [Starlink] Starlink "beam spread" Thread-Index: AQHYvJEXyQbfZvqfy0+iI2U6KcW8JK3H9suA Date: Tue, 30 Aug 2022 17:32:11 +0000 Message-ID: References: <1661878433.14064713@apps.rackspace.com> In-Reply-To: <1661878433.14064713@apps.rackspace.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [72.205.91.47] Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Classification-ID: 8e87adbf-b212-479e-9757-2ed68c0e7a03-1-1 X-Sender-ID: doc@searls.com Subject: Re: [Starlink] Starlink "beam spread" X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 Aug 2022 17:32:13 -0000 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 limi= t to what's possible with the system? I ask the first question because Starlink has been deorbiting quite a few s= atellites... https://spacenews.com/spacex-launches-starlink-satellites-as-it-deorbits-or= iginal-ones/ https://www.space.com/spacex-starlink-satellite-deorbit-video ... while launching many new ones.=20 For example, there will be a Falcon launch from Vandenberg, of several doze= n 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-falco= n-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 atm= osphere, 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 no= t here in Santa Barbara often enough. But I am here now, so I'll be shootin= g 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 wrote: >=20 > I have no clue why this matters (other than this is in color). > =20 > The phased array antennas used by Starlink are quite limited - in particu= lar, there are 4 on each satellite and each earth-ground path is half-duple= x, TDM, essentially. Limited by hardware. The problem of signal equalizatio= n and quantization limits prevent "space division multiplexing" and "freque= ncy division multiplexing" in practice. > =20 > 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 anten= nas on the satellite.=20 >=20 > trying to increase the coverage of an individual satellite basically mean= s serving more dishys per satellite, with less total bit rate, and much lon= ger latency due to the half duplexness. > =20 > Now if the total bit rate of a sat-to-dishy link were, say, 1 Gigabit, li= ke an 802.11ac AP gives you, and the turnaround time were under 1 microseco= nd rather than 4 msec. maybe then you could get reasonable Internet servic= e to dishys. > =20 > 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.= =20 > =20 > Sorry to rain on all the techy dreaming. > =20 > First, it's worth looking at all the problems currently in WiFi performan= ce when you share an AP with multiple active stations using 100's of Gb/s o= n the average (not just occasionally). > =20 > Dave - you tried in "make-wifi-fast", and the architecture gets in the wa= y 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 hug= e variability if you share the AP at all, for these reasons). > =20 > Starlink is a good "last resort" service as constituted. But fiber and la= st few-hundred meters wireless is SO much better able to deliver good Inter= net service scalably. > Even that assumes fixing the bufferbloat that the Starlink folks don't se= em to be able to address... > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink