From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vsmx002.dclux.xion.oxcs.net (vsmx002.dclux.xion.oxcs.net [185.74.65.108]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 8A2E53B29D for ; Tue, 26 Jul 2022 09:36:11 -0400 (EDT) Received: from proxy-2.proxy.oxio.ns.xion.oxcs.net (proxy-2.proxy.oxio.ns.xion.oxcs.net [197.248.130.130]) by mx-out.dclux.xion.oxcs.net (Postfix) with ESMTPA id C96758C034F for ; Tue, 26 Jul 2022 13:36:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dclux.xion.oxcs.net; s=mail1; t=1658842570; bh=iK+Gwg7gFt41PAAy1M7ewS8+yMguz7OHwuVQhTXriBU=; h=Date:From:To:In-Reply-To:References:Subject:From; b=LSpVVx//q4Nf8os9g7fi3g6E4xZlf+iYbG5M/wF76tl6/YB+IWNTTqRqyGgJ9LqOp QoOxlkhPCO0izlmR6h1+MxVxF/LE+Jg4xzyhK5DULWmtlh9idVtgDpaY+v+VkL6L4P tmoXn/1A5YsIWeeaHZ6CI6Yvhmd6scxDs1/tFNrsNyfL8pmzHgGc9AZhP1AfDnuN/z V9r5E05RanlDluNCuhEyVxDMNC/i/bGg55f/TakI0NdOCVnJ/pbq7SIczE0VT0FWGf plYZ70AyyO24Vj5YJqufvf4DjfkN1Kb7qaZjDx74Si0gnUucOMneAyi0vja3Kk79Fs 9t0o/hWU9Nycg== Date: Tue, 26 Jul 2022 16:35:58 +0300 From: Mike Puchol To: starlink@lists.bufferbloat.net Message-ID: <3d8ae0b7-3f37-417c-9e54-76e6f9e08991@Spark> In-Reply-To: <13620203-c86f-d6d3-ed46-841109de105f@auckland.ac.nz> References: <13620203-c86f-d6d3-ed46-841109de105f@auckland.ac.nz> X-Readdle-Message-ID: 3d8ae0b7-3f37-417c-9e54-76e6f9e08991@Spark MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="62dfedc3_1d545c4d_d91b" X-VadeSecure-Status: LEGIT X-VADE-STATUS: LEGIT Subject: Re: [Starlink] starlink extensions over uk 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, 26 Jul 2022 13:36:11 -0000 --62dfedc3_1d545c4d_d91b Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline In essence, yes - the difference is in GSO protection, not minimum elevat= ion. As for the interference, the main worry is not primary feeder links (e.g.= those from earth stations such as Goonhilly), those have controlled buil= ds, so that no two antennas can interfere (including when SpaceX co-locat= es a gateway, GSO protections still apply). The interference is directly in-band, as the Ku and Ka bands are used bot= h by satellite TV, GEO data systems, and Starlink. Thus, if a Starlink sa= tellite in-line between a satellite TV customer and the GEO satellite, th= e satellite TV customer would experience considerable interference. This = is why Starlink satellites, gateways, or user terminals cannot transmit a= nywhere between 10=C2=BA above and 10=C2=BA below the GSO arc (18=C2=BA p= reviously). This presentation on the subject was shared by a friend earlier, it is a = really good read on the topic:=C2=A0https://www.itu.int/en/ITU-D/Regional= -Presence/AsiaPacific/Documents/Events/2017/Aug-ISS2017/PAPER=5FWorkshop=5F= S3=5FTimur.pdf Phased array antennas are notoriously prone to generating considerable si= delobes, unlike e.g. a Cassegrain dish. A good article on these (and miti= gations) can be found here:=C2=A0https://www.mwrf.com/technologies/system= s/article/21143497/analog-devices-phasedarray-antenna-patterns-part-6side= lobes-and-tapering These sidelobes contribute to the interference, and have been a major sou= rce of complaints by the likes of Viasat and others - whereby they claim = SpaceX doesn=E2=80=99t consider the additive effects of sidelobes from do= zens or hundreds of ESAs on satellites and terminals, against a single vi= ctim earth station or satellite. Best, Mike On Jul 26, 2022, 16:10 +0300, Ulrich Speidel via Starlink , wrote: > So then the difference really is just in the GSO protection settings I = guess. > The GSO protection is - to an extent - also patch protection. After all= - who'd need satellite TV if everyone could watch the same TV via LEOs=3F= But consider that: > > =E2=80=A2 Interference to GEO sats from Starlink & Co. is out of band. = I'm not sure what the out-of-band emissions profiles of dishys are, but I= 'd imagine we'd be looking at the usual few dozen dB below peak. > =E2=80=A2 Distance to GSO is around 64 times (2=5E6) larger than to Sta= rlink's orbits - GEO sats see around 1/4000th ((2=5E6)=5E-2) of the power= from a ground station that the Starlink satellite in front of it sees. T= hat's 36 dB in extra separation. > =E2=80=A2 Dishy is comparatively small in cross-section, and that sever= ely limits its gain. Most serious GEO uplink applications that I'm aware = of use dishes more like 8 times dishy's cross section. That's another 9 d= B or so in separation between a Starlink dishy signal and signal directed= specifically at a GEO sat just from the overall size. Uplinks from gatew= ays are likely to be much more of an issue (always on and probably higher= power as well as =7E6 dB higher antenna gain judging from the photos I'v= e seen), but then again these point away from the GSO when serving birds = further north. > =E2=80=A2 My understanding (correct me if you think I'm wrong here): It= 's also possible that Dishy's nature as a phased array helps here. Why=3F= Out-of-band interference results from intermodulation and other unwanted= emissions from the power amplifiers (PA) of transmitters. Where these ar= e fed into a dish from a single PA, their amplitudes get amplified by the= gain of the dish. Now say we're trying to replace that dish by an array = with N antennas and N associated PAs that feed at the appropriate phase. = Then each element (individual PA with associated antenna) needs to contri= bute P/N of the total transmit power P of the big PA & dish. Now remember= that power is proportional to the square of the amplitude. As long as th= e wanted signal components from the PA are correlated - and they have to = be for the phased array to work - their N amplitudes add up, meaning the = total output power of the wanted signal across all elements is proportion= al to N=5E2. So each element only needs to contribute an amplitude propor= tional to 1/N in order to produce the wanted output at the correct power.= However, now each PA produces its own dirt signal. But unlike the wanted= signal, these unwanted signals aren't necessarily all correlated between= the elements. As a result, the amplitudes of the unwanted signals from t= he PAs will partially cancel out as the signal combines into the beam tha= t is being formed. So only the powers of these uncorrelated unwanted sign= als add up, but their amplitudes don't, meaning we now have an unwanted s= ignal power that is proportional only to N rather than N=5E2, resulting i= n a higher ratio of wanted signal to unwanted signal. Again that'd help a= lot with separation in an array with lots of elements and associated PAs= . That said, published research into the unwanted emissions of phased arr= ays is still a bit in its infancy, and I can't profess to understand enou= gh about Dishy's innards or the level of correlation between unwanted emi= ssions in the array, but I'd consider it possible that this allows for so= me relaxation on the GSO protection parameters when it comes to Starlink.= > > On 26/07/2022 9:06 am, Mike Puchol via Starlink wrote: > > Your calculations are =E2=80=9CBack of the Envelope Approved=E2=80=9D= :-) > > > > My simulator can be found at https://starlink.sx and runs on your bro= wser (desktop only). I have just released v1.10.6, which adds a slider fo= r setting the GSO protection. This is the difference in Sweden from 18=C2= =BA (as used until recently) versus 10=C2=BA (as found in recent ITU fili= ngs for STEAM-1B): > > > > <18=5Fvs=5F10=5FGSO.png> > > > > Minimum elevation in both cases is 25=C2=BA, so that variable is unch= anged. > > > > Best, > > > > Mike > > On Jul 25, 2022, 11:35 +0300, Ulrich Speidel via Starlink , wrote: > > > I haven't got Mike's nice software but I got snail mail today, so l= et's try the back of one of the envelopes. > > > 53 degrees north (where the existing constellation tops out) is rou= ghly the latitude of Nottingham or Stoke-on-Trent. Note that this is also= the latitude with the largest number of birds per km (or mile, if you so= prefer) of parallel. They sit almost cheek to jowl there. > > > Now the northern tip of the UK's main islands is at around 59 degre= es north - that's six degrees more. One degree of latitude is roughly equ= ivalent to 10,000 km / 90 degrees =3D 111 km, so we're talking around a d= evilish 666 km to the north of Nottingham here as the crow flies. > > > Lets assume Dishy points itself due south at 59 degrees. The birds = are at about 550 km. So doing a flat earth approximation for the moment, = we're having to point at a satellite 550 km up from 660 km away - that gi= ves an elevation of about 40 degrees (=3Darctan(550/660)). Ballpark. Now = reduce that by the 6 degrees of difference to account for the curvature o= f the earth and we still have around 34 degrees, allowing for a bit of le= eway either side if the closest bird isn't actually due south but a bit t= o the east or west. Again, ballpark, but we're nowhere near 25 degrees ye= t. > > > So I'd say that should cover it nicely=3F Where does my envelope er= r=3F GEO arc protection aside for the moment, of course. And of course ju= st because Starlink offers you service doesn't mean that it's actually co= ntinuous. > > > On 25/07/2022 8:59 am, Dave Taht via Starlink wrote: > > > > =46or those of you that don't follow mike's twitter feed... > > > > > > > > https://twitter.com/mikepuchol/status/1551288485713149952 > > > > > > > > -- > > > > =46Q World Domination pending: https://blog.cerowrt.org/post/stat= e=5Fof=5Ffq=5Fcodel/ > > > > Dave T=C3=A4ht CEO, TekLibre, LLC > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= > > > > Starlink mailing list > > > > Starlink=40lists.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=40auckland.ac.nz > > > http://www.cs.auckland.ac.nz/=7Eulrich/ > > > **************************************************************** > > > > > > > > > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F > > > Starlink mailing list > > > Starlink=40lists.bufferbloat.net > > > https://lists.bufferbloat.net/listinfo/starlink > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F > > Starlink mailing list > > Starlink=40lists.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=40auckland.ac.nz > http://www.cs.auckland.ac.nz/=7Eulrich/ > **************************************************************** > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F > Starlink mailing list > Starlink=40lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink --62dfedc3_1d545c4d_d91b Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
In essence, yes - the difference is in GSO protecti= on, not minimum elevation.

As for the interference, the main worry is not primary feeder links (e.g.= those from earth stations such as Goonhilly), those have controlled buil= ds, so that no two antennas can interfere (including when SpaceX co-locat= es a gateway, GSO protections still apply).

The interference is directly in-band, as the Ku and Ka bands are used bot= h by satellite TV, GEO data systems, and Starlink. Thus, if a Starlink sa= tellite in-line between a satellite TV customer and the GEO satellite, th= e satellite TV customer would experience considerable interference. This = is why Starlink satellites, gateways, or user terminals cannot transmit a= nywhere between 10=C2=BA above and 10=C2=BA below the GSO arc (18=C2=BA p= reviously).

This presentation on the subject was shared by a friend earlier, it is a = really good read on the topic:&=23160;https://www.it= u.int/en/ITU-D/Regional-Presence/AsiaPacific/Documents/Events/2017/Aug-IS= S2017/PAPER=5FWorkshop=5FS3=5FTimur.pdf

Phased array antennas are notoriously prone to generating considerable si= delobes, unlike e.g. a Cassegrain dish. A good article on these (and miti= gations) can be found here:&=23160;https://www.= mwrf.com/technologies/systems/article/21143497/analog-devices-phasedarray= -antenna-patterns-part-6sidelobes-and-tapering

These sidelobes contribute to the interference, and have been a major sou= rce of complaints by the likes of Viasat and others - whereby they claim = SpaceX doesn=E2=80=99t consider the additive effects of sidelobes from do= zens or hundreds of ESAs on satellites and terminals, against a single vi= ctim earth station or satellite.

Best,

Mike
On Jul 26, 2022, 16:10 +0300, Ulric= h Speidel via Starlink <starlink=40lists.bufferbloat.net>, wrote:

So then the difference really is just in the GSO protection settings I= guess.

The GSO protection is - to an extent - also patch protection. After al= l - who'd need satellite TV if everyone could watch the same TV via LEOs=3F= But consider that:

  • Interference to GEO sats from Starlink & Co. is out of band. I'm = not sure what the out-of-band emissions profiles of dishys are, but I'd i= magine we'd be looking at the usual few dozen dB below peak.
  • Distance to GSO is around 64 times (2=5E6) larger than to Starlink's = orbits - GEO sats see around 1/4000th ((2=5E6)=5E-2) of the power from a = ground station that the Starlink satellite in front of it sees. That's 36= dB in extra separation.
  • Dishy is comparatively small in cross-section, and that severely limi= ts its gain. Most serious GEO uplink applications that I'm aware of use d= ishes more like 8 times dishy's cross section. That's another 9 dB or so = in separation between a Starlink dishy signal and signal directed specifi= cally at a GEO sat just from the overall size. Uplinks from gateways are = likely to be much more of an issue (always on and probably higher power a= s well as =7E6 dB higher antenna gain judging from the photos I've seen),= but then again these point away from the GSO when serving birds further = north.
  • My understanding (correct me if you think I'm wrong here): It's also = possible that Dishy's nature as a phased array helps here. Why=3F Out-of-= band interference results from intermodulation and other unwanted emissio= ns from the power amplifiers (PA) of transmitters. Where these are fed in= to a dish from a single PA, their amplitudes get amplified by the gain of= the dish. Now say we're trying to replace that dish by an array with N a= ntennas and N associated PAs that feed at the appropriate phase. Then eac= h element (individual PA with associated antenna) needs to contribute P/N= of the total transmit power P of the big PA & dish. Now remember tha= t power is proportional to the square of the amplitude. As long as the wa= nted signal components from the PA are correlated - and they have to be f= or the phased array to work - their N amplitudes add up, meaning the tota= l output power of the wanted signal across all elements is proportional t= o N=5E2. So each element only needs to contribute an amplitude proportion= al to 1/N in order to produce the wanted output at the correct power. How= ever, now each PA produces its own dirt signal. But unlike the wanted sig= nal, these unwanted signals aren't necessarily all correlated between the= elements. As a result, the amplitudes of the unwanted signals from the P= As will partially cancel out as the signal combines into the beam that is= being formed. So only the powers of these uncorrelated unwanted signals = add up, but their amplitudes don't, meaning we now have an unwanted signa= l power that is proportional only to N rather than N=5E2, resulting in a = higher ratio of wanted signal to unwanted signal. Again that'd help a lot= with separation in an array with lots of elements and associated PAs. Th= at said, published research into the unwanted emissions of phased arrays = is still a bit in its infancy, and I can't profess to understand enough a= bout Dishy's innards or the level of correlation between unwanted emissio= ns in the array, but I'd consider it possible that this allows for some r= elaxation on the GSO protection parameters when it comes to Starlink.
On 26/07/2022 9:06 am, Mike Puchol via= Starlink wrote:
Your calculations are =E2=80=9CBack of the Envelope= Approved=E2=80=9D :-)&=23160;

My simulator can be found at https://starlink.sx and runs on your browser (de= sktop only). I have just released v1.10.6, which adds a slider for settin= g the GSO protection. This is the difference in Sweden from 18=C2=BA (as = used until recently) versus 10=C2=BA (as found in recent ITU filings for = STEAM-1B):

<18=5Fvs=5F10=5FGSO.png>

Minimum elevation in both cases is 25=C2=BA, so that variable is unchange= d.

Best,

Mike
On Jul 25, 2022, 11:35 +0300, Ulric= h Speidel via Starlink <starlink=40lists.bufferbloa= t.net>, wrote:

I haven't got Mike's nice software but I got snail mail today, so let'= s try the back of one of the envelopes.

53 degrees north (where the existing constellation tops out) is roughl= y the latitude of Nottingham or Stoke-on-Trent. Note that this is also th= e latitude with the largest number of birds per km (or mile, if you so pr= efer) of parallel. They sit almost cheek to jowl there.

Now the northern tip of the UK's main islands is at around 59 degrees = north - that's six degrees more. One degree of latitude is roughly equiva= lent to 10,000 km / 90 degrees =3D 111 km, so we're talking around a devi= lish 666 km to the north of Nottingham here as the crow flies.

Lets assume Dishy points itself due south at 59 degrees. The birds are= at about 550 km. So doing a flat earth approximation for the moment, we'= re having to point at a satellite 550 km up from 660 km away - that gives= an elevation of about 40 degrees (=3Darctan(550/660)). Ballpark. Now red= uce that by the 6 degrees of difference to account for the curvature of t= he earth and we still have around 34 degrees, allowing for a bit of leewa= y either side if the closest bird isn't actually due south but a bit to t= he east or west. Again, ballpark, but we're nowhere near 25 degrees yet.<= br />

So I'd say that should cover it nicely=3F Where does my envelope err=3F= GEO arc protection aside for the moment, of course. And of course just b= ecause Starlink offers you service doesn't mean that it's actually contin= uous.

On 25/07/2022 8:59 am, Dave Taht via S= tarlink wrote:
=46or those of you that don'= t follow mike's twitter feed...

https://twitter.com/mikepuchol/status/15512= 88485713149952

--
=46Q World Domination pending: https://blog.cer= owrt.org/post/state=5Fof=5Ffq=5Fcodel/
Dave T=C3=A4ht CEO, TekLibre, LLC
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
Starlink mailing list
S= tarlink=40lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/starlink
--  =20
****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speid=
el=40auckland.ac.nz  =20
http://www.cs.auckland.ac=
.nz/=7Eulrich/
****************************************************************
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
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-- =20
****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel=40auckland.ac.nz =20
http://www.cs.auckland.ac.nz/=7Eulrich/
****************************************************************
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