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 5D1723B29D for ; Wed, 5 Jun 2024 02:12:25 -0400 (EDT) Received: from proxy-18.proxy.shared.ns.xion.oxcs.net (proxy-18.proxy.shared.ns.xion.oxcs.net [73.162.31.53]) by mx-out.dclux.xion.oxcs.net (Postfix) with ESMTPA id C6148A60C5C for ; Wed, 5 Jun 2024 06:12:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dclux.xion.oxcs.net; s=mail1; t=1717567944; bh=CQnNXD6P1wkkRrNZQnJ8VWEEoH1890V+6RLfsrXD9N0=; h=Date:From:To:In-Reply-To:References:Subject:From; b=ZyjJojWr38GSxUmnpO2Mzs5EWqS2i6tcZXgxkogWRPx26/9EbptqrCuQM9CvBtndB OZCiGIFN82FcYUtPTje/z4S+mEU7sq+Xp83UvBl23MOi+LZ6OeTQPgZ2eLsIslr4JZ nUGvMq7wlcbse+IAF7T5DdahMZnZDd1A8qENX5YrimPOlL73y9QPxKoQ5fE5TipjE6 dJsaYFEuWbUTVDR2ADcGjkBDua1dsIjLq0mHrcYX2sGnAfBdzyqp4XSzxKdU722iv3 Y43Gtw5t6vYxPNdqgJ7v5msfvHfbZLzf3D81X4lNbr6T7rWl7UWS0tXbGG9FMugjUB IS6m7qw/yQvEg== Date: Tue, 4 Jun 2024 23:12:09 -0700 From: Mike Puchol To: Michael Richardson via Starlink Message-ID: In-Reply-To: <350685C2-FF39-4EE4-93A5-1BE6EE9AC6C7@gmx.de> References: <32AD770E-336E-4CF4-8B1B-8AE7353981CC@ieee.org> <9687.1717527495@obiwan.sandelman.ca> <1011428206.2534598.1717542074644@www.openxchange.eu> <350685C2-FF39-4EE4-93A5-1BE6EE9AC6C7@gmx.de> X-Readdle-Message-ID: eed44c16-69cd-454c-a0fe-79fc7997efd1@Spark MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="666001c3_6c190298_5bb2" X-VadeSecure-Status: LEGIT X-VADE-STATUS: LEGIT Subject: Re: [Starlink] SpaceX/Starlink says it's ready for a fall satellite-to-cell service with T-Mobile 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: Wed, 05 Jun 2024 06:12:25 -0000 --666001c3_6c190298_5bb2 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline The doppler shift will change as the satellite transitions overhead, this= is very clear if you look at a spectrum capture of the narroband beacons= with a static LNB, and can be corrected by the user terminal, as it is e= xpecting this shift and has software written specifically to deal with it= . In the case of e.g. LTE, a UE is not designed to cater for a changing dop= pler shift, so this is compensated by the satellite. In a theoretical MIM= O configuration where multipath is achieved by using beams from multiple = satellites towards a UE=E2=80=99s location, the signals such as P-SS and = S-SS from each satellite would arrive at the UE at different times, frequ= encies, and power levels. Here is an interesting paper that discusses the topic:=C2=A0https://arxiv= .org/pdf/1706.06013 Best, Mike On Jun 4, 2024 at 21:47 -0700, Sebastian Moeller , wro= te: > Curious, is that doppler correction applied individually per dishy, or = per cell=3F If the latter do cells extend ahead or behind the satellite's= projection onto the globe, or is there one or more beams ahead an anothe= r one or more behind=3F > > > > On 5 June 2024 06:16:02 CEST, Mike Puchol via Starlink wrote: > > > Yes, they correct doppler in a single stream - what I was alluding = to is the MIMO advantage of terrestrial networks which cannot be easily r= eplicated from multiple satellites, as the UE cannot correct multiple dop= pler shifts and timing advances unless it implements an NTN-specific appr= oach. > > > > > > Best, > > > > > > Mike > > > On Jun 4, 2024 at 20:17 -0700, David Lang , wrote:= > > > > Mike Puchol wrote: > > > > > > > > > Something else that's much harder to implement is MIMO, as you = don't get path > > > > > diversity from a satellite. AST claims they will do this by usi= ng more than > > > > > one satellite, however they haven't answered basic questions su= ch as how will > > > > > the UE compensate the huge differences in doppler shift on top = of the multiple > > > > > paths. > > > > > > > > for the starlink version, the satellite adjusts it's transmit/rec= eive > > > > frequencies to correct for the doppler shift so that the phones d= on't need to. > > > > > > > > David Lang > > > > > -- > Sent from my Android device with K-9 Mail. Please excuse my brevity. --666001c3_6c190298_5bb2 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
The doppler shift will change as the satellite tran= sitions overhead, this is very clear if you look at a spectrum capture of= the narroband beacons with a static LNB, and can be corrected by the use= r terminal, as it is expecting this shift and has software written specif= ically to deal with it.

In the case of e.g. LTE, a UE is not designed to cater for a changing dop= pler shift, so this is compensated by the satellite. In a theoretical MIM= O configuration where multipath is achieved by using beams from multiple = satellites towards a UE=E2=80=99s location, the signals such as P-SS and = S-SS from each satellite would arrive at the UE at different times, frequ= encies, and power levels.

Here is an interesting paper that discusses the topic:&=23160;https://arxiv= .org/pdf/1706.06013

Best,

Mike
On Jun 4, 2024 at 21:47 -0700, Seba= stian Moeller <moeller0=40gmx.de>, wrote:
Curious, is that doppler correction applied individ= ually per dishy, or per cell=3F If the latter do cells extend ahead or be= hind the satellite's projection onto the globe, or is there one or more b= eams ahead an another one or more behind=3F


On 5 June 2024 06:16:02 CEST, Mike Puchol via Starl= ink <starlink=40lists.bufferbloat.net> wrote:
Yes, they cor= rect doppler in a single stream - what I was alluding to is the MIMO adva= ntage of terrestrial networks which cannot be easily replicated from mult= iple satellites, as the UE cannot correct multiple doppler shifts and tim= ing advances unless it implements an NTN-specific approach.

Best,

Mike
On Jun 4, 2024 at 20:17 -0700, Davi= d Lang <david=40lang.hm>, wrote:
Mike Puchol wrote:

Something else that's much harder to implem= ent is MIMO, as you don't get path
diversity from a satellite. AST claims they will do this by using more th= an
one satellite, however they haven't answered basic questions such as how = will
the UE compensate the huge differences in doppler shift on top of the mul= tiple
paths.

for the starlink version, the satellite adjusts it's transmit/receive
frequencies to correct for the doppler shift so that the phones don't nee= d to.

David Lang

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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