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<div class="moz-cite-prefix">On 27/09/2023 8:00 am, David Lang via
Starlink wrote:<br>
</div>
<blockquote type="cite" cite="mid:9q304pqs-778s-2s16-455s-604qnn43082q@ynat.uz">
On Tue, 26 Sep 2023, Jim Forster wrote:<br>
<br>
> This is all true (as much as I understand), Worth noting as
well, is that with <br>
> LEOs if one satellite is maxed out serving a cell, then
getting a second <br>
> satellite to help with that cell mean adding *lots* more
satellites. If <br>
> adjacent cells had very different loads then I guess nearby
unloaeded <br>
> satellites could help out their busy neighbors. But areas
with busy cells <br>
> close together would mean doubling the number of satellites
and therefore <br>
> platform Capex. Whereas terrestrial towers can be densified
in busy areas.<br>
<br>
In 2021 when SpaceX had launched 1800 satellites they said that
once all of them <br>
reached operational altitude they would be able to provide global
coverage.<br>
<br>
They now have >4k satellites in operation and (if fully
approved) are aiming at <br>
~10x that number eventually. That leaves a lot of additional
satellites to <br>
provide additional coverage for busy cells or smaller cells.<br>
</blockquote>
<p>There's a minor issue that I'm not convinced people take into
account. Simply putting more satellites in orbit doesn't
necessarily create more system capacity - it also takes spectrum
to accommodate the up- and downlink capacity.</p>
<p>And therein lies a bit of a challenge. In terrestrial
cellularised communication, one can leverage proximity between
base station and UE to reduce power emission to a point where
neither can be heard too far away. This allows re-use of the same
part of the spectrum a bit further down the road. But that only
works because we can build base stations within a few hundred
metres of where the users are. The moment we need to project
capacity from kilometres away, we're no longer economical with our
spectrum resource. At that point, we're leveraging low user
density.</p>
<p>When cellular networks start out, the base stations tend to be on
top of high vantage points: towers, high buildings, hills. As a
network gains customers, the base stations migrate down the slopes
- the hills now serve as welcome obstacles to isolate the base
stations in the valleys from each other spectrum-wise. Your cells
shrink in size and your transmissions drop in power.<br>
</p>
<p>The problem with a LEO system such as Starlink is that migrating
down from orbit is not an option. You have to project your
capacity from many hundreds of km away. You can to an extent use
beamforming etc. to direct your transmissions at targets on the
ground, but the side lobes from your phased arrays pretty much
render your transmit frequency unusable for any other satellite
for hundreds of miles around. <br>
</p>
<p>Going to E band - fine, but even that is a limited resource, and
it has its other issues, too.</p>
<blockquote type="cite" cite="mid:9q304pqs-778s-2s16-455s-604qnn43082q@ynat.uz">
<br>
I agree terrestrial towers can be densified more easily in a
specific area.<br>
<br>
I'm saying that the crossover point where the density favors
terrestrial towers <br>
is significantly denser than the original author was stating. (and
as more sats <br>
are launched, will move further)<br>
<br>
There's also the fact that satellite densification covers all
areas, where <br>
terrestrial tower densification only covers that area. So around
the already <br>
dense areas, you will have tower densification happening, pushing
out, <br>
leveraging the nearby wired infrastructure. But you may see a
different <br>
situation in areas where small communities are growing and you
have to setup the <br>
tower and wired infrastructure from scratch.<br>
<br>
scenario:<br>
<br>
a village that is a 30 min drive from the next community and
doesn't <br>
have much fiber run to it. As it grows, you can't just put in
towers without <br>
also running tens of miles of fiber to the area, so densification
of towers in <br>
the area is significantly harder than seeing the suburbs of a
large city grow <br>
where fiber is just a couple miles away.<br>
<br>
David Lang<br>
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</blockquote>
<pre class="moz-signature" cols="72">--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
The University of Auckland
<a class="moz-txt-link-abbreviated" href="mailto:u.speidel@auckland.ac.nz">u.speidel@auckland.ac.nz</a>
<a class="moz-txt-link-freetext" href="http://www.cs.auckland.ac.nz/~ulrich/">http://www.cs.auckland.ac.nz/~ulrich/</a>
****************************************************************
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