[Starlink] Comprehensive Measurement Study on Starlink Performance Published

[Ulrich Speidel]

On 27/02/2024 7:21 pm, David Lang wrote:
> ...snip
> > The point though is that these sparsely populated areas aren't where 
> the
> > scalability issue arises. Capacity needs to be where the demand for 
> it is.
>
> I only partially agree with you here. Yes, capacity that isn't needed 
> doesn't
> matter, but I think that the capacity where there aren't other options 
> matters
> more than in the more densly populated areas where there are other 
> options (and
> I say this as a starlink user living in the Los Angeles area, a fairly 
> densely
> populated area) I use Starlink as a backup now, but I do periodically 
> test it
> and verify that it is acceptable for work + other uses.
The pinchpoint thus far seems to have been the suburban and lifestyle 
block belts - basically where fibre doesn't reach for whatever reason, 
but where people with the wealth to afford Starlink (or fibre if it were 
offered) live. My bog standard example here in NZ are your IT project 
manager who wants to live on a lifestyle block out bush. They're dime a 
dozen here and Starlink serves them now even when they couldn't 
previously get fibre.
> >>> If you put in fibre today, you know that by upgrading the 
> endpoints over
> >>> time, you can get orders of magnitude of extra bandwidth if needed.
> >>
> >> If you can get fibre, you should get fibre (with starlink as a 
> possible
> >> backup). SpaceX has said many times that Starlink is never going to be
> >> competitive to fibre
> >>
> >> if you can get fibre, you aren't under-connected.
> > Tick. But 2 billion plus can't, or at least not yet. The question is 
> how many
> > of them might Starlink & Co be able to assist in due course?
>
> what information do you have about the distribution of these 2B 
> under-connected?
My particular "pet case" are Pacific Islanders on islands with 
populations too small / poor to afford a submarine fibre connection. 
These are a somewhat interesting case in that they are just a couple of 
million all up I guess, with numbers shrinking as fibre does get laid. 
Essentially, anyone with 10k plus population and under 1000 km (~600 
miles) to the next cable access point is now a member of the club - 
having a rich nation or large diaspora backing you helps, but beyond 
that it's distance, GDP and politics that govern the game. Starlink can 
(and does now) serve most of the remaining islands, however what makes 
life interesting here is that these islands are often quite densely 
populated, which with growth in Starlink endpoints makes for reduced 
capacity per user. Kiribati for example currently sees around 10 
Starlink kits arriving on every flight into Tarawa in the western part 
of the country (3 flights a week). I'm sure some more arrive by boat 
every few weeks - air freight is expensive (around US$400 per unit). 
Some of these will no doubt go to the outer islands, but Starlink is now 
having a visible presence on roofs there (my PhD student was up there 
and installed one for his family as well as two as part of our project). 
There is no official service yet but regional roaming works well (while 
the power is on, which it hasn't always been lately).
>
> (and as someone who just a couple years ago was on a 8m down/1m up 
> connection,
> what is the definition of 'under-connected'?, 
That's under-connected in my book.
>
> but as I understand the reverse-engineering of the starlink system, a 
> given cell
> is currently only serviced by one satellite at a time.
Are we sure here? One (classic) Dishy is served by one satellite at a 
time, but a cell (which can contain multiple DIshys) almost has to be 
serviced by multiple sats to get around obstruction issues (Starlink is 
now quite tolerant of these. Try to put it in a tight spot where it 
can't see the northern sky at your place in LA and tell me whether it 
still connects. If it does, then your cell gets served by multiple sats).
>
> >>>  But now you want to serve cellphones on the ground which have 
> smaller
> >>> antennas by a factor of I'd say about 16:1 aperture-wise. So you 
> need to
> >>> make your antennas in space 16 times larger just to maintain what 
> you had
> >>> with Dishy.
> >>
> >> the cell service is not intended to compete with the Dishy, just be an
> >> emergancy contact capability
> >
> > Here's how one of the local partner organisation here spins it. Much 
> more
> > than just an emergency contact capability:
> >
> > https://one.nz/why-choose-us/spacex/ 
> <https://one.nz/why-choose-us/spacex>
> >
> > (Judge for yourself whether this instils the impression that you're 
> going to
> > get 5G level service off this. You really need to read the small print!)
>
> yeah, that does seem to imply more than it can offer. Elon has been 
> pretty vocal
> that each cell is something like 70 miles in diameter, and the available
> bandwidth needs to be shared across all users. Text messages should 
> always work,
> voice will probably work, and as the system gets built out, data will 
> happen,
> but will be slow due to the sharing.
Yep, that's what I'd expect also.
>
> > It's not that easy. Adding satellites in the first instance is just 
> adding
> > transmitters, and unless you have spectrum to accommodate these, 
> then even if
> > the satellites' on-board bandwidth is higher, it doesn't translate 
> into as
> > much extra capacity. Spectrum comes in terms of extra Hertz, and in 
> terms of
> > spatial beam separation. The former is limited in that they don't 
> make any
> > more of it, and the latter is a matter of antenna size and getting 
> antenna
> > side lobes sufficiently far down. And we know that SpaceX are 
> running close
> > to spectral capacity in some areas.
>
> I am assuming that the fact that they have planned for 10x satellites 
> (~45k
> satellites up from the ~5k they have now) means that they have a plan 
> to be able
> to use that many efficiently. I have no inside knowlege, so I am 
> speculating
> about this.

A lot of what is meant to go up there is meant to use higher bands, 
which means "more bandwidth" but with caveats relating to obstruction by 
atmospheric phenomena. So that wouldn't quite scale I guess.

There are also other reasons for why you'd want more birds:

  * Path diversity on ISLs to avoid "busy center" issues
  * Having each satellite look after fewer users on the ground allows
    for more bandwidth per user overall due to spatial diversity.
  * Better illumination of the ground.
  * Higher capacity in equatorial areas (where GSO protection takes a
    good chunk out of what's directly overhead).
  * Redundancy.

>
> > Assuming that the spatial distribution of the under-connected is 
> somewhat
> > similar to Starlink's current customer base in terms of densities, 
> we need
> > that factor of 1000.
>
> I think there are a lot of early adopters for who Starlink is a 
> luxury, not a
> lifeline. 
I think we're well past that point here. Last year's cyclone was the 
best sales push Elon could have hoped for. You no longer get a discount 
here for living rurally like last year. But you can get deprioritised 
service.
> I think the under-connected are going to be in more sparse areas than
> the early adopters. I have friends and family in rural areas, and 
> awareness of
> Starlink is only slowly penetrating there.
The slow penetration of modernity into US rural areas seems to be a 
particularly American problem - it's not been an issue here or in the 
Pacific.
>
> I'm seeing increased use for mobile applications here in the US, 
> including in
> built-up areas.
Interesting.
>
>
> > So which factor in terms of capacity growth should we expect of 
> Starlink & Co
> > over today?
>
> not enough information. I agree it's something to watch, I'm just more
> optomistic about it than you are.
OK, let's see how this pans out.
>
> >>> And then you need to provision some to compete with extra capacity 
> you
> >>> wanted, and then some to cope with general growth in demand per 
> client.
> >>> And then you have to transmit that same viral cat video over and over
> >>> again through the same pipe, too.
> >>
> >> True, although if you can setup a community gateway of some sort to 
> share
> >> one satellite connection, you gain efficiency (less housekeeping 
> overhead
> >> or unused upload timeslots), and have a place that you can implement
> >> caches.
> >
> > Indeed. Or if you provide a feed to a local ISP. But Starlink still 
> focuses
> > on direct to site, as does every other LEO provider FAIK.
>
> SpaceX is diversifying thier offerings, including boats, planes, and very
> high-performance community gateways.
The latter run under "business" here and the data rates they talk about 
aren't all that appealing given that this is what I see on a roaming 
subscription already. But who knows!
>
> I'd love to see more tech folks supporting this sort of thing.
>
> I would especially like to see us put together disaster kits that can 
> take one
> uplink and spread it around. We've seen SpaceX being willing to donate 
> dishy
> kits, but being able to spread the hotspot island out from direct wifi 
> range of
> the dishy to be able to cover a larger area would be worth quite a bit 
> (and
> don't forget the need for power for the system)

Yes - that's a lesson that's been learned here.

After last year's cyclone, a lot of local civil defence posts and marae 
here have acquired Starlink kits and generators (NB: marae are compound 
facilities operating as a focal point for indigenous Māori life. Most 
are capable of housing and feeding large groups of people at relatively 
short notice, and they are almost everywhere. Often used for 
conferences, retreats, weddings, funerals, public meetings, and not just 
by Māori).

One of the problems with disaster kits is their power use. Dishy uses 
between 40 and 100W when "idle" with a laptop connected via Ethernet, 
but uses noticeably more power (up to around 150 W on RX and slightly 
less on TX) when receiving significant data volumes, most likely due to 
the complex DSP needed to decode from the phased array.

Half that and you could power it off a car cigarette lighter socket with 
some ease. Would be interesting to hear how the latest generation Dishy 
stacks up there. Oleg - have you measured?

-- 

****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel at auckland.ac.nz  
http://www.cs.auckland.ac.nz/~ulrich/
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