[Starlink] Comprehensive Measurement Study on Starlink Performance Published

[Ulrich Speidel]

All good points ... see below.

On 27/02/2024 2:13 pm, David Lang wrote:
> On Tue, 27 Feb 2024, Ulrich Speidel wrote:
>
>> On 27/02/2024 12:19 pm, David Lang wrote:
>>> On Tue, 27 Feb 2024, Ulrich Speidel via Starlink wrote:
>
>>> There are large areas with poor or non-existant cell coverage.
>>>
>>> Outside the US, scaling of Starlink can happen just by providing 
>>> coverage to locations that don't yet have coverage with no 
>>> additional satellites.
>> But what's the population of these areas? Generally quite sparse. (Or 
>> politically disinclined to accept Starlink service)
>
> per square mile? low. But there are a LOT of square miles, and those 
> areas are ones where it's very expensive per-user to run fiber (even 
> to cell towers or wireless ISP towers)
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.
>
> There are governments politically disinclined to allow cell service, 
> not so much the users. And some of the opposition is not opposition to 
> Internet service, but rather being protective of existing providers. 
> Protectionism can be defeated in time.
Tick.
>
>>> In terms of scaling existing areas, larger antennas can reduce cell 
>>> size, you can have more than one satellite cover a given cell, they 
>>> are looking at eventually having lower satellites, which again will 
>>> let them reduce the cell size.
>>
>> Lower orbit = more drag = shorter lifetime, and the reduction in 
>> footprint isn't actually that significant. Larger antennas = fewer 
>> sats per launch = more expensive system.
>
> and at the same time SpaceX is working to massivly reduce the launch 
> costs.
Yep, but much of the gains there have been made.
>
>
>> 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?
>
>> If you can reduce distance between satellite and ground station by a 
>> factor of 2, all else being equal, theoretically you'd also reduce 
>> footprint to a quarter, but that's assuming you don't need to worry 
>> about antenna sidelobes. But say we can, and then that gives us a 
>> factor of 4 in terms of capacity as long as our user density is the 
>> same. It also buys us an extra 6 dB in received signal power and 
>> hence an extra 2 bits per symbol. That's another factor of 4 at best 
>> if you go from 1 to 3 bits/symbol. Larger antennas: Doubling antenna 
>> size gives you 3 dB in gain or an extra bit per symbol. So that turns 
>> into a game of diminishing margins pretty quickly, too.
>
> add in the ability for multiple satellites to serve a single cell and 
> you can get a noticable multiple as well
Not in terms of capacity - but in terms of a better distribution of it. 
Already happening - most places can now "see" dozens of Starlink 
satellites above the horizon.
>
>
>>  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/

(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!)

>
>> That's a far cry from what is needed to get from two million or so 
>> customers to supply two billion unconnected or under-connected. For 
>> that, we need a factor of 1000.
>
> without knowing what the user density of those under-connected are, 
> it's going to be really hard to get concrete arguments.
>
> Spacex is intending to launch ~10x as many satellites as they have 
> now, and the full 'v2' satellites are supposed to be 10x the bandwidth 
> of the V1s (don't know how they compare to the v2 minis), that's a 
> factor of 100x there. 

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.

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.

> Is another 10x in the under-served areas being in less dense areas 
> really that hard to believe?
>
> And Starlink will hopefully not be the only service, so it shouldn't 
> have to serve everyone.
So which factor in terms of capacity growth should we expect of Starlink 
& Co over today?
>
>> 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.

-- 
****************************************************************
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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