Re: [Starlink] apnic piece on starlink

[David Lang <david@lang.hm>]

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On Sat, 8 Apr 2023, Ulrich Speidel wrote:

> On 8/04/2023 12:10 am, David Lang wrote:
>> I will note that in the Starlink plans, there are plans
>> to put a layer of satellites at a sigificantly lower altitude.
> I should add to this that this would seem like a good strategy, except of 
> course that this comes with its own set of challenges. Earth observation 
> satellites in particular are abundant in lower orbits - if you have a camera 
> on board, you want to be as close to your subject as you can. So there isn't 
> quite as much space down there as there is further up.
>
> Residual atmospheric drag at lower altitudes is also higher, which means you 
> either need to take more fuel to compensate (=heavier satellite & fewer sats 
> per launch) or you need to replace the satellites more often.
>
> You also need more satellites for global coverage in a shell like this.
>
> Also, as you mostly look at satellites sideways when you're a ground station, 
> the path length and therefore the path loss isn't necessarily all that much 
> lower - going from 550 km to 275 km gives you an extra 6 dB of gain if the 
> satellite is straight overhead, but that advantage shrinks as you move away 
> from zenith.

the published plan is a shell at ~340km (7500 satellites) in addition to the one 
at ~550km (and a possible 'long haul' shell at ~750km with <1k satellites)

>> By launching 10x as many satellites, and each one being able to handle 10x 
>> the data, they _may_ get to 100x, but that is really going to be pushing it. 
>> (note that this is for ~10x the number of satellites lauched by everyone 
>> other than SpaceX since Sputnik)
>
> Having seen figures of ~45k sats bandied around for some proposed 
> mega-constellations, the 10x number of satellites might just work out.

regulatory approval required, but starlink is aiming for ~42k satellites, they 
are only approved for somewhere around 10-12k so far and I believe they are 
nearing 4k in orbit.

> Whether we'll get to 10x the capacity per satellite is another question 
> altogether given spectral constraints.

yes, to get to this sort of capacity, you need to have multiple satellites 
covering each cell at a given time, which per the research published not that 
long ago was not yet the case.

> With ISLs, one could in principle free 
> up part of the gateway traffic spectrum by putting gateways in areas that are 
> devoid of other users, but quite how practical that is given that remote 
> areas are where LEOs will be needed most is a good question.

supporting terminal-to-terminal traffic also opens interesting possibilities 
(although less than we would like due to the server-centric nature of current 
Internet usage)

> One option that could push things a little further in conjunction with LEOs 
> would be HAPS  - high altitude platform systems, essentially solar-powered 
> UAVs that act as stratospheric cell towers with tours of duty measured in 
> weeks or months. These could use lasers as backhaul to LEO networks, yet 
> project comparatively narrow phased array beams to users on the ground. A 
> HAPS flying at 30 km overhead has a path loss that's around 25 dB below that 
> of a LEO sat at 550 km, and a clear optical path to the satellites above. 
> Technology isn't quite there yet - essentially, we're at the point where 
> solar cells have become performant enough in conjunction with batteries that 
> have become light enough to allow sustainable cyclic recharging of a UAV's 
> flight systems. But there are still issues to be addressed around the excess 
> power required to operate a cell site in the sky and or course all the 
> regulatory and safety aspects associated with operating things that don't 
> burn up when they come down.

Google shuttered project Loon (balloons to do this rather than UAVs) in the last 
year or two

>> If you can get fiber, it's always going to be better than a wireless option, 
>> DSL is threatened by Starlink in many suburbs, cablemodems depend so much on 
>> the ISP it's hard to say
>
> This is an interesting comment. Completely agree on the fibre aspect.
>
> DSL I think is threatened more by fibre than Starlink in most places (except 
> the US perhaps), which has basically displaced most DSL connections where it 
> became available. We were on DSL here till 2017, and as fibre was on the 
> horizon for a while, the company that runs the cable network here on behalf 
> of the telcos stopped investing in new DSLAM modules, instead preferring to 
> switch customers with problematic ones to modules that had become available 
> as a result of customers migrating to fibre. We found ourselves with a weird 
> problem literally overnight one day - intermittent disconnects lasting a 
> minute or two. These persisted through a change of DSL router, and logging 
> these for a few days showed a clear diurnal peak time pattern - so it was 
> obvious we were dealing with DSLAM-side crosstalk issues here. I asked to be 
> switched to a different DSLAM. This was an odyssee of support calls given 
> that you cannot call the lines folk directly - you must call your retail ISP, 
> who pays someone in India a few rupees to tell you to reboot your router to 
> make the problem go away. By the time I'd educated their 3rd tier support 
> about what crosstalk was, I'd literally spent many many hours on the phone to 
> India. Eventually, they switched me over to a new DSLAM and the problem went 
> away for a few months, just to return as they kept rewiring more legacy 
> customers.

when I switched from cablemodem to 129k SDSL in 2002, my usable bandwidth 
significantly improved.

> For those who still have DSL now, VDSL plans start at less than half of what 
> Starlink charges, with potentially comparable data rates, so not everyone 
> will want to switch.

I live in the greater LA area, in the middle of a town of >125k The best DSL I 
can get takes two phone lines to give me 8m down 1m up (in theory I should get 
10/2 but the line quality doesn't support it), and this costs me significantly 
more than starlink does.

> Where I see uptake of Starlink in urban areas here is by (a) geeks and (b) 
> folk who want a (secondary) connection that is independent of local telcos 
> that run inane call centres in India.

As more people work from home, just having a secondary connection becomes more 
important.

> Cable TV and cable modems are of course pretty much unheard of here - are 
> there any cable modems / ISPs that do more than a few dozen Mb/s down?

yes, cable modems can push 1G. I have one at 600/30 (but as a business line with 
static IP addresses, it costs me about triple the starlink connection)

David Lang