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SpaceX launches another 60 Starlink satellites while setting two reuse records

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Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#131

Post by ianai »

mastax wrote: post #109
Paul-ish wrote: post #92

Earlier quoted context omitted.

Netflix claims an UHD stream is 25 Mbps. This is probably the most demanding use case for your average consumer, but it may not be a rare use case in the near future. Each satellite can support 800 UHD streams. That doesn't seem sufficient if each satellite covers a large geographic area. This suggests to me a low data cap and/or rate, perhaps comparable to DSL.

12,000 satellites is the current FCC approved launch figures, I believe. 20Gbps per satellite but I don't know if that's full duplex or how much is divided between terminal/gateway, so lets divide that in half. For simplicity let's say they only sell consumer-grade 100Mbps connections, which are oversubscribed 100x as is typical. Divide the possible number of customers by 3 to account for uneven geographic distributi…

Another calculation is revenue per satellite per customer served. Would 100k per month per satellite finance these things long term?

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#133

Post by pfundstein »

derekp7 wrote: post #123
BoorishBears wrote: post #67

Earlier quoted context omitted.

People already covered why that's not possible with Starlink, but in-car WiFi is already incredibly cheap and works well. My Volt included unlimited data for 20$ a month, and it was fast enough for streaming video and worked at times where my phone didn't (presumably because of the better positioned antenna)

What do you use in-car wifi for, that you couldn't already use your existing unlimited cell data plan for? I have unlimited data, plus "unlimited" hotspot on my t-mobile phone for a really reasonable price (the unlimited hotspot throttles down after a certain point, but even that speed is still plenty for what I used it for -- I only which I could explicitly tell it I want to use the throttled speed gigabytes now, an…

Might be useful if you use a laptop on the go, or networking with the car's entertainment and other systems?

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#134

Post by tbabb »

jandrese wrote: post #64
tim58 wrote: post #44

Earlier quoted context omitted.

So theoretically the more remote a location the faster the starlink will be because it is shared by fewer people. Which is the exact inverse for wired infrastructure.

Except that the more remote your location the further you likely are from the nearest ground station, which means more hops through the satellite network before you get back down to the ground, higher latency, and reduced total throughput of the system. The system Starlink is trying to beat is BGAN and regional Ku/Ka providers. If you're expecting them to beat the pants off of your terrestrial wired service you're pr…

> the more remote your location the further you likely are from the nearest ground station

I thought downlinks were going to be pizza box-sized antennae. Why would it be far away from you? That could live on your roof.

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#135

Post by _flgt »

paulsutter wrote: post #114
_flgt wrote: post #96

Earlier quoted context omitted.

Each RF hop is going to have more latency than fiber for RF physical layer processing. Forward error correction intentionally uses large frames to spread out burst errors.

Sounds speculative. Given link bandwidths and likely error rates, it seems better to allow the higher layers to retransmit than to optimize for correcting burst errors. Especially given Starlink's goal to control latency.

I haven't seen a link budget. Do you have a link for one about the "likely error rates"?

My guess is Starlink is going to need FEC for Doppler effects and multipath in urban environments. Maybe they will be able to overcome multipath with modulation. But Doppler shift will be significant with LEO.

The latest 802.11n standards have been increasing physical layer frame sizes, not decreasing them. I don't know of any modern wireless standard that doesn't use FEC. Coding gain is significant in most link budgets I have seen.

The last satellite RF downlink I worked with was for JPSS-1 in LEO nearly 6 years ago. There was a (255, 223) Reed-Solomon code with an interleave depth of 4 frames. So you effectively had to receive 1024 bytes, decode, and you got 4x 223 bytes worth of information. While latency wasn't a major concern, this scheme seemed pretty standard to me. If you don't believe me, the spec is public information:

https://www.star.nesdis.noaa.gov/jpss/documents/CDFCB/GSFC_4...

I'm sure SpaceX is trying really hard to control latency - so it doesn't get out of hand! One set of RF processing here, another over there, each with their own filters and decoding algorithms and then you have an extra 100 ms of delay in the system.

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#136

Post by thinkcontext »

tus88 wrote: post #21
Havoc wrote: post #18

4th reuse. Wow didn't realise they were that deep in already. Thought reuse was still conceptual

The latest revision of the Falcon 9 was intended to have re-use counts in the dozens. The previous revision...maybe 1-2.

I believe the official line is 10 with just inspections, 100 with refurbishment. If Starship's timeline and cost structure is to be believed its not likely any F9B5s will reach 10, as it will be obsolete.

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#137

Post by wmf »

_flgt wrote: post #96
paulsutter wrote: post #73

Earlier quoted context omitted.

You want to downlink near the server, not near the client. Packets will move 40% faster through vacuum than through fiber.

Each RF hop is going to have more latency than fiber for RF physical layer processing. Forward error correction intentionally uses large frames to spread out burst errors.

Tell that to the HFT people.

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#138

Post by _flgt »

wmf wrote: post #137
_flgt wrote: post #96

Earlier quoted context omitted.

Each RF hop is going to have more latency than fiber for RF physical layer processing. Forward error correction intentionally uses large frames to spread out burst errors.

Tell that to the HFT people.

Is this some fixed point-to-point line of sight terrestrial microwave link? I'd believe that could do it. Do HFT people ever communicate with spacecraft though?

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#139

Post by paulsutter »

_flgt wrote: post #135
paulsutter wrote: post #114

Earlier quoted context omitted.

Sounds speculative. Given link bandwidths and likely error rates, it seems better to allow the higher layers to retransmit than to optimize for correcting burst errors. Especially given Starlink's goal to control latency.

I haven't seen a link budget. Do you have a link for one about the "likely error rates"? My guess is Starlink is going to need FEC for Doppler effects and multipath in urban environments. Maybe they will be able to overcome multipath with modulation. But Doppler shift will be significant with LEO. The latest 802.11n standards have been increasing physical layer frame sizes, not decreasing them. I don't know of any mo…

Elon talks about 20ms or 10ms, not 100. He wouldn’t be wrong by a factor of 10. You’re really just speculating based on some non IP based overarchitected mil spec monstrosity you’ve seen before

https://mobile.twitter.com/elonmusk/status/11329039145865297...

Besides we’re talking about the latency of the satellite to satellite links, not the downlink (since that’s the difference between using a downlink close to the client vs close to the server).

Re: SpaceX launches another 60 Starlink satellites while setting two reuse records

#140

Post by randomsearch »

gt565k wrote: post #22

Can't wait to see every Tesla become a wifi hotspot hooked up to Starlink. Traditional ISPs are in trouble if the Starlink latency is really in the sub 100ms due to the LEO distance advantage. Global coverage with decent latency! I wonder if that's why google dipped out on rolling out fiber infrastructure. Physical infrastructure is about to become obsolete as more advancements in wireless tech and satellite internet…

I heard from a constellation internet company that fibre will always be the go-to solution as far as they were concerned - they’re going for marketers where fibre isn’t available.
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