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SpaceX just got FCC approval to launch 7,518 satellites

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Re: SpaceX just got FCC approval to launch 7,518 satellites

#31

Post by Filligree »

Tuna-Fish wrote: post #21
zjaffee wrote: post #3

Does anyone have any context on what sort of internet speeds satellite internet has been benchmarked to provide. I can't imagine the latency being anywhere near good enough to do many of the high bandwidth things people use the internet for today.

Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you…

> Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you live on the equator, directly underneath the satellite. For someone living in the temperate regions, typical real rtts are in the 700ms area.

This doesn't check out.

The radius of Earth is 6,300km. Assuming a receiver on the north pole, the total distance should only be sqrt((35786 + 6300)^2 + 6300^2) = 42555km, which isn't notably larger than the 36000km at the equator.

I'm sure you're still right about the latency, but it can't be just distance doing it.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#32

Post by [deleted] »

TrueDuality wrote: post #20
zjaffee wrote: post #3

Does anyone have any context on what sort of internet speeds satellite internet has been benchmarked to provide. I can't imagine the latency being anywhere near good enough to do many of the high bandwidth things people use the internet for today.

There were recently two simulations done on possible latencies based on the FCC filings. You can find the video simulations in the links at the bottom of this post. You can see international links that have latencies lower than the existing internet by a significant margin. Unfortunately neither of those simulations take into account that the first iteration has been changed to only use radio and no laser links. [0]:…

[deleted]

Re: SpaceX just got FCC approval to launch 7,518 satellites

#33

Post by bargl »

This is such a cool problem.

We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth.

These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move.

But these are going to be moving and changing all the time so you'll have to connect to multiple satellites every day. I'm spit balling here but they'll probably be overhead for 10 minutes? Think about switching your router every 10 minutes. Or you get a rainy day and your signal clarity goes down. Or you are over the equator in a band that is used strictly for GEO.

This is going to be a super cool problem to solve. And I'm sure I don't even understand the half of it.

Edit: Sorry example of router is pretty bad. It's more like running your phone but you have to specifically aim your antenna at each tower that you're passing while driving. The complexity is moving nature of the network and the targeting nature of the antennas. I have 0 clue if phone signals are targeted but I believe they are radial signals and more like a beacon than a laser.

Load balancing these can be a pain as well because if you get too much signal on an antenna it can actually block all signal.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#34

Post by stcredzero »

creeble wrote: post #22

Curious how this will pan out. It's a shocking contrast to be in or near a city and have broadband speeds, and then be just a few dozen miles outside one and have... literally nothing. I just loaned my Iridium phone to a friend who was going to the jungle, and although he was able to make the data connection work, even doing email at 2400 baud(!) proved useless. Inmarsat is faster, but vastly more expensive. Outside…

even doing email at 2400 baud(!) proved useless

In the late 90's I did a lot of my grad school coding and implemented a website for a state agency though 9600 baud modems. EMACS was great in those days, precisely because it's a Lisp machine OS masquerading as a text editor. I used to read USENET news, read my email, do my work, shuffle between multiple remotely logged in shells, all through EMACS.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#35

Post by Tuna-Fish »

ilrwbwrkhv wrote: post #2

i think the price should be around 35 dollars per month

At the beginning, it will be nowhere near that. The price of the receiving antenna alone will be in the range of $10k-$1k. So for the first phase they are mostly interested in providing backhaul for remote cell towers and the like, and service for the odd people living in the sticks who are willing to pay through the nose for the ability to have both great internet and live in the middle of nowhere.

Then, once the antennas are in proper mass production and cheap enough, they have an investment of a couple of $B worth of satellites to pay for. So long as they can provide something no other ISP can (low-latency access in the middle of nowhere), I very much doubt their prices will be lower than those ISPs.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#36

Post by jimison »

dr_orpheus wrote: post #12
spaceribs wrote: post #9

Earlier quoted context omitted.

You'd be surprised, this article describes round-trip times to be 25ms to 35ms and gigabit speeds: https://arstechnica.com/information-technology/2018/02/space... Who knows if they'll actually reach these speeds/latencies in practice though, that remains to be seen.

Yeah, a significant portion of the latency is just the distance to the existing satellites in geosynchronous orbit. For light to get out and back to the geo belt is around 240 ms, excluding any other factors. Getting up to the promised gigabit speed will be significant challenge. The original demo satellites that SpaceX launched only had data rates of ~15 Mbps.

Perhaps their true market will be for industrial IOT devices that need to connect from all over the world.

If I'm selling large HVAC units with cloud monitoring functionality, it'd be attractive to ship units that are pre-connected to SpaceX's satellite network. I wouldn't have to worry about setting up agreements with multiple cellular providers or having to depend on site-provided Wifi/ethernet.

The point is, those devices could very lucrative for SpaceX without requiring as much bandwidth (no need to stream Netflix).

Re: SpaceX just got FCC approval to launch 7,518 satellites

#37

Post by walrus01 »

Tuna-Fish wrote: post #21
zjaffee wrote: post #3

Does anyone have any context on what sort of internet speeds satellite internet has been benchmarked to provide. I can't imagine the latency being anywhere near good enough to do many of the high bandwidth things people use the internet for today.

Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you…

Not all satellite internet, currently, is dependent on geostationary. Read up on o3b's network and architecture, which has been operational for several years now. The cost, however, is basically "if you have to ask, you can't afford it". O3b is a market option for ISPs and telecoms in very remote or island areas that were previously dependent upon leasing Ku or C band transponder megahertz.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#39

Post by walrus01 »

Filligree wrote: post #31
Tuna-Fish wrote: post #21

Earlier quoted context omitted.

Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming you…

> Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming yo…

in practical real world use the absolute minimum ping time you'll see from a 1:1 dedicated capaacity (SCPC) link via geostationary, from end terminal to larger earth station, is 489 to 491 ms. This will vary up to 495ms depending on modem modulation/framing and FEC type, and actual line of sight distance to satellite (low inclination aim angle for the antenna, if you're not directly under the satellite, vs two sites that are directly under it as viewed from geostationary).

Ignoring TDMA oversubscribed VSAT networks for the moment, there are a number of different possible modulation schemes and FEC types, and FEC code rate (payload vs FEC percentages), and things that are unique to different SCPC modems, which will vary the modulation by a few ms beyond pure speed of light.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#40

Post by reaperducer »

bargl wrote: post #33

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…

Or you are over the equator in a band that is used strictly for GEO.

It's my understanding that this constellation is going to be significantly lower than GEO, so that's not a problem.

Also, the dead zones are toward the poles, but those are mitigated in phase two.

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