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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

#21
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 live on the equator, directly underneath the satellite. For someone living in the temperate regions, typical real rtts are in the 700ms area.

Starlink and OneWeb are different in that they intend to use a lot of satellites in low orbits to maintain constant coverage. This is technically much harder, not the least because you need thousands of satellites to get reasonably good coverage, but also because the ground station and the satellite transceiver both need to track each other. This was not technically feasible before, but modern AESA antennas can steer their signal without having to move the antenna, and can both transmit and receive multiple simultaneous beams and very rapidly move the beams around when doing time-sharing.

The minimum round-trip time to something very close to you and also close to it's own ground station will be on the order of 10ms. However, where the system really shines is long distance communication. The satellites will pass the signal between each other using lasers, and will get the signal to the other side of the earth much faster than terrestrial fiber, both because laser in vacuum travels substantially faster than one in fibre, and also because the fibres don't get to follow ideal great circle paths.

Independent researches have evaluated the likely latencies of the system, and the results are frankly shocking. For example, today on the existing fiber network, rtt between London and Singapore is ~160ms. On Starlink, the rtt will be ~90ms.

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

#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 of those two, there is no global solution.

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

#23

Earlier quoted context omitted.

I live in Bolivia, South America, the impact a global ISP would have cannot be overstated, in developing countries internet prices are still extremely expensive, up until a month ago I was paying around USD 60 for 10Mbps, and that was the best price I could find in my city, the second largest in the country.

Yep, same here (Brazil). I suppose SpaceX plans to start with us-only offerings. I also suppose it will take a while until it reaches developing countries. Does anyone have a better take on this?

The satellites will be everywhere, so not having offerings outside the US seems like it would be leaving money on the table. I could imagine it might take them awhile just to manage the logistics of selling a product in many countries, though. Maybe they'll partner with established companies for that part?

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

#24
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.

I had Hughes satellite service for a while. Bandwidth was good. Latency was terrible. For surfing the web and streaming content it was fine. For anything twitchy, like driving a computer desktop through terminal services or any kind of gaming, it was nigh unusable. Plus, there were fairly low data caps that limited how much streaming one could do. The big difference with Hughes and SpaceX is that Hughes satellites ar…

SpaceX and One Web both have an unfortunately low number of ground stations per square km, so remote areas can have a receiver for everyone, and urban areas will max out the number of receivers pretty quickly.

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

#25
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.

"Regular old satellite internet" is very high latency because it's few satellites in high orbit. SpaceX is doing many satellites in low orbit, resulting in much shorter paths and low latency. Latency for medium to long distances could be better than regular fiber, both because of straigher paths and because speed of light in the relative vacuum of the satellites' orbits is higher than speed of light in fiber. We don'…

I'd expect the first and easy goal to be to sell high speed access to airline passengers.

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

#27
post #5

Earlier quoted context omitted.

You're conflating bandwidth and latency. Not much needs both high bandwidth and low latency. The latency has the potential to be better than the current internet backbone when going intercontinental due to straighter paths, but it'll be higher when going to your local AWS, probably. Bandwidth is anyone's guess.

The amount of BW is based on how much spectrum you have (see Shannon's Law). I am not sure how much they have. Also, I am not sure they will have enough power to provide in building service.

> Also, I am not sure they will have enough power to provide in building service.

The issue for that is the wavelengths they are using. Their properties basically completely rule out any kind of in-building service, there needs to be a clear uninterrupted path between the receiver and the transmitter. (But they penetrate water well, so should not have a problem with clouds.)

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

#28

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.

These satellites are planned below 2000km altitude, where the radio signal delay is more like 3 milliseconds. It should be comparable to accessing AWS us-east datacenters from St. Louis MO

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

#29
post #18

Do they need more than US approval to launch satellites into international space?

This FCC approval is to be able to talk between orbit and the ground in the US. SpaceX needs approval from other countries for the same, in order to offer service there.

Launch approvals are a separate thing.

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

#30
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…

Iridium already employs SpaceX for their launches.
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