Comment by Scoundreller
1 year ago
So which points are getting “faster than fibre” latency because of this? Extra distance up and down, but make up for it on the long-haul.
Won’t beat HF radio though.
1 year ago
So which points are getting “faster than fibre” latency because of this? Extra distance up and down, but make up for it on the long-haul.
Won’t beat HF radio though.
Optical fiber has an index of refraction of around 1.6, so signals travel at around 0.6c. For a perfectly straight cross-continental link (5,000km) with no delays from amplification/retransmission, that's about 26 milliseconds. Assuming the satellites are directly overhead, Starlink adds another 500km up and down, making the minimum possible latency around 20 milliseconds. The real number might be slightly higher or lower depending on the location of the satellites.
My guess is the real latency depends mostly on the latency of relay nodes (either satellites or routers on earth), not the medium through which signals travel.
Number of hops definitely matters more usually. For example I'm about 150 miles from Azure East US 2 (richmond, va), and at the speed of light that should be sub 2ms round trip, but actual latency to it is ~30ms. But I'm sure I'm going through dozens of switches/routers to get there. What Starlink buys you is that you get to go straight to a satellite, then a laser in a vacuum to other satellite(s) and then a ground station that's likely already at an IXP or very close to one.
Could also be shit routing.
Some big ISPs here refused to locally peer with some cheaper providers, so some packets to a local data centre (5 miles away) in Toronto would round trip through Chicago and back.
If they wanted a direct connection; they wanted them to pay for transit.
That could already be the case. Round trip time to the ~500km orbit is about 4 milliseconds (+ all other network elements before, after and in between). They claim to have a >5000km link running for significant time. Now think of a fibre link of that length and how many repeaters / routers will be needed due to attenuation and physical constraints. I can clearly see a path where Starlink laser links could be a viable option to subsea cables - at least for some priority traffic...
a few random outages which happened near places some oligarch's yacht has visited recently and it'll become the priority backhaul.
I see folks in the Pentagon doing a collective /phew that this project is online in the next decade, multiple times.
Starlink adds a latency penalty of tens of milliseconds going through the atmosphere. Each round trip is four hops through the clouds. I expect most of this delay is forward error correction, combined with lower bandwidth of the radios.
On top of that, you may have queuing in each satellite.
Finally, the satellite laser links aren’t pointing exactly in the direction you want to your packets to travel. They’re at some diagonal, and the packets need to tack back and forth, which wastes distance. Think the streets of Manhattan.
This is just incorrect. The speed of light through atmosphere is almost identical to speed of light in a vacuum. There's no latency penalty for traveling through the atmosphere. The one-way time delay to a Starlink satellite is about 2 milliseconds.
It's possible for starlink to beat radio, because radio can't always go straight to the target. If I wanted a radio link from NY->Tokyo, what would that path look like?
It would look like the HF radio bouncing off the ionosphere. I have contacted someone in Japan from Oregon. The downside of HF is that the bandwidth is low with 30MHz across the entire band.
There was company recently wanting to do high-frequency trading on HF because of the quickest path.
I'm curious how much the curved route affects the effective speed of communication with skywaves. You also have many situations where communication becomes impossible due to space weather or other atmospheric phenomena.
True, it would be bouncing around between ground and the atmosphere (when it works at all).
Why would we expect faster than fibre?
The speed of light in a vacuum is roughly 50% higher than the speed of light in fiber.
I will note that this is the case for conventional fiber-optic cable. The newer hollow-core fiber cables transmit light at nearly c. As far as I know hollow-core has not seen wide-spread use, but it will be interesting if trans-continental connections switch over.
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The area between a starlink receiver on the ground and a satellite isn’t a vacuum
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Is attenuation in a vacuum also better?
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Also, as pointed out elsewhere, the number of hops is the biggest contributor to latency.