IMHO the shannon limit and basic laws of RF/path loss and channel capacity say that satellite is not a true competitor to backbone links by singlemode fiber. For the equivalent of "last mile" services, yes, but not as a replacement for laying fiber between points A and B.
The entire data throughput capacity of a current generation, 5500 kilogram, geostationary Ka-band satellite that costs $185 million to build and launch is much, much less than the 80 channel x 100 Gbps per channel DWDM system you can run on two strands of 9/125 singlemode fiber. And vastly less than the 144, 288 or 864 strand count fiber cable you would see laid between two cities by a carrier-of-carriers operator like Zayo these days.
It is fabulous to see more competition for high priced monthly-leased transport kHz/MHz from geostationary satellite operators. O3b was an amazing thing (and still is). More competition is good. But it's a pipe dream to say that satellite backhaul will ever be preferable to fiber carrying N x 10GbE circuits or a 100GbE circuit...
I really appreciate your comments. This stuff needs to be out there more.
I expect crosslinks and backhaul up/down will be multipath laser w adaptive optics, not RF. As you say the physics demands it.
At 1100 km altitude each satellite has vacuum line-of-site to any other satellite within 6000 km (ground track). By "skipping" satellites you gain extra bandwidth capacity and reduce latency. Easy to route around damage, with no single point of failure (unlike fiber in certain areas). Obviously this will all be optimized with network and timing analysis to hell and back, just like fiber.
LEO has advantages of lower distance traveled, dramatically lower attenuation, faster speed of light, fewer hops, no cable breaks to fix, and no actual cable to run (which the expensive part of fiber, after all). You just build the repeaters, and exploit the fact that the exosphere is really transparent.
Musk, a guy who knows his physics and math, predicts in that youtube video that they'll ultimately do "more than half" of all long distance traffic. He also acknowledges that they have to 'skate to where the puck will be' re: telecommunication technology or they'll end up dead like innumerable predecessors. It's an interesting watch.
> IMHO the shannon limit and basic laws of RF/path loss and channel capacity say that satellite is not a true competitor to backbone links by singlemode fiber. For the equivalent of "last mile" services, yes, but not as a replacement for laying fiber between points A and B.
The filing states they'll be using free space optics / lasers between satellites. The Ka/Ku links are only for the initial uplink and downlink.
> But it's a pipe dream to say that satellite backhaul will ever be preferable to fiber carrying N x 10GbE circuits or a 100GbE circuit...
It is not a pipe dream. Free space optics in... well space, have a 50% propagation latency advantage vs terrestrial fiber. This helps equalize things somewhat.
> The Ka/Ku links are only for the initial uplink and downlink.
Then there's a huge bottleneck, if the links from the satellite constellation as a whole to the trunk earth stations (not the CPEs) are high capacity Ka-band, there's RF issues with capacity...
It's like if you have a network that's composed of a whole lot of 10GbE backbone links from router to router and your IP transit connection to upstream ISPs/the global v4/v6 routing table goes through one 1000BaseLX link.
No, it's nothing like that. They're talking about highly localized signals via phased arrays on both sides. Additionally you underestimate the capacity of wireless: LTE has no problem doing 30 bits per 1 hz of spectrum. These will run at a lot more than a 1 gbit globally shared last mile.
Keep in mind that you don't really need to compete with fiber if you believe there are enough unserved people. I think his comments were misleading since they probably won't target that market. Another problem with Leo is that the rate of consumption is going up extremely fast on the internet. By the time this launches the total capacity of their system may sound like a lot, but it's spread over all the satellites uniformly. So what do you have to do if you want to double your capacity? You need to launch another 4400. They're essentially going to play a game where they need to keep up launches fairly quickly to go with the rate of internet consumption. I also believe the ground cost will be interesting, especially the user terminal. Typically phased array is so expensive that they'll need to sell it at a loss.
The entire data throughput capacity of a current generation, 5500 kilogram, geostationary Ka-band satellite that costs $185 million to build and launch is much, much less than the 80 channel x 100 Gbps per channel DWDM system you can run on two strands of 9/125 singlemode fiber. And vastly less than the 144, 288 or 864 strand count fiber cable you would see laid between two cities by a carrier-of-carriers operator like Zayo these days.
It is fabulous to see more competition for high priced monthly-leased transport kHz/MHz from geostationary satellite operators. O3b was an amazing thing (and still is). More competition is good. But it's a pipe dream to say that satellite backhaul will ever be preferable to fiber carrying N x 10GbE circuits or a 100GbE circuit...
https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore...
https://en.wikipedia.org/wiki/Noisy-channel_coding_theorem