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SpaceX has US Federal Communications
Committee (FCC) approval to build a constellation of 4,425 low Earth orbit satellite communication. It will use phased array antennas for up and downlinks and laser communication between
global low-latency high bandwidth coverage.
Mark Handley, University College London, built a simulator based on the FCC
filings to understand the latency properties of the network.
They evaluate how to use the laser links to provide a network and look at the problem of routing on this network. They enter the SpaceX Starlink network can provide more than just 3000 kilometers of terrestrial optical fiber network.
Delay is Not an Option: Low Latency Routing in Space
As network bandwidths have increased, they have evolved to be the limiting factor for many networked systems, ranging from the extremes of high-frequency trading, to the more mundane effects of latency on VoIP, online gaming, and web performance. Fundamentally, once in a while, it has been addressed to the world, and it has been addressed to the world.
In Starlink's initial phase, 1,600 satellites in 1,150 km altitude orbits will provide connectivity to all regions of the world. A second phase adds another 2,825 satellites in orbits ranging from 1,100 km to 1325 km, increasing density of coverage at lower latitudes and providing coverage at least as far as 70 degrees North. Finally, additional FCC filing SpaceX provides launching an additional 7,518 satellites in approximately 340 km VLEO orbits. Mark only examined the LEO constellation.
The inverse square law suggests that it could be more important than the EDRS (European Data Relay System). In 2014, the European Data Relay System (EDRS) achieved 1.8 Gb / s from LEO to geostationary earth orbit (GEO), across a distance of 45,000 km. Most Starlink distances will be 1000 km or less.
It seems likely that free-space laser link speeds of 100 Gb / s or higher will be possible.
Mark Handley speculates what @SpaceX / @elonmusk is up to if FCC filings are anything to go on …
Icnp2018 – so … many … satellites … pic.twitter.com/SdLqauoOBs– Andrew Moore (@ awm22) September 25, 2018
A dense LEO constellation like Starlink has two main advantages over terrestrial networks. First, it can connect almost anywhere, however remote. Second, the speed of light in a bone vacuum 47% higher than in optical fiber. The ability to connect anywhere is important, but we are providing a low-cost, high-speed, low-latency a premium service.
Already there are new private links between New York and Chicago, London and Frankfurt, and London and Paris. These links have relatively low capacity compared to fiber, but are of high enough value to the finance industry to be worth building new low latency links.
Simulations show dense LEO constellations have very many paths available, and many of them are of similar latency. This allows groundstations to be much more conservative when they move to the lower path, using timescales much longer than the latency of the broadcast load reports, so avoiding instability. This is an interesting direction for future routing work on dense LEO constellations.
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