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 OT: a large computer network - 66 nodes, planet scale 
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Joined: Wed Jan 09, 2013 6:54 pm
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Just reading about Iridium - they have a network of 66 satellites, each communicating with four neighbours and providing global coverage - at 2400 bits per second per ground connection.

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Each satellite can support up to 1100 concurrent phone calls at 2400 bit/s and weighs about 1,500 lb (680 kg). The satellites each contain seven Motorola/Freescale PowerPC 603E processors running at roughly 200 MHz, connected by a custom backplane network. One processor is dedicated to each cross-link antenna ("HVARC"), and two processors ("SVARC"s) are dedicated to satellite control, one being a spare. Late in the project an extra processor ("SAC") was added to perform resource management and phone call processing.

The cellular look down antenna has 48 spot beams arranged as 16 beams in three sectors. The four inter-satellite cross links on each satellite operate at 10 Mbit/s.

As of mid 2016, Iridium has experienced in-orbit failures which cannot be corrected with in-orbit spare satellites, thus only 64 of the 66 satellites required for seamless global coverage are in operation.

(From the Wikipedia article)


As you may know, the network cost some $6 billion to put up, then quickly went bankrupt. Eventually bought for $35 million and made profitable, now beginning to put up a new constellation of 66 satellites with 6 spares, for about $3 billion.

Sounds like Iridium is presently the only satellite constellation to forward call data from one satellite to another.


Sun Jun 25, 2017 11:20 am
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