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February 23, 2008

Japan’s Internet Access Satellite Is a Mistake

CNN reports that “Japan launched a rocket Saturday carrying a satellite that will test new technology that promises to deliver "super high-speed Internet" service to homes and businesses around the world… If the technology proves successful, subscribers with small dishes will connect to the Internet at speeds many times faster than what is now available over residential cable or DSL services… the Associated Press said the satellite would offer speeds of up to 1.2 gigabytes per second [nb. with a seventeen foot dish].”

Sounds good but it isn’t.

What neither the Associated Press nor CNN picked up is the altitude at which the satellite is intended to orbit, probably because they don’t understand why that’s important. Slashdot was a little more discerning, however: they picked up that it is intended to be geostationary (always appearing in the same spot in the sky so that antennae can be pointed at it). Physics (and the release from the Japanese AerospaceExploration Agency) tell us that a geostationary satellite must be 22, 000 miles above the earth. Other laws of physics say that radio signals are going to take more than a tenth of a second to get there and the same time to get back; the universe apparently doesn’t allow faster speeds.

Not only does that mean that these satellites won’t be good for interactive gaming (as Slashdot points out) and that they’ll be terrible for VoIP; they also won’t work well for web browsing. That matters! A modern web page is built in many interactions between your computer and the host of the website (much more detail here); the minimum time for each of those interactions is half a second because the signal has to go up and down to get to the server and up and down to get back to you. Those half a seconds don’t sound like much but they add up (this delay is called “latency”). If you use satellite, you know how slow page builds are and how may pages just break during the delay. Unfortunately fast data rates don’t help when latency is the problem.

The satellite’ll be good for email; it’s a good backup to oceanic fiber that seems to be getting cut lately. It will NOT do what the Japanese Agency’s press release says: “…even in some areas where major ground infrastructure for the Internet is difficult to establish, people can enjoy the same level of Internet service as that in urban areas.” Cable, DSL, and even terrestrial wireless measure latency in milliseconds (thousandths of a second); latency is very often MORE important than bandwidth in determining the quality of Internet experience. Anyone who thinks geostationary satellites are an acceptable way to bring broadband to rural areas doesn’t understand how the modern web works.

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