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I'm curious about understanding how wi-fi reception works when the receptor is moving. What is the infrastructure to access internet from laptops on planes, trains, etc.?

Edit: The default answer seems to be: "you need a router in the moving vehicle and your laptop connects to that router". I'm aware of that part of the picture...

Now, my curiosity is about how the moving router is connected to Internet, what technology is used to do it? The plane scenario is answered by Mark. Is the same for trains or boats?

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The plane will have a router that your laptop is always connected to for the duration of the flight. The plane will then have a system that keeps an internet connection established between itself and the ground.

This Wikipedia page shows that one implementation works just like a cell phone network where there are a number of towers on the ground that the plane can contact and it will switch between towers as it travels across the country.

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the same basic principle will work for train-, ferry- and bus-based wifi networks. the upstream connection may be cell tech, or another system like satellite, usually depending on what's available in the locations served. –  quack quixote Feb 9 '10 at 18:08
    
This article mentions some technical details on the subject nytimes.com/2010/09/28/business/28road.html –  JuanZe Sep 30 '10 at 19:34

Wi-fi for a moving laptop works only if the router is moving together with the laptop, otherwise the connection will be lost.

It will work on an airplane only if there's a router on the airplane to which your laptop can connect and stay connected during the flight.

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The first sentence is incorrect. WiFi (802.11) allows for roaming--moving from one physical network to another. Now, it won't work on a plane, which moves far too fast. Also, WiFi cells would be too small. However, if your company uses WiFi and you walk from one end of the building to another, you should remain connected. –  CarlF Jan 28 '10 at 14:39
    
@CarlF: One would still need to connect to the other networks. Unless specifically set up in a company building, it wouldn't work in the general case. –  harrymc Jan 28 '10 at 16:27
    
Yeah, you need the same SSIDs. –  Nathaniel Feb 9 '10 at 19:30

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