A pedagogical account of how broadband in trains (will) work on the ESA website:
21Net [Anglo-Belgian operator with Siemens as technological partner] is working to design and implement a Wi-Fi (Wireless LAN) access system for use on trains with the capability of multimedia, broadband internet and intranet access. The initial target market is high-speed trains in Western Europe where journey times allow for its use. (...) The 21Net system architecture is based on two-way Ku-band satellite transmission to provide connectivity between the internet backbone and a master server on the train. Direct reception of satellite television channels on the same satellite is also possible.A hub earth station provides the connection from the backbone (and from the network operations centre) via the satellite directly to a low-profile tracking antenna on the train. GPRS and Wi-Fi access between the train and available networks (e.g. in stations and in tunnels) is also provided. On the train, Wi-Fi (wireless LAN) connections are used between the master server and customers with Wi-Fi enabled laptops and PDAs
The project started on 1st March 2004 with the Baseline Design Review one month later. Two three-month trials on different high speed trains are foreseen in October-December 2004 and February- April 2005. The project is expected to be concluded in May 2005.