Pre-WiMax on rails

T-mobile starts to offer free WiFi access for rail commuters between London and Brighton using a Pre WiMax technology. When the WiMax signal gets lost, the system migrates to GPRS. Here is the big picture: a commuter's WiFi interface talks to an antenna mounted on the roof of the carriage, which in turns talks to base stations by the side of the track. From there an ADSL 2Mbps link is available to an ISP.

The system is actually using an 802.16d standard, rather than the highly anticipated 802.16e. That is why it is called Pre-WiMax.