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Firm tests Wi-Fi on moving San Francisco trains

updated 01:30 pm EST, Fri February 1, 2008

Wi-Fi Rail on BART Trains

Overcoming what it says is a key obstacle to getting Internet access into public transit, Wi-Fi Rail today revealed that it has finished installing and deploying one of the first truly functional underground Wi-Fi systems for trains. In testing since the summer, a system deployed at four stops along the BART (Bay Area Rapid Transit) network in San Francisco has been providing 802.11g wireless access in between the stations regardless of the station or the trains' moving speed. A combination of strategically placed transmitters, amplifiers, and receivers (including some inside the rail cars) keeps the signal strong even along bends in the track; it also provides enough overlap that the connection remains uninterrupted even at 65 miles an hour, Wi-Fi Rail says.

The network also uses single-mode fiber connections to the main network at multiple points in the tunnels, promising a fast connection to the Internet regardless of the number of people on the network. Average speeds are said to top 15 megabits per second and are stable enough that several live video streams and downloads can run uninterrupted, even as a given rail car switches between hotspots.

Wi-Fi Rail has not said if or when it expects a fully commercialized launch of the network across BART beyond the beta test area or in other cities but expects to see the technology deployed in other cities and services in the near future.

By Electronista Staff
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  1. Flying Meat

    Dedicated MacNNer

    Joined: Jan 2007



    Now if only BART went anywhere I need to go. :P

    Are you listening city hall, and Muni?!! ;)

  1. msuper69

    Professional Poster

    Joined: Jan 2000


    the train speed...

    ... is irrelevant.

    Radio signals travel at the speed of light. The train's speed has no effect.

  1. chulitomio

    Fresh-Faced Recruit

    Joined: May 2004



    If you weren't just positing an assumption, and had at least *looked* at studies, you'd know that the train's speed *does* have an effect on wifi. Distance from basestations, loss rate, signal strength, *and speed*, cause intermittent disruptions often breaking meta sessions into multiple mini sessions. These are called 'grey areas.' Once things are on the move, (surprise) things get complicated.

    Radio waves travel at the speed of light in a vacuum. On earth, where the BART IS, the signals are as subject to air resistance as any other airborne object.

    All this information, just sitting there on the internet you're on. Huh.

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