Re:How NYC’s subway got wireless in the tunnels
by jdietrich on Monday February 19, 2018 @02:49AM
(#16411401)
Transport for London are currently trialling in-tunnel 4G service on the Waterloo & City line, with a full rollout across the whole London Underground network planned for 2019.
The tunnel gauge isn't a major problem. The standard technology for providing wireless coverage inside tunnels is a leaky feeder or radiating cable - a length of coax cable with a perforated shield. The leaky feeder acts like an antenna with a very elongated radiation pattern. As long as the distance between stations isn't too great, then you don't actually need to put any equipment inside the tunnel other than a length of cable.
https://tfl.gov.uk/info-for/media/press-releases/2017/novemb...
The tunnel gauge isn't a major problem. The standard technology for providing wireless coverage inside tunnels is a leaky feeder or radiating cable - a length of coax cable with a perforated shield. The leaky feeder acts like an antenna with a very elongated radiation pattern. As long as the distance between stations isn't too great, then you don't actually need to put any equipment inside the tunnel other than a length of cable.
https://en.wikipedia.org/wiki/Leaky_feeder