O ye technical types (I can’t think of a better way to ask a bunch of sane technical people a hairy question than blogging it) how hard would it be to cram a high-bitrate, bi-directional signal into an ordinary stretch of train track? The length of said track could be tens of kilometers (metropolitan), or hundreds (rural, interstate)
The thing is, it would be truly sweet to have viable wi-fi broadband on the train, be it metropolitan commuter trains, or rural ones. To do this, one first needs to build a nice stable data pipe between a ground-based point-of-presence, and one or more big heavy chunks of rolling-stock per train which periodically vanish under the earth (or at least dive into deep trenches). After brief thought, the obvious answer is that there’s already a colossal pile of pre-existing cabling in the form of the tracks and overhead power cables (where electrified). Indeed, this is already used for signalling purposes and ‘train detection’.
The question is: can you cram 100Mbps (say) over it without lots of (expensive) new relays and repeaters? Can you do so without screwing up the existing system? etc.
Any insights/suggestions/links, anyone?