I’m currently on a high speed train between France and Switzerland and wondering how my cell phone is able to keep up with my very rapidly changing position and generally keep data connectivity?
In: Technology
In rural areas, cell phone companies use towers that span rather large ranges (25+km radius). They will also typically be overlaid so that one tower failure will not cause an outage. Imagine a whole bunch of triangles with 20km sides (approximately, because terrain).
So somewhere in that 20km, your cell phone has to decide to jump from one tower to another. It’ll monitor the signal strength of the towers and do a handoff from the one getting weaker to the one getting stronger. If you’re on a train going 200km/h, then it only has to do this once every six minutes or so (depending on how exactly you’re traveling from tower A to tower B, but they tend to be built along infrastructure), which is more than enough time to handle it. The process itself takes only seconds.
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