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So if I follow, you’re saying that because London’s underground is older than Tokyo’s, it somehow changes the physical environment of the tunnels or their surro

• Symbiote 9mo ago
  The tunnels are particularly narrow and lived with iron rings. There's less space for adding equipment.
• TheOtherHobbes 9mo ago
  There is very limited clearance inside the tunnels, and a lot of electrical noise from existing systems.
• Havoc 9mo ago
  You’ve not been in London’s deep underground lines I take it? Some of the tunnels are so ancient and cramped that tall people can’t stand straight in most of the carriages. As the article says there just isn’t space to add equipment. Same reason they’re struggling to add air conditioning to older lines - no clearance The recently built lines had 5G etc from the start. It’s not difficult when the environment isn’t constraining you. Even malls add indoor 5g these days
• redleader55 9mo ago
  The way this is usually done is through a radiating wire that goes on the wall from station to station. This solution requires a lot of power. The stations in London are very small, leaving very little space for a transformer that can provide said power. Because of that they rely on directional antennas that cover sections of the tunnel - but those need to be straight, otherwise another antenna is required to cover that corner. There is also very little head-room in the tube tunnels in London. You can see how things get more and more complicated as you dig deeper into the problem.