[teeray]

The other fun use case related to trains is tons of subscribers on a moving train doing handoffs between towers. Ideally everyone would use the train's wifi, but that rarely happens because the service is shit. Instead you likely have gigantic traffic hitting the MME trying to detach and reattach phones... and then everyone moves out of the new tower's service area... so on and so forth. Hopefully the 5G core's separation of some of MME's responsibilities will help this scenario.

[toomuchtodo]

Could the train not have a 5G base station to aggregate traffic over reliable backhaul?

[teeray]

I think it might be more difficult than it would seem... everything I’ve seen so far in telecom has the assumption that the gNB (the base station) has a fixed location relative to neighboring gNBs. That’s what would facilitate handoffs. You would have to reconfigure parts of the core network as the train moves, so that you could smoothly handle the instance where someone takes a call on the train, disembarks, and the train pulls away. I don’t think the topology is that malleable.