I know a bit about LTE. There are multiple ways it can be handled. I won't use the LTE specific terms because I'm not a pretentious ass.
The devices send CQI (Channel quality indicator) messages. If the base station misses so many CQI's in a certain time period it disconnects the device. That covers bad signal, LOS, and lots of other conditions. The EPC is centrally located and all the base stations talk to it. Being the brains of the operation, it has data from all the devices, and it's supposed to be able to determine when the user device would get better service from another base station, and it can explicitly tell the device to switch. This is generally supposed to be hitless. The end user device can decide the connection is dead, but it doesn't get to dictate which base station it connects to. If it's lost signal, and whatever timeouts have expired, then it will select a base station with the strongest signal and go into idle mode. The EPC should see that it's connected and send instructions on where it should connect to. That's based on any number of criteria, not just signal level obviously. The EPC telling the device to switch base stations should be hitless, but any of these other scenarios requires something to timeout before switching base stations, so the end user would just suffer for a few minutes before the device reconnects. I don't know any reason why a home internet device wouldn't switch base stations. Mobility is a built in feature so they'd have to explicitly stop it if they didn't want it to happen. If it has a directional antenna then it might be de-facto stuck on one tower, of course. If the backhaul to the tower is down, the devices won't (or shouldn't) just stay connected to the dead tower. The EPC will know it can't talk to those base stations, and the base stations know they can't talk to the EPC. Barring a misconfiguration, I'd expect a short downtime and then the device connects somewhere else. What works while roaming would be up to the agreements between the providers. -Adam ________________________________ From: AF <[email protected]> on behalf of Ken Hohhof <[email protected]> Sent: Tuesday, August 12, 2025 2:36 PM To: 'AnimalFarm Microwave Users Group' <[email protected]> Subject: [AFMUG] mobile and 5G Home Internet when a celltower is offline Who here knows more than I do about how cellular networks work during a celltower outage? Would I be correct to assume that if, for example, a Verizon tower is offline, your mobile phone would connect to another nearby Verizon tower? And that you could not only make voice calls and send text messages, but also use your phone as a hotspot for Internet? And that if there was no other Verizon tower in range, your phone would roam to a T-Mobile or AT&T tower? And in that case, could you still use the hotspot feature? Now, what about Home Internet service? Would I be correct to assume no roaming and probably not even another Verizon tower? If your designated tower is down, no home Internet? One last question, if the tower has power and all the electronics is running but the backhaul to the tower is down (like a fiber cut), do phones still connect to the tower but have no service? Or will they move to another tower?
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