I'm really starting to wonder: Did I unintentionally send some kind of bat signal through time, channeling Bellhead objections to the feasibility of VoIP that have been thoroughly and empirically disproven years ago when the POTS largely switched to NGN and IETF standards, and people around the world have moved on entirely to Internet-based OTT VoIP services?
No, they do, exclusively. LTE and beyond don’t even support circuit switched calls anymore.
Bellhead wasn’t intended in a derogatory way, just as a reference to the “Netheads vs. Bellheads” schools of thinking about networks.
I do have great respect for historical phone systems and the clever engineers making them work. In terms of absolute reliability, I think VoIP was indeed a step back (although I think that’s mainly due to modern engineering and QA practices than inherent limitations).
(from https://www.ericsson.com/en/reports-and-papers/white-papers/...)
Circuit switched fallback means falling back to 3G or 2G (or maybe CDMA) for voice calls; if such networks are no longer available in a given area, VoLTE is indeed mandatory if voice calls are to be supported. (Which is often mandated by regulations, so networks sometimes even block non-VoLTE UEs from attaching.)