[timv]

It's been more than a decade since I was involved with emergency services, but ~15 years ago there was a requirement (in Australia and elsewhere) that phones must be able to call emergency services from any available network even if the preferred carrier did not have service in that area. I assume that is still the case.

That requirement forces phones to have some degree of special handling for emergency calls. It may have required (or been interpreted to require) that a phone make emergency calls over 3G if VoLTE was unavailable. I can imagine someone deciding that means "lets just use 3G for all emergency calls" because who ever expected a case where 4G was available and 3G was not.

[Dylan16807]

> because who ever expected a case where 4G was available and 3G was not

I'd expect that to be everyone that thought about it for more than a few seconds. Both because eventual replacement was obvious and because sometimes you only have partial coverage.

[freshcupoftea]

You may or may not be familiar with some of the use cases here in Australia. 3G coverage was more widespread and reliable for low bandwidth use cases, right up until the end. It was 4G that would have partial coverage, not 3G. 3G was often forced by IoT vendors, or routers using cellular for out of band management, due to its superior ability to penetrate through buildings. Same with ATMs, payment terminals, emergency telephones in lifts or out on the highways. People in regional areas would also force set their phones to 3G, to stop them flapping between a poor signal 4G network and the consistent, but slower, 3G network.

Many DAS/Distributed Antenna Systems, essentially networks of antennas placed inisde buildings to extend cellular coverage indoors, are costly and must be approved on a per-operator basis. Some of the DAS solutions requirements I've seen to provide full coverage for Optus, Telstra and Vodafone in 4G only in a 30 story building or medium sized mall, wanted 18 full racks, 100 amp 3 phase power connectivity, 15kw minimum redudancy cooling capacity, 8 hours of battery backup for all racks and cooling, all located in the centre of the facility to minmize cable runs. As a result, high quality DAS systems don't exist in every large building or campus environment. Even in 2024, we see buildings nearing the end of construction before the developer bothers to consider an appropriate DAS system, and at that point they balk at the space and location requirements, and refuse to understand why a DAS can't just be installed in 4RU in a crammed comms room thats the size of a domestic bathroom.