Originally Posted by Lorin Schultz Does a phone need to have UMA-specific hardware to work, or will any wifi-capabe phone work if it has the right software? The list of phones that will work with my carrier's wifi calling is so short that I have to wonder if there's some kind of significant technical obstacle? If not, why isn't everyone supporting this?
I can't say for sure, but I strongly suspect any phone with enough processing power can do it - in theory. It really depends on what part of the system handles the conversion of voice into GSM packets. If that's happening in software, and then the packets are handed to the radios, then it should be possible for the software the re-direct those packets to the WiFi. That's really all there is to UMA. However, if the *sound* is sent to the chip, and the chip handles both packetizing and transmission, then it might not be possible.
I strongly suspect that the iPhone works in the former fashion, and this feature should just magically appear when you install iOS8. On older phones, pre-smartphone, most of this took place in custom silicon, which of course couldn't be changed in this manner. So you had to buy a special handset, and for whatever reason, it was always a crappy model. This, I feel, is the main reason for the lack of UMA uptake - that and the 27-step installation process!
When UMA first came out, you had to select among a bunch of hard-to-get handsets that were all lousy, wait weeks for it to arrive, and then find out that it may or may not work on your 1mbps connection after fiddling with it for an hour doing setup. And for this you get to pay another $15 a month. Needless to say there wasn't much take-up. So, ten years later, handset people are going "well no one used it, so no one wants it" and they don't bother adding it.
If my suspicions are correct, UMA is about to become extremely popular. This isn't UMA on some candy bar you're forced to use because your company put in an Astericks server. This is UMA that you get for free on the most popular phone in the world. I suspect the problem, if there is one, is that the carriers aren't ready for this, in the same fashion that they weren't ready for the data the 3G dropped on their networks in 2008. They need to install a piece of equipment known as a GANC, and I really don't know if there's enough of them.