Don’t get too excited by Apple’s announcement of a Voice over IP service on the iPhone 3.0. It strains credulity that AT&T would open up the iPhone to work on third party VoIP networks, so presumably the iPhone’s VoIP service will be locked down to AT&T.
AT&T has a large network of Wi-Fi hotspots where iPhone users can get free Wi-Fi service. The iPhone VoIP announcement indicates that AT&T may be rolling out voice over Wi-Fi service for the iPhone. It will probably be SIP, rather than UMA, the technology that T-Mobile uses for this type of service. It is likely to be based on some flavor of IMS, especially since AT&T has recently been rumored to be spinning up its IMS efforts for its U-verse service, which happens to include VoIP. AT&T is talking about a June launch.
An advantage of the SIP flavor of Voice over Wi-Fi is that unlike UMA it can theoretically negotiate any codec, allowing HD Voice conversations between subscribers when they are both on Wi-Fi; wouldn’t that be great? The reference to the “Voice over IP service” in the announcement is too cryptic to determine what’s involved. It may not even include seamless roaming of a call between the cellular and Wi-Fi networks (VCC).
AT&T has several Wi-Fi smartphones in addition to the iPhone. They are mostly based on Windows Mobile, so they can probably be enabled for this service with a software download. The same goes for Blackberries. Actually, RIM may be ahead of the game, since it already has FMC products in the field with T-Mobile, albeit on UMA rather than SIP, while Windows Mobile phones are generally ill-suited to VoIP.