Iphone 5 no wifi calling (dropped in iOS 8 GM). I am posting this around the web as no-one has clarified it, everyone believes that Apple simply wants to force users to buy a new device. That isn't the whole story.
iOS 8 beta 3 up to the GM release allowed the iPhone 5 to "enable" wifi calling on the T-Mobile network. Some users reported that it did indeed work when they tried it. Likely what they did was place or receive a call on the wifi network. However, the full range of the feature was to allow a seamless transfer of a call from wifi to cellular. And it was discovered that not all iPhone 5 models were fully hardware compatible.
Many users do not understand why the iPhone 5c, but not the iPhone 5, supports wifi calling, citing the similar A6 SOC used. What they do not grasp is that the reason for the loss of the feature lies in the antenna used, not the SoC.
iPhone 5 was released in September of 2012 for use on the CDMA network of Verizon and the GSM network for AT&T. The different models used different antenna chips that made them physically unable to work on alternate network frequencies. In March of 2013, t-mobile received the iPhone 5, with a small modification to the iPhone 5- a change in the carrier antenna that supported AWS bands for T-mobile.
Source : http://www.everymac.com/systems/apple/iphone/iphone-faq/differences-between-ipho ne-5-models.html
The GSM version previously sold by and for AT&T since September of 2012 would work on the edge, 3G and 4g networks, but not the 1700 MHz AWS band of T-Mobile. This allowed 21mbps LTE but prevented use on the more capable 42mbps dc-hsdpa band in many market areas.
Source : http://support.apple.com/en-us/HT202720
Therefore, not all iPhone 5 phones support all of T-Mobile's frequency bands. More specifically, an iPhone 5 sold by T-Mobile would work, but an iPhone 5 sold by AT&T or by Apple prior to March 2013 would not. The resale and possible migration of these phones to T-mobile network could not be prevented, which would cause a mixed user environment for T-mobile. In some cases, users with a GSM iPhone 5 would be therefore able to make or receive a wifi call, but the phone would be unable to hand off the call to an available cellular network as it lacked a compatible antenna. The GSM iPhone 5c radio (and newer devices) however supports all T-Mobile frequencies, allowing for seamless handoff of wifi calls.
While some would argue that allowing wifi calling would be a benefit in and of itself, and this would only affect some iPhone 5 users who wish to a) migrate to T-Mobile and b) take advantage of wifi calling, Apple and T-Mobile also have an interest in persuading users to purchase a device that would fully benefit from a seamless calling experience. Rather than have users complain that the feature is crippled and calls were dropped as wifi signal was lost, Apple removed the feature before mass adoption for the lesser exposure of criticism for not allowing a feature in the first place.
As for AT&T, all iPhone5 models could support wifi calling and seamless handoff to available cellular GsM networks, but AT&T has not addressed rolling out wifi calling until late 2015/2016. At that point Apple will have released iOS 9, perhaps even iOS 10 may be released. Given that most iPhones enjoy about 4 years upgradeability (4 iOS versions [source: http://en.m.wikipedia.org/wiki/List_of_iOS_devices]), and the iPhone 5 is still a 32 bit architecture, the iPhone 5 will likely only support iOS 9, and be at end-of-life anyway at that point, signaling that users should abandon the device anyway as AT&T rolls out the wifi calling support. Thus giving support for the iPhone5 device for AT&T users would be a small consideration.
