The latest version of Android Open Source Project (AOSP), Android 5.1.1_r5, was publicly released by Google on June 25th. The update to the source code brings about numerous bug fixes and tweaks, while including a cool new feature that especially stands out for the possibilities it promises to bring to our smartphones, if carriers and OEMs play ball. The feature happens to be Wi-Fi calling, which in theory, should allow users to make and receive calls and texts to and from other mobiles and land-line phones on a supported Android-based device, even without access to a cellular network. Of course, since the feature uses Wi-Fi to connect your call, it goes without saying that you need to be in a Wi-Fi hotspot for the feature to work. The feature itself is nothing new, with apps like Skype, Hangouts and WhatsApp already having made it possible to place phone calls over the internet (Wi-Fi or otherwise) by using a technology known as VoIP (Voice-over-Internet-Protocol). However, this new feature, which is as yet supported by very few networks worldwide, will allow users to call even fixed-line telephones, simply by using the recipient's phone number, just like any regular call.
The reality however is not as rosy as it may seem. As mentioned earlier, the feature itself needs support both from your carrier and from your device manufacturer, to work. If your carrier doesn't support the feature, you're basically out of luck. Very few carriers as of today, support the feature; amongst them, are Sprint and T-Mobile in the US and EE and O2 in the UK. Developers believe that porting the feature to a device on an unsupported network is a task of mammoth proportions - to the point of being a practical impossibility. While many might be also hoping that the code and thereupon, the functionality, can be ported over to devices which do not officially support the feature out the box, it might be a step too far in reality - even though, it is still technically possible in some cases. Developers say, bringing this feature to unsupported devices would require massive amounts of re-writing of the 'kernels and other deep software levels', which could potentially brick devices for good.
According to them, the code would actually benefit the makers of custom ROMs, who can now implement the feature in their software aimed at compatible handsets like Samsung's Galaxy S6, LG's G4 and HTC's One M9, which are among a whole host of devices that already support the feature. While the source code is first and foremost for the Nexus 6, it can, in all likelihood, be ported to other stock and AOSP-based ROMs for dozens of devices. While it's still not beyond the highly skilled and ingenious developers within the Android community, it would probably be for the best if you didn't hold your breath for the feature to be activated on your Nexus 4 or 5 any time soon, as neither of those devices support Wi-Fi calling.