Wi-Fi calling: everything you need to know
Got bad signal in your house? This could solve all your problems

Apple included loads of new features in the iPhone 6 and iPhone 6 Plus but perhaps one of the most exciting hasn't really been shouted about.

The one I'm talking about is Wi-Fi calling, a very clever idea that will change the amount of time you spend out of signal. It's new to the iPhone but it's also available on the latest Android handsets as well.

Essentially, this feature lets your smartphone use a Wi-Fi signal to make and receive calls and send texts rather than your mobile network.

Best of all, if you're on a call using your Wi-Fi connection and you move out of range the smartphone will seamlessly switch your call to use your mobile network connection instead.

I spoke to EE, the first network operator to offer Wi-Fi calling in the UK, about whether its service will seamlessly switch between cellular and Wi-Fi networks.

Wi-Fi calling
Apple announced that T-Mobile in the US and EE in the UK would offer Wi-Fi calling

An EE spokesperson informed me that at launch the service will not be able to handover seamlessly, however this will be enabled as part of 'phase two', which will launch in 2015.

What are the benefits?

There are a number of benefits to Wi-Fi calling, with the most obvious being if you get little or no mobile reception in your house. With your smartphone connected to the Wi-Fi network you won't need to worry about missing an important call.

Making calls over Wi-Fi could also mean you're not using up the minutes on your contract, so it may even save you money.

With the proliferation of Wi-Fi hotspots that can be found everywhere from cafés to public transport, there's a good chance that you could end up being connected to Wi-Fi networks more often than your mobile network.

Wi-Fi calling
EE has revealed its plans for Wi-Fi Calling, though some questions remain

Wi-Fi calling and Voice over IP

Making phone calls over the internet using a wireless connection isn't particularly new, with Voice over Internet Protocol (VoIP) services such as Skype becoming increasingly popular.

While VoIP lets you use Wi-Fi to make calls to mobile and landline numbers, there are a number of key differences between the two technologies.

For example, if you want to use Skype to make phone calls over Wi-Fi to mobile or landlines you'll need a Skype account and the Skype app installed on your device. You'll then need to buy Skpye credit to make those calls.

Wi-Fi calling
Skype will cut out if you go out of Wi-Fi range, but proper Wi-Fi enabled calls will be able to switch between Wi-Fi and mobile networks

The beauty of Wi-Fi calling is that there are no extra apps, and no extra costs or subscriptions. Instead, it's all rolled into your contract and fully integrated with your smartphone's standard phone app. In practise making a Wi-Fi call should be no different to when you're making a normal phone call.

Another big difference between VoIP services and Wi-Fi calling is that VoIP calls can't automatically switch from Wi-Fi to mobile networks. So, if you're on a Skype call and you walk out of range of your Wi-Fi network, your call will be dropped.

How does it work?

Wi-Fi calling seems to be cropping up more regularly, no doubt thanks to Apple's high profile endorsement, but the technology has in fact been around for a while, usually known by the less glamorous moniker of Generic Access Network (or GAN for short).

This technology lets cell phone packets that are traditionally transmitted over the air using mobile data to use Wi-Fi networks to connect calls, rather than traditional cell towers.

Your call goes from your smartphone onto the internet via a Wi-Fi connection, which then gets passed onto the GAN Controller (the device that replaces the cellphone towers), which then passes the call onto the phone network.

I contacted the mobile networks to find out more about how Wi-Fi calling services would work. EE, the first to bring the feature to the iPhone 6, told me "Wi-Fi calling is not an app. And it's not a VoIP service as we know it today. Rather, it's a 'carrier grade' voice service – calls are secured and managed through our core network using IMS – IP Multimedia Subsystem."

"So you can make or receive a call just like you're on the mobile network, even when your only connection is Wi-Fi."

The IMS technology used by EE means that you won't need any additional hardware, just a modern smartphone and any Wi-Fi network.