Wifi calling and VoLTE: Do you know the best calling standards?

"VoLTE 1". That's what it says in the info bar on my mobile. Suddenly the display changes. Now it doesn't say anything except that I have a 4G network. The mobile network can change quickly depending on the mobile and the settings. When a new phone comes onto the market, one of the most frequently asked questions is whether the new phone can do wifi calling. But what is wifi calling and what are the requirements in addition to wifi?

Because I've noticed that many of my colleagues don't even know what VoLTE means and which standards they use to make calls, I'll try to explain the individual network standards here, including wifi calling.

The old ones: UMTS and GSM

You normally make calls using the old standards if you don't have an LTE network. Or if you use an ancient bone as a mobile that is not 4G-capable. UMTS, or Universal Mobile Telecommunications System, is the third generation of mobile telephony and is therefore also known as 3G. GSM is also known as 2G.

There are several extensions to UMTS. The most relevant are HSPA and HSPA+. These allow data rates to be increased, which improves call quality. The term "EDGE" will probably also ring a bell. EDGE is an extension of GSM in which the data rate has also been increased.

The mostly good thing: Voice over LTE

Most mobile phone calls today are made via the VoLTE standard. VoLTE stands for Voice over LTE, LTE is the fourth generation of mobile telephony (4G). With VoLTE, you make calls via the fast 4G network. Before VoLTE existed, the LTE network was only used for data connections. Depending on the smartphone you are using, it will show you before the call that the call is being made via VoLTE.

With VoLTE, the connection setup is much faster than with the older standards. My parents have been refusing to take out a mobile phone subscription for some time and therefore still have a prepaid card. They are with Swisscom, where VoLTE is only available with plans. When I call them, it takes an unusually long time for the connection to be established. By the time it rings for the first time, I could almost make myself a coffee. The call quality is also generally better with VoLTE. This is because the frequency spectrum is larger, as is the bandwidth, which all in all ensures better transmission.

Why not always VoLTE?

However, not all calls are made via the VoLTE network. One reason for this is the network coverage in Switzerland. The 4G network is still not available everywhere. If there is no 4G network, you have to make calls on UMTS or even GSM. 4G access is also limited with some plans.

And even if you theoretically have 4G reception, you may still be using UMTS, as your phone automatically selects the best network. If you often have no network at home, you can try switching off 4G telephony. In places where the network is very busy - at festivals or other events - it can also help to manually switch your mobile to 3G or even 2G. With Android, you can deactivate this under "Settings", "Mobile network" and then "Preferred network type". With iOS, you can find the item under "Settings", then "Mobile network" and under "Data options" you can deactivate LTE.

Wifi calling: actually great

Wifi calling is still relatively new and a pretty cool thing. With wifi calling, you make calls via the wifi network instead of the mobile network. The whole thing is also sometimes called VoWifi, which stands for Voice over Wifi. Wifi calling is particularly interesting for people who don't have a good mobile phone network at home. In this case, wifi telephony can really solve the problem. If you leave the wifi network, the call should be transferred to the LTE network - it should. In practice, this usually doesn't work for me.

You have to set up wifi calling in the settings on your phone; your phone won't switch networks just like that. If your phone supports the function and you are in a working WLAN, you can activate Wifi Calling on Android under Settings, Mobile Network. On iOS, you can find the whole thing under Settings, Phone and then go to the menu item Wifi calling.

But unfortunately not every phone is capable of this. Here is a list from Sunrise that lists some phones that are capable of wifi calling - including mobile phone-specific instructions. All newer models from Honor, for example, are also capable of wifi calling, but they are not on the list. Basically, you need at least Android 7.0 or iOS 10.3, otherwise you can forget it anyway.

In addition to your phone, it also depends on your provider. So the actually great Wifi Calling is not easy to get.

This is what it looks like for wifi calling with our three major providers

Wifi calling sounds great, but it doesn't always work and, depending on the provider, you may be charged for the connection, especially abroad, despite having WiFi.

With Swisscom, you can make calls via Wi-Fi with all inOne and Infinity plans, depending on your provider. As with VoLTE, this is not possible with a prepaid plan. It only works with Swisscom if you are on the Swiss network. If you're abroad, you can't avoid annoying roaming costs with Wifi Calling. However, you can call someone who is abroad via WLAN. However, unlike Whatsapp or Skype, the connection is not free - because it is mediated and set up by Swisscom.

With Sunrise, the service can also only be used in Switzerland; roaming is not possible here either. The service works with all Sunrise plans and with the new Sunrise prepaid plans. However, you will be charged for the phones at your normal tariffs - so you can't save money with it.

Only Salt makes an exception: Wifi calling is possible abroad. Salt promises that the whole thing works without roaming charges. Wifi calls are billed in the same way as your calls on the Swiss network. <p