IMPORTANT: This article applies only to specific products and/or operating systems. Check Applicable Products and Categories for details.
What is VoIP?
Voice over Internet Protocol (VoIP), also known as Voice call over IP, is a SIP (Session Initiation Protocol) call technology. VoIP is a communication method which converts analogue voice into digital data packets and sends them over the Internet to make online voice calls.
VoIP calls are not dependant on your operator and don't require a SIM card. All you need is Internet access (Wi-Fi or mobile data), a VoIP app (e.g. Skype) or a VoIP SIP account.
VoIP services are either free or come with a charge:
- You can download applications such as Skype, Viber or WhatsApp to make free online VoIP calls and reach other Skype, Viber or WhatsApp users respectively.
- You can pay a VoIP provider and set up your own VoIP SIP account in your phone. With a SIP account, you can call both mobile and landline numbers.
- NOTE: You don’t need a SIP account to use Skype, Viber, WhatsApp etc.
What is VoWiFi?
Voice over Wi-Fi (VoWiFi), also known as Wi-Fi Calling, is a Wi-Fi-based commercial telephony voice call service provided by different network operators. Thanks to Wi-Fi Calling you can make and answer calls via a Wi-Fi network, instead of using your mobile network.
- Is your mobile network coverage poor or unavailable?
- Is your smartphone connected to Wi-Fi?
If you answered ‘Yes’ both times, Wi-Fi calling might be the perfect solution for you. Wi-Fi Calling can enable or improve your calls in places lacking cellular signal (e.g. an underground basement or a well-insulated building).
Wi-Fi Calling doesn’t rely on a mobile signal but on a strong Wi-Fi connection. This means you can make Wi-Fi calls when your phone is in Flight Mode, when it doesn’t receive a 2G, 3G or 4G signal and even when it doesn’t have a SIM card. However, certain requirements must be met for Wi-Fi calls to work on your phone.
- What do you need to use VoWiFi/Wi-Fi Calling?
- How do I know if my device and subscription support VoWiFI?
- What is the difference between VoIP and VoWiFi?
- Smooth transition between VoWiFi and VoLTE
- How do I know if Wi-Fi Calling is working?
- Does VoWiFi/Wi-Fi Calling offer better call quality?
- How much do Wi-Fi calls cost?
- Can I make emergency calls with VoWiFi?
Making a VoWiFi call is the same as making a regular call. You don’t need a separate app. Nevertheless, to use Wi-Fi Calling, the following conditions must be met:
- Your device’s software is updated to the latest version.
- Your subscription (including SIM card) must support Wi-Fi Calling for your device model. In other words, your device must be Wi-Fi Calling-capable and compatible.
- Your mobile must be connected to a (strong) Wi-Fi network.
- You can’t access the VoWiFi service while travelling abroad.*
- You need to know the recipient's phone number.
- Always contact your mobile network operator to check if your subscription and SIM card support VoWiFi/Wi-Fi calling.
- Many network operators share lists of devices compatible with VoWiFi on their websites.
- VoWiFi/Wi-Fi Calling must be turned on in your device’s settings. If your device has the ‘Wi-Fi Calling’ setting, you should be able to toggle the ‘Wi-Fi Calling’ setting On and Off.
- VoIP transfers voice data packets over the Internet to the switched telephone network, while VoWiFi/Wi-Fi Calling reaches your carrier over the Internet instead of a cell tower to establish a phone line.
- VoIP calls don’t depend on the operator, unlike VoWiFi calls. VoWiFi can only be set up by your mobile network provider, as the set-up authentication process happens in the SIM.
Once VoWiFi is activated on your mobile, your phone will switch to VoWiFi (Wi-Fi Calling) whenever your mobile signal is too weak, but a Wi-Fi connection is present.
However, if you leave the Wi-Fi range during a Wi-Fi call or if your Wi-Fi connection isn’t strong enough, your smartphone will switch to the mobile network.
If 4G/LTE* is selected as your phone’s Network mode and you’re within the range of a 4G/LTE network, your phone will automatically switch to VoLTE (Voice over data) and the call will continue. This transition is not possible when calling over Wi-Fi with a separate VoIP app, such as Skype, WhatsApp, etc.
If VoWiFi doesn’t have VoLTE to fall back to, VoWiFi switches to 3G or 2G, if available. This transition makes the call drop.
*The terms 4G and LTE refer to the same technology and can be used interchangeably.
Some mobile operators display a VoWiFi (Wi-Fi Calling) icon on your smartphone’s screen during a Wi-Fi call. Some mobile operators don’t include VoWiFi icons, but there is a simple way to see if you're using this service:
- Make sure the VoWiFi settings are enabled in your smartphone and you’re connected to Wi-Fi.
- Disable your mobile data, then try to make a call in an area where you would usually get a very poor mobile coverage. If the call quality has improved, you’re using Wi-Fi Calling.
To check if your subscription and SIM card support VoWiFi/Wi-Fi Calling, contact your mobile network operator.
Attention: You must enable Wi-Fi Calling manually to use it. Wi-Fi Calling settings don’t get transferred after performing a factory data reset or switching to a different device.
Wi-Fi Calling can enable or improve your calls in places with a poor mobile network signal, given that your Wi-Fi connection is strong and stable. If the Wi-Fi network you’re connected to has many users or is involved in bandwidth-intensive activities (e.g. video streaming), you may experience poor audio quality issues during Wi-Fi calls.
For information about Wi-Fi calling charges, please contact your service provider as they depend on your contract.
In most countries, a VoWiFi call is billed in the same way as a regular call over the mobile network (2G, 3G, 4G).
In some countries, calling emergency numbers over VoWiFi is not possible.
However, there is always a fallback option. If you try to make an emergency call over Wi-Fi and this option is not available, your device will automatically use the mobile network, as long as it’s within the range of the mobile network.