What is VoLTE and what do you need to use it?


The VoLTE stands for Voice Over LTE.  It is the technology that uses a high-speed fourth-generation of GSM network for providing audio and other multimedia services. 

LTE is a pure packet-switched network while in previous generations (3G/2G) there were two separate networks for packet and circuit switching.  This brings a new way for voice calls to work. Where a virtual voice circuit needs to be set up over a packet network.

Before VoLTE, a subscriber could use a data network for web browsing, and other activities over the Internet.   The VoLTE opens new options for subscribers and network operators by providing multimedia services over high-speed internet connections. The best part is that operators are no longer required to maintain two distinct networks, one for data and another for voice.

What is required for VoLTE?

To start using Voice Call over an LTE network, you need to make sure to follow.

  • The network sim card you are using supports the feature and is enabled by the mobile operator with your current plan.
  • The phone that you are using has capability for the VoLTE.
  • The network in your area is an LTE network.

What is VoLTE?

As we have talked about, it’s voice over an LTE network.  Because of the speed, the new fourth-generation network can offer brings a much richer experience for Audio, Video, etc. 

The SS7 network was used for voice on older networks (3G or 2G). Although voice packets are transferred utilizing a dedicated E1/T1 connection with reserved bandwidth. However, for today’s needs for applications, it is insufficient.

With VoLTE the connection can use an underlying channel with much higher bandwidth, which results in the possibility for High Definition(HD) video and audio calls.

What is the link between VoLTE and LTE?

With LTE, data speed is enhanced as compared to the previous generations, but the call was still on a 3G network.  When there is a voice call, the phone switches to 3G, and after the call completion, it again switches back to 4G-LTE.  Makes a temporary disconnect with the data. With VoLTE, there will be no such thing.

Advantages of VoLTE-

  • The call connects much faster and the call quality is much better because of the faster speed.
  • You can browse data and at the same time can talk to someone over Voice.
  • Brings more services as all have moved to the IP protocols for telephony.

Disadvantages –

Can not work on a basic phone, those do not have data capability at all. A mobile operator always needs to set a parallel network for Voice at least in some areas.

What does a subscriber need to do for VoLTE?

For a mobile subscriber, the phone should be VoLTE capable.  If not he has to upgrade the phone.  Once you are sure that the serving mobile operator supports the feature, you need to enable it in the handset.

How to enable it on Android? 

What are the obstacles that a mobile operator must overcome in order to support VoLTE?

Looks like it’s very simple to support the new calling feature. But it is not so. First, an operator upgraded to 4G-LTE from the previous 3G. The up-gradation process includes purchasing spectrum, deploying radio, and wired network components.  Newer network components bring new protocols. For example, the diameter is the new protocol in 4G roaming while in 3G SS7 was the protocol.

Now data is on with over 4G, but still, voice uses 3G fallback.  With Voice Over LTE, no more fallback will happen. But require new network components with additional protocols. IMSI is the core network for VoWifi. It uses primarily Session Initiation Protocol and other protocols e.g GTP.

Within IMS, sim becomes ISIM and it does on IMS network attach for Voice Call, SMS, USSD, etc.

Is WiFi calling is same as VoLTE?

Looks like both are IP-based but on a network level, both are far apart. The WiFi network is a non-3GPP network, that requires an additional ePDG to support Wifi Calling.  While VoLTE uses the same 3GPP network.

In VoLTE, the data is consumed from the subscriber data bundle, while in WiFi Calling data is used from the WiFi account.