1. VoLTE stands for Voice Over LTE.
2. Until VoLTE was launched, all the calls made from LTE network used to go to Circuit Switched Network.
3. VoLTE was launched after LTE was launched.
4. As 4G is fully PS service, to make calls before VoLTE, it would have to fallback to 2G/3G network.
5. VoLTE uses data packet to make voice calls, without 4G you cannot make VoLTE calls.
What are the advantages of VoLTE?
1. Better user experience.
2. Good Battery Life
3. During VoLTE calls, user will be able to browse internet.
4. HD voice calls.
5. Inbuilt support for video calls.
Introduction to IMS VoLTE architecture
Below is a high level architecture of IMS VoLTE architecture.
From the above image we can see that, we need LTE network to connect to IMS, from there IMS can be connected to another LTE network or PSTN.
IMS stands for IP Multimedia Subsystem. It is a part of 3GPP.
IMS is a standalone component.
It is an old concept, and it is never just for voice services. It is intended for MultiMedia services.
Hence IMS makes ideal for VoLTE.
A VoLTE enabled mobile will work out of the box. Users need not install other applications for VoLTE to work.
Building blocks of VoLTE
SIP Enabled <—-> LTE Network <—-> IMS Core <—-> Voice Core
Sip Enabled Mobile
2. MME, SGW, PGW
Other IMS Components
VoLTE Mobile Components
For VoLTE to work, there should be an application provided by Mobile manufacturer. And Mobile should be having a valid SIM card and should be connected to LTE Network.
1. SIM : It is used to connected GSM networks. It is also called as UICC (Universal Integrated Circuit)
2. USIM: It is used to connect to LTE network.
3. ISIM: It is used to connect VoLTE network. Stands for IP Multimedia Services Identity Module.
It has 2 components:
1. IMPI: IP Multimedia Private Identity
2. IMPU: IP Multimedia Public Identity.
It is like a telephone No or SIP URI.
1. It is a User Agent required to connect IMS network.
2. It is used to transmit and receive SIP messages.
3. It is an application that is installed by handset provider.