Voice over LTE

To be able to make a VoLTE call, the device, its firmware, and the mobile telephone providers on each end, as well as the inter-carrier connectivity must all implement the service in the area, and be able to work together.

VoLTE is based on the IP Multimedia Subsystem (IMS) architectural framework, with specific profiles for control and media planes of voice service.

This facilitates VoLTE on the LTE wireless broadband service defined by GSMA in PRD IR.92.

[citation needed] Not all devices that have been sold as 'VoLTE capable' support making calls to Emergency Numbers over 4G/LTE with VoLTE.

[12] In 2022 at the European Emergency Number Association (EENA) Conference Telecoms Expert Rudolf van der Berg made a presentation to the Conference outlining serious compatibility issues with VoLTE Calling and Emergency Calling.

[15] In early April 2024 this number was increased to more than 1 million devices in the media with no change to the government reporting.

[25] Unlike calling with 2G and 3G there is no single configuration for VoLTE that all devices and networks universally support.

[13] In some instances the retail versions of devices have been sold without VoLTE Calling on any networks (depending on brand/market/region).

[28] Equally some handsets purchased from another carrier or from another market may not be configured (in software) to support VoLTE on all networks within a given country.

Open Market configuration devices can work on competing Australian providers Optus & Vodafone.

[26] By modifying the firmware customers can use VoLTE calling, however the carrier may not recognise those devices as supported despite working correctly.

Android users are able to confirm if VoLTE is working by checking for the Device 'IMS Status' within a hidden Radio Info Debug menu.

An IMS Status of "Not Registered" and "Voice over LTE: Unavailable" indicates VoLTE is not enabled or working.

Typically the modem configurations are automatically loaded by the device firmware when inserting a sim card.

[34] In May 2014, Singtel introduced the world's first commercial "full-featured" VoLTE service in Singapore, only in combination with Galaxy Note 3, it was subsequently expanded.

[35] In June 2014, KT showcased the world's first cross-border roaming services based on Voice over LTE.

The South Korean operator partnered with China Mobile to develop VoLTE roaming services.

[36] In November 2014, Verizon and AT&T announced the companies are enabling VoLTE-to-VoLTE connections between their respective customers.

[citation needed] On December 31, 2022, Verizon shut down their CDMA network, therefore requiring devices to support LTE or 5G.

[47] Fraunhofer IIS has previously demonstrated an implementation of the AAC-ELD codec in VoLTE that they call "Full-HD Voice".