Voice over Long-Term Evolution (VoLTE) is a standard for high-speed wireless communication for mobile phones and data terminals. It is based on the IP Multimedia Subsystem (IMS) network, with specific profiles for control and media plans of voice service on LTE defined by GSMA in PRD IR.92. This approach results in the voice service (control and media planes) being delivered as data flows within the LTE data bearer. This means that there is no dependency on (or ultimately, requirement for) the legacy circuit-switched voice network to be maintained. VoLTE has up to three times more voice and data capacity than 3G UMTS and up to six times more than 2G GSM. Furthermore, it frees up bandwidth because VoLTE’s packets headers are smaller than those of unoptimized VoIP/LTE.
In October 2014, operators based on IMS local breakout architecture with home routing systems.
In November 2014, Verizon and AT&T announced the companies are enabling VoLTE-to-VoLTE connections between their respective customers. VoLTE interoperability between Verizon and AT&T customers began in 2015. Testing and design are being done between both companies using third party networks such as Alcatel-Lucent.
On 11 July 2015, SEATEL Cambodia announced the world's first commercial 100% VoLTE service without 2G/3G in Cambodia.
On 14 September 2015, Orange Romania has launched the VoLTE service for Samsung users in Romania.
On 30 November 2015, Telenor Denmark launched VoLTE for all Samsung Galaxy S6 phones, which has since been followed by additional Samsung and Apple models.
On 30 June 2016, YTL's YES launches 4G LTE service to become Malaysia's FIRST VoLTE service provider.
In June 2016 Movistar Peru launched commercial VoLTE service in Peru, starting in Lima and Callao for Samsung Galaxy S6, S6 Edge and LG G4 phones. Service will be enabled progressively in other departments and handsets. Movistar Peru is the first operator in the country offering this service.
On 5 September 2016, India's first 4G-only network Jio launched their commercial VoLTE service without 2G/3G based services.
In October 2016, Orange Polska launched commercial VoLTE service in Poland.
In November 2016, T-Mobile (Poland) launched commercial VoLTE service in Poland.
On 7 December 2016, Telenor Denmark launched VoLTE for all phones with VoLTE support.
On 8 March 2017, Cosmote is the first operator that launched VoLTE (and VoWiFi) service in Greece.
On 24 April 2017, TIM launched VoLTE for all phones with VoLTE support in Italy.
In June 2017, Pakistan's Largest telecom operator Jazz has tested VoLTE over its network. Jazz plans to commercially launch it in July 2017.
In June 2017, Bahrain's Largest telecom operator Batelco has semi-launched the service to iOS users.
In July 2017, Digi.Mobil (RCS & RDS) will be the second carrier that launches commercial VoLTE services in Romania. (Confirmed)
In July 2017, TIM Brasil was the first carrier to sell VoLTE on Brazil.
In August 2017, Proximus was the first to activate VoLTE in Belgium. Customers were notified by SMS that the service was available.
A list of commercial VoLTE deployments around the world can be found in the main article above.
For planned VoLTE deployments see GSA Evolution to LTE report – VoLTE global status (Page 87ff).
To ensure compatibility, 3GPP demand at least AMR-NB codec (narrow band), but the recommended speech codec for VoLTE is Adaptive Multi-Rate Wideband (AMR-WB), also known as HD Voice. This codec is mandated in 3GPP networks that support 16 kHz sampling.
Fraunhofer IIS has proposed and demonstrated "Full-HD Voice", an implementation of the AAC-ELD (Advanced Audio Coding – Enhanced Low Delay) codec for LTE handsets. Where previous cell phone voice codecs only supported frequencies up to 3.5 kHz and upcoming wideband audio services branded as HD Voice up to 7 kHz, Full-HD Voice supports the entire bandwidth range from 20 Hz to 20 kHz. For end-to-end Full-HD Voice calls to succeed however, both the caller and recipient's handsets as well as networks have to support the feature.