Voice over LTE (VoLTE) is an
LTE high-speed
wireless communication
Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
standard for
mobile phones and data terminals, including
Internet of things (IoT) devices and wearables. VoLTE has up to three times more voice and data capacity than older
3G UMTS and up to six times more than
2G GSM
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital cellular networks used by mobile devices such as ...
. It uses less bandwidth because VoLTE's packet
headers are smaller than those of unoptimized VoIP/LTE.
VoLTE calls are usually charged at the same rate as other calls.
To be able to make a VoLTE call, the device, its firmware, and the mobile telephone provider must all implement the service in the area, and be able to work together. VoLTE has been marketed as
HD Voice
Wideband audio, also known as wideband voice or HD voice, is high definition voice quality for telephony audio, contrasted with standard digital telephony "toll quality". It extends the frequency range of audio signals transmitted over telephone ...
by some carriers, but this is not the same as the VoLTE standard. Moreover, HD+ (EVS) is what actually is used only in LTE; HD Voice was available in 3G too.
Overview
VoLTE is based on the
IP Multimedia Subsystem
The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-styl ...
(IMS) architectural framework, with specific profiles for
control
Control may refer to:
Basic meanings Economics and business
* Control (management), an element of management
* Control, an element of management accounting
* Comptroller (or controller), a senior financial officer in an organization
* Controlli ...
and
media planes of voice service. This facilitates VoLTE on the
LTE wireless broadband service defined by
GSMA
The GSM Association (commonly referred to as 'the GSMA' or ''Global System for Mobile Communications'', originally ''Groupe Spécial Mobile'') is an industry organisation that represents the interests of mobile network operators worldwide. More ...
in PRD IR.92. The approach results in the voice service (control and media planes) being delivered as data flows within the LTE data bearer, with no dependency on (or ultimately, requirement for) the
circuit-switched
Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel ( circuit) through the network before the nodes may communicate. The circuit guarantees the full ...
voice network to be in the call path.
As of February 2019 there were 253 operators investing in VoLTE in 113 countries globally, including 184 operators with commercially launched VoLTE-HD voice service in 87 countries, up from 137 operators in 65 countries 12 months previously, according to data from the
Global Mobile Suppliers Association
The Global mobile Suppliers Association (GSA) is a not-for-profit industry organisation representing companies in the mobile communication industry.
GSA actively promotes 3GPP technology such as 3G; 4G; 5G.
GSA is a market representation partn ...
. By August 2019, these numbers had risen to 262 operators investing in VoLTE in 120 countries and 194 operators with launched VoLTE-HD voice services in 91 countries.
History
Beginning in August 2012,
MetroPCS launched the world's first commercial VoLTE services in
Dallas, Texas
Dallas () is the third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the fourth-largest metropolitan area in the United States at 7.5 million people. It is the largest city in and seat of Dallas County w ...
, in the
United States, alongside the first VoLTE phone, the LG Connect 4G. 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.
In June 2014,
KT showcased the world's first cross-border
roaming services based on Voice over LTE. The South Korean
operator
Operator may refer to:
Mathematics
* A symbol indicating a mathematical operation
* Logical operator or logical connective in mathematical logic
* Operator (mathematics), mapping that acts on elements of a space to produce elements of another s ...
partnered with
China Mobile
China Mobile is the trade name of both China Mobile Limited () and its ultimate controlling shareholder, China Mobile Communications Group Co., Ltd. (, formerly known as China Mobile Communications Corporation, "CMCC"), a Chinese state-ownedSt ...
to develop VoLTE roaming services.
In November 2014,
Verizon and
AT&T
AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile te ...
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 were performed between both companies using third party networks such as
Alcatel-Lucent
Alcatel–Lucent S.A. () was a French–American global telecommunications equipment company, headquartered in Boulogne-Billancourt, France. It was formed in 2006 by the merger of France-based Alcatel and U.S.-based Lucent, the latter being a su ...
. This was stated to have been completed in November 2017.
On July 11, 2015, SEATEL Cambodia announced the world's first commercial 100% VoLTE service without 2G/3G in Cambodia.
As of 2020, almost all new phones for sale can use VoLTE.
By December 31, 2022,
Verizon Wireless
Verizon is an American wireless network operator that previously operated as a separate division of Verizon Communications under the name Verizon Wireless. In a 2019 reorganization, Verizon moved the wireless products and services into the divi ...
plans to retire their
2G and
3G CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication ...
networks in favor of
4G LTE and
5G NR. Customers with
CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication ...
-only devices (as well as older
4G LTE that do not have HD Voice capability) will be required to upgrade their devices by the shutoff date. Verizon stopped activating CDMA-only devices on their network in 2018, and had previously planned to shut down 3G service in 2019, but extended the timeline for shutting down the 3G network twice
— first to December 31, 2020, and then to December 31, 2022, which the VP of Network Engineering says "will not be extended again." The company indicated the delays were in an effort to "minimize disruptions" to its customers still utilizing the 3G network. Less than 1% of Verizon's customers were still using 3G, as of March 2021, and many of the 3G-connected devices are integrated devices, such as smart utility meters and home burglar alarms.
Voice quality
To ensure compatibility,
3GPP demand at least
AMR-NB codec (narrow band), but the recommended speech codec for VoLTE is
Adaptive Multi-Rate Wideband
Adaptive Multi-Rate Wideband (AMR-WB) is a patented wideband speech audio coding standard developed based on Adaptive Multi-Rate encoding, using a similar methodology to algebraic code-excited linear prediction (ACELP). AMR-WB provides improved ...
(AMR-WB), also known under the trademark HD Voice after GSMA's certification program. This codec is mandated in 3GPP networks that are capable of 16 kHz sampling.
In addition, many carriers and devices can use
Enhanced Voice Services
Enhanced Voice Services (EVS) is a superwideband speech audio coding standard that was developed for VoLTE. It offers up to 20 kHz audio bandwidth and has high robustness to delay jitter and packet losses due to its channel aware coding an ...
(EVS). This is a superwideband (50–14,000 Hz) or fullband (20–20,000 Hz) codec backwards-compatible with AMR-WB.
This codec is also known under the trademark HD Voice+, after GSMA's certification program. GSMA has proposed to make EVS mandatory just like AMR-WB.
[ (Both the carrier and the two calling devices must be capable of using the codec for it to be used.)
Fraunhofer IIS has previously demonstrated an implementation of the codec in VoLTE that they call "Full-HD Voice". It has not gained any standard status or real-world adoption.] They have since reused the term "Full-HD Voice" for EVS in fullband mode (HD+ is also used).[
]
See also
* QoS Class Identifier (QCI) – the mechanism used in VoLTE networks to allocate proper Quality of Service to bearer traffic
* Voice over NR
* Video over LTE
* Wideband audio
*Enhanced Voice Services
Enhanced Voice Services (EVS) is a superwideband speech audio coding standard that was developed for VoLTE. It offers up to 20 kHz audio bandwidth and has high robustness to delay jitter and packet losses due to its channel aware coding an ...
*List of LTE networks
This is a list of commercial Long-Term Evolution (LTE) networks around the world, grouped by their frequency bands.
Some operators use multiple bands and are therefore listed multiple times in respective sections.
General information
* For te ...
References
{{Mobile telecommunications standards
LTE (telecommunication)
Mobile technology
Telecommunications-related introductions in 2012
Voice over IP