Voice over LTE (VoLTE) is an LTE high-speed wireless communication standard for voice calls using mobile phones and data terminals. VoLTE has up to three times more voice and data capacity than older 3G UMTS and up to six times more than 2G GSM. 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 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 has been marketed as "HD voice" by some carriers, but this is a broader concept. Moreover, HD+ (EVS) is used only in LTE; HD voice was available in 3G too.
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. [1] 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 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. [2] 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. [3]
There are several issues of the VoLTE deployment :
Beginning in August 2012, MetroPCS launched the world's first commercial VoLTE services in Dallas, Texas, in the United States, alongside the first VoLTE phone, the LG Connect 4G. [8] 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. [9] 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. [10]
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 were performed between both companies using third party networks such as Alcatel-Lucent. [11] This was stated to have been completed in November 2017. [12]
On July 11, 2015, SEATEL Cambodia announced the world's first commercial 100% VoLTE service without 2G/3G in Cambodia. [13] [14] [15] [16] [17]
As of 2020, almost all new phones for sale have the potential to support VoLTE.[ citation needed ]
On December 31, 2022, Verizon shut down their CDMA network, therefore requiring devices to support LTE or 5G. Customers with CDMA-only devices and LTE devices without VoLTE support would have been required to switch to a VoLTE-capable device by that 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 [18] — 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. As of March 2021, less than 1% of Verizon's customers were still using 3G, and many of the 3G-connected devices are integrated devices, such as smart utility meters and home burglar alarms. [19]
Additionally, certain Verizon-compatible handsets were blocked from Verizon's CDMA network even before December 31, 2022, even if the device supported CDMA (for instance, unlocked devices with support for Sprint or Chinese CDMA networks), therefore requiring VoLTE support when used on Verizon. This includes CDMA-capable versions of the Apple iPhone 12 and 13 series, Samsung Galaxy S21, Google Pixel 5a, and OnePlus 6T to 9. Devices lacking CDMA support such as the Pixel 6 and above, US-sold OnePlus 10 Pro and 10T devices, and select iPhones including the iPhone 14 as well as older "GSM" models with an Intel modem will only work on Verizon in VoLTE mode.
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 under the trademark HD Voice after GSMA's certification program. This codec is mandated in 3GPP networks that are capable of 16 kHz sampling. [20]
In addition, many carriers and devices can use Enhanced Voice Services (EVS). This is an up to superwideband (20–16,000 Hz) or fullband (20–20,000 Hz) codec backwards-compatible with AMR-WB. [21] This codec is also known under the trademark HD Voice+, after GSMA's certification program. [22] GSMA has proposed to make EVS mandatory just like AMR-WB. [21] (Both the carrier(s), any interconnect and the two calling devices must be capable of using the codec for it to be used.) The AMR-WB+ codec has a wide bit-rate range, from 5.2 to 48 kbit/s. EVS offers a wide range of bit rates from 5.9 kbit/s to 128 kbit/s, allowing service providers to optimize network capacity and call quality as desired for their service, so VoLTE does not ensure high call quality. [21]
Fraunhofer IIS has previously demonstrated an implementation of the AAC-ELD codec in VoLTE that they call "Full-HD Voice". It has not gained any standard status or real-world adoption. [23] They have since reused the term "Full-HD Voice" for EVS in fullband mode (HD+ is also used). [21]
3G is the third generation of wireless mobile telecommunications technology. It is the upgrade over 2G, 2.5G, GPRS and 2.75G Enhanced Data Rates for GSM Evolution networks, offering faster data transfer, and better voice quality. This network was superseded by 4G, and later on by 5G. This network is based on a set of standards used for mobile devices and mobile telecommunications use services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. 3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV.
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 divisions Verizon Consumer and Verizon Business, and stopped using the Verizon Wireless name. Verizon is the second-largest wireless carrier in the United States, with 144.8 million subscribers as of December 31, 2023. It currently has the largest network in the United States with their LTE network covering 70% of the United States.
4G is the fourth generation of broadband cellular network technology, succeeding 3G and preceding 5G. A 4G system must provide capabilities defined by ITU in IMT Advanced. Potential and current applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing, and 3D television.
United States Cellular Corporation is an American mobile network operator. It is a subsidiary of Telephone and Data Systems Inc.. The company was formed in 1983 and is headquartered in Chicago, Illinois. UScellular is the fifth-largest wireless carrier in the United States, with 4,656,000 subscribers in 426 markets in 21 states as of the 2nd quarter of 2023. The organization was previously known as U.S. Cellular.
Telus Mobility is a Canadian wireless network operator and a division of Telus Communications which sells wireless services in Canada on its numerous networks. It operates 5G, LTE and HSPA+ on its mainstream networks. Telus Mobility is the second-largest wireless carrier in Canada, with 10.6 million subscribers as of Q3 2020.
Sprint Corporation was an American telecommunications company. Before being acquired by T-Mobile US on April 1, 2020, it was the fourth-largest mobile network operator in the United States, serving 54.3 million customers as of June 30, 2019. The company also offered wireless voice, messaging, and broadband services through its various subsidiaries under the Boost Mobile and Open Mobile brands and wholesale access to its wireless networks to mobile virtual network operators.
Ice Wireless is a Canadian mobile network operator and telecommunications company that provides 4G/LTE mobility services, mobile broadband Internet, and fixed line telephone in Canada's northern territories: Yukon, the Northwest Territories, Nunavut, and Nunavik, Quebec. The company's corporate headquarters are located in Markham, Ontario.
Wi-Fi calling refers to mobile phone voice calls and data that are made over IP networks using Wi-Fi, instead of the cell towers provided by cellular networks. Using this feature, compatible handsets are able to route regular cellular calls through a wireless LAN (Wi-Fi) network with broadband Internet, while seamlessly change connections between the two where necessary. This feature makes use of the Generic Access Network (GAN) protocol, also known as Unlicensed Mobile Access (UMA).
Mobile VoIP or simply mVoIP is an extension of mobility to a voice over IP network. Two types of communication are generally supported: cordless telephones using DECT or PCS protocols for short range or campus communications where all base stations are linked into the same LAN, and wider area communications using 3G or 4G protocols.
In telecommunications, a femtocell is a small, low-power cellular base station, typically designed for use in a home or small business. A broader term which is more widespread in the industry is small cell, with femtocell as a subset. It typically connects to the service provider's network via the Internet through a wired broadband link ; current designs typically support four to eight simultaneously active mobile phones in a residential setting depending on version number and femtocell hardware, and eight to sixteen mobile phones in enterprise settings. A femtocell allows service providers to extend service coverage indoors or at the cell edge, especially where access would otherwise be limited or unavailable. Although much attention is focused on WCDMA, the concept is applicable to all standards, including GSM, CDMA2000, TD-SCDMA, WiMAX and LTE solutions.
Airvana was acquired by CommScope in 2015. Prior to that, the company was an independent provider of small cells and femtocells based on fourth generation (4G) Long Term Evolution (LTE) and third-generation (3G) CDMA2000 EV-DO mobile broadband technologies. Airvana products enable mobile operators to deliver 3G and 4G cellular data services indoors.
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 lines, resulting in higher quality speech. The range of the human voice extends from 100 Hz to 17 kHz but traditional, voiceband or narrowband telephone calls limit audio frequencies to the range of 300 Hz to 3.4 kHz. Wideband audio relaxes the bandwidth limitation and transmits in the audio frequency range of 50 Hz to 7 kHz. In addition, some wideband codecs may use a higher audio bit depth of 16 bits to encode samples, also resulting in much better voice quality.
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Yemen Mobile is a CDMA2000 network provider founded in Yemen in 2004 by the Yemen ministry of telecommunication and it is the first CDMA network operator in the Middle East. Yemen Mobile CDMA system is based on Huawei equipment. According to the 3GPP2 standard, CDMA2000 system is fully compatible with IS-95 cellular phones, so any IS-95 phone will work with Yemen mobile. In 2012, Yemen mobile implemented ZTE equipment besides Huawei as well as using LG-Nortel network in some eastern parts of the country. Yemen Mobile is the first 3G company in Yemen that provides CDMA2000 1x and 1xEV-DO services. Yemen mobile was established in 2004 as a third wireless operator in Yemen and initially provided voice services alongside data services which enable their customers to use data and the Internet at a speed of 153 kbit/s by implementing the CDMA2000 1xRTT standard. By 2007, it had jumped to the top of mobile operators in the country in term of subscribers number and coverage.
MagtiCom, Ltd. is a Georgian telecoms company founded on February 12, 1996 by Dr. George (Gia) Jokhtaberidze. On September 22, 1997 the Company made the first commercial call from its mobile network. The services offered by MagtiCom involve as follows: mobile telephony; mobile internet ; Cable fixed telephony (VoIP); internet television (IPTV) and fiber-optic internet. Since 2016 MagtiCom started to provide IPTV, VoIP and fiber-optic internet.
3G mobile telephony was relatively slow to be adopted globally. In some instances, 3G networks do not use the same radio frequencies as 2G so mobile operators must build entirely new networks and license entirely new frequencies, especially so to achieve high data transmission rates. Other delays were due to the expenses of upgrading transmission hardware, especially for UMTS, whose deployment required the replacement of most broadcast towers. Due to these issues and difficulties with deployment, many carriers delayed acquisition of these updated capabilities.
Airtel India commonly known as Airtel, is the second largest provider of mobile telephony and third largest provider of fixed telephony in India, and is also a provider of broadband and subscription television services. The brand is operated by several subsidiaries of Bharti Airtel, with Bharti Hexacom and Bharti Telemedia providing broadband fixed line services and Bharti Infratel providing telecom passive infrastructure service such as telecom equipment and telecom towers. Currently, Airtel provides 5G, 4G and 4G+ services all over India. Currently offered services include fixed-line broadband, and voice services depending upon the country of operation. Airtel had also rolled out its VoLTE technology across all Indian telecom circles.
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 and improved packet loss concealment. It has been developed in 3GPP and is described in 3GPP TS 26.441. The application areas of EVS consist of improved telephony and teleconferencing, audiovisual conferencing services, and streaming audio. Source code of both decoder and encoder in ANSI C is available as 3GPP TS 26.442 and is being updated regularly. Samsung uses the term HD+ when doing a call using EVS.
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