LTE in unlicensed spectrum (LTE-Unlicensed, LTE-U) is an extension of the

Long-Term Evolution In telecommunications, long-term evolution (LTE) is a standard for wireless broadband communication for cellular mobile devices and data terminals. It is considered to be a "transitional" 4G technology, and is therefore also referred to as 3 ...

(LTE) wireless standard that allows cellular network operators to offload some of their data traffic by accessing the unlicensed 5 GHz frequency band. LTE-Unlicensed is a proposal, originally developed by

Qualcomm Qualcomm Incorporated () is an American multinational corporation headquartered in San Diego, California, and Delaware General Corporation Law, incorporated in Delaware. It creates semiconductors, software and services related to wireless techn ...

, for the use of the

4G LTE In telecommunications, long-term evolution (LTE) is a standard for wireless broadband communication for cellular mobile devices and data terminals. It is considered to be a "transitional" 4G technology, and is therefore also referred to as 3 ...

radio communications technology in

unlicensed spectrum Spectrum management is the process of regulating the use of radio frequencies to promote efficient use and gain a net social benefit.Martin Cave, Chris Doyle, William Webb, ''Modern Spectrum Management'', Cambridge University Press, 2007 The ter ...

, such as the 5 GHz band used by

802.11a IEEE 802.11a-1999 or 802.11a was an amendment to the IEEE 802.11 wireless local network specifications that defined requirements for an orthogonal frequency-division multiplexing (OFDM) communication system. It was originally designed to support w ...

and

802.11ac IEEE 802.11ac-2013 or 802.11ac is a wireless networking standard in the IEEE 802.11 set of protocols (which is part of the Wi-Fi networking family), providing high-throughput wireless local area networks (WLANs) on the 5 GHz band. The stan ...

compliant

Wi-Fi Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...

equipment. It would serve as an alternative to carrier-owned

Wi-Fi hotspot A hotspot is a physical location where people can obtain Internet access, typically using Wi-Fi technology, via a wireless local-area network (WLAN) using a router connected to an Internet service provider. Public hotspots may be created by ...

s. Currently, there are a number of variants of LTE operation in the unlicensed band, namely LTE-U, License Assisted Access (LAA), MulteFire, sXGP and CBRS.

LTE in Unlicensed spectrum (LTE-U)

The first version of LTE-Unlicensed is called LTE-U and is developed by the LTE-U Forum to work with the existing 3GPP Releases 10/11/12. LTE-U was designed for quick launch in countries, such as the United States and China, that do not mandate implementing the listen-before-talk (LBT) technique. LTE-U would allow cellphone carriers to boost coverage in their cellular networks, by using the unlicensed 5 GHz band already

populated Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

by Wi-Fi devices. LTE-U is intended to let cell networks boost data speeds over short distances, without requiring the user to use a separate Wi-Fi network as they normally would. It differs from

Wi-Fi calling Wi-Fi calling, also called VoWiFi, 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 r ...

; there remains a control channel using LTE, but all data (not just phone calls) flows over the unlicensed 5 GHz band, instead of the carrier's frequencies. In 2014, the LTE-U Forum was created by

Verizon Verizon Communications Inc. ( ), is an American telecommunications company headquartered in New York City. It is the world's second-largest telecommunications company by revenue and its mobile network is the largest wireless carrier in the ...

, in conjunction with

Alcatel-Lucent Alcatel-Lucent S.A. () was a multinational telecommunications equipment company, headquartered in Boulogne-Billancourt, Paris, France. The company focused on Fixed line telephone, fixed, Mobile phone, mobile and telecommunications convergence, ...

Ericsson (), commonly known as Ericsson (), is a Swedish multinational networking and telecommunications company headquartered in Stockholm, Sweden. Ericsson has been a major contributor to the development of the telecommunications industry and is one ...

, and

Samsung Samsung Group (; stylised as SΛMSUNG) is a South Korean Multinational corporation, multinational manufacturing Conglomerate (company), conglomerate headquartered in the Samsung Town office complex in Seoul. The group consists of numerous a ...

as members. The forum collaborates and creates technical specifications for

base station Base station (or base radio station, BS) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a " land station in the land mobile service." A base station is called '' node B'' in 3G, '' eNB'' in L ...

s and consumer devices passing LTE-U on the unlicensed 5 GHz band, as well as coexistence specs to handle traffic contention with existing Wi-Fi devices.

T-Mobile T-Mobile is the brand of telecommunications by Deutsche Telekom Deutsche Telekom AG (, ; often just Telekom, DTAG or DT; stylised as ·T·) is a partially state-owned German telecommunications company headquartered in Bonn and the largest telec ...

and

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 div ...

have indicated early interest in deploying such a system as soon as 2016. While cell providers ordinarily rely on the

radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...

to which they have exclusive licenses, LTE-U would share space with Wi-Fi equipment already inhabiting that band – smartphones, laptops and tablets connecting to home broadband networks, free hotspots provided by businesses, and so on. As of late January 2019, there were three LTE-U deployed/launched networks in three countries; eight further operators are investing in the technology in the form of trials or pilots in seven countries.GSA
LTE in Unlicensed and Shared Spectrum: Trials, Deployments and Devices
(January 2019)

License Assisted Access (LAA)

The second variant of LTE-Unlicensed is Licensed Assisted Access (LAA) and has been standardized by the 3GPP in Rel-13. LAA adheres to the requirements of the LBT protocol, which is mandated in Europe and Japan. It promises to provide a unified global framework that complies with the regulatory requirements in the different regions of the world. * 3GPP Rel-13 defines LAA only for the downlink (DL). * 3GPP Rel-14 defines enhanced-Licensed Assisted Access (eLAA), which includes uplink (UL) operation in the unlicensed channel. * 3GPP Rel-15 The technology continued to be developed in 3GPP's release 15 under the title Further Enhanced LAA (feLAA).

uses the term License Assisted Access (LAA) to describe similar technology. LAA is the

3rd Generation Partnership Project The 3rd Generation Partnership Project (3GPP) is an umbrella term for a number of standards organizations which develop protocols for mobile telecommunications. Its best known work is the development and maintenance of: * GSM and related 2G and ...

's (3GPP) effort to standardize operation of LTE in the Wi-Fi bands. It uses a contention protocol known as listen-before-talk (LBT), mandated in some European countries, to coexist with other Wi-Fi devices on the same band.

MulteFire

MulteFire is another variant of LTE in unlicensed bands and has been proposed as a standalone version of LTE for small cells. This variant will use only the unlicensed spectrum as the primary and only carrier, and it will provide an opportunity for neutral hosts to deploy LTE in the future. The idea of standalone operation of LTE in unlicensed bands was originally proposed by a small minority of vendors in 3GPP but rejected by the network operators who wanted the technology to be reliant on their licensed spectrum holdings. This technology is now developed by th
MuLTEfire Alliance

Controversy

The proposed use of LTE-U by

mobile phone network A cellular network or mobile network is a telecommunications network where the link to and from end nodes is wireless and the network is distributed over land areas called ''cells'', each served by at least one fixed-location transceiver (suc ...

operators is the subject of controversy in the telecommunications industry. In June 2015,

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

sent the

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...

(FCC) of the United States a 25-page protest, making an argument against LTE-U in highly technical detail. Since Google's study did not use actual LTE-U equipment in the tests, some industry experts have called its conclusions into question, with one commenter calling the study "utterly artificial and speculative" and "embarrassing". In August 2015, the

Wi-Fi Alliance The Wi-Fi Alliance is a non-profit organization that owns the Wi-Fi trademark. Manufacturers may use the trademark to brand products certified for Wi-Fi interoperability. It is based in Austin, Texas. History Early IEEE 802.11, 802.11 product ...

and

National Cable & Telecommunications Association NCTA, formerly known as the National Cable & Telecommunications Association (NCTA), is a trade association representing the Internet in the United States, broadband and Cable television in the United States, cable television industries in the U ...

(NCTA) also voiced opposition to LTE-U approval before more testing can be done, citing concerns that it would severely degrade performance of other Wi-Fi devices. Also in August 2015,

responded to the allegations made in Google's whitepaper in a detailed filing with the

FCC The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains ju ...

. Qualcomm stated that it conducted tests that were "specifically designed to replicate (to the fullest extent possible) the test scenarios cited in Google’s FCC filing, in particular", and that they "collectively showed that LTE-U coexists very well with Wi-Fi when LTE-U is operating either above or below Wi-Fi’s Energy Detect ('ED') level." Qualcomm explained that the divergence in results was caused by the fact that "the testing the opposing parties conducted for LTE-U/Wi-Fi coexistence below the ED level utilized extremely pessimistic and impractical technical assumptions", whereas Qualcomm's tests were conducted "using a far more realistic setup", including actual LTE-U equipment (versus signal generators in Google's study). In May 2016, the New York City Mayor's Office sent a letter to the FCC, 3GPP, Wi-Fi Alliance, and IEEE, expressing concern over LTE-U interference with Wi-Fi, given the City's broad investment in the technology. These concerns were discussed at a public event. In June 2016 the Wi-Fi Alliance announced its co-existence test plan would be ready in August. In FCC filings, Qualcomm, Verizon and T-Mobile said they plan to use this plan, some with the aim of full implementation before the end of 2016. However, in August 2016, Qualcomm demurred. “The latest version of the test plan released by the Wi-Fi Alliance lacks technical merit, is fundamentally biased against LTE-U, and rejects virtually all the input that Qualcomm provided for the last year, even on points that were not controversial,” said Dean Brenner, senior vice president of government affairs. Qualcomm asserts that the plan biased in favor of Wi-Fi, and also that the testing regimen is extended to cover not just LTE-U, but also LAA, despite it already being a 3GPP standard. Verizon also opposed the test plan, saying it was "fundamentally unfair and biased". Research from the University of Chicago in 2021 also showed a marked decrease in Wi-FI performance when LAA was in active use.

Deployments

In November 2016 Verizon, separate to the Wi-Fi Alliance coexistence plan, filed a Special Temporary Authority (STA) application with the FCC to test 40 small cells in the 5 GHz band. According to a separate filing, Verizon will conduct the tests in Oklahoma City, Raleigh and Cary, North Carolina, and Irving, Texas. In February 2017, the FCC approved the use of LTE-U on base stations manufactured by Ericsson and Nokia. As of June 26, 2017, T-Mobile declared that they have successfully launched LTE-U in Bellevue, Washington; Brooklyn, New York; Dearborn, Michigan; Las Vegas, Nevada; Richardson, Texas; and Simi Valley, California. In January 2019, the

Global Mobile Suppliers Association The Global mobile Suppliers Association (GSA) is a not-for-profit industry organisation representing suppliers in the mobile communication industry. GSA actively promotes 3GPP technology such as 3G; 4G; 5G. GSA is a market representation partn ...

reported that 32 operators are investing in LAA across 21 countries; this had increased to 37 operators in 21 countries by July 2019.GSA
Unlicensed & Shared Spectrum Report
July 2019 Eight of these have announced LAA network launches in six countries, while 29 operators are trialling or deploying the technology in 18 countries. The GSA also identified 21 chipsets containing modems that support one or more of LTE-U, LAA, LWA or CBRS from vendors including GCT,

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

Mediatek MediaTek Inc. (), sometimes informally abbreviated as MTK, is a Taiwanese fabless semiconductor company that designs and manufactures a range of semiconductor products, providing chips for wireless communications, high-definition television, h ...