LTE (telecommunication)

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In telecommunications, long-term evolution (LTE) is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA standards. It improves on those standards' capacity and speed by using a different radio interface and core network improvements. [1] [2] LTE is the upgrade path for carriers with both GSM/UMTS networks and CDMA2000 networks. Because LTE frequencies and bands differ from country to country, only multi-band phones can use LTE in all countries where it is supported.

Contents

Terminology

The standard is developed by the 3GPP (3rd Generation Partnership Project) and is specified in its Release 8 document series, with minor enhancements described in Release 9. LTE is also called 3.95G and has been marketed as 4G LTE and Advanced 4G;[ citation needed ] but the original version did not meet the technical criteria of a 4G wireless service, as specified in the 3GPP Release 8 and 9 document series for LTE Advanced. The requirements were set forth by the ITU-R organisation in the IMT Advanced specification; but, because of market pressure and the significant advances that WiMAX, Evolved High Speed Packet Access, and LTE bring to the original 3G technologies, ITU-R later decided that LTE and the aforementioned technologies can be called 4G technologies. [3] The LTE Advanced standard formally satisfies the ITU-R requirements for being considered IMT-Advanced. [4] To differentiate LTE Advanced and WiMAX-Advanced from current 4G technologies, ITU has defined the latter as "True 4G". [5] [6]

Overview

LTE tower in Argentina. Antena 4G LTE .jpg
LTE tower in Argentina.
Unofficial logo LTE-Logo.jpg
Unofficial logo
An Android phone showing LTE connection Android LTE signal.png
An Android phone showing LTE connection
LTE modem Samsung 4G LTE modem-4.jpg
LTE modem
4G+ modem Huawei 4G+ Modem.jpg
4G+ modem
HTC ThunderBolt, the second commercially available LTE smartphone HTC Thunderbolt.jpg
HTC ThunderBolt, the second commercially available LTE smartphone

LTE stands for Long-Term Evolution [7] and is a registered trademark owned by ETSI (European Telecommunications Standards Institute) for the wireless data communications technology and a development of the GSM/UMTS standards. However, other nations and companies do play an active role in the LTE project. The goal of LTE was to increase the capacity and speed of wireless data networks using new DSP (digital signal processing) techniques and modulations that were developed around the turn of the millennium. A further goal was the redesign and simplification of the network architecture to an IP-based system with significantly reduced transfer latency compared with the 3G architecture. The LTE wireless interface is incompatible with 2G and 3G networks, so that it must be operated on a separate radio spectrum.

The idea of LTE was first proposed in 1998, with the use of the COFDM radio access technique to replace the CDMA and studying its Terrestrial use in the L band at 1428 MHz (TE) In 2004 by Japan's NTT Docomo, with studies on the standard officially commenced in 2005. [8] In May 2007, the LTE/SAE Trial Initiative (LSTI) alliance was founded as a global collaboration between vendors and operators with the goal of verifying and promoting the new standard in order to ensure the global introduction of the technology as quickly as possible. [9] [10]

The LTE standard was finalized in December 2008, and the first publicly available LTE service was launched by TeliaSonera in Oslo and Stockholm on December 14, 2009, as a data connection with a USB modem. The LTE services were launched by major North American carriers as well, with the Samsung SCH-r900 being the world's first LTE Mobile phone starting on September 21, 2010, [11] [12] and Samsung Galaxy Indulge being the world's first LTE smartphone starting on February 10, 2011, [13] [14] both offered by MetroPCS, and the HTC ThunderBolt offered by Verizon starting on March 17 being the second LTE smartphone to be sold commercially. [15] [16] In Canada, Rogers Wireless was the first to launch LTE network on July 7, 2011, offering the Sierra Wireless AirCard 313U USB mobile broadband modem, known as the "LTE Rocket stick" then followed closely by mobile devices from both HTC and Samsung. [17] Initially, CDMA operators planned to upgrade to rival standards called UMB and WiMAX, but major CDMA operators (such as Verizon, Sprint and MetroPCS in the United States, Bell and Telus in Canada, au by KDDI in Japan, SK Telecom in South Korea and China Telecom/China Unicom in China) have announced instead they intend to migrate to LTE. The next version of LTE is LTE Advanced, which was standardized in March 2011. [18] Services commenced in 2013. [19] Additional evolution known as LTE Advanced Pro have been approved in year 2015. [20]

The LTE specification provides downlink peak rates of 300 Mbit/s, uplink peak rates of 75 Mbit/s and QoS provisions permitting a transfer latency of less than 5  ms in the radio access network. LTE has the ability to manage fast-moving mobiles and supports multi-cast and broadcast streams. LTE supports scalable carrier bandwidths, from 1.4  MHz to 20 MHz and supports both frequency division duplexing (FDD) and time-division duplexing (TDD). The IP-based network architecture, called the Evolved Packet Core (EPC) designed to replace the GPRS Core Network, supports seamless handovers for both voice and data to cell towers with older network technology such as GSM, UMTS and CDMA2000. [21] The simpler architecture results in lower operating costs (for example, each E-UTRA cell will support up to four times the data and voice capacity supported by HSPA [22] ).

History

3GPP standard development timeline

Cellular network standards and generation timeline Cellular network standards and generation timeline.svg
Cellular network standards and generation timeline

Carrier adoption timeline

Most carriers supporting GSM or HSUPA networks can be expected to upgrade their networks to LTE at some stage. A complete list of commercial contracts can be found at: [59]

The following is a list of top 10 countries/territories by 4G LTE coverage as measured by OpenSignal.com in February/March 2019. [70] [71]

RankCountry/TerritoryPenetration
1Flag of South Korea.svg  South Korea 97.5%
2Flag of Japan.svg  Japan 96.3%
3Flag of Norway.svg  Norway 95.5%
4Flag of Hong Kong.svg  Hong Kong 94.1%
5Flag of the United States.svg  United States 93.0%
6Flag of the Netherlands.svg  Netherlands 92.8%
7Flag of the Republic of China.svg  Taiwan 92.8%
8Flag of Hungary.svg  Hungary 91.4%
9Flag of Sweden.svg  Sweden 91.1%
10Flag of India.svg  India 90.9%

For the complete list of all the countries/territories, see list of countries by 4G LTE penetration.

LTE-TDD and LTE-FDD

Long-Term Evolution Time-Division Duplex (LTE-TDD), also referred to as TDD LTE, is a 4G telecommunications technology and standard co-developed by an international coalition of companies, including China Mobile, Datang Telecom, Huawei, ZTE, Nokia Solutions and Networks, Qualcomm, Samsung, and ST-Ericsson. It is one of the two mobile data transmission technologies of the Long-Term Evolution (LTE) technology standard, the other being Long-Term Evolution Frequency-Division Duplex (LTE-FDD). While some companies refer to LTE-TDD as "TD-LTE" for familiarity with TD-SCDMA, there is no reference to that abbreviation anywhere in the 3GPP specifications. [72] [73] [74]

There are two major differences between LTE-TDD and LTE-FDD: how data is uploaded and downloaded, and what frequency spectra the networks are deployed in. While LTE-FDD uses paired frequencies to upload and download data, [75] LTE-TDD uses a single frequency, alternating between uploading and downloading data through time. [76] [77] The ratio between uploads and downloads on a LTE-TDD network can be changed dynamically, depending on whether more data needs to be sent or received. [78] LTE-TDD and LTE-FDD also operate on different frequency bands, [79] with LTE-TDD working better at higher frequencies, and LTE-FDD working better at lower frequencies. [80] Frequencies used for LTE-TDD range from 1850 MHz to 3800 MHz, with several different bands being used. [81] The LTE-TDD spectrum is generally cheaper to access, and has less traffic. [79] Further, the bands for LTE-TDD overlap with those used for WiMAX, which can easily be upgraded to support LTE-TDD. [79]

Despite the differences in how the two types of LTE handle data transmission, LTE-TDD and LTE-FDD share 90 percent of their core technology, making it possible for the same chipsets and networks to use both versions of LTE. [79] [82] A number of companies produce dual-mode chips or mobile devices, including Samsung and Qualcomm, [83] [84] while operators CMHK and Hi3G Access have developed dual-mode networks in Hong Kong and Sweden, respectively. [85]

History of LTE-TDD

The creation of LTE-TDD involved a coalition of international companies that worked to develop and test the technology. [86] China Mobile was an early proponent of LTE-TDD, [79] [87] along with other companies like Datang Telecom [86] and Huawei, which worked to deploy LTE-TDD networks, and later developed technology allowing LTE-TDD equipment to operate in white spaces—frequency spectra between broadcast TV stations. [73] [88] Intel also participated in the development, setting up a LTE-TDD interoperability lab with Huawei in China, [89] as well as ST-Ericsson, [79] Nokia, [79] and Nokia Siemens (now Nokia Solutions and Networks), [73] which developed LTE-TDD base stations that increased capacity by 80 percent and coverage by 40 percent. [90] Qualcomm also participated, developing the world's first multi-mode chip, combining both LTE-TDD and LTE-FDD, along with HSPA and EV-DO. [84] Accelleran, a Belgian company, has also worked to build small cells for LTE-TDD networks. [91]

Trials of LTE-TDD technology began as early as 2010, with Reliance Industries and Ericsson India conducting field tests of LTE-TDD in India, achieving 80 megabit-per second download speeds and 20 megabit-per-second upload speeds. [92] By 2011, China Mobile began trials of the technology in six cities. [73]

Although initially seen as a technology utilized by only a few countries, including China and India, [93] by 2011 international interest in LTE-TDD had expanded, especially in Asia, in part due to LTE-TDD's lower cost of deployment compared to LTE-FDD. [73] By the middle of that year, 26 networks around the world were conducting trials of the technology. [74] The Global LTE-TDD Initiative (GTI) was also started in 2011, with founding partners China Mobile, Bharti Airtel, SoftBank Mobile, Vodafone, Clearwire, Aero2 and E-Plus. [94] In September 2011, Huawei announced it would partner with Polish mobile provider Aero2 to develop a combined LTE-TDD and LTE-FDD network in Poland, [95] and by April 2012, ZTE Corporation had worked to deploy trial or commercial LTE-TDD networks for 33 operators in 19 countries. [85] In late 2012, Qualcomm worked extensively to deploy a commercial LTE-TDD network in India, and partnered with Bharti Airtel and Huawei to develop the first multi-mode LTE-TDD smartphone for India. [84]

In Japan, SoftBank Mobile launched LTE-TDD services in February 2012 under the name Advanced eXtended Global Platform (AXGP), and marketed as SoftBank 4G (ja). The AXGP band was previously used for Willcom's PHS service, and after PHS was discontinued in 2010 the PHS band was re-purposed for AXGP service. [96] [97]

In the U.S., Clearwire planned to implement LTE-TDD, with chip-maker Qualcomm agreeing to support Clearwire's frequencies on its multi-mode LTE chipsets. [98] With Sprint's acquisition of Clearwire in 2013, [75] [99] the carrier began using these frequencies for LTE service on networks built by Samsung, Alcatel-Lucent, and Nokia. [100] [101]

As of March 2013, 156 commercial 4G LTE networks existed, including 142 LTE-FDD networks and 14 LTE-TDD networks. [86] As of November 2013, the South Korean government planned to allow a fourth wireless carrier in 2014, which would provide LTE-TDD services, [77] and in December 2013, LTE-TDD licenses were granted to China's three mobile operators, allowing commercial deployment of 4G LTE services. [102]

In January 2014, Nokia Solutions and Networks indicated that it had completed a series of tests of voice over LTE (VoLTE) calls on China Mobile's TD-LTE network. [103] The next month, Nokia Solutions and Networks and Sprint announced that they had demonstrated throughput speeds of 2.6 gigabits per second using a LTE-TDD network, surpassing the previous record of 1.6 gigabits per second. [104]

Features

Much of the LTE standard addresses the upgrading of 3G UMTS to what will eventually be 4G mobile communications technology. A large amount of the work is aimed at simplifying the architecture of the system, as it transitions from the existing UMTS circuit + packet switching combined network, to an all-IP flat architecture system. E-UTRA is the air interface of LTE. Its main features are:

Voice calls

cs domLTE CSFB to GSM/UMTS network interconnects LTE-CSFB-E-UTRAN-UTRAN-GERAN-Interfaces.svg
cs domLTE CSFB to GSM/UMTS network interconnects

The LTE standard supports only packet switching with its all-IP network. Voice calls in GSM, UMTS and CDMA2000 are circuit switched, so with the adoption of LTE, carriers will have to re-engineer their voice call network. [106] Four different approaches sprang up:

Voice over LTE (VoLTE)
Circuit-switched fallback (CSFB)
In this approach, LTE just provides data services, and when a voice call is to be initiated or received, it will fall back to the circuit-switched domain. When using this solution, operators just need to upgrade the MSC instead of deploying the IMS, and therefore, can provide services quickly. However, the disadvantage is longer call setup delay.
Simultaneous voice and LTE (SVLTE)
In this approach, the handset works simultaneously in the LTE and circuit switched modes, with the LTE mode providing data services and the circuit switched mode providing the voice service. This is a solution solely based on the handset, which does not have special requirements on the network and does not require the deployment of IMS either. The disadvantage of this solution is that the phone can become expensive with high power consumption.
Single Radio Voice Call Continuity (SRVCC)

One additional approach which is not initiated by operators is the usage of over-the-top content (OTT) services, using applications like Skype and Google Talk to provide LTE voice service. [107]

Most major backers of LTE preferred and promoted VoLTE from the beginning. The lack of software support in initial LTE devices, as well as core network devices, however led to a number of carriers promoting VoLGA (Voice over LTE Generic Access) as an interim solution. [108] The idea was to use the same principles as GAN (Generic Access Network, also known as UMA or Unlicensed Mobile Access), which defines the protocols through which a mobile handset can perform voice calls over a customer's private Internet connection, usually over wireless LAN. VoLGA however never gained much support, because VoLTE (IMS) promises much more flexible services, albeit at the cost of having to upgrade the entire voice call infrastructure. VoLTE may require Single Radio Voice Call Continuity (SRVCC) in order to be able to smoothly perform a handover to a 2G or 3G network in case of poor LTE signal quality. [109]

While the industry has standardized on VoLTE, early LTE deployments required carriers to introduce circuit-switched fallback as a stopgap measure. When placing or receiving a voice call on a non-VoLTE-enabled network or device, LTE handsets will fall back to old 2G or 3G networks for the duration of the call.

Enhanced voice quality

To ensure compatibility, 3GPP demands at least AMR-NB codec (narrow band), but the recommended speech codec for VoLTE is Adaptive Multi-Rate Wideband, also known as HD Voice. This codec is mandated in 3GPP networks that support 16 kHz sampling. [110]

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. [111] 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. [112]

Frequency bands

The LTE standard covers a range of many different bands, each of which is designated by both a frequency and a band number:

As a result, phones from one country may not work in other countries. Users will need a multi-band capable phone for roaming internationally.

Patents

According to the European Telecommunications Standards Institute's (ETSI) intellectual property rights (IPR) database, about 50 companies have declared, as of March 2012, holding essential patents covering the LTE standard. [119] The ETSI has made no investigation on the correctness of the declarations however, [119] so that "any analysis of essential LTE patents should take into account more than ETSI declarations." [120] Independent studies have found that about 3.3 to 5 percent of all revenues from handset manufacturers are spent on standard-essential patents. This is less than the combined published rates, due to reduced-rate licensing agreements, such as cross-licensing. [121] [122] [123]

See also

Related Research Articles

The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP, UMTS is a component of the International Telecommunication Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. UMTS uses wideband code-division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.

<span class="mw-page-title-main">3G</span> Third generation of wireless mobile telecommunications technology

3G is the third generation of wireless mobile telecommunications technology. It is the upgrade to 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 by 5G. This network is based on a set of standards used for mobile devices and mobile telecommunications services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications set by the International Telecommunication Union. 3G is used in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV.

<span class="mw-page-title-main">WiMAX</span> Wireless broadband standard

Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options.

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.

Multimedia Broadcast Multicast Services (MBMS) is a point-to-multipoint interface specification for existing 3GPP cellular networks, which is designed to provide efficient delivery of broadcast and multicast services, both within a cell as well as within the core network. For broadcast transmission across multiple cells, it defines transmission via single-frequency network configurations. The specification is referred to as Evolved Multimedia Broadcast Multicast Services (eMBMS) when transmissions are delivered through an LTE network. eMBMS is also known as LTE Broadcast.

<span class="mw-page-title-main">E-UTRA</span> 3GPP interface

E-UTRA is the air interface of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) upgrade path for mobile networks. It is an acronym for Evolved UMTS Terrestrial Radio Access, also known as the Evolved Universal Terrestrial Radio Access in early drafts of the 3GPP LTE specification. E-UTRAN is the combination of E-UTRA, user equipment (UE), and a Node B.

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).

<span class="mw-page-title-main">Mobile broadband</span> Marketing term

Mobile broadband is the marketing term for wireless Internet access via mobile networks. Access to the network can be made through a portable modem, wireless modem, or a tablet/smartphone or other mobile device. The first wireless Internet access became available in 1991 as part of the second generation (2G) of mobile phone technology. Higher speeds became available in 2001 and 2006 as part of the third (3G) and fourth (4G) generations. In 2011, 90% of the world's population lived in areas with 2G coverage, while 45% lived in areas with 2G and 3G coverage. Mobile broadband uses the spectrum of 225 MHz to 3700 MHz.

<span class="mw-page-title-main">LTE Advanced</span> Mobile communication standard

LTE Advanced is a mobile communication standard and a major enhancement of the Long Term Evolution (LTE) standard. It was formally submitted as a candidate 4G to ITU-T in late 2009 as meeting the requirements of the IMT-Advanced standard, and was standardized by the 3rd Generation Partnership Project (3GPP) in March 2011 as 3GPP Release 10.

International Mobile Telecommunications-Advanced are the requirements issued by the ITU Radiocommunication Sector (ITU-R) of the International Telecommunication Union (ITU) in 2008 for what is marketed as 4G mobile phone and Internet access service.

Sony Semiconductor Israel Ltd., formerly known as Altair Semiconductor, is an Israeli developer of high performance single-mode Long Term Evolution (LTE) chipsets. The company's product portfolio includes baseband processors, RF transceivers and a range of reference hardware products. Founded in 2005, Altair employs 190 employees in its Hod Hasharon, Israel headquarters and R&D center, and has regional offices in the United States, Japan, China, India, Finland, and France. Altair Semiconductor was the first chipset vendor to receive certification from Verizon Wireless to run on its 4G LTE network. Altair has also powered several devices launched on Verizon's network including the Ellipsis 7 tablet and HP Chromebook 11.6"LTE. In January 2016, it was announced that Sony was acquiring Altair for $212 Million. Altair was renamed Sony Semiconductor Israel on March 29, 2020.

<span class="mw-page-title-main">Voice over LTE</span> High-speed wireless communication functionality

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.

The Asia-Pacific Telecommunity (APT) band plan is a type of segmentation of the 612–806 MHz band formalized by the APT in 2022–2023 and 2008-2010 respectively and specially configured for the deployment of mobile broadband technologies. This segmentation exists in two variants, FDD and TDD, that have been standardized by the 3rd Generation Partnership Project (3GPP) and recommended by the International Telecommunication Union (ITU) as segmentations A5 and A6, respectively. The APT band plan has been designed to enable the most efficient use of available spectrum. Therefore, this plan divides the band into contiguous blocks of frequencies that are as large as possible taking account of the need to avoid interference with services in other frequency bands. As the result, the TDD option includes 100 MHz of continuous spectrum, while the FDD option comprises two large blocks, one of 45 MHz for uplink transmission in the lower part of the band and the other also of 45 MHz for downlink transmission in the upper part. As defined in the standard, both FDD and TDD schemes for the 700 MHz band include guard bands of 5 MHz and 3 MHz at their lower and upper edges, respectively. The FDD version also includes a centre gap of 10 MHz. The guard bands serve the purpose of mitigating interference with adjacent bands while the FDD centre gap is required to avoid interference between uplink and downlink transmissions. The two arrangements are shown graphically in figures 1 and 2.

<span class="mw-page-title-main">HiSilicon</span> Chinese fabless semiconductor manufacturing company, fully owned by Huawei

HiSilicon is a Chinese fabless semiconductor company based in Shenzhen, Guangdong province and wholly owned by Huawei. HiSilicon purchases licenses for CPU designs from ARM Holdings, including the ARM Cortex-A9 MPCore, ARM Cortex-M3, ARM Cortex-A7 MPCore, ARM Cortex-A15 MPCore, ARM Cortex-A53, ARM Cortex-A57 and also for their Mali graphics cores. HiSilicon has also purchased licenses from Vivante Corporation for their GC4000 graphics core.

<span class="mw-page-title-main">Airtel India</span> Indian telecommunications company

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.

The Intel XMM modems are a series of 4G LTE, LTE Advanced, LTE Advanced Pro and 5G modems found in many phones, tablets, laptops and wearables developed by Intel Mobile Communications. Intel Mobile Communications was formed after Intel acquired the Wireless Solutions (WLS) division of Infineon early in 2011 for US$1.4 billion.

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Further reading