3GPP Long Term Evolution

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LTE (Long Term Evolution) is the project name of a new high performance air interface for cellular mobile communication systems. It is the last step toward the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile telephone networks. Where the current generation of mobile telecommunication networks are collectively known as 3G (for "third generation"), LTE is marketed as 4G. However, it does not fully comply with the IMT Advanced 4G requirements. Most major mobile carriers in the United States and several worldwide carriers have announced plans to convert their networks to LTE beginning in 2009. The world's first publicly available LTE-service was opened by TeliaSonera in the two Scandinavian capitals Stockholm and Oslo on the 14th of December 2009. LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) which will be introduced in 3rd Generation Partnership Project (3GPP) Release 8. Much of 3GPP Release 8 will focus on adopting 4G mobile communications technology, including an all-IP flat networking architecture. On August 18, 2009, the European Commission announced it will invest a total of €18 million into researching the deployment of LTE and 4G candidate system LTE Advanced.

While it is commonly seen as a mobile telephone or common carrier development, public safety agencies in the US<> have also endorsed LTE as the preferred technology for the new 700 MHz public-safety radio band. Agencies in some areas have filed for waivers hoping to use the 700 MHz spectrum with other technologies in advance of the adoption of a nationwide standard.

Overview

The LTE specification provides downlink peak rates of at least 100 Mbps, an uplink of at least 50 Mbps and RAN round-trip times of less than 10 ms. LTE supports scalable carrier bandwidths, from 20 MHz down to 1.4 MHz and supports both frequency division duplexing (FDD) and time division duplexing (TDD).

Part of the LTE standard is the System Architecture Evolution, a flat IP-based network architecture designed to replace the GPRS Core Network and ensure support for, and mobility between, some legacy or non-3GPP systems, for example GPRS and WiMax respectively.

The main advantages with LTE are high throughput, low latency, plug and play, FDD and TDD in the same platform, improved end-user experience and simple architecture resulting in low operating costs. LTE will also support seamless passing to cell towers with older network technology such as GSM, cdmaOne, W-CDMA (UMTS), and CDMA2000.

Current state

While 3GPP Release 8 is an unratified, formative standard, much of the Release addresses upgrading 3G UMTS to 4G mobile communications technology, which is essentially a mobile broadband system with enhanced multimedia services built on top.

The standard includes:

  • For every 20 MHz of spectrum, peak download rates of 326.4 Mbit/s for 4x4 antennas, and 172.8 Mbit/s for 2x2 antennas.
  • Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum using a single antenna.
  • Five different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminals will be able to process 20 MHz bandwidth.
  • At least 200 active users in every 5 MHz cell. (Specifically, 200 active data clients)
  • Sub-5ms latency for small IP packets
  • Increased spectrum flexibility, with spectrum slices as small as 1.5 MHz (and as large as 20 MHz) supported (W-CDMA requires 5 MHz slices, leading to some problems with roll-outs of the technology in countries where 5 MHz is a commonly allocated amount of spectrum, and is frequently already in use with legacy standards such as 2G GSM and cdmaOne.) Limiting sizes to 5 MHz also limited the amount of bandwidth per handset
  • Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance. This statement should be treated with caution. Comment: Without considering the radio propagation environment and the frequency used (looks like it will be 2.6 GHz in EU), it is meaningless to talk about cell size. For a given power budget, the higher the frequency, the more challenging range becomes in a mobile cellular system.
  • Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as cdmaOne or CDMA2000)
  • Support for MBSFN (Multicast Broadcast Single Frequency Network). This feature can deliver services such as Mobile TV using the LTE infrastructure, and is a competitor for DVB-H-based TV broadcast.
  • PU2RC as a practical solution for MU-MIMO. The detailed procedure for the general MU-MIMO operation is handed to the next release, e.g., LTE-Advanced, where further discussions will be held.

A large amount of the work is aimed at simplifying the architecture of the system, as it transits from the existing UMTS circuit + packet switching combined network, to an all-IP flat architecture system.

Timetable

  • In early 2008, LTE test equipment began shipping from several vendors, and at the Mobile World Congress 2008 in Barcelona Ericsson demonstrated the world’s first end-to-end mobile call enabled by LTE on a small handheld device. Motorola demonstrated a LTE RAN standard compliant eNodeB and LTE chipset at the same event.
  • In December 2008, the Rel-8 specification was frozen for new features meaning only essential clarifications and corrections were permitted.
  • In January 2009, the ASN.1 code was frozen. The Rel-8 standard was complete enough that hardware designers had been designing chipsets, test equipment and base stations for some time. LTE standards development continues with 3GPP Release 9 which was frozen in December 2009. Updates to all 3GPP specifications are made every quarter and can be found at the 3GPP web site.
  • On December 14, 2009, the world's first publicly available LTE-service was opened by TeliaSonera in the two Scandinavian capitals Stockholm and Oslo.

An "All IP Network" (AIPN)

Next generation networks are based upon Internet Protocol (IP). See, for example, the Next Generation Mobile Networks Alliance (NGMN) http://www.ngmn.org

In 2004, 3GPP proposed IP as the future for next generation networks and began feasibility studies into All IP Networks (AIPN). Proposals developed included recommendations for 3GPP Release 7(2005), which are the foundation of higher level protocols such as LTE. These recommendations are part of the 3GPP System Architecture Evolution (SAE). Some aspects of All-IP networks, however, were already defined as early as release 4.

E-UTRAN Air Interface

Release 8's air interface, E-UTRA (Evolved UTRAN, the E- prefix being common to the evolved equivalents of older UMTS components) would be used by UMTS operators deploying their own wireless networks. It's important to note that Release 8 is intended not just for use over E-UTRA, but is also intended for use over any other IP network, including WiMAX and WiFi, and even wired networks.

The proposed E-UTRAN system uses OFDMA for the downlink (tower to handset) and Single Carrier FDMA (SC-FDMA) for the uplink and employs MIMO with up to four antennas per station. The channel coding scheme for transport blocks is turbo coding and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver.

The use of Orthogonal frequency-division multiplexing (OFDM), a system where the available spectrum is divided into many thin carriers, each on a different frequency, each carrying a part of the signal, enables E-UTRAN to be much more flexible in its use of spectrum than the older CDMA based systems that dominated 3G. CDMA networks require large blocks of spectrum to be allocated to each carrier, to maintain high chip rates, and thus maximize efficiency. Building radios capable of coping with different chip rates (and spectrum bandwidths) is more complex than creating radios that only send and receive one size of carrier, so generally CDMA based systems standardize both. Standardizing on a fixed spectrum slice has consequences for the operators deploying the system: too narrow a spectrum slice would mean the efficiency and maximum bandwidth per handset suffers; too wide a spectrum slice, and there are deployment issues for operators short on spectrum. This became a major issue with the US roll-out of UMTS over W-CDMA, where W-CDMA's 5 MHz requirement often left no room in some markets for operators to co-deploy it with existing GSM standards.

LTE supports both FDD and TDD mode. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD is alternating using the same spectral resources used for UL and DL, separated by guard time. Each mode has its own frame structure within LTE and these are aligned with each other meaning that similar hardware can be used in the base stations and terminals to allow for economy of scale. The TDD mode in LTE is aligned with TD-SCDMA as well allowing for coexistence. Ericsson demonstrated at the MWC 2008 in Barcelona for the first time in the world both LTE FDD and TDD mode on the same base station platform.

Downlink

LTE uses OFDM for the downlink – that is, from the base station to the terminal. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. It is a well-established technology, for example in standards such as IEEE 802.11a/g, 802.16, HIPERLAN-2, DVB and DAB.

In the time domain there is a radio frame that is 10 ms long and consists of 10 sub frames of 1 ms each. Every sub frame consists of 2 slots where each slot is 0.5 ms. The subcarrier spacing in the frequency domain is 15 kHz. Twelve of these subcarriers together (per slot) is called a resource block so one resource block is 180 kHz. 6 Resource blocks fit in a carrier of 1.4 MHz and 100 resource blocks fit in a carrier of 20 MHz.

In the downlink there are three main physical channels. The Physical Downlink Shared Channel (PDSCH) is used for all the data transmission, the Physical Multicast Channel (PMCH) is used for broadcast transmission using a Single Frequency Network, and the Physical Broadcast Channel (PBCH) is used to send most important system information within the cell. Supported modulation formats on the PDSCH are QPSK, 16QAM and 64QAM.

For MIMO operation, a distinction is made between single user MIMO, for enhancing one user's data throughput, and multi user MIMO for enhancing the cell throughput.

Uplink

In the uplink, for the Physical Uplink Shared channel (PUSCH) only, LTE uses a pre-coded version of OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA). This is to compensate for a drawback with normal OFDM, which has a very high peak-to-average power ratio (PAPR). High PAPR requires expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. SC-FDMA solves this problem by grouping together the resource blocks in a way that reduces the need for linearity, and so power consumption, in the power amplifier. A low PAPR also improves coverage and the cell-edge performance.

In the uplink there are two physical channels. While the Physical Random Access Channel (PRACH) is only used for initial access and when the UE is not uplink synchronized, all the data is sent on the Physical Uplink Shared Channel (PUSCH). Supported modulation formats on the uplink data channel are QPSK, 16QAM and 64QAM.

If virtual MIMO / Spatial division multiple access (SDMA) is introduced the data rate in the uplink direction can be increased depending on the number of antennas at the base station. With this technology more than one mobile can reuse the same resources.

Frequency bands and channel bandwidths

From Tables 5.5-1 "E-UTRA Operating Bands" and 5.6.1-1 "E-UTRA Channel Bandwidth" of 3GPP TS 36.101 (Release 8.4.0), the following table lists the specified frequency bands of LTE and the channel bandwidths each listed band supports:


E-UTRA
Operating Band 		Uplink (UL)
Operating Band
BS Receive
UE Transmit 		Downlink (DL)
Operating Band
BS Transmit
UE Receive 		Duplex Mode Channel
Bandwidths (MHz) 		Alias Region(s)
001 I (1) 017 1920 MHz to 1980 MHz 017 2110 MHz to 2170 MHz FDD 5, 10, 15, 20 UMTS IMT, "2100" Japan, Europe, Asia
002 II (2) 012 1850 MHz to 1910 MHz 012 1930 MHz to 1990 MHz FDD 1.4, 3, 5, 10, 15, 20 PCS, "1900" Canada, United States, Latin America
003 III (3) 010 1710 MHz to 1785 MHz 010 1805 MHz to 1880 MHz FDD 1.4, 3, 5, 10, 15, 20 DCS 1800, "1800" Finland, Hong Kong
004 IV (4) 009 1710 MHz to 1755 MHz 013 2110 MHz to 2155 MHz FDD 1.4, 3, 5, 10, 15, 20 AWS, "1.7/2.1 GHz" Canada, US, Latin America
005 V (5) 005 824 MHz to 849 MHz 005 869 MHz to 894 MHz FDD 1.4, 3, 5, 10 Cellular 850, UMTS850 Canada, US, Australia
006 VI (6) 006 830 MHz to 840 MHz 006 875 MHz to 885 MHz FDD 5, 10 UMTS800 Japan
007 VII (7) 021 2500 MHz to 2570 MHz 021 2620 MHz to 2690 MHz FDD 5, 10, 15, 20 IMT-E, "2.5 GHz" EU
008 VIII (8) 007880 MHz to 915 MHz 007925 MHz to 960 MHz FDD 1.4, 3, 5, 10 GSM, UMTS900, EGSM900 EU, Latin America
009 IX (9) 012 1749.9 MHz to 1784.9 MHz 011 1844.9 MHz to 1879.9 MHz FDD 5, 10, 15, 20 UMTS1700 Canada, US, Japan
010 X (10) 011 1710 MHz to 1770 MHz 013 2110 MHz to 2170 MHz FDD 5, 10, 15, 20 UMTS,IMT 2000 Brazil, Uruguay, Ecuador, Peru
011 XI (11) 008 1427.9 MHz to 1452.9 MHz 008 1475.9 MHz to 1500.9 MHz FDD 5, 10, 15, 20 PDC Japan (Softbank, KDDI, DoCoMo)
012 XII (12) 001 698 MHz to 716 MHz 001 728 MHz to 746 MHz FDD 1.4, 3, 5, 10
013 XIII (13) 003 777 MHz to 787 MHz 003 746 MHz to 756 MHz FDD 1.4, 3, 5, 10 Verizon's 700 MHz Block C
014 XIV (14) 004 788 MHz to 798 MHz 004 758 MHz to 768 MHz FDD 1.4, 3, 5, 10 700 MHz Block D
017 XVII (17) 002 704 MHz to 716 MHz 002 734 MHz to 746 MHz FDD 1.4, 3, 5, 10 AT&T's 700 MHz Block B
033 XXXIII (33) 016 1900 MHz to 1920 MHz TDD 5, 10, 15, 20
034 XXXIV (34) 020 2010 MHz to 2025 MHz TDD 5, 10, 15
035 XXXV (35) 014 1850 MHz to 1910 MHz TDD 1.4, 3, 5, 10, 15, 20
036 XXXVI (36) 019 1930 MHz to 1990 MHz TDD 1.4, 3, 5, 10, 15, 20
037 XXXVII (37) 017 1910 MHz to 1930 MHz TDD 5, 10, 15, 20
038 XXXVIII (38) 023 2570 MHz to 2620 MHz TDD 5, 10 EU
039 XXXIX (39) 015 1880 MHz to 1920 MHz TDD 5, 10, 15, 20
040 XL (40) 021 2300 MHz to 2400 MHz TDD 10, 15, 20 IMT-2000 China

Technology Demos

  • In September 2006, Siemens Networks (today Nokia Siemens Networks) showed in collaboration with Nomor Research the first live emulation of a LTE network to the media and investors. As live applications two users streaming an HD-TV video in the downlink and playing an interactive game in the uplink have been demonstrated.
  • The first presentation of an LTE demonstrator with HDTV streaming (>30 Mbit/s), video supervision and Mobile IP-based handover between the LTE radio demonstrator and the commercially available HSDPA radio system was shown during the ITU trade fair in Hong Kong in December 2006 by Siemens Communication Department.
  • In February 2007, Ericsson demonstrated for the first time in the world LTE with bit rates up to 144 Mbit/s
  • In September 2007, NTT docomo demonstrated LTE data rates of 200 Mbit/s with power consumption below 100 mW during the test.
  • In November 2007, Infineon presented the world’s first RF transceiver named SMARTi LTE supporting LTE functionality in a single-chip RF silicon processed in CMOS
  • At the February 2008 Mobile World Congress:
    • Huawei demonstrated Long Term Evolution ("LTE") applications by means of multiplex HDTV services and mutual gaming that has transmission speeds of 100 Mbps.
    • Motorola demonstrated how LTE can accelerate the delivery of personal media experience with HD video demo streaming, HD video blogging, Online gaming and VoIP over LTE running a RAN standard compliant LTE network & LTE chipset.
    • Ericsson (now a part of ST-Ericsson) demonstrated the world’s first end-to-end LTE call on handheld Ericsson demonstrated LTE FDD and TDD mode on the same base station platform.
    • Freescale Semiconductor demonstrated streaming HD video with peak data rates of 96 Mbit/s downlink and 86 Mbit/s uplink.
    • NXP Semiconductors (now a part of ST-Ericsson) demonstrated a multi-mode LTE modem as the basis for a software-defined radio system for use in cellphones.
    • picoChip and Mimoon demonstrated a base station reference design. This runs on a common hardware platform (multi-mode / software defined radio) with their WiMAX architecture.
  • In April 2008, Motorola demonstrated the first EV-DO to LTE hand-off - handing over a streaming video from LTE to a commercial EV-DO network and back to LTE.
  • In April 2008, LG Electronics and Nortel demonstrated LTE data rates of 50 Mbit/s while travelling at 110 km/h.
  • In April 2008 Ericsson unveiled its M700 mobile platform, the world’s first commercially available LTE-capable platform, with peak data rates of up to 100 Mbit/s in the downlink and up to 50 Mbit/s in the uplink. The first products based on M700 will be data devices such as laptop modems, Expresscards and USB modems for notebooks, as well other small-form modems suitable for consumer electronic devices. Commercial release is set for 2009, with products based on the platform expected in 2010.
  • In November 2008 Motorola demonstrated industry first over-the-air LTE session in 700 MHz spectrum
  • Researchers at Nokia Siemens Networks and Heinrich Hertz Institut have demonstrated LTE with 100 Mbit/s Uplink transfer speeds.
  • At the February 2009 Mobile World Congress:
    • Huawei demonstrated the world' s first unified frequency-division duplex and time-division duplex (FDD/TDD) long-term evolution (LTE) solution.
    • Aricent gave a demonstration of LTE eNodeB layer2 stacks.
    • Setcom Streaming a Video
    • Infineon demonstrated a single-chip 65 nm CMOS RF transceiver providing 2G/3G/LTE functionality
    • Launch of ng Connect program, a multi-industry consortium founded by Alcatel-Lucent to identify and develop wireless broadband applications.
    • Motorola provided LTE drive tour on the streets of Barcelona to demonstrate LTE system performance in a real-life metropolitan RF environment
  • In May 2009 Setcom Streaming HD Video at GSMA MWC and LTE World Summit
  • In July 2009 Nujira demonstrated efficiencies of more than 60% for an 880 MHz LTE Power Amplifier
  • In August 2009, Nortel and LG Electronics demonstrated the first successful handoff between CDMA and LTE networks in a standards-compliant manner
  • In August 2009, Alcatel-Lucent receives FCC certification for LTE base stations for the 700 MHz spectrum band.
  • In September 2009, Nokia Siemens Networks demonstrated world's first LTE call on standards-compliant commercial software.
  • In October 2009, Ericsson and Samsung demonstrated interoperability between the first ever commercial LTE device and the live network in Stockholm, Sweden.
  • In October 2009, Alcatel-Lucent's Bell Labs, Deutsche Telekom Laboratories, the Fraunhofer Heinrich-Hertz Institut and antenna supplier Kathrein conducted live field tests of a technology called Coordinated Multipoint Transmission (CoMP) aimed at increasing the data transmission speeds of Long Term Evolution (LTE) and 3G networks.
  • In November 2009, Alcatel-Lucent completed first live LTE call using 800 MHz spectrum band set aside as part of the European Digital Dividend (EDD).
  • In November 2009, Nokia Siemens Networks and LG completed first end-to-end interoperability testing of LTE.
  • On December 14, 2009, the first commercial LTE deployment was opened in Stockholm and Oslo by the Swedish-Finnish network operator TeliaSonera and its Norweigan brandname NetCom (Norway). The offered modem device was manufactured by Samsung (dongle GT-B3710), and the network infrastructure by Huawei (in Oslo) and Ericsson (in Stockholm). TeliaSonera incorrectly branded the service "4G". An introductory test showed a TCP goodput of 42.8 Mbit/s downstreams and 5.3 Mbit/s upstreams in the Stockholm network.

Carrier adoption

Most carriers supporting GSM or HSUPA networks can be expected to upgrade their networks to LTE at some stage:

  • AT&T Mobility has stated that they intend on upgrading to LTE as their 4G technology in 2011, but will introduce HSUPA and HSPA+ as bridge standards.
  • TeliaSonera has started network built up in Stockholm and Oslo, and will follow up in Copenhagen when a license in Denmark has been bought/granted. The networks are still only for testing. There are no indications of a public live date.
  • In January 2009 TeliaSonera signed a contract for an LTE network with Huawei covering Oslo, Norway. Under the agreement, Huawei will provide an end-to-end LTE solution including LTE base stations, core network and OSS (Operating Support System).
  • In January 2009 Ericsson and TeliaSonera announced the signing of a commercial LTE network. The roll-out of the 4G mobile broadband network will offer the highest data rates ever realized, with the best interactivity and quality. This network will cover Sweden’s capital Stockholm and the contract is Ericsson’s first for commercial deployment of LTE.
  • T-Mobile, Vodafone, France Télécom and Telecom Italia Mobile have also announced or talked publicly about their commitment to LTE.
  • In August 2009 Telefónica selected six countries to field-test LTE in the succeeding months: Spain, the United Kingdom, Germany and the Czech Republic in Europe, and Brazil and Argentina in Latin America.
  • On November 24th, 2009 Telecom Italia announced the first outdoor pre-commercial experimentation in the world, deployed in Torino and totally integrated into the 2G/3G network currently in service.

Despite initial development of the rival UMB standard, which was designed as an upgrade path for CDMA networks, most operators of networks based upon the latter system have also announced their intent to migrate to LTE, resulting in discontinuation of UMB development.

  • Verizon Wireless completed its first test LTE data calls in August 2009 and plans to deploy LTE beginning in 2010 with system-wide deployment completed in 2013.
  • Bell Mobility has stated their intention to use LTE as a future upgrade to their HSDPA network.
  • Telus Mobility has announced that it will adopt LTE as its 4G wireless standard.
  • MetroPCS recently announced that it would be using LTE for its upcoming 4G network.
  • The newly formed China Telecom/China Unicom and Japan's KDDI have announced they have chosen LTE as their 4G network technology.
  • Cox Communications has its first tower for wireless LTE network build-out. Wireless services should launch late 2009.
  • AlMadar Aljadeed, the biggest Libyan Mobile Phone operator, has announced adopting the LTE technology passing straight from 2G Technology to 4G.
  • The Dutch telecom provider KPN announced that it will use LTE for its 4G network.
  • The Irish telco Digiweb is currently operating a 4G service in the Dublin area.

See also

Further reading

External links

3GPP Projects and Presentations

Specifications

Industry reaction

Whitepapers and other information

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