3GPP Long Term Evolution

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LTE (Long Term Evolution) is the next major step in mobile radio communications, and will be introduced in 3rd Generation Partnership Project (3GPP) Release 8.

The aim of this 3GPP project is to improve the Universal Mobile Telecommunications System (UMTS) mobile phone standard and provide an enhanced user experience and simplified technology for next generation mobile broadband. Researchers and development engineers worldwide – representing more than 60 operators, vendors and research institutes – are participating in the joint LTE radio access standardization effort.

While 3GPP Release 8 has yet to be ratified as a standard, much of the standard will be oriented around upgrading UMTS to 4G mobile communications technology, and an all-IP flat architecture system.


[edit] Overview

LTE meets the requirements of next generation networks including downlink peak rates of at least 100Mbit/s, 50 Mbit/s in the uplink and RAN (Radio Access Network) round-trip times of less than 10ms. LTE supports flexible carrier bandwidths, from 1.4MHz up to 20MHz as well as both FDD (Frequency Division Duplex) and TDD (Time Division Duplex).

The goals for LTE include improving spectral efficiency, lowering costs, improving services, making use of new spectrum and refarmed spectrum opportunities, and better integration with other open standards. The architecture that will result from this work is called EPS (Evolved Packet System) and comprises E-UTRAN (Evolved UTRAN) on the access side and EPC (Evolved Packet Core) on the core side. EPC is also known as SAE (System Architecture Evolution) and E-UTRAN is also known as LTE.

The main advantages with LTE are high throughput, low latency, plug and play from day one, FDD and TDD in the same platform, superior end-user experience and simple architecture resulting in low Operating Expenditures (OPEX). LTE will also support seamless connection to existing networks, such as GSM, CDMA and WCDMA.

[edit] Current State

While 3GPP Release 8 has yet to be ratified as a standard, much of the standard will be oriented around upgrading UMTS to 4G mobile communications technology, which is essentially a mobile broadband system with enhanced multimedia services built on top.

The standard includes:

  • Peak download rates of 326.4 Mbit/s for 4x4 antennas, 172.8 Mbit/s for 2x2 antennas for every 20 MHz of spectrum. [1]
  • Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum.[1]
  • 5 different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminal will be able to process 20 MHz bandwidth.
  • At least 200 active users in every 5 MHz cell. (i.e., 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
  • 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)
  • Supports 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 has been adopted to use in 3GPP LTE standard. 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.

[edit] Timetable

The LTE standard reached the functional freeze milestone in December 2008. Official ratification is expected in March 2009[dated info]. The standard has been complete enough that hardware designers have been designing chipsets, test equipment and base stations for some time. LTE test equipment has been shipping from several vendors since early 2008 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.[2] Motorola demonstrated a LTE RAN standard compliant eNodeB and LTE chipset at the same event.

[edit] An "All IP Network" (AIPN)

A characteristic of next generation networks are that they are based upon core internet protocol TCP/IP. This provides users with richer communications experience including enhanced voice, video, and messaging services and advanced multimedia solutions.

In 2004, 3GPP proposed Transmission Control Protocol/Internet Protocol (TCP/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)[3], 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[4].

The 3GPP is defining IP-based, flat network architecture as part of the System Architecture Evolution (SAE) effort. LTE–SAE architecture and concepts have been designed for efficient support of mass-market usage of any IP-based service. The architecture is based on an evolution of the existing GSM/WCDMA core network, with simplified operations and smooth, cost-efficient deployment.

[edit] E-UTRA Air Interface

Release 8's air interface, E-UTRA (Evolved UTRA, 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 for use over any IP network, including WiMAX and WiFi, and even wired networks.[5]

The proposed E-UTRA 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.[6]

The use of 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-UTRA 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. 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.

[edit] 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/b/g, 802.16, HIPERLAN-2, DVB and DAB.

In the time domain you have 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.

Supported modulation formats on the downlink data channels 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.

[edit] Uplink

In the uplink, 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 such 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.

Supported modulation formats on the uplink data channels 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.[7]

[edit] 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.[8]
  • 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[9]
  • In September 2007, NTT docomo demonstrated LTE data rates of 200 Mbit/s with power consumption below 100mW during the test.[10]
  • At the February 2008 Mobile World Congress:
    • 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.[11]
    • Ericsson demonstrated the world’s first end-to-end LTE call on handheld [12] 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 . [13]
    • NXP Semiconductors demonstrated a multi-mode LTE modem as the basis for a software-defined radio system for use in cellphones. [14]
    • 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. [15]
  • 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.[16]
  • 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.
  • Researchers at Nokia Siemens Networks and Heinrich Hertz Institut have demonstrated LTE with 100 Mbit/s Uplink transfer speeds.[7]

[edit] Carrier adoption

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

  • Rogers Wireless has stated that they intend on initially launching their LTE network in Vancouver by February 2010, just in time for the Winter Olympics. [18]
  • AT&T Mobility has stated that they intend on upgrading to LTE as their 4G technology, but will introduce HSUPA and HSPA+ as bridge standards. [19]
  • Telia Sonera 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 indication of a public live date.
  • T-Mobile, Vodafone, France Télécom and Telecom Italia Mobile have also announced or talked publicly about their commitment to LTE.

Despite initial development of a the rival UMB standard 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 is presently testing its LTE network[20] and Selects Ericsson and Alcatel-Lucent as Primary Network Vendors for LTE Network.
  • Bell Mobility plans to start LTE deployment in 2009-2010[21]
  • Telus Mobility has announced that it will adopt LTE as its 4G wireless standard.[22]
  • MetroPCS recently announced that it would be using LTE for its upcoming 4G network.[23]
  • The newly formed China Telecom/Unicom[24] and Japan's KDDI[25] have announced they have chosen LTE as their 4G network technology.
  • On Dec 2008 Telia Sonera has signed a contract for world's first commercial LTE network construction with chinese Huawei Technologies.
  • 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.

[edit] See also

[edit] References

  1. ^ a b http://cp.literature.agilent.com/litweb/pdf/5989-7898EN.pdf
  2. ^ [1]
  3. ^ 3GPP TR 22.978 All-IP network (AIPN) feasibility study
  4. ^ 3GPP Work Item 31067
  5. ^ 3GPP LTE - See System Architecture Evolution
  6. ^ 3GPP LTE presentation Kyoto May 22rd 2007
  7. ^ a b Researchers demo 100 Mbit/s MIMO with SDMA / virtual MIMO technology
  8. ^ Nomor Research: World's first LTE demonstration
  9. ^ [2]
  10. ^ NTT DoCoMo develops low power chip for 3G LTE handsets
  11. ^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9249_9178_23
  12. ^ [3]
  13. ^ Gardner, W. David. "Freescale Semiconductor To Demo LTE In Mobile Handsets", Information Week, February 8 2008.
  14. ^ Walko, John "NXP powers ahead with programmable LTE modem", EETimes, January 30 2008.
  15. ^ Walko, John "PicoChip, MimoOn team for LTE ref design", EETimes, February 4 2008.
  16. ^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9422_9351_23
  17. ^ Nortel and LG Electronics Demo LTE at CTIA and with High Vehicle Speeds :: Wireless-Watch Community
  18. ^ "Rogers LTE launch details revealed; 4G in Vancouver by February 2010". http://www.boygeniusreport.com/2009/02/19/rogers-lte-launch-details-revealed/. 
  19. ^ "AT&T develops wireless broadband plans". http://www.telecoms.com/itmgcontent/tcoms/news/articles/20017502859.html. Retrieved on 2008-08-25. 
  20. ^ Verizon Wireless Tests 4G Mobile Wireless Network
  21. ^ Bell announces strategic 3G wireless network investment, maximizing consumer choice in mobile data and confirming its path forward to 4G LTE wireless
  22. ^ reportonbusiness.com: Wireless sales propel Telus results
  23. ^ MetroPCS Chooses LTE For 4G Wireless Network
  24. ^ CDMA operators will choose LTE, says ZTE
  25. ^ Japan's KDDI Selects LTE Core as Next-Generation Mobile Broadband Solution from Hitachi and Nortel

[edit] Further reading

  • M. Ergen, "Mobile Broadband - Including WiMAX and LTE", Springer, NY, 2009
  • H. Ekström, A. Furuskär, J. Karlsson, M. Meyer, S. Parkvall, J. Torsner, and M. Wahlqvist, "Technical Solutions for the 3G Long-Term Evolution," IEEE Commun. Mag., vol. 44, no. 3, March 2006, pp. 38–45
  • E. Dahlman, H. Ekström, A. Furuskär, Y. Jading, J. Karlsson, M. Lundevall, and S. Parkvall, "The 3G Long-Term Evolution - Radio Interface Concepts and Performance Evaluation," IEEE Vehicular Technology Conference (VTC) 2006 Spring, Melbourne, Australia, May 2006
  • K. Fazel and S. Kaiser, Multi-Carrier and Spread Spectrum Systems: From OFDM and MC-CDMA to LTE and WiMAX, 2nd Edition, John Wiley & Sons, 2008, ISBN 978-0-470-99821-2

[edit] External links for more information

[edit] 3GPP Projects and Presentations

[edit] Specifications

[edit] Industry reaction

[edit] Whitepapers and other information

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