LTE (Long Term Evolution) is the next major step in mobile radio communications, and it 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. 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 towards a 4G mobile communications technology and an all-IP flat architecture system.
The aim of this 3GPP project is to improve the Universal Mobile Telecommunications System (UMTS) mobile phone standard. 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 towards a 4G mobile communications technology and an all-IP flat architecture system.
Overview
LTE provides downlink peak rates of at least 100Mbit/s, 50 Mbit/s[1] 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 Duplexing) 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,[1] 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, FDD and TDD in the same platform, improved end-user experience and simple architecture resulting in low operating expenditures. LTE will also support seamless connection to existing networks such as GSM, CDMA and WCDMA.[1]
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. [2]
Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum.[2]
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
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.
Timetable
In December 2008, Rel-8 specification was locked. In March 2009, the ASN.1 code was locked. 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.[3] Motorola demonstrated a LTE RAN standard compliant eNodeB and LTE chipset at the same event.
An "All IP Network" (AIPN)
A characteristic of next generation networks are that they are based upon core internet protocol TCP/IP. 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),[4] 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.[5]
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.
E-UTRAN Air Interface
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.[7]
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-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[8]. 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
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, 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.
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[10], all the data is being send 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.[11]
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.[12]
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[13]
In September 2007, NTT docomo demonstrated LTE data rates of 200 Mbit/s with power consumption below 100mW during the test.[14]
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.[15]
Ericsson demonstrated the world’s first end-to-end LTE call on handheld [16] 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 . [17]
NXP Semiconductors demonstrated a multi-mode LTE modem as the basis for a software-defined radio system for use in cellphones. [18]
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. [19]
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.[20]
In April 2008, LG Electronics and Nortel demonstrated LTE data rates of 50 Mbit/s while travelling at 110 km/h. [21]
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.[11]
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 at the Mobile World Congress in Barcelona.
Carrier adoption
Most carriers supporting GSM or HSUPA 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. [22]
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. [23]
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 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 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 is presently testing its LTE network[24] and selects Ericsson and Alcatel-Lucent as Primary Network Vendors for LTE Network.
Bell Mobility plans to start LTE deployment in 2009-2010[25]
Telus Mobility has announced that it will adopt LTE as its 4G wireless standard.[26]
MetroPCS recently announced that it would be using LTE for its upcoming 4G network.[27]
The newly formed China Telecom/Unicom[28] and Japan's KDDI[29] have announced they have chosen LTE as their 4G network technology.
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.
References
^ a b c A Primer on LTE
^ a b http://cp.literature.agilent.com/litweb/pdf/5989-7898EN.pdf
^ [1]
^ 3GPP TR 22.978 All-IP network (AIPN) feasibility study
^ 3GPP Work Item 31067
^ 3GPP LTE - See System Architecture Evolution
^ 3GPP LTE presentation Kyoto May 22rd 2007
^ Nomor Research Newsletter: Overview LTE Time Division Duplex
^ Nomor Research Newsletter: LTE Physical Layer Signals and Channels
^ Nomor Research Newsletter: LTE Random Access Channel
^ a b Researchers demo 100 Mbit/s MIMO with SDMA / virtual MIMO technology
^ Nomor Research: World's first LTE demonstration
^ [2]
^ NTT DoCoMo develops low power chip for 3G LTE handsets
^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9249_9178_23
^ [3]
^ Gardner, W. David. "Freescale Semiconductor To Demo LTE In Mobile Handsets", Information Week, February 8 2008.
^ Walko, John "NXP powers ahead with programmable LTE modem", EETimes, January 30 2008.
^ Walko, John "PicoChip, MimoOn team for LTE ref design", EETimes, February 4 2008.
^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9422_9351_23
^ Nortel and LG Electronics Demo LTE at CTIA and with High Vehicle Speeds :: Wireless-Watch Community
^ "Rogers LTE launch details revealed; 4G in Vancouver by February 2010". http://www.boygeniusreport.com/2009/02/19/rogers-lte-launch-details-revealed/.
^ "AT&T develops wireless broadband plans". http://www.telecoms.com/itmgcontent/tcoms/news/articles/20017502859.html. Retrieved on 2008-08-25.
^ Verizon Wireless Tests 4G Mobile Wireless Network
^ Bell announces strategic 3G wireless network investment, maximizing consumer choice in mobile data and confirming its path forward to 4G LTE wireless
^ reportonbusiness.com: Wireless sales propel Telus results
^ MetroPCS Chooses LTE For 4G Wireless Network
^ CDMA operators will choose LTE, says ZTE
^ Japan's KDDI Selects LTE Core as Next-Generation Mobile Broadband Solution from Hitachi and Nortel
Further reading
F. Khan, "LTE for 4G Mobile Broadband - Air Interface Technologies and Performance", Cambridge University Press, 2009
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
External links for more information
3GPP LTE homepage
Public LTE Discussion Forum
3GPP Projects and Presentations
3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description
3GPP AIPN Workitem
"3GPP Evolution: LTE and SAE" by Francois Courau at Alcatel (Chairman of 3GPP TSG RAN)
Specifications
3rd Generation Partnership Project (3GPP); Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN)
3rd Generation Partnership Project (3GPP); Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved UTRA
Industry reaction
"Mobile Broadband: The Global Evolution of UMTS/HSPA - 3GPP Release 7 and Beyond" by 3G Americas
Experience LTE by Motorola
Verizon Wireless Global LTE Deployment Plans
Whitepapers and other information
EDGE, HSPA, LTE: Broadband Innovation (PDF)
"LTE performance for initial deployments" by Nokia Siemens Networks
Long Term Evolution (LTE): An Introduction – Ericsson White Paper "The Long Term Evolution of 3G" on Ericsson Review, no. 2, 2005
"3G Long-Term Evolution" by Dr. Erik Dahlman at Ericsson Research
"Long-Term 3G Evolution - Radio Access" by Dr. Stefan Parkvall at Ericsson Research
"3GPP Long-Term Evolution / System Architecture Evolution: Overview" by Ulrich Barth at Alcatel
Dahlman, Parkvall, Skold and Beming, 3G Evolution: HSPA and LTE for Mobile Broadband, Academic Press, Oxford, UK, 2007
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
"3GPP LTE & 3GPP2 LTE Standardization" by Dr. Lee, HyeonWoo at Samsung Electronics
Nomor Research Newsletter: Overview LTE Time Division Duplex
"Trends in Mobile Network Architectures" by Dr. Michael Schopp at Siemens Networks
"Overview of the 3GPP LTE Physical Layer" by James Zyren and Dr. Wes McCoy, Freescale Semiconductor
“Growing momentum brings LTE closer to becoming a commercial reality”
^ a b c A Primer on LTE
^ a b http://cp.literature.agilent.com/litweb/pdf/5989-7898EN.pdf
^ [1]
^ 3GPP TR 22.978 All-IP network (AIPN) feasibility study
^ 3GPP Work Item 31067
^ 3GPP LTE - See System Architecture Evolution
^ 3GPP LTE presentation Kyoto May 22rd 2007
^ Nomor Research Newsletter: Overview LTE Time Division Duplex
^ Nomor Research Newsletter: LTE Physical Layer Signals and Channels
^ Nomor Research Newsletter: LTE Random Access Channel
^ a b Researchers demo 100 Mbit/s MIMO with SDMA / virtual MIMO technology
^ Nomor Research: World's first LTE demonstration
^ [2]
^ NTT DoCoMo develops low power chip for 3G LTE handsets
^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9249_9178_23
^ [3]
^ Gardner, W. David. "Freescale Semiconductor To Demo LTE In Mobile Handsets", Information Week, February 8 2008.
^ Walko, John "NXP powers ahead with programmable LTE modem", EETimes, January 30 2008.
^ Walko, John "PicoChip, MimoOn team for LTE ref design", EETimes, February 4 2008.
^ http://www.motorola.com/mediacenter/news/detailpf.jsp?globalObjectId=9422_9351_23
^ Nortel and LG Electronics Demo LTE at CTIA and with High Vehicle Speeds :: Wireless-Watch Community
^ "Rogers LTE launch details revealed; 4G in Vancouver by February 2010". http://www.boygeniusreport.com/2009/02/19/rogers-lte-launch-details-revealed/.
^ "AT&T develops wireless broadband plans". http://www.telecoms.com/itmgcontent/tcoms/news/articles/20017502859.html. Retrieved on 2008-08-25.
^ Verizon Wireless Tests 4G Mobile Wireless Network
^ Bell announces strategic 3G wireless network investment, maximizing consumer choice in mobile data and confirming its path forward to 4G LTE wireless
^ reportonbusiness.com: Wireless sales propel Telus results
^ MetroPCS Chooses LTE For 4G Wireless Network
^ CDMA operators will choose LTE, says ZTE
^ Japan's KDDI Selects LTE Core as Next-Generation Mobile Broadband Solution from Hitachi and Nortel
Further reading
F. Khan, "LTE for 4G Mobile Broadband - Air Interface Technologies and Performance", Cambridge University Press, 2009
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
External links for more information
3GPP LTE homepage
Public LTE Discussion Forum
3GPP Projects and Presentations
3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description
3GPP AIPN Workitem
"3GPP Evolution: LTE and SAE" by Francois Courau at Alcatel (Chairman of 3GPP TSG RAN)
Specifications
3rd Generation Partnership Project (3GPP); Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN)
3rd Generation Partnership Project (3GPP); Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved UTRA
Industry reaction
"Mobile Broadband: The Global Evolution of UMTS/HSPA - 3GPP Release 7 and Beyond" by 3G Americas
Experience LTE by Motorola
Verizon Wireless Global LTE Deployment Plans
Whitepapers and other information
EDGE, HSPA, LTE: Broadband Innovation (PDF)
"LTE performance for initial deployments" by Nokia Siemens Networks
Long Term Evolution (LTE): An Introduction – Ericsson White Paper "The Long Term Evolution of 3G" on Ericsson Review, no. 2, 2005
"3G Long-Term Evolution" by Dr. Erik Dahlman at Ericsson Research
"Long-Term 3G Evolution - Radio Access" by Dr. Stefan Parkvall at Ericsson Research
"3GPP Long-Term Evolution / System Architecture Evolution: Overview" by Ulrich Barth at Alcatel
Dahlman, Parkvall, Skold and Beming, 3G Evolution: HSPA and LTE for Mobile Broadband, Academic Press, Oxford, UK, 2007
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
"3GPP LTE & 3GPP2 LTE Standardization" by Dr. Lee, HyeonWoo at Samsung Electronics
Nomor Research Newsletter: Overview LTE Time Division Duplex
"Trends in Mobile Network Architectures" by Dr. Michael Schopp at Siemens Networks
"Overview of the 3GPP LTE Physical Layer" by James Zyren and Dr. Wes McCoy, Freescale Semiconductor
“Growing momentum brings LTE closer to becoming a commercial reality”
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