Hindawi Publishing CorporationEURASIP Journal on Wireless Communications and NetworkingVolume 2009, Article ID 472124, 3 pagesdoi:10.1155/2009/472124

Editorial

3GPP LTE and LTE-Advanced

Bruno Clerckx,1 Angel Lozano,2 Stefania Sesia,3 Cornelius van Rensburg,4

and Constantinos B. Papadias5

1 Communication Laboratory, Samsung Advanced Institute of Technology, Samsung Electronics,Yongin-Si 446-712, South Korea

2 Department of Information and Communication Technologies, Universitat Pompeu Fabra,08002 Barcelona, Spain

3 ST-NXPWireless - SW/FW/Algorithm Group, European Telecommunications Standard Institute (ETSI),Mobile Competence Center, 06921 Sophia Antipolis Cedex, France

4 Wireless R&D Laboratory, Huawei Technologies, Plano, TX 75075, USA5 Broadband Wireless and Sensor Networks, Athens Information Technology, P.O. Box 68,Markopoulo Avenue, Peania 19002, Athens, Greece

Correspondence should be addressed to Bruno Clerckx, bruno.clerckx@gmail.com

Received 17 September 2009; Accepted 17 September 2009

Copyright © 2009 Bruno Clerckx et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A new cellular standard, termed Long-Term Evolution (LTE),also referred to as Evolved UMTS Terrestrial Radio Access(E-UTRA), is currently being defined to replace the UMTSthird-generation system. LTE-Advanced, in turn, refers to themost advanced version of LTE that was initiated about oneyear ago.

LTE represents a radical new step forward for thewireless industry, targeting order-of-magnitude increasesin bit rates with respect to its predecessors by means ofwider bandwidths and improved spectral efficiency. Beyondthe improvement in bit rates, LTE aims to provide ahighly efficient, low-latency, packet-optimized radio accesstechnology offering enhanced spectrum flexibility.

The LTE design presents radical differences at everylayer. Like many other communication technologies (e.g.,digital video and audio broadcasting, DSL, wireless LANs),the physical layer uses OFDM waveforms in order to avoidthe intersymbol interference that typically arises in highbandwidth systems. In terms of radio access, CDMA hasgiven away to time and frequency multiple access. Onedifferentiating aspect of the LTE standard is that from theonset, MIMO is an integral component, and not an add-on feature. At the network layer, a flatter architecture isbeing defined that represents the transition from the exist-ing UTRA network, which combines circuit- and packet-switching, to an all-IP system.

The objective of this special issue is to disseminate newadvances in both the physical and medium access controllayers that are applicable to the LTE and LTE-Advancedtechnologies. Out of 23 submissions, we selected 13 papersfor inclusion in this special issue. Papers have been classifiedin 6 categories. The first category (papers 1 and 2) consistsof two tutorials and provides an introduction to the LTEsystem. The second category (papers 3 to 5) focuses onMIMO issues including Single-User MIMO (SU-MIMO)and Multi-User MIMO (MU-MIMO). The third category(paper 6) addresses the design of a practical scheduler forLTE. The fourth category (papers 7 to 10) focuses on multipleaccess (uplink) and specifically on Single-Carrier FDMA(SC-FDMA). The fifth category (papers 11 and 12) opensthe way to LTE-Advanced and on relay architectures. Thelast category investigates the applicability of the 3GPP LTEinterface to satellite transmission.

We hope that this excellent collection of papers willhelp the interested readers to identify a number of keychallenges and opportunities that lie within the LTE andLTE-Advanced cellular standards, contributing not only toa better understanding of these systems but eventually alsoto the incorporation of techniques that will further boost theperformance of the corresponding deployed networks.

A more detailed description of each category and thecorresponding papers is as follows.

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Two tutorial papers introduce the LTE system. Thepaper by Martin-Sacristan et al. provides a broad intro-duction to LTE, describing the core functionalities and thesystem requirements. It briefly introduces LTE-Advancedrequirements and technologies currently under study. Leeet al. provide in their invited paper a tutorial on MIMOtechnologies. Being active players in the standardization ofLTE and LTE-Advanced, they go beyond a simple descriptionof MIMO and provide insightful explanations as to why thesefeatures have been adopted.

Three papers address MIMO issues. The first two papersfocus on MU-MIMO while the last one focuses on SU-MIMO.

The paper by Shu et al. proposes an optimal MU-MIMO linear precoding scheme with linear (MMSE) detec-tion based on particle swarm optimization. It shows thatsuch a scheme significantly outperforms other well-knownapproaches (e.g., precoding schemes based on channel blockdiagonalization). Combined with the use of demodulationreference signals, the proposed scheme may be a goodcandidate for MU-MIMO in 3GPP LTE-Advanced.

The paper by Komulainen proposes some linear uplink(UL) MU-MIMO beamforming schemes for cellular TDDsystems. The UL scheme is designed to coexist with down-link (DL) MU-MIMO block zero-forcing by coordinatedtransmit-receive processing. It relies on the channel stateinformation of the zero-forced DL channels to precode ULtransmission. The proposed scheme is shown to outperformSU-MIMO transmission combined with user selection aswell as UL antenna selection. The proposed concept may bea promising candidate for 3GPP LTE-Advanced.

The paper by Yang examines the performance of var-ious kinds of antenna selection schemes in MIMO sys-tems with limited size antenna arrays and nonnegligiblemutual coupling. It is shown that the performance ofantenna selection is closely related to the antenna spac-ing and that appropriate selection schemes are requiredwhen mutual coupling is taken into account. Results indi-cate that soft selection always outperforms hard selec-tion. This study provides novel insight into the deploy-ment of antenna selection in both 3GPP LTE and LTE-Advanced.

One paper addresses the design of a scheduler for3GPP LTE downlink. In particular, the paper by Sadiqet al. proposes a complete and practical scheduler withlow computational complexity by integrating state-of-the-art techniques regarding resource allocation, fast algo-rithms, and scheduling. Simulations covering both PHYand MAC layers are performed and demonstrate thevarious design tradeoffs to be made in the selection ofthe queue-and-channel-aware QoS scheduling policies tocope with the diverse mix of traffic of an LTE down-link.

Performance of 3GPP LTE uplink multiple access basedon SC-FDMA is discussed in the following four papers.Wu et al. compares the information rate achieved by SC-FDMA and OFDMA with linear frequency-domain equaliz-ers. Based on some geometrical interpretation, it is shownthat the loss incurred by SC-FDMA can be mitigated by

exploiting multiuser diversity and spatial diversity. 3GPP LTEuplink performance evaluations confirm those findings.

The paper by Svensson et al. proposes a novel uplinkmultiple access scheme denoted as B-IFDMA (Block Inter-leaved Frequency Division Multiple Access). In the presenceof realistic channel estimation at the receiver and imperfectchannel state information at the transmitter, B-IFDMAis shown to outperform the currently adopted SC-FDMAmethod. Additional benefits in terms of amplifier and energyefficiency, robustness to frequency offsets, and Dopplerspreads are detailed.

The paper by Assimi et al. investigates the design ofHybrid Automatic Repeat reQuest (HARQ) for single-carriertransmission as in 3GPP LTE UL. Here, transmit diversitytechniques are introduced for HARQ retransmissions; thisis because in slow fading environments, retransmittingidentically the same packet does not provide additionaldiversity gain. The authors investigate the performanceof both cyclic-frequency-shift-diversity and bit-interleaving-diversity using theoretical analysis and simulations. Thechoice of a specific diversity scheme is shown to depend onthe desired performance/complexity tradeoff and the systemparameters.

Karakaya et al. further address the problem of sensitivityof SC-FDMA to frequency offsets. A novel Kalman filter-based method is introduced, enabling the tracking of thechannel taps in the time domain, to mitigate the intercarrierinterference under high Doppler spreads. This method isevaluated under various scenarios to assess the impact of thedesign parameters on the performance.

The following two papers introduce new technologiesbased on relay for LTE-Advanced.

The paper by Teyeb et al. proposes to enhance theLTE architecture by performing dynamic relaying whilemaintaining backward compatibility with LTE Release 8. Aflexible, efficient, and self-organizing multihop architectureis introduced where relays can be linked to base stations onan “as need” basis rather than in a fixed manner.

The paper by Peters et al. focuses on the problemof the extra interference added by the presence of relays,which is currently mostly overlooked. They also analyze theperformance of various kinds of half-duplex relay strate-gies in interference-limited environments. The performancebenefits of those strategies are discussed as a function ofdeployment scenarios and the system parameters.

The last paper by Bastia et al. studies the applicabilityof 3GPP LTE to satellite transmissions. With the introduc-tion of several new features such as inter-TTI interleavingtechniques that exploit the existing HARQ structure of LTE,Peak-to-Average Power Ratio (PAPR) reduction techniques,and preamble sequence design for random access, it is shownthat the existing terrestrial air interface can be adopted fortransmission over satellite links.

Acknowledgments

We would like to thank the authors for contributing to thisspecial issue and to the reviewers for providing fast feedback

EURASIP Journal on Wireless Communications and Networking 3

and constructive remarks that helped improve the quality ofthe manuscripts. We also thank the Editor-in-Chief and theeditorial office for their support through the entire editingprocess.

Bruno ClerckxAngel LozanoStefania Sesia

Cornelius van RensburgConstantinos B. Papadias

Photograph © Turisme de Barcelona / J. Trullàs

Preliminary call for papers

The 2011 European Signal Processing Conference (EUSIPCO 2011) is thenineteenth in a series of conferences promoted by the European Association forSignal Processing (EURASIP, www.eurasip.org). This year edition will take placein Barcelona, capital city of Catalonia (Spain), and will be jointly organized by theCentre Tecnològic de Telecomunicacions de Catalunya (CTTC) and theUniversitat Politècnica de Catalunya (UPC).EUSIPCO 2011 will focus on key aspects of signal processing theory and

li ti li t d b l A t f b i i ill b b d lit

Organizing Committee

Honorary ChairMiguel A. Lagunas (CTTC)

General ChairAna I. Pérez Neira (UPC)

General Vice ChairCarles Antón Haro (CTTC)

Technical Program ChairXavier Mestre (CTTC)

Technical Program Co Chairsapplications as listed below. Acceptance of submissions will be based on quality,relevance and originality. Accepted papers will be published in the EUSIPCOproceedings and presented during the conference. Paper submissions, proposalsfor tutorials and proposals for special sessions are invited in, but not limited to,the following areas of interest.

Areas of Interest

• Audio and electro acoustics.• Design, implementation, and applications of signal processing systems.

l d l d d

Technical Program Co ChairsJavier Hernando (UPC)Montserrat Pardàs (UPC)

Plenary TalksFerran Marqués (UPC)Yonina Eldar (Technion)

Special SessionsIgnacio Santamaría (Unversidadde Cantabria)Mats Bengtsson (KTH)

FinancesMontserrat Nájar (UPC)• Multimedia signal processing and coding.

• Image and multidimensional signal processing.• Signal detection and estimation.• Sensor array and multi channel signal processing.• Sensor fusion in networked systems.• Signal processing for communications.• Medical imaging and image analysis.• Non stationary, non linear and non Gaussian signal processing.

Submissions

Montserrat Nájar (UPC)

TutorialsDaniel P. Palomar(Hong Kong UST)Beatrice Pesquet Popescu (ENST)

PublicityStephan Pfletschinger (CTTC)Mònica Navarro (CTTC)

PublicationsAntonio Pascual (UPC)Carles Fernández (CTTC)

I d i l Li i & E hibiSubmissions

Procedures to submit a paper and proposals for special sessions and tutorials willbe detailed at www.eusipco2011.org. Submitted papers must be camera ready, nomore than 5 pages long, and conforming to the standard specified on theEUSIPCO 2011 web site. First authors who are registered students can participatein the best student paper competition.

Important Deadlines:

P l f i l i 15 D 2010

Industrial Liaison & ExhibitsAngeliki Alexiou(University of Piraeus)Albert Sitjà (CTTC)

International LiaisonJu Liu (Shandong University China)Jinhong Yuan (UNSW Australia)Tamas Sziranyi (SZTAKI Hungary)Rich Stern (CMU USA)Ricardo L. de Queiroz (UNB Brazil)

Webpage: www.eusipco2011.org

Proposals for special sessions 15 Dec 2010Proposals for tutorials 18 Feb 2011Electronic submission of full papers 21 Feb 2011Notification of acceptance 23 May 2011Submission of camera ready papers 6 Jun 2011