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Hindawi Publishing CorporationJournal of Electrical and Computer EngineeringVolume 2010, Article ID 659295, 2 pagesdoi:10.1155/2010/659295

Editorial

LTE/LTE-Advanced Cellular Communication Networks

Cyril Leung,1 Raymond Kwan,2 Seppo Hamalainen,3 and Wenbo Wang4

1 Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, BC, Canada V6T 1Z42 Centre for Wireless Network Design, University of Bedfordshire, Bedfordshire LU1 3JU, UK3 NSN Research, Nokia Siemens Networks, 02610 Espoo, Finland4 Key Laboratory of Universal Wireless Communication, Beijing University of Posts and Telecommunications (BUPT),Beijing 100876, China

Correspondence should be addressed to Cyril Leung, [email protected]

Received 29 September 2010; Accepted 29 September 2010

Copyright © 2010 Cyril Leung 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.

From humble beginnings in the 1980s with bulky 1G analoghandsets, the wireless cellular communications industrynow enjoys a major presence in most countries, withnearly 5 billion subscribers worldwide and revenues in theone trillion USD range. Consumer demand for services isexpected to grow rapidly in the next few years, fuelled bynew applications such as mobile web-browsing, video down-loading/streaming, online gaming, and social networking.The commercial deployment of 3G networks began with3GPP UMTS/WCDMA in 2001 and has evolved into currentUMTS/HSPA networks. To maintain a competitive edge,3GPP UMTS networks need to support higher bit rates,improved spectrum efficiencies, and lower delays, all at areduced cost. A well-planned and natural evolution to 4Gnetworks is considered essential. Long-term evolution (LTE)and LTE-Advanced are important steps in this transition.LTE technology demonstrations began as early as 2006 andcommercial LTE networks are starting to be deployed bywireless carriers worldwide.

This special issue consists of five papers. The first threepapers focus on LTE: there is a survey paper on resourcescheduling and interference mitigation techniques, a paperon resource scheduling for the provision of different services,and a paper on a method for improving the tradeoff betweenservice quality and radio coverage for enhanced multimediabroadcast and multicast service (E-MBMS). The other twopapers are focused on LTE-A: one paper discusses distributedalgorithms for solving two self-configuration problems andthe other examines the performance of decode-and-forwardrelaying.

Resource scheduling and interference mitigation will beinstrumental in the success of LTE. In the first paper, “Asurvey of scheduling and interference mitigation in LTE,”Kwan and Leung present an overview of downlink anduplink resource scheduling techniques, including tradeoffsinvolved in selecting a channel quality indicator reportingscheme. A variety of methods which have been proposedfor reducing intercell interference (ICI) in order to improvethe link quality for cell-edge users are also described. Thepaper includes a brief discussion of the challenges for LTE-Advanced network designers.

The issue of joint radio resource allocation for multipleservices is challenging, as each service is associated withdifferent characteristics and quality of service requirements.In the second paper, “Scheduling for improving systemcapacity in multiservice 3GPP LTE,” Lima et al. address theissue of scheduling algorithms for multiple services in LTE, inwhich resources are jointly allocated. Their proposed schemetakes into account different traffic characteristics as well ascurrent achieved satisfaction level of each service. Resultsshow that the proposed scheme can provide significantcapacity improvement over conventional approaches.

Video broadcast and multicast services are expected toplay a very important role in future mobile communications.One of the key techniques for improving performance is theuse of hierarchical modulation (HM). In HM, users withpoorer channel qualities can access data via a low-rate butmore error-protected “base-layer” (BL). On the other hand,users with better channel qualities can access the high-rate“enhanced layer” (EL) associated with less error protection.

2 Journal of Electrical and Computer Engineering

The aim is to provide a good design tradeoff betweenservice quality and coverage. In the third paper, “Hierarchicalmodulation with vector rotation for E-MBMS transmission inLTE systems,” Zhao et al. propose the use of vector rotationto improve the performance of the ELs in the context ofLTE multicast/broadcast networks. Simulation results showthat the proposed method can provide significant benefitsfor video quality and coverage compared to conventionalschemes.

In LTE-Advanced systems, the number of availableprimary component carriers (PCCs) and physical cell IDs(PCIs) are limited and their assignment can be formulatedas graph coloring problems. In the fourth paper, “Distributedgraph coloring for self-organization in LTE networks,” Ahmedet al. investigate algorithms for solving these problems in adistributed fashion, considering both real-valued and binarypricing of interference. The number of component carriersneeded to select conflict-free PCCs and the number of PCIsneeded to assign confusion-free PCIs are estimated fromsimulations.

Decode-and-forward relaying is likely to play an impor-tant role in LTE-Advanced networks. In the fifth paper, “Onthe coverage extension and capacity enhancement of inbandrelay deployments in LTE-Advanced networks,” Saleh et al.investigate the coverage extension capabilities and capacityenhancements achievable with in-band Type 1 and Type 1brelaying within the LTE-Advanced framework in differentpropagation scenarios. System level simulation results showthat the gains from employing these two types of relays varygreatly, depending on the deployment environment.

It is evident that this special issue does not cover manyother important areas of relevance to LTE/LTE-Advancednetworks. Nonetheless, we hope that readers will find theinformation presented to be interesting and useful. We thankall the authors who responded to the call for papers. Wealso wish to acknowledge all the reviewers for their dedicatedefforts in ensuring a high standard for the selected papers.

Cyril LeungRaymond Kwan

Seppo HamalainenWenbo Wang

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