Kaiser, Thomas

Oppermann, Ian

Porcino, Domenico

Institutionelles Repositorium der Leibniz Universität Hannover

Hindawi Publishing CorporationEURASIP Journal on Applied Signal ProcessingVolume 2006, Article ID 34659, Pages 1–3DOI 10.1155/ASP/2006/34659EditorialWireless Location Technologies and ApplicationsThomas Kaiser,1 Ian Oppermann,2 and Domenico Porcino31Department of Electrical Engineering and Information Technology, Communication Systems Group,Leibniz University of Hannover, Appelstraße 9A, 30167 Hannover, Germany2Centre for Wireless Communications (CWC), University of Oulu, Oulu 90014, Finland3Wireless Group, Philips Research Laboratories, Cross Oak Lane, Redhill, Surrey RH1 5HA, UKReceived 30 July 2006; Accepted 30 July 2006Copyright © 2006 Thomas Kaiser 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.Technologies for location and tracking are fast maturing withan array of new techniques, new algorithms, system designs,and trials bringing location-based services into everyday life.This once niche technology is maturing and gaining wideracceptance, thus finding more and more applications everyday.The development of communications systems that in-clude location and tracking capabilities has generated greatinterest also in the fields of cellular and wireless local/per-sonal area networks. A host of potential new services canbe enabled by suitably accurate location and tracking facil-ities in conjunction with appropriate communications anddata transfer platforms. Researchers worldwide are pushingthe boundaries of precision, low-cost, component reusabil-ity, and ease of field deployment.From established radio techniques, such as WLAN (e.g.,IEEE 802.11 a/b/g) to emerging WPAN networks (e.g., Blue-tooth and IEEE 802.15.4) to newer ultra-wideband (UWB)systems (e.g., IEEE 802.15.3a and IEEE 802.15.4a), and fur-ther previously unconsidered technologies such as digitalTV signals, a common denominator to drive adoption andgrowth is implementing innovative services on top of datatransfer. Whether the positioning techniques are based onsignal strength, time of flight, or fingerprinting techniques,they oﬀer the potential to improve and optimize traditionalservices (as diverse as flight navigation or data routing) orbring to life new applications relying on the knowledge ofthe location of the wireless nodes.A large number of issues must be addressed tomove fromcoarse delay measurement to useful range estimation fortracking purposes. Issues include generation of accurate de-lay/ranging estimates, proper operation in dense multipathenvironments, delay/ranging information sharing betweennodes, computationally eﬃcient algorithms, algorithms forlow infrastructure environments, dealing with nonline ofsight as well as integration with usable applications. The aimof this special issue is to address the state of the art in wire-less location technologies and applications with particularemphasis on accurate results in low infrastructure environ-ments. We classified the 16 contributions into 3 major cate-gories, namely, performance analysis, algorithms, and systems/applications.“Systematic errors and location accuracy in wireless net-works” by Harri Saarnisaari and Timo Bra¨ysy is the firstpaper in the category “performance analysis” and providesa unified error-propagation-law-based tool to analyze mea-surement and systematic errors. The tool is used in order tocompare hyperbolic (time delay based), direction finding, re-ceived signal strength (RSS), and relative RSS (RRSS), loca-tion systems. The obtained analytical results verify several in-tuitive expectations, for example, that the hyperbolic meth-ods are sensitive to network synchronization errors.In the paper “Autonomous positioning techniques basedon Crame´r-Rao lower bound analysis” by Mats Rydstro¨m etal. the problem of autonomously locating asynchronous sen-sor nodes in a wireless network is addressed, where the num-ber of processing resources needed will beminimized. An op-timal scheme for sensor clock-oﬀset cancellation is proposedin the first part of the paper, while the second part concernsabout a divide-and-conquer approach for suboptimal posi-tioning, which is also based on the corresponding Crame´r-Rao lower bound (CRB).The next paper “Crame´r-Rao type bounds for localiza-tion” by Cheng Chang and Anant Sahai studies the localiza-tion problem in sensor networks, which is also based on thefundamental CRB for noisy range measurements. They in-vestigate the impact of a priori knowledge of the postion of afew reference nodes and prove some invariances of the CRB2 EURASIP Journal on Applied Signal Processingas well as its extension to large networks for diﬀerent wirelesssignal propagation models.The last paper of this category is “Performance evalua-tion of indoor localization techniques based on RF powermeasurements from active or passive devices” by DamianoDe Luca et al. In this contribution the authors discussed theperformance of networks of indoor RF identification (RFID)localization units based on signal strength analysis on a fixedgrid against prerecorded RF maps. The paper discusses alsothe maintenance and installation costs of active versus pas-sive tags and the eﬀects of the tag population.When considering tracking of objects, many position cal-culations must be performed per second representing a con-siderable computational burden. Techniques which reducecomplexity of a single positioning calculation, or whichmakeuse of the availability of other information to reduce the needfor the number of calculations per second can yield consid-erable savings. This is particularly important for handheldor battery powered devices. These issues are addressed in thenext category “algorithms.”The paper “A constrained least squares approach to mo-bile positioning: algorithms and optimality” by K. W. Che-ung et al. addresses a complexity constrained approach toposition calculation which supports relatively high accuracy.Many location-based techniques are dependent on de-termining the angle or time of arrival of multiple signals.The accuracy of identifying the arrival time or angle di-rectly impacts the accuracy of the positioning results. Thepaper “Adaptive subchip multipath resolving for wireless lo-cation systems” by Nabil R. Yousef et al. describes a tech-nique for improving the accuracy of identification of mul-tipath time/angle of arrival which may then be used to sig-nificantly improve the position estimate.Similarly, the paper “Time of arrival estimation for UWBlocalizers in realistic environments” by Chiara Falsi et al. ex-amines the time of arrival estimation problem (almost trivialunder ideal conditions) under the real world constraints ofimperfect reception, noise, and other mitigating factors.In “Robust estimator for non-line-of-sight error mitiga-tion in indoor localization” by R. Casas et al. a robust regres-sion techniques to detect and reject nonline-of-sight (NLoS)measures is proposed. The technique is suitable in environ-ments with little infrastructure requirements and relies onmultilateration and a least-median-of-squares criterion.In the paper “Application of beamforming in wireless lo-cation estimation” by Kamran Sayrafian-Pour and DominikKaspar it is assumed that the receiver is equipped with a cir-cular antenna array so that beamforming becomes feasible.This property basically enables a single receiver to estimateand track the position of a mobile transmitter. The feasibil-ity of this methodology is investigated and the accuracy im-provements are demonstrated.A similar approach is considered in the paper “Blind mo-bile positioning in urban environment based on ray-tracinganalysis” by Shohei Kikuchi et al. The signals received by asingle base station equipped with an antenna array are com-bined with an a priori ray-tracing analysis that is based onhighly accurate three-dimensional terrain data. Moreover,the approach is entirely “blind,” so that neither a training se-quence nor a specific waveform from the mobile terminal isrequired.The paper “Particle filtering algorithms for tracking amaneuvering target using a network of wireless dynamic sen-sors” by Joaquı´n Mı´guez and Antonio Arte´s-Rodrı´guez takesa novel approach and explores the application of a complexyet reasonably accurate technique to wireless network.The paper “Feedforward delay estimators in adverse mul-tipath propagation for Galileo and modernized GPS signals”by Elena Simona Lohan et al. is a useful reference for the re-searchers engaged in the global navigation satellite systems(GNSS). It presents a good analysis (and attempt of reduc-tion) of the severe multipath eﬀects on the line of sight de-lay measurement via the use of feedforward delay estima-tion techniques. The authors present an extensive review ofknown methods and extend them to BOC-modulated pseu-dorandom codes, also taking into account the needed com-putational resources in state-of-the-art, low-power DSPs.The third category of papers in this special issue toucheson “systems and applications” involving location-based sys-tems.The paper “A new position location system using DTVtransmitter identification watermark signals” by XianbinWang et al. presents the innovative idea of using transmit-ter identification RF watermarking by analyzing the DTVsignals. These signals are transmitted at much higher powerthan satellite signals and can also be recorded with good ac-curacy indoors and could be used as a reference for timingand time of flight information. The performance of a test sys-tem has been tested via simulations and an initial field trial.The paper “Practical network-based techniques for mo-bile positioning in UMTS” by Jakub Borkowski and JukkaLempia¨inen shows results of research on cellular positioningfor 3G systems. Two main methods are presented and evalu-ated: the ECID + RTT (enhanced cell identification + roundtrip time) and the PCM (pilot correlation method). In bothcases the authors show the merits (precision, system simplic-ity) and drawbacks (complexity costs, eﬀects on system ca-pacity) of each method showing how they could evolve inhybrid satellite-cellular positioning networks.The paper “A new location estimation system for wirelessnetworks based on linear discriminant functions and hiddenMarkov models” by Galo Nun˜o-Barrau and Jose´ M. Pa´ez-Borrallo examines a technique for applying structural infor-mation to enhance the performance of position estimationleading to improved performance in diﬀerent network types.The work is applicable to a number of diﬀerent technologies.In the paper “An innovative gateway for indoor position-ing” by G. F.Marias et al. a novel entity called gatewayWLANlocation center (GWLC) is proposed, which incorporates aunified framework for retrieving location data of users andobjects in heterogeneous indoor and WLAN-based commu-nication systems. The design principles and the functionalityof the GWLC are elaborated and real experiments demon-strate the performance of the gateway.The paper “Advanced integration of WiFi and iner-tial navigation systems for indoor mobile positioning” byThomas Kaiser et al. 3Fre´de´ric Evennou and Franc¸ois Marx presents an aided deadreckoning navigation structure and signal processing algo-rithms for self localization of an autonomous mobile deviceby fusing pedestrian deadreckoning andWiFi signal strengthmeasurements. The benefits of the proposed architecture areevaluated and compared with the pureWiFi and inertial nav-igation systems.Hundreds of researchers worldwide have contributed tothis special issue submitting their latest research, reviewingpapers, suggesting changes, and improvements in successiveiterations. We would like to thank them all for a great eﬀortover a year’s work and collaboration. We would also like tosend our special thanks to the publisher and the editor-in-chief for their patience and useful suggestions along the pathto the finalization of the issue.We are confident that this special issue will become a use-ful reference for the current status of play and stimulate fur-ther research on wireless location technologies in the monthsto come.We wish all the best to all those following and work-ing in this exciting positioning field!Thomas KaiserIan OppermannDomenico PorcinoThomas Kaiser received the Ph.D. degree in1995 with distinction and the German Ha-bilitation degree in 2000, both from Ger-hard Mercator University Duisburg and inelectrical engineering. In the summer of2005 he joined Stanford’s Smart AntennaResearch Group (SARG) as a Visiting Pro-fessor. Now he holds a Chair on commu-nication systems at the University of Han-nover, Germany, and is the Founder of thespin-oﬀ company mimoOn GmbH. He has published more than100 papers and has coedited four books on ultra-wideband andsmart antenna systems. He is the founding Editor-in-Chief of theIEEE Signal Processing Society E-Letter. His research interest fo-cuses on applied signal processing with emphasis on multiantennasystems, especially its applicability to ultra-wideband systems.Ian Oppermann is currently the Directorof Performance Products within the Soft-ware Business Group of Nokia Networks,Finland. Within his product developmentportfolio are leading edge network planningand optimization tools for 2G and 3G tech-nologies. Before joining Nokia, he was theDirector of the Centre for Wireless Com-munications (CWC), a self-funded researchcentre inOulu, Finland. At the CWC, he wasresponsible for looking at “beyond 3G” mobile systems includingultra-wideband (UWB), cellular and noncellular networks. From1996 to 2002, he was CTO of an Australian software developmentcompany developing network planning and optimization tools. Heholds undergraduate degrees in science (1990) and electrical engi-neering (1992) from the University of Sydney, Australia. He alsoearned his Ph.D. degree from the University of Sydney in 1997,where his thesis explored CDMA physical layer technologies. In2005, he completed an MBA at the University of London.Domenico Porcino received his Dott. Ing.degree in electronics engineering from Po-litecnico di Torino, Italy, with main empha-sis on mobile communications. He startedhis career with Philips Research Labora-tories (PRL), UK, engaging in researchand development activities for low-powerradio devices. While at Philips, he hasbeen involved in the design and testing ofa transceiver chip for low-power wirelesstelemetry devices, simulation of novel RF receiver architectures andbaseband processing for GPS receivers, and baseband developmentfor third-generation mobile phones. For the last five years he hasbeen leading PRL activities in the ultra-wideband (UWB) domain,looking at a variety of topics such as propagation, wideband anten-nas, regulations, ranging, and video streaming. Author of severalpublications and patent applications, he has also held coordinatingroles in the ULTRAWAVES (EC IST FP5) and PULSERS (EC ISTFP6) projects.

Wireless location technologies and applications

Thomas Kaiser

Ian Oppermann

Domenico Porcino

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Wireless Location Technologies and Applications

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Wireless location technologies and applications

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