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Signal Processing Techniques in Network-Aided Positioning: A Survey of State-ofthe-Art Positioning Designs
- IEEE Signal Processing Magazine
, 2005
"... [A survey of state-of-the-art positioning designs] The U.S. Federal Communications Commission (FCC) requires that the precise location of all enhanced 911 (E911) callers be automatically determined. This requirement has motivated the development of cellular-aided positioning. To facilitate emergency ..."
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Cited by 97 (3 self)
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[A survey of state-of-the-art positioning designs] The U.S. Federal Communications Commission (FCC) requires that the precise location of all enhanced 911 (E911) callers be automatically determined. This requirement has motivated the development of cellular-aided positioning. To facilitate emergency services, the FCC has mandated that 95 % of all handsets sold be location compatible by the end of December 2005 [1]. Wireless positioning has also been found very useful for other applications besides E911 service, ranging from vehicle navigation and network optimization to resource management and automated billing. Ubiquitous computing and location-aware computing also necessitate that we develop techniques for estimating the location of mobile users in both outdoor and indoor environments. Various positioning systems have been proposed for use in ubiquitous computing [2]. As an essential prerequisite for ubiquitous computing, mobile positioning techniques, linked with wireless networks, have increasingly provided mobile users with opportunities to access personal information, corporate data, and shared resources anytime, anywhere. Positioning systems can be grouped in many different ways, including indoor versus outdoor systems or cellular versus sensor network positioning designs, as shown in Figure 1.
Network-based wireless location
- IEEE Signal Process. Mag
, 2005
"... [Challenges faced in developing techniques for accurate wireless location information] Wireless location refers to the geographic coordinates of a mobile subscriber in cellular or wireless local area network (WLAN) environments. Wireless location finding has emerged as an essential public safety fea ..."
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[Challenges faced in developing techniques for accurate wireless location information] Wireless location refers to the geographic coordinates of a mobile subscriber in cellular or wireless local area network (WLAN) environments. Wireless location finding has emerged as an essential public safety feature of cellular systems in response to an order issued by the Federal Communications Commission (FCC) in 1996. The order mandated all wireless service providers to deliver accurate location information of an emergency 911 (E-911) caller to public safety answering points (PSAPs). The FCC mandate aims to solve a serious public safety problem caused by the fact that, at present, a large proportion of all 911 calls originate from mobile phones, the location of which cannot be determined with existing technology. However, many difficulties intrinsic to the wireless environment make meeting the FCC objective challenging; these challenges include channel fading, low signal-to-noise ratios (SNRs), multiuser interference, and multipath conditions. In addition to emergency services, there are many other applications for wireless location technology, including monitoring and tracking for security reasons, location sensitive
Molisch, “The tradeoff between processing gains of an impulse radio UWB system in the presence of timing jitter,” in preparation
, 2004
"... In time hopping impulse radio, Nf pulses of duration Tc are transmitted for each symbol. This gives rise to two types of processing gain: (i) pulse combining gain, which is a factor Nf, and (ii) pulse spreading gain, which is Nc = Tf/Tc, where Tf is the mean interval between two subsequent pulses. T ..."
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Cited by 16 (12 self)
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In time hopping impulse radio, Nf pulses of duration Tc are transmitted for each symbol. This gives rise to two types of processing gain: (i) pulse combining gain, which is a factor Nf, and (ii) pulse spreading gain, which is Nc = Tf/Tc, where Tf is the mean interval between two subsequent pulses. This paper investigates the trade-off between these two types of processing gain with and without random polarity codes in the presence of timing jitter. Approximate expressions for bit error probability are derived for both coded and uncoded systems over additive white Gaussian noise channels and are used as the criterion to choose optimal Nf and Nc values. The effects of timing jitter and multiple access interference on the selection of optimal system parameters are explained through theoretical analysis. Simulation studies support the theoretical results.
Hidden Markov models for radio localization in mixed LOS/NLOS conditions
- IEEE Trans. Signal Process
, 2007
"... Abstract—This paper deals with the problem of radio localization of moving terminals (MTs) for indoor applications with mixed line-of-sight/non-line-of-sight (LOS/NLOS) conditions. To reduce false localizations, a grid-based Bayesian approach is proposed to jointly track the sequence of the position ..."
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Abstract—This paper deals with the problem of radio localization of moving terminals (MTs) for indoor applications with mixed line-of-sight/non-line-of-sight (LOS/NLOS) conditions. To reduce false localizations, a grid-based Bayesian approach is proposed to jointly track the sequence of the positions and the sight conditions of the MT. This method is based on the assumption that both the MT position and the sight condition are Markov chains whose state is hidden in the received signals [hidden Markov model (HMM)]. The observations used for the HMM localization are obtained from the power-delay profile of the received signals. In ultrawideband (UWB) systems, the use of the whole power-delay profile, rather than the total power only, allows to reach higher localization accuracy, as the power-profile is a joint measurement of time of arrival and power. Numerical results show that the proposed HMM method improves the accuracy of localization with respect to conventional ranging methods, especially in mixed LOS/NLOS indoor environments. Index Terms—Bayesian estimation, hidden Markov models (HMM), mobile positioning, source localization, tracking algorithms,
NLOS Mitigation using Linear Programming in Ultra-Wideband Location-Aware Networks
- IEEE transactions on Vehicular Technology
, 2007
"... Abstract—In this paper, we propose a linear-programming (LP) approach to the problem of nonline-of-sight (NLOS) mitigation in ad hoc ultrawideband wireless networks. The locations of “unlocalized ” nodes can be estimated using range or distance estimates from location-aware “anchor ” nodes. In the a ..."
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Cited by 14 (3 self)
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Abstract—In this paper, we propose a linear-programming (LP) approach to the problem of nonline-of-sight (NLOS) mitigation in ad hoc ultrawideband wireless networks. The locations of “unlocalized ” nodes can be estimated using range or distance estimates from location-aware “anchor ” nodes. In the absence of LOS between the unlocalized and anchor nodes, e.g., in indoor networks, the NLOS range estimates can be significantly biased. The direct incorporation of these biased range estimates into practical location estimators, such as the least squares estimator, without the mitigation of these bias errors, can potentially lead to severe degradation in the accuracy of node-location estimates. On the other hand, with certain geometries of anchor nodes, NLOS range estimates can be used to improve the accuracy of location estimation. Furthermore, discarding the biased range estimates may not be a viable option, as the number of range estimates available may be limited. We present a novel NLOS-bias mitigation scheme based on LP, that 1) allows us to incorporate NLOS range information into location estimation, but 2) does not allow NLOS bias errors to degrade node-localization accuracy. Index Terms—Line of sight (LOS), location estimation, mobile ad hoc networks, non-LOS (NLOS) environment, time-of-arrival (TOA) estimation, ultrawideband (UWB), wireless networks. I.
Biesen, “Fingerprinting localization in wireless networks based on received-signal-strength measurements: A case study on wimax networks
- IEEE Trans. Veh. Technol
, 2010
"... N.B.: When citing this work, cite the original article. ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to ..."
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Cited by 11 (2 self)
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N.B.: When citing this work, cite the original article. ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Sethares, “Distance Estimation Using Bidirectional Communications Without Synchronous Clocking
"... A fundamental problem when locating sensors in a network is to estimate the distance between pairs of sensors. This paper considers a variety of time-of-arrival and phase-shift approaches that use bidirectional signalling to bypass the need for accurate synchronous clocking. The measurement techniqu ..."
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Cited by 9 (2 self)
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A fundamental problem when locating sensors in a network is to estimate the distance between pairs of sensors. This paper considers a variety of time-of-arrival and phase-shift approaches that use bidirectional signalling to bypass the need for accurate synchronous clocking. The measurement techniques are simulated and analyzed to assess the accuracy of the distance estimation. The analysis demonstrates trade-offs between the accuracy of the oscillators, the accuracy of the subsequent distance estimation, and the complexity of the methods. EDICS: SEN-COLB Collaborative Signal Processing; SPC-DETC Detection, Estimation, and Demodulation. 1
Pulse Distortion Caused by Cylinder Diffraction and Its Impact on
- UWB Communications,” IEEE Trans. Veh. Tech., Resubmitted
, 2006
"... Abstract — One of the characteristics of UWB signals is pulse distortion, inherently determined by its huge bandwidth. Using cylinder model as an example, pulse distortion and its impacts on UWB system performance have been investigated. Although a lot of papers addressed the pulse distortion issue, ..."
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Cited by 5 (4 self)
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Abstract — One of the characteristics of UWB signals is pulse distortion, inherently determined by its huge bandwidth. Using cylinder model as an example, pulse distortion and its impacts on UWB system performance have been investigated. Although a lot of papers addressed the pulse distortion issue, quantifying the impacts of pulse distortion on the system performance appears to be novel. The simulation result shows that a SNR loss caused by template mismatch could reach as high as 4dB. It is also found that the range error caused by pulse distortion is much larger than the Cramer Rao Lower Bound (CRLB) and thus another source of errors fundamentally limiting the accuracies of time of arrivals (TOA) of a received signal. These results have direct applications in timing synchronization and positioning. I.
