124 research outputs found
A Time-based Passive Source Localization System for Narrow-band Signal
Time-based indoor localization has been investigated for several years but the accuracy of existing solutions is limited by several factors, e.g., imperfect synchronization, signal bandwidth and indoor environment. In this paper, we compare two time-based localization algorithms for narrow-band signals, i.e., multilateration and fingerprinting. First, we develop a new Linear Least Square (LLS) algorithm for Differential Time Difference Of Arrival (DTDOA). Second, fingerprinting is among the most successful approaches used for indoor localization and typically relies on the collection of measurements on signal strength over the area of interest. We propose an alternative by constructing fingerprints of fine-grained time information of the radio signal. We offer comprehensive analytical discussions on the feasibility of the approaches, which are backed up by evaluations in a software defined radio based IEEE 802.15.4 testbed. Our work contributes to research on localization with narrow-band signals. The results show that our proposed DTDOA-based LLS algorithm obviously improves the localization accuracy compared to traditional TDOA-based LLS algorithm but the accuracy is still limited because of the complex indoor environment. Furthermore, we show that time-based fingerprinting is a promising alternative to power-based fingerprinting
A Survey of Positioning Systems Using Visible LED Lights
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe
A Differential Positioning System Using Modulation Correlation of Signals of Opportunity
Global Navigation Satellite Systems (GNSS) have become the positioning systems of choice for many applications. However, GNSS signals are susceptible to obstruction, interference and jamming. Therefore, to maximize robustness and integrity, it is necessary to employ a dissimilar positioning technology that can operate independently and back-up GNSS. One such technology exploits âsignals of opportunityâ â signals that are designed for purposes other than navigation. This paper presents a system that uses amplitude modulation (AM) radio broadcasts in the medium frequency (MF) band. At these frequencies, the predominant ground-wave propagation mode offers better coverage in remote areas and over sea than is achievable with higher frequency signals. The system is differential and operates by correlating modulation information between the reference and user receivers. A system of this form mitigates the deterioration in and around buildings encountered in prior systems and can provide absolute position using fewer signals than a system using only carrier phase. The system presented in this paper uses generalized cross correlation to obtain time difference of arrival measurements that are subsequently used for position determination. Preliminary results indicate the system provides a robust position solution. Moreover, the system offers the potential to be combined with carrier phase measurements to achieve enhanced performance, while the modulation correlation technique is readily extendable to other types of signal
Wireless Positioning Applications in Multipath Environments
Funklokalisierung in der Umgebung mit der Mehrwegeausbreitung
In den vergangenen Jahren wurde zunehmend Forschung im Bereich drahtlose Sensornetzwerk (engl. âWireless Sensor Networkâ) betrieben. Lokalisierung im Innenraum ist ein vielversprechendes Forschungsthema, das in den Literaturen vielfĂ€ltig diskutiert wird. Jedoch berĂŒcksichtigen die meisten Arbeiten einen wichtigen Faktor nicht, nĂ€mlich die Mehrwegeausbreitung, welche die Genauigkeit der Lokalisierung beeinflusst. Diese Arbeit bezieht sich auf Lokalisierungsanwendungen in UWB (Ultra-Breitband-Technologie)- und WLAN (drahtloses lokales Netzwerk)- Systemen im Fall von Mehrwegeausbreitung. Zur Steigerung der Robustheit der Lokalisierungsanwendungen bei Mehrwegeausbreitung wurden neuartige Lokalisierungsalgorithmen, die auf der Auswertung der Ankunftszeit (engl. âTime of Arrivalâ, ToA), der empfangenen SignalstĂ€rke (engl. âReceived Signal Strengthâ, RSS) und dem Einfallswinkel (engl. âAngle of Arrivalâ, AoA) basieren, vorgestellt und untersucht. Bei Mehrwegeausbreitung ist die Fragen den direkten Pfad zu lösen, da der direkte Pfad (engl. âDirect Pathâ, DP) schwĂ€cher als anderer Pfad sein kann. In dieser Arbeit werden daher neuartige Algorithmen zur Flankendetektion der empfangenen Signale fĂŒr UWB Systeme entwickelt, um die Positionsbestimmung zu verbessern: Es gibt die kooperative Flankendetektion (engl. âJoint Leading Edge Detectionâ, JLED), die
erweiterte maximalwahrscheinlichkeitbasierte KanalschĂ€tzung (engl. âImproved Maximum Likelihood Channel Estimationâ, IMLCE) und die Flankendetektion mit untervektorraumbasiertem Verfahren (engl. âSubspace based Approachesâ, SbA). Bei der kooperativen Flankendetektion werden zwei Kriterien herangezogen nĂ€mlich
die minimale FlĂ€che und das minimale mittlere Quadrat des SchĂ€tzfehlers (engl. âMinimum Mean Squared Errorâ, MMSE). Weiterhin wird ein monopulsbasierter KanalschĂ€tzer (engl. âMonopulse based Channel Estimatorâ, MCE) entwickelt, um die möglicherweise falsche Kombinationen der Flanken (engl. âLeading Edge Combinationâ, LEC) auszuschlieĂen. Zudem wird in der Arbeit der erweiterte MLCE
vorgestellt, der aus einem groben und einem genauen SchĂ€tzungsschritt besteht. Bei dem neuartigen untervektorraumbasierten Verfahren werden ein statischer und ein Schwundkanal untersucht. Im ersten Fall wird die Kombination der RĂŒckwĂ€rtssuchalgorithmus mit untervektorraumbasierten Verfahren untersucht. Zudem wird im zweiten Fall ein untervektorraumbasierte Verfahren im Frequenzbereich vorgestellt. FĂŒr die RSS-basierte Lokalisierung wird ein Fingerabdruckverfahren (engl. âFingerprint Approachâ) und ein neuartiger EntfernungsschĂ€tzer basierend auf der
Kanalenergie entwickelt und implementiert. SchlieĂlich wird in der Arbeit ein Lokalisierungssystem mit WinkelschĂ€tzern inklusive einer entsprechenden Kalibrierung auf einer 802.11a/g Hardwareplattform
vorgestellt. Dazu wird ein neuartiger TrÀgerschÀtzer und KanalschÀtzer entwickelt.In the past several years there has been more growing research on Wireless Sensor Network (WSN). The indoor localization is a promising research topic, which is discussed variously in some literatures. However, the most work does not consider an important factor, i.e. the multi-path propagation, which affects the accuracy of the indoor localization. This work dealt with the indoor localization applied in UWB (Ultra Wide Band) and WLAN (Wireless Local Area Network) systems in the case of
multi-path propagation.
To improve the robustness of the applications of localization in the case of multi-path propagation, novel localization algorithms based on the evaluation of the Time of Arrival (ToA), the Received Signal Strength (RSS) and the Angle of Arrival (AoA) were proposed and investigated. In the ToA based localization systems, the detection of shortest signal propagation time plays a critical role. In the case of multi-path
propagation, the Direct Path (DP) needs to be resolved because the DP may be weaker than Multi Path Components (MPC). Thus the novel algorithms for leading edge detection were developed in this work in order to improve the accuracy of localization, namely Joint Leading Edge Detection (JLED), Improved Maximum Likelihood Channel Estimation (IMLCE) and the leading edge detection with Subspace based
Approaches (SbA).
Two criteria were proposed and referenced for the JLED, namely Minimum Area (MA) and Minimum Mean Squared Error (MMSE). Furthermore, a monocycle-based channel estimator was developed to mitigate the fake LECs (Leading Edge Combination). The estimation error of JLED was theoretically analyzed and simulated for evaluation of the estimator. IMLCE consists of a coarse and a fine estimation step.
The coarse position of the first correlation peak shall be found with the Search Back Algorithms (SBA), which is followed by MLCE-algorithms.
The novel SbA was investigated in a static and a fading channel. In the former case, the iterative algorithm, which combines SbA with SBA, was investigated. In the latter case, the FD-SbA (Frequency Domain - SbA) was proposed, which requires to calculate the covariance matrix in the FD.
For the RSS based localization, fingerprint approach and the novel channel energy based distance estimator were investigated and developed in this dissertation.
Finally, a localization system using AoA estimation and the initial calibration was presented on an 802.11a/g hardware platform. A novel Carrier Frequency Offset (CFO) estimator and channel estimator were investigated and developed. The measurement campaigns were made for one, two and four fixed stations, respectivel
Realization Limits of Impulse-Radio UWB Indoor Localization Systems
In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them
Algorithms for propagation-aware underwater ranging and localization
MenciĂłn Internacional en el tĂtulo de doctorWhile oceans occupy most of our planet, their exploration and conservation are one of
the crucial research problems of modern time. Underwater localization stands among the
key issues on the way to the proper inspection and monitoring of this significant part of our
world. In this thesis, we investigate and tackle different challenges related to underwater
ranging and localization. In particular, we focus on algorithms that consider underwater
acoustic channel properties. This group of algorithms utilizes additional information
about the environment and its impact on acoustic signal propagation, in order to improve
the accuracy of location estimates, or to achieve a reduced complexity, or a reduced
amount of resources (e.g., anchor nodes) compared to traditional algorithms.
First, we tackle the problem of passive range estimation using the differences in the
times of arrival of multipath replicas of a transmitted acoustic signal. This is a costand
energy- effective algorithm that can be used for the localization of autonomous
underwater vehicles (AUVs), and utilizes information about signal propagation. We study
the accuracy of this method in the simplified case of constant sound speed profile (SSP)
and compare it to a more realistic case with various non-constant SSP. We also propose
an auxiliary quantity called effective sound speed. This quantity, when modeling acoustic
propagation via ray models, takes into account the difference between rectilinear and
non-rectilinear sound ray paths. According to our evaluation, this offers improved range
estimation results with respect to standard algorithms that consider the actual value of
the speed of sound.
We then propose an algorithm suitable for the non-invasive tracking of AUVs or
vocalizing marine animals, using only a single receiver. This algorithm evaluates the
underwater acoustic channel impulse response differences induced by a diverse sea
bottom profile, and proposes a computationally- and energy-efficient solution for passive
localization.
Finally, we propose another algorithm to solve the issue of 3D acoustic localization
and tracking of marine fauna. To reach the expected degree of accuracy, more sensors
are often required than are available in typical commercial off-the-shelf (COTS) phased
arrays found, e.g., in ultra short baseline (USBL) systems. Direct combination of multiple
COTS arrays may be constrained by array body elements, and lead to breaking the optimal array element spacing, or the desired array layout. Thus, the application of
state-of-the-art direction of arrival (DoA) estimation algorithms may not be possible. We
propose a solution for passive 3D localization and tracking using a wideband acoustic
array of arbitrary shape, and validate the algorithm in multiple experiments, involving
both active and passive targets.Part of the research in this thesis has been supported by the EU H2020 program under
project SYMBIOSIS (G.A. no. 773753).This work has been supported by IMDEA Networks InstitutePrograma de Doctorado en IngenierĂa TelemĂĄtica por la Universidad Carlos III de MadridPresidente: Paul Daniel Mitchell.- Secretario: Antonio FernĂĄndez Anta.- Vocal: Santiago Zazo Bell
A Linear Subspace Approach to Burst Communication Signal Processing
This dissertation focuses on the topic of burst signal communications in a high interference environment. It derives new signal processing algorithms from a mathematical linear subspace approach instead of the common stationary or cyclostationary approach. The research developed new algorithms that have well-known optimality criteria associated with them. The investigation demonstrated a unique class of multisensor filters having a lower mean square error than all other known filters, a maximum likelihood time difference of arrival estimator that outperformed previously optimal estimators, and a signal presence detector having a selectivity unparalleled in burst interference environments. It was further shown that these improvements resulted in a greater ability to communicate, to locate electronic transmitters, and to mitigate the effects of a growing interference environment
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