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Selected Topics in Signal Processing, IEEE Journal of

Issue 5 • Date Oct. 2009

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Displaying Results 1 - 19 of 19
  • Table of contents

    Page(s): C1 - C4
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  • IEEE Journal of Selected Topics in Signal Processing publication information

    Page(s): C2
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    Freely Available from IEEE
  • Introduction to the Issue on Advanced Signal Processing for GNSS and Robust Navigation

    Page(s): 737 - 739
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  • A Fast Satellite Selection Algorithm: Beyond Four Satellites

    Page(s): 740 - 747
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1010 KB) |  | HTML iconHTML  

    Satellite selection is an important executive logic to prevent unnecessary navigation signals in the first place for Global Positioning System (GPS) receivers with limited number of channels and real-time processing power, such as those used in mobile phones, cars, and space crafts. In this paper, we propose a fast satellite selection algorithm to select more than four satellites based on the optimal geometries, which can obtain the smallest geometric dilution of precision (GDOP) values. The main idea of this fast algorithm is to select a subset of all satellites in view whose geometry is the most similar to the optimal geometry. Computer simulation shows that the consumed time of this algorithm is very close to that of the quasi-optimal satellite selection algorithm and obviously lower than that of the traditional optimal satellite selection algorithm to minimize GDOP factor, but the increased GDOP values relative to the minimal GDOP values are much smaller than those of the quasi-optimal satellite selection algorithm. View full abstract»

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  • Criteria to Improve Time-Delay Estimation of Spread Spectrum Signals in Satellite Positioning

    Page(s): 748 - 763
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    Positioning accuracy in satellite navigation systems depends on time-delay estimation (TDE) between satellite transmitted codes and local receiver replicas. This paper explores the fundamental limits of TDE accuracy of spread spectrum signals making use of estimation theory. In particular, this contribution derives some criteria to improve positioning accuracy in the additive white Gaussian noise (multipath-free) scenario, focusing on the (satellite) transmitter side of a direct sequence spread spectrum (DS-SS) system. Three different solutions based on the minimization of the variance of the TDE are presented. The first method derives a design criterion for the shaping pulse format. The second approach outlines a method to design binary pseudorandom spreading sequences. The third solution considers a joint shaping pulse-spreading code optimization to derive band-limited, non-binary spreading waveforms. Performance of the proposed solutions is compared with that of existing DS-SS signals for current satellite positioning systems. Possible countermeasures to the effects of multipath propagation are also discussed. View full abstract»

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  • A Nonlinear Filtering Approach for Robust Multi-GNSS RTK Positioning in Presence of Multipath and Ionospheric Delays

    Page(s): 764 - 776
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1053 KB) |  | HTML iconHTML  

    In this paper, we develop a new approach of precise positioning using three carrier phase multi-Global Navigation Satellite System (GNSS) measurements in presence of multipath and ionospheric delays. We propose a new nonlinear filter to estimate the user position as well as all the unknown parameters including the integer ambiguities and the ionospheric errors. First, we use a kernel representation of the conditional density and apply a local linearization which yields a Kalman-like correction enhancing the particle filter correction. This new particle Kalman filter approach, is designed to be efficient for the non-Gaussian state and nonlinear measurements model, reduces the number of needed particles, and reduces the risk of divergence. The proposed procedure for multifrequency ambiguity resolution is based on four steps: 1) at each epoch, we compute the float solution adaptively to the dynamic environment by minimizing the noise level and estimating the ionospheric errors using the proposed robust Bayesian particle Kalman filter (RobPKF); 2) we introduce a new carrier phase multipath indicator and use it to derive a related constraint to reject integers candidates that are affected by multipath errors; 3) we apply the LAMBDA method to search the integer ambiguities; and finally 4) validate the fixed solution using a statistical test. We show in this work that the efficient integration of multifrequency/multisystem carriers provides more redundancy in the measurements and better observability for multipath and ionospheric errors estimation for long-baseline RTK positioning. A major advantage of this method is that it is independent of frequencies choice and therefore can be applied for any multi-GNSS measurements (e.g., Global Positioning System (GPS), Galileo, and their combination). Real-time and postprocessing test results show the effectiveness of the developed overall real-time kinematic (RTK) software. View full abstract»

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  • Augmentation of XNAV System to an Ultraviolet Sensor-Based Satellite Navigation System

    Page(s): 777 - 785
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (767 KB) |  | HTML iconHTML  

    X-ray pulsar-based navigation (XNAV) using one X-ray detector is investigated as an augmentation to the capability of an ultraviolet (UV) sensor-based satellite autonomous navigation system. The satellite state dynamics are analyzed to establish the dynamical equations of the satellite autonomous navigation system. A time transformation equation that accounts for relativistic effects is presented and the measurement model of the XNAV system is derived using pulse phase information from only one pulsar. The measurement model of the UV sensor-based satellite navigation system is presented using the Earth image information from the UV sensor. In order to integrate the measurements from the X-ray sensor and the UV sensor, a federated filter is developed to provide the optimal simultaneous estimation of position and velocity of the satellite. The concept is demonstrated on a GPS orbit and a geosynchronous orbit and it is found that the performance of the integrated satellite navigation system is improved with respect to that of the UV sensor-based satellite navigation system. View full abstract»

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  • Use of Deeply Integrated GPS/INS Architecture and Laser Scanners for the Identification of Multipath Reflections in Urban Environments

    Page(s): 786 - 797
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2118 KB) |  | HTML iconHTML  

    This paper investigates the constructive use of multipath reflections of Global Positioning System (GPS) signals for navigation in urban environments. Urban navigation applications are generally characterized by a significant presence of multipath signals. In order to maintain reliable and accurate navigation capabilities, it is critical to distinguish between direct signal and multipath. At the same time, multipath reflections can be exploited as additional measurements for those cases where the number of direct path satellites is insufficient to compute the navigation solution. The paper develops a method for the identification of multipath reflections in received satellite signals: i.e., multipath is separated from direct signal and a line-of-site between the GPS receiver and a multipath reflecting object is determined. Once multipath reflections are identified, they can be used constructively for navigation. The method presented in the paper exploits an open-loop batch-processing GPS receiver, laser scanner and inertial navigation system (INS) to identify multipath reflections in received satellite signals. Experimental GPS, inertial and laser scanner data collected in real urban environments are applied to demonstrate identification of multipath reflections. View full abstract»

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  • Fusing GNSS, Dead-Reckoning, and Enhanced Maps for Road Vehicle Lane-Level Navigation

    Page(s): 798 - 809
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    Nowadays, it is common that road vehicle navigation systems employ maps to represent the vehicle positions in a local reference. The most usual process to do that consists in the estimation of the vehicle positioning by fusing the Global Navigation Satellite System (GNSS) and some other aiding sensors data, and the subsequent projection of these values on the map by applying map-matching techniques. However, it is possible to benefit from map information also during the process of fusing data for positioning. This paper presents an algorithm for lane-level road vehicle navigation that integrates GNSS, dead-reckoning (odometry and gyro), and map data in the fusion process. Additionally, the proposed method brings some benefits for map-matching at lane level because, on the one hand, it allows the tracking of multiple hypothesis and on the other hand, it provides probability values of lane occupancy for each candidate segment. To do this, a new paradigm that describes lanes as piece-wise sets of clothoids was applied in the elaboration of an enhanced map (Emap). Experimental results in real complex scenarios with multiple lanes show the suitability of the proposed algorithm for the problem under consideration, presenting better results than some state-of-the-art methods of the literature. View full abstract»

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  • Interference Mitigation in a Repeater and Pseudolite Indoor Positioning System

    Page(s): 810 - 820
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    The widespread use of the personal navigation devices makes indoor positioning a major technological issue. The development perspectives of location-based services dramatically increase the importance of developing adequate solutions. In this paper, we carry out a theoretical study of an indoor positioning technique based on time-delayed Global Navigation Satellite Systems (GNSS) repeaters. It is a simple solution deploying minimal infrastructure which can use either outdoor repeated Global Positioning System (GPS) signals or a single signal generator. However, the positioning method presents limitations in terms of correlation and tracking performances. The paper presents theoretical approaches in order to overcome the interference problems and to improve the quality of the GPS signal reception. The new system based on ldquorepealitesrdquo (that comes from repeater and pseudolite) makes the best use of repeater and pseudolites in order to allow a fair continuity of the GNSS service indoors. View full abstract»

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  • Robust Indoor Positioning Provided by Real-Time RSSI Values in Unmodified WLAN Networks

    Page(s): 821 - 831
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    The positioning methods based on received signal strength (RSS) measurements, link the RSS values to the position of the mobile station(MS) to be located. Their accuracy depends on the suitability of the propagation models used for the actual propagation conditions. In indoor wireless networks, these propagation conditions are very difficult to predict due to the unwieldy and dynamic nature of the RSS. In this paper, we present a novel method which dynamically estimates the propagation models that best fit the propagation environments, by using only RSS measurements obtained in real time. This method is based on maximizing compatibility of the MS to access points (AP) distance estimates. Once the propagation models are estimated in real time, it is possible to accurately determine the distance between the MS and each AP. By means of these distance estimates, the location of the MS can be obtained by trilateration. The method proposed coupled with simulations and measurements in a real indoor environment, demonstrates its feasibility and suitability, since it outperforms conventional RSS-based indoor location methods without using any radio map information nor a calibration stage. View full abstract»

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  • High-Precision Robust Broadband Ultrasonic Location and Orientation Estimation

    Page(s): 832 - 844
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    This paper presents an indoor broadband ultrasonic system for estimation of a mobile device's 3-D location and three-axis orientation using beacons. It presents the first implementation and characterization of a real frequency hopping spread spectrum-based ultrasonic positioning system, a novel application of uniform circular array angle of arrival estimation techniques to indoor location-orientation estimation and a novel hybrid algorithm for location-orientation estimation. The performance of the system was assessed experimentally. The system has been shown to provide better accuracy, robustness to noise and multipath than other previously reported indoor ultrasonic location or orientation estimation systems with comparable range in the typical office environment tested. The prototype provided location estimates with an error of less than 1.5 cm and and error of less than 4.5deg in the yaw, 3deg in the pitch and 3.5deg in the roll, in 95% of cases. View full abstract»

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  • Multi-Channel Distance Measurement With IEEE 802.15.4 (ZigBee) Devices

    Page(s): 845 - 859
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1548 KB) |  | HTML iconHTML  

    The addition of positioning capabilities to low-cost communications such as IEEE 802.15.4 compliant (ZigBee) networks can open up interesting markets, in particular if existing hardware and standard communications packets can be used for this purpose. High-precision localization requires large transmission bandwidths and thus the use of multiple frequency-channels. In the presence of oscillator frequency uncertainty the coherent synthesis of individual measurements poses a challenge. This paper proposes a particular frequency-hopping and signal processing scheme by which most transmitter and receiver frequency-errors can be eliminated in signal processing. Measurements show that high precision distance estimation with errors down to a few cm can be achieved. View full abstract»

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  • RSSI-Based Indoor Localization and Tracking Using Sigma-Point Kalman Smoothers

    Page(s): 860 - 873
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1369 KB) |  | HTML iconHTML  

    Solutions for indoor tracking and localization have become more critical with recent advancement in context and location-aware technologies. The accuracy of explicit positioning sensors such as global positioning system (GPS) is often limited for indoor environments. In this paper, we evaluate the feasibility of building an indoor location tracking system that is cost effective for large scale deployments, can operate over existing Wi-Fi networks, and can provide flexibility to accommodate new sensor observations as they become available. This paper proposes a sigma-point Kalman smoother (SPKS)-based location and tracking algorithm as a superior alternative for indoor positioning. The proposed SPKS fuses a dynamic model of human walking with a number of low-cost sensor observations to track 2-D position and velocity. Available sensors include Wi-Fi received signal strength indication (RSSI), binary infra-red (IR) motion sensors, and binary foot-switches. Wi-Fi signal strength is measured using a receiver tag developed by Ekahau, Inc. The performance of the proposed algorithm is compared with a commercially available positioning engine, also developed by Ekahau, Inc. The superior accuracy of our approach over a number of trials is demonstrated. View full abstract»

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  • Joint Particle Filter and UKF Position Tracking in Severe Non-Line-of-Sight Situations

    Page(s): 874 - 888
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    The performance of localization techniques in a wireless communication system is severely impaired by biases induced in the range and angle measures because of the non-line-of-sight (NLOS) situation, caused by obstacles in the transmitted signal path. However, the knowledge of the line-of-sight (LOS) or NLOS situation for each measure can improve the final accuracy. This paper studies the localization of mobile terminals (MT) based on a Bayesian model for the LOS-NLOS evolution. This Bayesian model does not require having a minimum number of LOS measures at each acquisition. A tracking strategy based on a particle filter (PF) and an unscented Kalman filter (UKF) is used both to estimate the LOS-NLOS situation and the MT kinetic variables (position and speed). The approach shows a remarkable reduction in positioning error and a high degree of scalability in terms of performance versus complexity. View full abstract»

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  • Robust Tracking and Geolocation for Wireless Networks in NLOS Environments

    Page(s): 889 - 901
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    We address the problem of robust tracking and geolocation using time of arrival estimates in wireless networks. Especially in urban or indoor environments and hilly terrains, these estimates are often contaminated by interference due to non-line-of-sight (NLOS) propagation. Standard techniques such as least-squares are inadequate as they lead to erroneous position estimates. We propose robust methods for tracking and geolocation based on a semi-parametric approach that does not require specification of the noise density. Unlike conventional, minimax based, robust techniques, we show that our proposed techniques are more robust as they adapt automatically to the interfering environment. Specifically, we propose a robust extended Kalman filter for tracking a mobile terminal based on robust semi-parametric estimators. Numerical studies for different network scenarios illustrate a substantial gain in performance compared to standard robust competitors. View full abstract»

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  • IEEE Journal of Selected Topics in Signal Processing Information for authors

    Page(s): 902 - 903
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    Freely Available from IEEE
  • IEEE ICIP 2010

    Page(s): 904
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    Freely Available from IEEE
  • IEEE Signal Processing Society Information

    Page(s): C3
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    Freely Available from IEEE

Aims & Scope

The Journal of Selected Topics in Signal Processing (J-STSP) solicits special issues on topics that cover the entire scope of the IEEE Signal Processing Society including the theory and application of filtering, coding, transmitting, estimating, detecting, analyzing, recognizing, synthesizing, recording, and reproducing signals by digital or analog devices or techniques.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Fernando Pereira
Instituto Superior Técnico