Ultra-wideband Localization Research Articles

NLOS identification for UWB localization based on import vector machine

Ultra-Wide Band (UWB) based localization is one of the most promising techniques for high accuracy localization. The crucial factor that aggravates the localization precision is None-Line-of-Sight (NLOS) propagation. To address this issue, we propose a novel NLOS identification algorithm with feature selection strategy and a localization algorithm based on Import Vector Machine (IVM) with high accuracy and low complexity. The feature selection strategy further meliorates the classification accuracy. The probability outputs of IVM is employed by the localization algorithm and yields higher positioning accuracy than its counterpart methods – Support Vector Machine (SVM) and Relevance Vector Machine (RVM). Simulation results prove that IVM is a robust and efficient method for NLOS identification and localization.

Comparing Digital Phase-Locked Loop and Kalman Filter for Clock Tracking in Ultrawideband Location System

For timing and synchronization system, digital phase-locked loop (DPLL) and Kalman filter all have been widely used as the clock tracking and clock correction schemes for the similar structure and properties. This paper compares the two schemes used for ultrawideband (UWB) location system. The improved Kalman filter is more immune to interference.

Calibrating Away Inaccuracies in Ultra Wideband Range Measurements: A Maximum Likelihood Approach

A calibration framework for an ultra-wideband localization system employing inertial measurement units is presented. No external motion capture system or other sensors are required for the calibration procedure. Given a covariance function for the error in the range measurements, a range measurement model based on a Gaussian process is obtained by maximizing the joint likelihood of angular rate, acceleration, and range measurements. The framework is experimentally evaluated, and it is shown how the resulting measurement model, integrated in a standard Kalman filter, can be used for real-time localization on a platform with limited computational resources. The calibration significantly improves the localization accuracy for randomly generated trajectories and different localization system setups.

Improving the Robustness of Control-Grade Ultra-Wideband Localization

Ultra-wideband based localization technologies gained more and more attention over the recent years. Most of the predominant research focusses on two-way ranging based system topologies that feature limited multi-user scalability. This work aims to improve the accuracy and robustness of a highly scalable control-grade time-difference of arrival based localization system. The specific goal addressed in this work is to improve the robustness under non-line-of-sight conditions using ultra-wideband specific signal quality assessment and inertial sensor fusion. The accuracy of the proposed method is experimentally analyzed in two experiments. One experiment evaluates the performance under best-case conditions. A second experiment introduces strong interference through moving assets. Here, an accuracy improvement of over 60 % could be achieved compared to previous results. In order to relate those results, an experimental comparison to a widely used angle of arrival capable state of the art ultra-wideband localization system is made. It could be shown that the proposed method is more accurate than the state of the art in the strong interference scenario.

Energy Autonomous UWB Localization

In the new scenarios foreseen by the Internet of Things (IoT), industrial and consumer systems will be required to detect and localize tagged items with high accuracy using cheap, energy autonomous, and disposable tags. This paper discusses system-level and circuit-level aspects to be adopted for future generation passive radio-frequency identification (RFID) tags with localization capabilities. It is argued that RFID-enabled localization strategies, combining ultra-wideband (UWB) backscattering for communication/localization purposes and UHF for “on demand” powering of battery-less tags can be successfully exploited to this purpose. The proposed architecture adopts a small number of reference nodes, acting both as UWB readers and as UHF power sources. Architectural and circuital considerations on different design choices for the UWB-RFID tag are discussed, focusing on available off-the-shelf components. Power budget constraints for UWB backscattering operation and UHF wireless powering are derived in worst-case conditions. Furthermore, the simulation results, verified with experiments, prove the feasibility of cm-level localization accuracy at distances of several meters even in indoor scenarios where multi-path fading might be present.

Comparing Ubisense, BeSpoon, and DecaWave UWB Location Systems: Indoor Performance Analysis

Most ultrawideband (UWB) location systems already proposed for position estimation have only been individually evaluated for particular scenarios. For a fair performance comparison among different solutions, a common evaluation scenario would be desirable. In this paper, we compare three commercially available UWB systems (Ubisense, BeSpoon, and DecaWave) under the same experimental conditions, in order to do a critical performance analysis. We include the characterization of the quality of the estimated tag-to-sensor distances in an indoor industrial environment. This testing space includes areas under line-of-sight (LOS) and diverse non-LOS conditions caused by the reflection, propagation, and the diffraction of the UWB radio signals across different obstacles. The study also includes the analysis of the estimated azimuth and elevation angles for the Ubisense system, which is the only one that incorporates this feature using an array antenna at each sensor. Finally, we analyze the 3-D positioning estimation performance of the three UWB systems using a Bayesian filter implemented with a particle filter and a measurement model that takes into account bad range measurements and outliers. A final conclusion is drawn about which system performs better under these industrial conditions.

Augmenting Ultra-Wideband Localization with Computer Vision for Accurate Flight

Ultra-wideband radio networks enable low-cost, low-computation robot localization in semi-structured environments; however, previous results have shown that these localization systems suffer from spatially-varying measurement biases, leading to a spatially-varying offset between the physical and the estimated position. In tasks where absolute positioning or high tracking accuracy is required, this offset can lead to failure of the task. This paper proposes augmenting ultra-wideband-based localization with visual localization to improve estimation accuracy for critical tasks. It also presents a control strategy that takes the camera measurement process into account, and allows the ultra-wideband system’s measurement biases to be learned and compensated over multiple executions of the task. This bias compensation can be used to improve the accuracy of the task in the case of visual impairment. The effectiveness of the proposed framework is demonstrated by accurately flying a quadrocopter to a landing platform using on-board estimation and control.

A Novel Biomechanical Model-Aided IMU/UWB Fusion for Magnetometer-Free Lower Body Motion Capture

The available human body inertial motion capture (MoCap) systems are aided by magnetometers to remove the drift error in yaw angle estimation, which in turn limits their application in the presence of long-lasting magnetic disturbances in indoor environments. This paper introduces a magnetometer-free algorithm for lower-body MoCap including 3-D localization and posture tracking by fusing inertial sensors with an ultrawideband (UWB) localization system and a biomechanical model of the human lower body. Using our novel Kalman filter-based fusion algorithm, the UWB localization data aided by the biomechanical model can eliminate the drift in inertial yaw angle estimation of the lower-body segments. This magnetometer-free yaw angle estimation makes the algorithm insensitive to the magnetic disturbances. The algorithm is benchmarked against the optical MoCap system for various indoor activities including walking, jogging, jumping, and stairs ascending/descending. The results show that the proposed algorithm outperforms the available magnetometer-aided algorithms in yaw angle tracking under magnetic disturbances. In a uniform magnetic field, the algorithm shows similar accuracies in localization and joint angle tracking when compared with the magnetometer-aided methods. The localization accuracy of the proposed method is better than 4.5 cm in a 3-D space and its accuracy for knee angle tracking is about 3.5° and 4.5° in low and high dynamic motions, respectively.

Numerical Investigation of an UWB Localization Technique for Unmanned Aerial Vehicles in Outdoor Scenarios

In this paper, the numerical investigation of an ultra wideband (UWB) localization technique suitable for the tracking and control of an unmanned aerial vehicle (UAV) in a specific outdoor scenario is presented. A set of UWB nodes are located on a moving/still ground station (GS) and interrogate an UWB node placed on the UAV that is flying in front of the GS. The distances between the GS-nodes and the UAV-node are estimated through a conventional two-way time-of-flight ranging method, one at a time, and then used in a multilateration algorithm. Due to the unavoidable relative motion between the UAV and the GS, the above distances are actually measured for different UAV-GS relative positions, and then, the UAV localization performance deteriorates as a function of the UAV-GS relative speed and the ranging-method processing time. An approach is here proposed to mitigate the above adverse effect, by exploiting an estimate of the UAV-GS relative speed along the GS forward direction. A preliminary numerical analysis is used to show that a decimeter order localization accuracy can be obtained for a tridimensional localization process.

High-Accuracy Tracking Using Ultrawideband Signals for Enhanced Safety of Cyclists

In this paper, an ultrawideband localization system to improve the cyclists’ safety is presented. The architectural solutions proposed consist of tags placed on bikes, whose positions have to be estimated, and anchors, acting as reference nodes, located at intersections and/or on vehicles. The peculiarities of the localization system in terms of accuracy and cost enable its adoption with enhanced risk assessment units situated on the infrastructure/vehicle, depending on the architecture chosen, as well as real-time warning to the road users. Experimental results reveal that the localization error, in both static and dynamic conditions, is below 50 cm in most of the cases.

Development and experimental evaluation of a 3D ultra-wideband localization system

Development and experimental evaluation of a 3D ultra-wideband localization system

A Gaussian mixture Bernoulli filter for extended target tracking with application to an ultra-wideband localization system

This paper presents a Gaussian mixture (GM) implementation of the Bernoulli filter for extended target tracking, which we call the extended target GM Bernoulli (ET-GM-Ber) filter. Closed form expressions for the ET-GM-Ber filter recursions are obtained. A clustering step is integrated into the measurement update stage in order to have a computationally tractable filter. Performance of the proposed filter is tested both on the simulated data and experimental data collected using an ultra-wideband (UWB) localization system. Simulations and experimental results demonstrate the accurate and effective performance of the proposed filter.

UWB-Aided Inertial Motion Capture for Lower Body 3-D Dynamic Activity and Trajectory Tracking

This paper introduces a novel method for simultaneous 3-D trajectory tracking and lower body motion capture (MoCap) under various dynamic activities such as walking and jumping. The proposed method uses wearable inertial sensors fused with an ultrawideband localization system using a cascaded Kalman filter-based sensor fusion algorithm, which consists of a separate orientation filter cascaded with a position/velocity filter. In addition, to further improve the joint angle tracking accuracy, anatomical constraints are applied to the knee joint. Currently, available self-contained inertial tracking methods are not only drift-prone over time but also their accuracy is degraded under fast movements with unstable ground contact states due to the lack of external references. However, our experimental results, which benchmark the system against a reference camera-based motion tracking system, show that the proposed fusion method can accurately capture the dynamic activities of a subject without drift. The results show that the proposed system can maintain similar accuracies between fast and slow motions in lower body MoCap and 3-D trajectory tracking. The obtained accuracies of the system for 3-D body localization and knee joint angle tracking for fast motions were less than 5 cm and 2.1°, respectively.

Experimental Investigation of 3-D Human Body Localization Using Wearable Ultra-Wideband Antennas

This paper presents experimental investigations and analysis of ultra-wideband localization of body-worn antennas in an indoor environment. Three-dimensional (3-D) tracking of wearable antennas placed on the upper human body is achieved using a compact and cost-effective antenna and time of arrival (TOA) localization techniques. Various features such as rms delay spread, kurtosis, and signal amplitude have been used to classify the channel type between each antenna location and base station. Non-line-of-sight identification and mitigation techniques have been used to enhance the accuracy of the localization technique applied. Geometric dilution of precision of the base-station configuration and numerical analysis on the radiation patterns for different locations of the body-worn antenna has been studied in terms of variation in localization accuracy. High-accuracy 3-D localization results in the range of 1–2 cm are obtained with the antennas placed on the limbs and 1–3 cm for the torso region. The accuracy achieved is 3 times better than commercially available UWB localization and tracking systems. The significantly high-accuracy results obtained for all antenna locations demonstrate the reliability and suitability of UWB technology for various indoor tracking and localization applications in the fields of healthcare, sports, and well-being.

A magnetometer-free indoor human localization based on loosely coupled IMU/UWB fusion.

The magnetic distortions in indoor environment affects the accuracy of yaw angle estimation using magnetometer. Thus, the accuracy of indoor localization based on inertial-magnetic sensors will be affected as well. To address this issue, this paper proposes a magnetometer-free solution for indoor human localization and yaw angle estimation. The proposed algorithm fuses a wearable inertial sensor consisting of MEMS-based accelerometer and gyroscope with a portable ultra-wideband (UWB) localization system in a cascaded two-step filter consisting of a tilt Kalman filter and a localization Kalman filter. By benchmarking against an optical motion capture system, the experimental results show that the proposed algorithm can accurately track position and velocity as well as the yaw angle without using magnetometer.

Harmonia

We introduce Harmonia, a new RF-based localization scheme that provides the simplicity, cost, and power advantages of traditional narrowband radios with the decimeter-scale accuracy of ultra wideband localization techniques. Harmonia is an asymmetric tag and anchor system, requiring minimal modifications to existing low-power wireless devices to support highfidelity localization with comparatively modest infrastructure costs. A prototype Harmonia design offers location estimates with an average-case error of 53.4 cm in complex, heavymultipath, indoor environments and captures location estimates at 56 Hz while requiring only 1.7 mA additional power draw for each tag and complying with all US UWB regulations. We believe this architecture's combination of accuracy, update rate, power draw, and system complexity will lead to a new point in the design space.

Assessment of the Contribution of Time Reversal on a UWB Localization System for Railway Applications

UWB radio has the potential to offer good performance in terms of localization precision. Time Reversal channel pre-filtering facilitates signal detection and also helps to increase the received energy in a targeted area. This paper assesses the quantitative and qualitative contributions of the Time Reversal (TR) technique associated with an Ultra Wideband (UWB) localization system applied to a railway odometry problem. The analytical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of the TR-UWB are given. The contribution of the TR technique associated with UWB radio to enhance the localization resolution is analysed. To perform these studies, and to be representative of the proposed railway application, a deterministic channel model is used. The analytical simulation and experimental results show that time reversal has very promising characteristics regarding its association with the UWB in terms of localization error. These results also indicate that the TR-UWB technique delivers improved performance over UWB only localization approach, that could benefit the development of the proposed railway application.

Spatial Layout, Social Structure, and Innovation in Organizations

Research on the enabling factors of innovation has most often addressed either the social component of organizations or the spatial dimensions involved in the innovation process. Few studies have examined the link from spatial layout and social networks to innovation. Social networks play important roles in structuring communication, collaboration, access to knowledge, and knowledge transformation. These processes are both antecedent to and part of the innovation process. Spatial layout structures patterns of circulation, proximity, awareness of others, and encounter in an organization. These interrelationships become fundamental to the development of social networks, especially those networks critical to the innovation process. This research explored associations between innovation within three partner organizations and the organization's social and spatial structure. The organizations included: A nonprofit life sciences institute dedicated to translational research on cancer, the research laboratories of a multinational software corporation, and the quality control group of an automobile manufacturer. The study applied spatial analysis to map and characterize physical space in conjunction with survey data capturing social contacts among researchers at the three organizations. For one partner organization, we augmented these tools with location-tracking methods. It could be argued that sociometric surveys capture the ‘perceived’ social network. Social networks researchers have been very interested in assessing ‘real’ networks either as reliability checks on sociometric survey networks, or as stand-alone networks. Our use of an ultrawideband location system allowed us to assess networks in real time. In interpreting our results, we suggest that through exposure to moving others, locations with high metric choice may provide the opportunities for serendipitous encounters among individuals who may come from disparate parts of an organization. Whereas low mean distance to others may provide the enhanced connections necessary to mobilize the resources and attention to move innovative ideas forward. Results demonstrate the salience of both social and spatial dimensions in the processes of innovation. The research suggests two strong factors that appear to influence our results: the institutional context which characterizes or prioritizes certain innovation outcomes; the extent to which the physical facility design of organizations tends to concentrate or spatially distribute the research unit. Our findings indicate that relationships between salutary network positions and beneficial locales themselves derive from institutional contexts that shape the priorities, opportunities, goals and practices of discovery. We suggest that innovation is a process that occurs at the intersection of social and physical space, and moves toward a sociospatial science of design for innovation.

Improved line‐of‐sight/non‐line‐of‐sight classification methods for pulsed ultrawideband localisation

Classification of line-of-sight (LOS) or non-LOS (NLOS) propagation is critical for most pulsed ultrawideband localisation systems. In this letter, first, the authors propose a two-dimensional (2D) LOS/NLOS classification scheme that uses skewness of the channel impulse/pulse response, which has not been used by existing work. The log-likelihood ratio of the 2D LOS/NLOS classification is used to determine the weights for localisation. Then, the authors derive an iterative Gauss-Newton method to solve the location of the target, which provides a higher accuracy than the Gauss-Newton method used in existing work. Finally, they investigate improved localisation by incorporating the statistics of NLOS bias as a result of LOS/NLOS classification into the cost function, and derive the statistics of the corresponding errors of location estimates. The proposed 2D LOS/NLOS classification scheme is compared with an existing 3D scheme to demonstrate its effectiveness.

A New RWLS Positioning Method Basing on Distance Information

In ultra-wideband (UWB) localization, the ranging precision will determine the localization performance directly. However not all the range measurements(RMs) have the same precision. In this paper, we propose a new weighted least square(WLS) positioning method, which will design the weighted values of each RM according to its reliability. We show the ranging reliability is closely related to the distance between the mobile station(MS) and anchor nodes(ANs). Moreover, if design each weighted value fusing distance with non-line-of-sight(NLOS) identification result, the localization performance will be enhanced. Simulation results show our method performs better than those commonly used WLS methods.