In this paper, six low-cost pulse generator devices having sub-nanosecond transition time are analyzed and compared. Some of the possible applications for these devices are also described, along with an overview of the different approaches for sub-nanosecond pulse generation. Furthermore, the architecture and principle of operation of the realized prototypes are explained. The considered pulse generation techniques are based on logic gates, Step-Recovery Diodes, and transistors driven in the avalanche region. Some experimental results obtained by using an equivalent-time sampling oscilloscope and a spectrum analyzer are shown and discussed, providing both a time-domain and a frequency-domain characterization of the prototypes. Finally, an approach for the generation of modulated pulses in the 6-GHz band (for ultra-wideband applications) is investigated, and experimental results are provided.
This paper presents the development of a low-cost indoor ranging technique based on time-of-arrival (TOA) estimation, using short-pulse ultra-wideband (UWB) signals. The realized system includes two identical UWB transceiver devices, in which the receiver section is based on a tunnel diode detector and the pulse generation is performed by a common bipolar transistor driven in avalanche mode. An indirect measurement of the distance between the devices is obtained by measuring the frequency of the generated pulse train. A theoretical model of the system is described, and a statistical analysis is presented, including the closed-form evaluation of the Cramer-Rao lower bound (CRLB) on the distance estimation and showing the asymptotic statistical efficiency of the proposed estimators. Furthermore, the principle of operation of the realized system prototypes is described, along with some implementation issues. Finally, experimental results are shown and discussed.
This paper presents the development of a low-cost indoor ranging technique based on Time-Of-Arrival (TOA) estimation, using Short-Pulse Ultra-Wideband (UWB) signals. The realized system includes two identical UWB transceiver devices, in which the receiver section is based on a tunnel diode detector and the pulse generation is performed by a common bipolar transistor driven in avalanche mode. An indirect measurement of the distance between the devices is obtained by measuring the frequency of the generated pulse train. A theoretical model of the system is described and a statistical analysis is presented, including the evaluation of the Cramer-Rao Lower Bound (CRLB) on the distance estimation. Furthermore the principle of operation of the realized system prototypes is described, along with some implementation issues. Finally experimental results are shown and discussed.
This paper presents a distance-measuring system based on the accurate round-trip time-of-flight measurement of single Ultra-Wideband pulses, propagating between two transceiver devices. The architectures of two realized devices, referred to as master and slave, are described The master device implements the time-interval measuring function, by means of a Time-to-Digital Converter integrated circuit, while the slave acts as pulse repeater Both devices are designed for low-cost realization and low-power operations. This paper also presents and discusses some experimental results obtained from the system prototype. Finally, some numerical simulations results are shown, which could provide an explanation for the non-idealities in the observed distance-measuring behaviour of the system.
This paper presents a distance-measuring system based on the accurate round-trip time-of-flight measurement of single ultrawideband pulses propagating between two transceiver devices. The architectures of two realized devices, which are referred to as the master and the slave, are described. The master device implements the time-interval measuring function by means of a time-to-digital converter (TDC) integrated circuit, whereas the slave acts as a pulse repeater. Both devices are designed for low-cost realization and low-power operations. Furthermore, two pulse-detection modules are described based on signal-threshold and energy detection, respectively. This paper also presents and discusses some experimental results that are obtained from the system prototype. Finally, some numerical simulation results, which provide an explanation for the nonidealities in the observed distance-measuring behavior of the system, are shown.
This paper presents a research activity aimed at developing an Ultra-Wideband sensor for personnel indoor localization, based on the round trip time measurement of Ultra-Wideband pulses. An approach combining flexibility, high measurement update rate and asynchronous operation with digital processing capability has been employed in the design of the sensor. The principle of operation of the proposed sensor, the architecture of the realized in-house test bed and the experimental setup are described and discussed.
The application of TDCs to wireless distance measurement problems is evaluated by means of experimental tests using a realized system. The system is capable of measuring the round-trip-time of ultra-wideband radio pulses propagating between two active transceivers, utilizing a commercial TDC with sub-nanosecond resolution. The results show an operational range of approximately 30 m in an indoor environment, with a distance-measurement error of less than 0.5 m in approximately 90% of the considered cases. Further, a discussion of the fundamental error sources is provided, analyzing the effect of RF interference, timing jitter, received signal strength, and propagation conditions.
This paper presents research to develop an ultrawideband ranging sensor for personnel indoor localization based on the measurement of the pulse round-trip time. An approach combining flexibility, a high measurement update rate, and asynchronous operation with digital processing capability has been employed in the design of the sensor. The principle of operation, the architecture of the realized sensor, and the experimental setup are described. Finally, the results of a ranging calibration and validation test are presented and discussed. In the validation procedure, a root-mean-square error of 29 cm and a maximum absolute error of 81 cm with an operational range of approximately 10 m were observed.
In this paper, we present a modular test bed for ultra wideband ranging. The test bed comprises a 6.5 GHz radio front end interfacing with a baseband pulse transceiver and round-trip-time measurement module and with a flexible digital control and processing platform. The proposed radio front end allows to reduce antenna size and interference from narrowband users, with respect to the baseband pulse transceiver. We provide experimental characterization results, therefore proving the concept for the proposed front end architecture in the context of the considered UWB test bed.
This paper presents the architecture of a test bed for indoor localization based on pulse Ultra-Wideband radio technology, mainly considering the localization of first responders as a target application. A modular design approach has been employed, therefore enabling comparison of different solutions and implementation of sensor fusion techniques for localization. The realized test bed provides range estimates based on the round-trip time of radio pulses, which is accurately measured by a time-to-digital converter without the need for nano-second-level clock synchronization. Furthermore, support for digital control and processing of the acquired raw data is provided by a field programmable gate array, allowing for flexibility and reconfigurability. Results of a preliminary characterization of the test bed are presented.
This paper presents an impulse-radio UWB experimental platform for ranging and positioning in GNSS-challenged environments. The platform is based on the two-way time-of-arrival principle of operation, which reduces architecture complexity and relaxes the synchronization requirements with respect to time-of-arrival or time-difference-of-arrival solutions. The modular architecture of the platform is described together with the design and features of its main components, namely the 5.6-GHz RF front end and the baseband module for measurement and processing. A set of experimental results obtained using the realized platform in an indoor office environment is presented and discussed. The platform provides a maximum range of about 30 m in line-of-sight conditions with an RMSE of the order of 40 cm.
To overcome the limitations of specific positioning techniques for mobile wireless nodes and achieve a high accuracy, the fusion of heterogeneous sensor information is an appealing strategy. In this paper, the problem of optimal fusion of ranging information typically provided by Ultra-Wideband radio with speed and absolute orientation information is addressed. A new distributed recursive estimation method is proposed. The method does not assume any motion model of mobile nodes and is based on a Pareto optimization. The challenging part of the new estimator is the characterization of the statistical information needed to model the optimization problem. The proposed estimator is validated by Monte Carlo simulations, and the performance is compared to several Kalman-based filters commonly employed for localization and sensor fusion. Much better performance is achieved, but at the price of an increased computational complexity.
Accurate estimation of the position of network nodes is essential, e.g., in localization, geographic routing, and vehicular networks. Unfortunately, typical positioning techniques based on ranging or on velocity and angular measurements are inherently limited. To overcome the limitations of specific positioning techniques, the fusion of multiple and heterogeneous sensor information is an appealing strategy. In this paper, we investigate the fundamental performance of linear fusion of multiple measurements of the position of mobile nodes, and propose a new distributed recursive position estimator. The Cramer-Rao lower bounds for the parametric and a-posteriori cases are investigated. The proposed estimator combines information coming from ranging, speed, and angular measurements, which is jointly fused by a Pareto optimization problem where the mean and the variance of the localization error are simultaneously minimized. A distinguished feature of the method is that it assumes a very simple dynamical model of the mobility and therefore it is applicable to a large number of scenarios providing good performance. The main challenge is the characterization of the statistical information needed to model the Fisher information matrix and the Pareto optimization problem. The proposed analysis is validated by Monte Carlo simulations, and the performance is compared to several Kalman-based filters, commonly employed for localization and sensor fusion. Simulation results show that the proposed estimator outperforms the traditional approaches that are based on the extended Kalman filter when no assumption on the model of motion is used. In such a scenario, better performance is achieved by the proposed method, but at the price of an increased computational complexity.
Accurate distributed estimation of the position of network nodes is essential formany applications, including localization, geographic routing, and vehicular networks. When nodes are mobile and their mobility pattern is unknown, there are not yet adequate techniques to achieve high accuracy and low estimation errors. In this paper, a new distributed estimator of the position of mobile nodes is proposed. No model of the mobility is assumed. The estimator combines heterogeneous information coming from pre-existing ranging, speed, and angular measurements, which is jointly fused by an optimization problem where the squared mean and variance of the localization error is minimized. Challenges of this optimization are the characterization of the moments of the noises that affect the measurements. The estimator is distributed in that it requires only local processing and communication among the nodes of the network. Numerical results show that the proposed estimator outperforms traditionalapproaches based on the extended Kalman filter.
The main purpose of this paper is to present a metrology-based view of the image quality assessment (IQA) field. Three main topics are developed. First, the state of the art in the field of IQA is presented, providing a classification of some of the most important objective and subjective IQA methods. Then, some aspects of the field are analyzed from a metrological point of view, also through a comparison with the software quality measurement area. In particular, a statistical approach to the evaluation of the uncertainty for IQA objective methods is presented, and the topic of measurement modeling for subjective IQA methods is analyzed. Finally, a vector approach for full-reference IQA is discussed, with applications to images corrupted by impulse and Gaussian noise. For these applications, the vector root mean squared error (VRMSE) and fuzzy VRMSE are introduced. These vector parameters provide a possible way to overcome the main limitations of the mean-squared-error-based IQA methods.
This paper presents the state of the art in the field of Image Quality Assessment (IQA), providing a classification of some of the most important objective and subjective IQA methods. Furthermore, some aspects of the field are analysed from a metrological point of view, also through comparison with the software quality measurement area. In particular a statistical approach to the evaluation of the uncertainty for IQA objective methods is presented and an example is provided. The topic of measurement modelling for subjective IQA methods is also analysed. Finally, a case study of images corrupted by impulse noise is discussed.
In this paper, a research activity aimed at developing an indoor positioning system is presented. The realized system prototype uses sensor fusion techniques to combine information from two sources: a local Ultra-Wideband (UWB) radio based distance-measuring system infrastructure and an Inertial Navigation System (INS). The UWB system provides a measure of distance between two transceivers by measuring the time-of-flight of pulses. Its principle of operation is briefly described, together with the main features of its architecture. Furthermore, the main characteristics of the INS and of the Extended Kalman Filter information fusion approach are presented. Finally, some experimental results are provided, relative to static and dynamic position measurements.
A research study aimed at developing a novel indoor positioning system is presented. The realized system prototype uses sensor fusion techniques to combine information from two sources: an in-house developed local Ultra-Wideband (UWB) radio-based ranging system and an inertial navigation system (INS). The UWB system measures the distance between two transceivers by recording the round-trip-time (RTT) of UWB radio pulses. Its principle of operation is briefly described, together with the main design features. Furthermore, the main characteristics of the INS and of the Extended Kalman Filter information fusion approach are presented. Finally, selected static and dynamic test scenario experimental results are provided. In particular, the advantages of the proposed information fusion approach are further investigated by means of a high dynamic test scenario.
This paper proposes a power estimation methodology which presents low complexity when implemented in hardware. Power estimation is done in digital and the radio signals are digitized using a 1-bit quantizer. An algorithm to estimate power is proposed. Power estimation of the signal is done while varying the threshold of the 1-bit quantizer. It is also shown that the proposed architecture can be used to estimate power of wideband radio channels.
In this paper we have proposed a technique for cooperative localization where localization is done in distributive fashion without using any additional broadcast by nodes. The method relies on a fixed scheduled ultra-wideband (UWB) pulse transmissions by nodes in a predetermined way. The advantages of the proposed method is simpler hardware, comparatively less pulse transmission in the system hence energy efficient and faster update rate.
In this letter we develop a solution for decentralized localization of transceiving nodes in wireless networks. By exploiting a common transmission schedule, this is achieved without any additional communication and dispels the need for synchronized nodes. We derive the Cramer-Rao bounds for the solution and formulate two practical estimators for localization. Finally, the solution and estimators are tested in numerical experiments.
The difficulties and possibilities connected to indoor positioning suggest using several sources of navigational information. Apart from the signal processing of the individual sources this gives rise to the need for information fusion. This article aims at presenting and describing the signal processing methods and issues faced when constructing a navigation system based on a local ultra wide band (UWB) ranging system and an inertial navigation system (INS). The signal processing methods within the individual systems are described together with techniques for fusing the information from them. Finally, filtering results of experimental data is presented with expected convergence properties and positioning accuracy of below ±4 cm.
In a motorized vehicle a number of easily measurable signals with frequency components related to the rotational speed of the engine can be found, e.g., vibrations, electrical system voltage level, and ambient sound. These signals could potentially be used to estimate the speed and related states of the vehicle. Unfortunately, such estimates would typically require the relations (scale factors) between the frequency components and the speed for different gears to be known. Consequently, in this article we look at the problem of estimating these gear scale factors from training data consisting only of speed measurements and measurements of the signal in question. The estimation problem is formulated as a maximum likelihood estimation problem and heuristics is used to find initial values for a numerical evaluation of the estimator. Finally, a measurement campaign is conducted and the functionality of the estimation method is verified on real data.
A full-reference method for objective assessment of image quality is presented. The approach aims at achieving an accurate characterization of the behavior of noise-reduction filters for color digital pictures. The proposed technique consists in the evaluation of a vector error whose components take into account key features such as noise cancellation and detail preservation affecting the luminance and chroma information of the image. Application examples dealing with different kinds of noise distributions are discussed. Results of computer simulations show that the proposed approach can be used to validate techniques for image denoising without the limitations of scalar image quality measurements and without resorting to visual inspection.
A method for adaptively setting the threshold of an energy detector for Ultra-Wideband radio systems is presented in this paper. The method, which is suitable for low-complexity and low-cost implementation, is based on the estimation of the input noise and interference power. Simulations and experimental results obtained from a prototype UWB system show that the proposed method can adaptively set the threshold of the detector. Therefore it is robust to changes in the interference power, and it can limit the false alarm rate.
There are several practical challenges in designing an ultra wideband (UWB) device for communication. From the physical layer perspective, signaling technique should be optimally designed to work in synergy with the underneath hardware to achieve maximum performance. In this paper we propose a new cost effective hardware architecture for UWB communication and propose a variant of pulse position modulation (PPM) method which achieves maximum bit rate under the practical constraints imposed by UWB hardware.
In this paper, we consider the schedule-based network localization concept, which does not requiresynchronization among nodes and does not involve communication overhead. The concept makesuse of a common transmission sequence, which enables each node to perform self-localization andto localize the entire network, based on noisy propagation-time measurements. We formulate theschedule-based localization problem as an estimation problem in a Bayesian framework. This pro-vides robustness with respect to uncertainty in such system parameters as anchor locations and timing devices. Moreover, we derive a sequential approximate maximum a posteriori (AMAP) estimator.The estimator is fully decentralized and copes with varying noise levels. By studying the fundamentalconstraints given by the considered measurement model, we provide a system design methodology which enables a scalable solution. Finally, we evaluate the performance of the proposed AMAPestimator by numerical simulations emulating an impulse-radio ultra-wideband (IR-UWB) wireless network.
We investigate a wireless network localization scenario in which the need for synchronized nodes is avoided. It consists of a set of fixed anchor nodes transmitting according to a given sequence and a self-localizing receiver node. The setup can accommodate additional nodes with unknown positions participating in the sequence. We propose a localization method which is robust with respect to uncertainty of the anchor positions and other system parameters. Further, we investigate the Cramer-Rao bound for the considered problem and show through numerical simulations that the proposed method attains the bound.
Pedestrian Dead-Reckoning (PDR) and Radio Frequency (RF) ranging/positioning are complementary techniques for position estimation but they usually locate different points in the body (RF in the head/hand and PDR in the foot). We propose to fuse the information from both navigation points using a constraint filter with an upper bound in the distance between the estimated positions of both sensors.