A compact system of direction finding has been developed for the past three years which operates on a set of seven collocated H.F. active antennas. It has been shown that the estimation of the direction of arrival can...
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ISBN:
(纸本)0780363396
A compact system of direction finding has been developed for the past three years which operates on a set of seven collocated H.F. active antennas. It has been shown that the estimation of the direction of arrival can be efficient as the diversity of their spatial responses replaces the space diversity of a classical array. That technique implies however a particular computation of the Music algorithm, noting that such an array is heterogeneous A significant number of experiments, which involved broadcast transmitters more than 700 kms far from the receiving site, validated this concept, Further on, a source separation of the H.F. multi paths is investigated, aiming to reduce the amplitude fading and to improve the bit error rate in a digital transmission. The paper propose a comparison of two possible techniques : a classical spatial filtering (Yeast mean squares filter) or a blind algorithm resorting to second order statistics.
Traffic jam is considered as a difficult problem to deal with in many cities around the world due to the continuously increasing number of vehicles compared to the available infrastructure. Traffic congestion signific...
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ISBN:
(纸本)9781538647523
Traffic jam is considered as a difficult problem to deal with in many cities around the world due to the continuously increasing number of vehicles compared to the available infrastructure. Traffic congestion significantly influences drivers travel journey, fuel consumption and air pollution. However, the most important factor has affected the delay of emergency vehicles, such as ambulances and police cars, leading to increased road deaths and significant financial losses. To reduce this problem, we propose an advanced traffic control allows rapid emergency services response in smart cities. This can be achieved through a traffic management system capable of implementing path planning in road network monitoring and driving the emergency vehicle in the best possible way to reach the hazard zone. The performance of the proposed algorithm is compared with two other algorithms over Birmingham city centre test scenarios. Simulation results show that the proposed approach improves traffic efficiency of emergency vehicles by an overall average of 21.78%, 29.32%, 32.79% and 46.77% in terms of travel time, fuel consumption, CO2 emission and average speed, respectively.
Early detection of fall risk in homes and assisted living facilities is essential in preventing debilitating injuries and improving the quality of life of older adults. Several studies have found increased gait variab...
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ISBN:
(纸本)9781665406338
Early detection of fall risk in homes and assisted living facilities is essential in preventing debilitating injuries and improving the quality of life of older adults. Several studies have found increased gait variability among community-living older adults with a history of falls. Quantitative 3D gait analysis in laboratories equipped with motion capture devices can be used to record and extract stride-to-stride gait fluctuations that are indicative of fall risk. Such facilities are very expensive, may not be easily accessible for aging and rural communities. Wearable sensors are a cheaper alternative to observe gait in natural settings;however, it can suffer from drift or other inaccuracies. RF sensors can be a game changer to reduce healthcare costs and disparities, improve quality of care, and facilitate aging-inplace by enabling frequent estimation of gait variability in natural settings. In particular, multi-channel frequency modulated continuous wave (FMCW) radar can be used to characterize gait and detect gait abnormalities. In this paper, multi-channel FMCW radar is used to measure gait dynamics in terms of steptime variability. The accuracy of RF measurements is validated via comparison with gold standards, such as the Vicon motion capture camera system. Step-time variability was compared for both normal walking and walking during visual perturbations generated through the use of a virtual reality headset. The accuracy of RF measurement is evaluated for single and multiple channel processing. Our results demonstrate that multi-channel RF sensors can be an effective tool for gait variability assessment in natural, in-home settings.
Motivated by multichannel radar detection applications in the presence of both white Gaussian noise and Gaussian clutter with unknown power, we develop maximum likelihood parameter estimates for the disturbance proces...
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Motivated by multichannel radar detection applications in the presence of both white Gaussian noise and Gaussian clutter with unknown power, we develop maximum likelihood parameter estimates for the disturbance process. Both cases with known and unknown white noise variance are treated. As the estimators do not admit closed-form solutions, numerical iterative procedures are developed that are guaranteed to at least converge to the local maximum. The developed estimates allow us to construct a generalized likelihood ratio test (GLRT) for the detection of a signal with constant but unknown amplitude. This GLRT has important applications in multichannel radar detection involving both white Gaussian noise and spherically invariant random process clutter and is shown to have better detection performance and CFAR property compared with existing statistics. (C) 2005 Elsevier Inc. All rights reserved.
Adaptive arrayprocessing has moved through several stages of evolution. First there was spatial only adaptation, using gradient based algorithms. Second was true space-time adaptivity using time-taps on multiple chan...
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ISBN:
(纸本)0780363396
Adaptive arrayprocessing has moved through several stages of evolution. First there was spatial only adaptation, using gradient based algorithms. Second was true space-time adaptivity using time-taps on multiple channels. Third came more rapid convergence, using sample matrix inversion strategies. Fourth came dimensionally large system solutions, which focused opt the need for reduced DOF such as beamspace, eigenspace, MUSIC, ESPRIT, BASS-ALE, etc. This paper argues that sue are on the threshold of the fifth generation of STAP;mainly STAP in the subband domain. Subband STAP, is an elegant and computationally efficient solution to the need for increasing bandwidth in radar and sonar processing as well as mobile communications. We begin by motivating the need for wider bandwidths, from a SAR imaging perspective. Next, we show that the computational burden of wideband STAP is untenable for existing and emerging military requirements. Having motivated a compelling need we then propose Subband STAP as a solution, motivated from an active sensor perspective. We describe Subband STAP as an extension of the familiar STAP 3D datacube (range, angle, Doppler) to a 4D hypercube (subband range, angle, subband Doppler, subband frequency). Subbanding allows us to overcome challenging wideband effects such as Doppler-frequency coupling, high-resolution range migration, target self-nulling channel decorrelation, and dispersion. We describe the challenges of Subband STAP interference rejection and subband recombination with artifacts.
This paper proposes a new algorithm to restore 3D single-photon Lidar images obtained under challenging realistic scenarios which include imaging multilayered targets such as semi-transparent surfaces or imaging throu...
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ISBN:
(纸本)9781538647523
This paper proposes a new algorithm to restore 3D single-photon Lidar images obtained under challenging realistic scenarios which include imaging multilayered targets such as semi-transparent surfaces or imaging through obscurants such as scattering media (e.g., water, fog). The Data restoration and exploitation is achieved by minimising an appropriate cost-function accounting for the data Poisson statistics and the available prior knowledge regarding the depth and reflectivity estimates. The proposed algorithm takes into account (i) the non-local spatial correlations between pixels, by using a convex non-local total variation (TV) regularizer, and (ii) the clustered nature of the returned photons, by using a collaborative sparse prior. The resulting minimization problem is solved using the alternating direction method of multipliers (ADMM) that offers good convergence properties. The algorithm is validated using both synthetic and real data which show the benefit of the proposed strategy in the sparse regime due to a fast acquisition or in presence of a high background due to obscurants.
The deployment of third generation CDMA-based wireless systems foresees a loading fraction that is smaller than one, i.e. the number of users per cell is scheduled to be significantly less than the spreading factor to...
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ISBN:
(纸本)0780363396
The deployment of third generation CDMA-based wireless systems foresees a loading fraction that is smaller than one, i.e. the number of users per cell is scheduled to be significantly less than the spreading factor to attain an acceptable performance. This means that a base station can set apart a subset of the codes, the excess codes, that it will not use. In the case of periodic codes (such as in the TDD mode of UMTS), the existence of excess codes implies the existence of a noise subspace, which can be used to cancel the interference coming from a neighboring base station. We introduce a SINR maximizing linear receiver to perform this interference reduction. In the case of aperiodic codes (such as in the FDD mode of UMTS), the noise subspace is time-varying. In this case, we introduce structured receivers that combine scrambling and descrambling operations with projections on code subspaces and linear time-invariant filters for equalization, interference cancellation and multipath combining. So the time-varying part of these receivers is limited to (de-)scrambling operations. The design of the various filter parts gets discussed. Performance improvements are illustrated via simulations.
In this paper, we address the problem of parameter estimation of multiple polynomial-phase signals (PPS) impinging on a multi-sensorarray. ne approach used herein is based on a state space modelization of the signal ...
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ISBN:
(纸本)0780382927
In this paper, we address the problem of parameter estimation of multiple polynomial-phase signals (PPS) impinging on a multi-sensorarray. ne approach used herein is based on a state space modelization of the signal by performing an Extended Kalman Filtering (EKF) to estimate the state. This method exploits the spatial information provided by a sensorarray resulting in considering different observations in the EKF equations. Simulation example supporting the theory is provided showing the efficiency of the resulting estimator by performance close to the Cramer-Rao Lower Bound (CRLB).
In arrayprocessing, lower bounds are used as a benchmark to evaluate the ultimate performance of estimators. Among these bounds, the Weiss-Weinstein bound (WWB) is known as the tightest bound of Weiss-Weinstein famil...
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By exploiting the cyclostationarity exhibited by most communication signals, in this paper, we propose a computationally efficient method for estimating the directions-of-arrival (DOA's) of coherent narrow-band si...
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ISBN:
(纸本)0780367200
By exploiting the cyclostationarity exhibited by most communication signals, in this paper, we propose a computationally efficient method for estimating the directions-of-arrival (DOA's) of coherent narrow-band signals impinging on a uniform linear array without eigendecomposition and spatial smoothing processes. An online implementation of this method is proposed for tracking the DOA's of moving signals in a multipath propagation environment. In the proposed algorithm, a combination of the cyclostationarity and a subarray scheme are used to decorrelate the signal coherency and to suppress the noise and interfering signals, while the noise subspace is estimated from the resulting cyclic correlation matrix through a linear operation. As a result, the proposed algorithm has the advantages of computational simplicity and robust detection capability.
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