We consider the problem of achieving high data rates for uplink transmission on multi-input, multi-output (MIMO) channels. We propose a soft decision space-time detection scheme of linear complexity in a turbo-coded a...
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ISBN:
(纸本)0780385454
We consider the problem of achieving high data rates for uplink transmission on multi-input, multi-output (MIMO) channels. We propose a soft decision space-time detection scheme of linear complexity in a turbo-coded architecture with a new form of iterative processing. Simulation results illustrate that the coded MIMO system is within 1.5 dB of the Shannon capacity limit on uncorrelated flat Rayleigh fading MIMO channels, where the receiver only possesses channel state information.
This paper is devoted to under-determined linear mixtures of independent random variables (i.e. with more inputs than outputs). Blind identifiability of general under-determined mixtures is first discussed, and the ma...
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ISBN:
(纸本)0780385454
This paper is devoted to under-determined linear mixtures of independent random variables (i.e. with more inputs than outputs). Blind identifiability of general under-determined mixtures is first discussed, and the maximum number of sources is given, depending on the hypotheses assumed. Then an algorithm proposed by Taleb, essentially usable for 2-dimensional mixtures, is extended to the complex field. A procedure is proposed in order to avoid the enormous increase in complexity. Computer simulations demonstrate the ability of the algorithm to identify mixtures of N QPSK sources received on 1 or 2 sensors.
We propose a novel direction-of-arrival (DOA) estimation method, which uses sensors of the receiving array, for spatially non-symmetric distributed sources characterized by multipath fading. Specifically, the probabil...
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ISBN:
(纸本)0780385454
We propose a novel direction-of-arrival (DOA) estimation method, which uses sensors of the receiving array, for spatially non-symmetric distributed sources characterized by multipath fading. Specifically, the probability density function (PDF) of a non-symmetric distribution is modeled as the summation of two Gaussian PDFs. The proposed algorithm is based on a covariance fitting and accurately estimates the DOA for a non-symmetricaly distributed source by determining the scaling ratio between the two Gaussians. Furthermore, the degree of angular spread is also evaluated by using these estimated parameters.
Speech is dramatically degraded when a distant microphone is used in real environments. One of the possible solutions is to use a microphone array to improve the quality of the recorded speech signal. In this paper we...
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ISBN:
(纸本)0780385454
Speech is dramatically degraded when a distant microphone is used in real environments. One of the possible solutions is to use a microphone array to improve the quality of the recorded speech signal. In this paper we present a robust beamformer that integrates the directional noise reduction capability of a modification of the Generalized Sidelobe Canceller with adaptive blocking matrix and the great performance of the Wiener postfiltering techniques against low-correlated noises. Experimental results show that the proposed integrated adaptive Wiener-filtering beamformer is at least as robust to directional and uncorrelated noise as conventional postfiltering of the output and presents a lower level of degradation of the speech signal.
We discuss dispersive wave propagation and show that the Wigner distribution is a powerful approach because it simplifies the issues immensely. We show that the spatial time-frequency arrayprocessing formulation of A...
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ISBN:
(纸本)0780385454
We discuss dispersive wave propagation and show that the Wigner distribution is a powerful approach because it simplifies the issues immensely. We show that the spatial time-frequency arrayprocessing formulation of Amin et al. can be viewed as a projection of a Wigner distribution in space, wavenumber, time and frequency. We also show that there is a very simple yet illuminating and accurate approximation between the Wigner distribution of a wave at two different spatial points. In particular, the Wigner distributions of the wave at two different locations are related by a frequencydependent time-shift that depends explicitly on the dispersion relation, in a very straight forward way.
In this paper, we develop and evaluate distributed implementations of source localization estimators from energy-based measurements obtained via an ad-hoc network of acoustic sensors. The distributed locally construct...
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ISBN:
(纸本)0780385454
In this paper, we develop and evaluate distributed implementations of source localization estimators from energy-based measurements obtained via an ad-hoc network of acoustic sensors. The distributed locally constructed algorithms that we present produce at each node a sequence of esLimates approximating a desired source localization algorithm. As our investigation reveals, the localization performance of these distributed algorithms depends on the type of desired localization algorithm, the network topology and the number of communication and fusion steps employed in these approximations.
In this paper we provide a tutorial description of recent results of the research activity at the University of Pisa on multibaseline (MB) InSAR processing. The main focus is on the problem of retrieving both heights ...
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ISBN:
(纸本)0780385454
In this paper we provide a tutorial description of recent results of the research activity at the University of Pisa on multibaseline (MB) InSAR processing. The main focus is on the problem of retrieving both heights and radar reflectivities of natural layover areas by means of a cross-track InSAR (XTI-SAR) system. It is formulated as the problem of detecting and estimating a multicomponent signal corrupted by multiplicative noise and by additive white Gaussian noise. The problem of estimating the number of signal components in the presence of speckle is also addressed. Finally, e brief mention is given to recent research trends on robust methods for non-perfectly calibrated arrays and on MB-SAR tomography, which is an extension of MB-InSAR for fill 3D mapping of semitransparent volume scattering layers.
This paper presents a new methodology for airborne wideband space-time adaptive processing (W-STAP) radar systems. In W-STAP, the wideband target signal is first decomposed into a series of narrowband signals. This is...
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ISBN:
(纸本)0780385454
This paper presents a new methodology for airborne wideband space-time adaptive processing (W-STAP) radar systems. In W-STAP, the wideband target signal is first decomposed into a series of narrowband signals. This is referred to as a sub-banding process. The different signals are then combined into a single reference sub-band (usually the center). STAP processing is then performed at this reference band. The combination process is done through a transformation from the different sub-bands into the reference one using the focusing approach [1]. In this method, non-sinaular transformation matrices are used. Compared to the conventional approach proposed in [2], the focusing technique provides greater Computational efficiency in wideband STAP systems.
The phenomenon Of supergain for a circular array and its robust version are presented. The superdirective array gain for the Circular array, although it is not so extreme as an endfire line array, Outperforms a lot ov...
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ISBN:
(纸本)0780385454
The phenomenon Of supergain for a circular array and its robust version are presented. The superdirective array gain for the Circular array, although it is not so extreme as an endfire line array, Outperforms a lot over that of a conventional beamformer in isotropic noise fields when the interelement spacings are less than one-half wavelength. However, optimum beamforming algorithms can be extremely sensitive to slight errors in array characteristics. The performance are known to degrade if some of underlying assumptions on the sensorarray violated. Therefore white noise gain constraint (WNC) is used to increase the robustness Of supergain beamforming against random errors. We show that the robust supergain beamforming can be reformulated in a form of second-order cone programming and resolved easily. Some Computer Simulations are also given to illustrate the presented approach.
This paper describes the problem caused by near-field sound sources. Formerly, the authors proposed a 2-ch passive subtractive beamformer with a single sharp notch for noise reduction. It is obvious that the single sh...
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ISBN:
(纸本)0780385454
This paper describes the problem caused by near-field sound sources. Formerly, the authors proposed a 2-ch passive subtractive beamformer with a single sharp notch for noise reduction. It is obvious that the single sharp notch is insufficient for dealing with near-field, non-point sound sources. To solve this problem, this paper presents the hybrid subtractive beamformer that is realized as a cascade connection of single subtractive beamformers. The number of connections depends on frequency to minimize the negative effect caused by spatial aliasing when an objective signal is assumed as a wide-band speech signal. The experimental results verifies that the hybrid beamformer has an advantage in reducing signal distortion over the original single subtractive beamformer.
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