In many signalprocessing applications of linear algebra tools, the signal part of a postulated model lies in a so-called signal sub-space, while the parameters of interest are in one-to-one correspondence with a cert...
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ISBN:
(纸本)0780385454
In many signalprocessing applications of linear algebra tools, the signal part of a postulated model lies in a so-called signal sub-space, while the parameters of interest are in one-to-one correspondence with a certain basis of this subspace. The signal subspace can often be reliably estimated from measured data, but the particular basis of interest cannot be identified without additional problem-specific structure. This is a manifestation of rotational indeterminacy, i.e., non-Uniqueness of low-rank matrix decomposition. The situation is very different for three- or higher-way arrays, i.e., arrays indexed by three or more independent variables, for which low-rank decomposition is unique under mild conditions. This has fundamental implications for DSP problems which deal with such data. This paper provides a brief tour of the basic elements of this theory, along with many examples of application in problems of current interest in the signalprocessing community.
Autofocus is imperative for inverse synthetic aperture radar (ISAR) imaging. In this paper an approach for ISAR autofocus is developed by use of second order statistics (SOS) of returned signals. The ISAR observation ...
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ISBN:
(纸本)0780385454
Autofocus is imperative for inverse synthetic aperture radar (ISAR) imaging. In this paper an approach for ISAR autofocus is developed by use of second order statistics (SOS) of returned signals. The ISAR observation model is established, the approach is verified and the relationship of the developed approach to other methods is investigated. The results of processing real data confirm the validity of proposed approach.
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 2sensors.
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.
We consider the problem of transmit downlink beamforming for wireless transmission in the context of certain broadcasting or multicasting applications wherein Channel State Information (CSI) is available at the transm...
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ISBN:
(纸本)0780385454
We consider the problem of transmit downlink beamforming for wireless transmission in the context of certain broadcasting or multicasting applications wherein Channel State Information (CSI) is available at the transmitter, and a common message is to be transmitted to the users. Unlike the usual "blind" isotropic broadcasting scenario, the availability of CSI allows transmit optimization. We adopt a minimum transmission power criterion, subject to prescribed minimum received signal-to-Noise Ratio (SNR) at each of the intended receivers. We also consider a related max-min SNR "fair" problem formulation subject to a transmit power constraint. The basic problem is non-convex and thus difficult to solved however, we show that a suitable reformulation allows the application of semidefinite relaxation (SDR) techniques. SDR yields a (generally approximate) solution, but in many cases our Solution is optimal, and in most cases it is within 3-4 dB from the optimal solution, which is often good enough in Our intended applications. While the focus of the paper is on a wireless Communication scenario, we also discuss related problems in downstream precoding for broadcasting in digital subscriber line systems.
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 narrowbandsignals. 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 narrowbandsignals. 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.
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.
A new algorithm based on Joint Power Control and Optimal Beamforming (JPCOB) has been developed in this work, whose major innovation is the cooperative transmission performed by the Base Stations involved in the syste...
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ISBN:
(纸本)0780385454
A new algorithm based on Joint Power Control and Optimal Beamforming (JPCOB) has been developed in this work, whose major innovation is the cooperative transmission performed by the Base Stations involved in the system. It also provides minimum total transmission power but achieving a certain Quality of Service (QoS) at each mobile. Moreover, a computationally efficient implementation of the proposed algorithm has been developed and some simulations have been carried out. Results show that cooperative transmission has higher computational cost that non cooperative methods, but reconfiguration capability and handover management is implied in the new JPCOB algorithm equations, whereas non-cooperative methods must count on handover situations.
A computationally efficient version of the affine projection (AP) algorithm avoiding matrix inversions is presented and developed for multichannel active noise control (ANC) systems. A comparative study of the classic...
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ISBN:
(纸本)0780385454
A computationally efficient version of the affine projection (AP) algorithm avoiding matrix inversions is presented and developed for multichannel active noise control (ANC) systems. A comparative study of the classical multichannel filtered-x LMS (MFXLMS), the multichannel filtered-x affine projection (MFXAP) and its computationally efficient version, named hereinafter new multichannel filtered-x affine projection (NMFXAP) algorithm, is carried out. Those aforementioned algorithms have been Simulated in a multichannel ANC system for local control. Simulations using real data have been carried out. The computational complexity of the algorithms is evaluated for different number of transducers. Although the proposed NMFXAP algorithm exhibits a slightly higher computational complexity than the MFXLMS, it keeps the convergence properties of the AP algorithms thus providing faster convergence speed than the MFXLMS. On the other hand, the NMFXAP shows a remarkable decrease of the number of operations per iteration compared to the MFXAP. This fact is due to a recursion used to calculate matrix inversions needed in the updating of the adaptive filter coefficients of the MFXAP algorithm. The proposed algorithm is specially suitable for real time multichannel ANC applications running on a Digital signalprocessing (DSP) card.
Wavefield Modeling is a formalism for arrayprocessing based on expressing the output of a sensors' array as a product of a wavefieId-independent sampling matrix and an array-independent coefficient vector. This a...
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