Time-frequency techniques have been successfully used in the analysis of non-stationary signals. Several approaches have been proposed that address concerns such as Time-Frequency (TF) resolution and the elimination o...
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ISBN:
(纸本)0819441880
Time-frequency techniques have been successfully used in the analysis of non-stationary signals. Several approaches have been proposed that address concerns such as Time-Frequency (TF) resolution and the elimination of cross-terms. In this work, a TF technique based on the use of Spatially variant Apodization (SvA) is introduced that focuses on the detection of non-stationary signals that consists of several components that have different amplitudes. The SvA approach is applied to the Short-Time Fourier Transform (STFT) to detect small intensity components that are buried in high sidelobes of other components. Resolution using the SvA is better than the resolution obtained using the STFT with non-rectangular windows. Synthesis can be performed using the overlap-add method. Because of the implementation of the SvA, the modified STFT using sidelobe apodization can have good resolution, detect small intensity components, and show no cross terms in the TF plane, given that stationarity can be assumed using an appropriate window length in the STFT.
Coherent adaptation algorithms are proposed for a beamformer in the WCDMA reverse link. The coherent adaptation algorithm improves the convergence speed by constraining the desired signal component of the filtered out...
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ISBN:
(纸本)0819441880
Coherent adaptation algorithms are proposed for a beamformer in the WCDMA reverse link. The coherent adaptation algorithm improves the convergence speed by constraining the desired signal component of the filtered output to be always coherent in phase with the reference signal at each iteration. With the coherent constraint, the performance of coherent methods is significantly improved. We present the simulation results that show the various desirable characteristics of coherent methods such as a fast convergence speed. insensitiveness to fading parameters over conventional methods.
We describe a fast and efficient algorithm for automatic detection and estimation of the fundamental frequency F0 of a harmonic time-domain signal. The method is based on differentiation of the short time Fourier tran...
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ISBN:
(纸本)0819441880
We describe a fast and efficient algorithm for automatic detection and estimation of the fundamental frequency F0 of a harmonic time-domain signal. The method is based on differentiation of the short time Fourier transform (STFT) phase, which is implemented as a cross-spectral product. In estimating and isolating the fundamental frequency, several enhancement processes are developed and applied to the TF surface to improve the signal quality. We describe the algorithm in detail and demonstrate the processing gain achieved at each step. In addition, we apply the algorithm to human speech to recover the pitch fundamental F0 and report the evaluation of the algorithm's performance on the Western Michigan vowel corpus [3].
Mainly digital images are under sampled. It is the same for SPOT digital image satellite. The very meaning is that the instrument is too much powerful for this sampling. The worth side effect is that artifacts (aliasi...
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ISBN:
(纸本)0819441880
Mainly digital images are under sampled. It is the same for SPOT digital image satellite. The very meaning is that the instrument is too much powerful for this sampling. The worth side effect is that artifacts (aliasing) are introduced in the image, the good side is that images can be improved if the sampling density is increased. In this paper we use images from the two HRvIR instruments onboard SPOT1-4 satellite to multiply by a factor two the density and the resolution of the image.
We present an efficient array processor for downdating the ULvD. The array processor exploits the block structure of the decomposition to determine the effective rank at every step of modification and maintains the ra...
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ISBN:
(纸本)0819441880
We present an efficient array processor for downdating the ULvD. The array processor exploits the block structure of the decomposition to determine the effective rank at every step of modification and maintains the rank-revealing nature of the decomposition throughout the steps by tracking exact quantities of Frobenius norms of all three blocks of the lower triangular factor in the decomposition. Thus. a deflation step that is necessary to compute its numerical rank can be often avoided. This feature of the algorithm is particularly attractive to its array processor implementation because the deflation steps usually require some condition estimation. and most of good condition estimators are not well pipelined.
signalprocessingalgorithms and architectures can use dynamic reconfiguration to exploit variations in signal statistics with the objectives of improved performance and reduced power consumption. Parameters provide a...
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ISBN:
(纸本)0780370414
signalprocessingalgorithms and architectures can use dynamic reconfiguration to exploit variations in signal statistics with the objectives of improved performance and reduced power consumption. Parameters provide a simple and formal way to characterize incremental changes to a computation and its computing mechanism. This paper examines five parameterized computations which are typically implemented in hardware for a wireless multimedia terminal: 1) motion estimation, 2) discrete cosine transform, 3) Lempel-Ziv lossless compression, 4) 3D graphics light rendering and 5) viterbi decoding, Each computation is examined for the capability of dynamically adapting the algorithm and architecture parameters to variations in their respective input signals. Dynamically reconfigurable low-power implementations of each computation are currently underway.
Low Power is an extremely important issue for future mobile radio systems. Channel decoders are essential building blocks of base-band signalprocessing units in mobile terminal architectures. Thus low power implement...
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ISBN:
(纸本)0780366336
Low Power is an extremely important issue for future mobile radio systems. Channel decoders are essential building blocks of base-band signalprocessing units in mobile terminal architectures. Thus low power implementations of advanced channel decoding techniques are mandatory. In this paper we present a low power implementation of the most sophisticated channel decoding algorithm (Turbo-decoding) on programmable architectures. Low power optimization is performed on two abstraction levels: on system level by the use of an intelligent cancellation technique, on implementation level by the use of dynamic voltage scaling. With these techniques we can reduce the worst case energy consumption to 55% using data of state-of-the-art processors. Our approach is also applicable for hardware implementations. To the best of our knowledge, this is the first in-depth study of low power implementations of Turbo-decoders based on voltage scheduling for third generation wireless systems.
Compressed video bitstreams require protection from channel errors in a wireless channel. The three-dimensional (3-D) SPIHT coder has proved its efficiency and its real-time capability in compression of video. A forwa...
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ISBN:
(纸本)0819441880
Compressed video bitstreams require protection from channel errors in a wireless channel. The three-dimensional (3-D) SPIHT coder has proved its efficiency and its real-time capability in compression of video. A forward-error-correcting (FEC) channel (RCPC) code combined with a single ARQ (automatic-repeat-request) proved to be an effective means for protecting the bitstream. In this paper, the need for ARQ is eliminated by making the 3-D SPIHT bitstream more robust and resistant to channel errors. Packetization of the bitstream and the reorganization of these packets to achieve scalability in bit rate and/or resolution in addition to robustness is demonstrated and combined with channel coding to not only protect the integrity of the packets, but also allow detection of packet decoding failures, so that only the cleanly recovered packets are reconstructed. In extensive comparative tests, the reconstructed video is shown to be superior to that of MPEG-2, with the margin of superiority growing substantially as the channel becomes noisier.
Adaptive array systems require the periodic solution of the well-known w = (R) over tilde (-1)v equation in order to compute optimum adaptive array weights. The covariance matrix (R) over tilde is estimated by forming...
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ISBN:
(纸本)0819441880
Adaptive array systems require the periodic solution of the well-known w = (R) over tilde (-1)v equation in order to compute optimum adaptive array weights. The covariance matrix (R) over tilde is estimated by forming a product of noise sample matrices X : (R) over tilde = (XX)-X-H. The operations-count cost of performing the required matrix inversion in real time can be prohibitively high for a high bandwidth system with a large number of sensors. Specialized hardware may be required to execute the requisite computations in real time. The choice of algorithm to perform these computations must be considered in conjunction with the hardware technology used to implement the computation engine. A systolic architecture implementation of the Givens rotation method for matrix inversion was selected to perform adaptive weight computation. The bit-level systolic approach enables a simple ASIC design and a very low power implementation. The bit-level systolic architecture must be implemented with fixed-point arithmetic to simplify the propagation of data through the computation cells. The Givens rotation approach has a highly parallel implementation and is ideally suited for a systolic implementation. Additionally, the adaptive weights are computed directly from the sample matrix X in the voltage domain, thus reducing the required dynamic range needed in carrying out the computations. An analysis was performed to determine the required fixed-point precision needed to compute the weights for an adaptive array system operating in the presence of interference. Based on the analysis results. it was determined that the precision of a floating-point computation can be well approximated with a 13-bit to 19-bit word length fixed point computation for typical system jammer-to-noise levels. This property has produced an order-of-magnitude reduction in required hardware complexity. A synthesis-based ASIC design process was used to generate preliminary layouts. These layouts were used t
This volume 2 of 2 of the conference proceedings contains 160 papers. Topics discussed include wireless communication and signalprocessing, algorithms for MIMO links, modulation and detection techniques, signal detec...
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This volume 2 of 2 of the conference proceedings contains 160 papers. Topics discussed include wireless communication and signalprocessing, algorithms for MIMO links, modulation and detection techniques, signal detection and classification, adaptive communications and arrays, image segmentation and frequency domain processing, multiple user/multiple access techniques, digital signalprocessing architectures, hyperspectral processing and multisignals or data fusion, computer arithmetic implementations and FPGA designs, radar and sonar processing, equalization and synchronization techniques, higher order statistical signalprocessing for communications, adaptive signalprocessing in communication, speech coding and processing, wireless systems, special arithmetic techniques, biomedical imaging and advanced modulation and channel estimation.
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