In digital mobile communications efficient compression algorithms are needed to encode speech or audio signals. As the determined source parameters are highly sensitive to transmission errors, robust source and channe...
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ISBN:
(纸本)0780370414
In digital mobile communications efficient compression algorithms are needed to encode speech or audio signals. As the determined source parameters are highly sensitive to transmission errors, robust source and channel decoding schemes are required. This contribution deals with an iterative source-channel decoding approach where a simple channel decoder and a softbit-source decoder are concatenated. We will mainly focus on softbit-source decoding which can be considered as error concealment technique. This technique utilizes residual redundancy remaining after source coding. In this paper we derive a new formula that shows how the residual redundancy transforms into the extrinsic information utilizable for iterative decoding. The derived formula opens several starting points for optimizations, e.g. it helps to find a robust index assignment. Furthermore, it allows the conclusion that softbit-source decoding is the limiting factor if applied to iterative decoding processes. Therefore, no significant gain will be obtainable by more than two iterations. This will be demonstrated by simulation.
We consider the problem of estimating continuous-time autoregressive (CAR) processes from discrete-time noisy observations. This can be done within a Bayesian framework using Markov chain Monte Carlo (MCMC) methods. E...
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ISBN:
(纸本)0780370414
We consider the problem of estimating continuous-time autoregressive (CAR) processes from discrete-time noisy observations. This can be done within a Bayesian framework using Markov chain Monte Carlo (MCMC) methods. Existing methods include the standard random walk Metropolis algorithm. On the other hand, least-squares (LS) algorithms exist where derivatives are approximated by differences and parameter estimation is done in a least-squares manner. In this paper, we incorporate the LS estimation into the MCMC framework to develop a new MCMC algorithm. This new algorithm is combined with the standard Metropolis algorithm and is found to improve performance compared to the standard MCMC algorithm. Simulation results are presented to support our findings.
In this paper we present an optimized DSP implementation of a modified error-feedback lattice least-square (EF-LSL) adaptive filtering algorithm. Simple measures that provide numerical stability for poor persistent ex...
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ISBN:
(纸本)0780370414
In this paper we present an optimized DSP implementation of a modified error-feedback lattice least-square (EF-LSL) adaptive filtering algorithm. Simple measures that provide numerical stability for poor persistent excitation are also proposed. As a result of the optimization and the stability measures, an efficient and stable implementation of a fast algorithm of the RLS family was attained. We present the results of an acoustic echo cancelling experiment performed with the implemented algorithm. With a 40 MIPS SHARC DSP, up to 290 adaptive filter coefficients can be used. This represents an effective alternative to algorithms of the LMS family, while still retaining the good convergence properties of the RLS family.
The effectiveness of small microphone arrays for in car use is investigated. These arrays are designed for speech enhancing at noise background within the cabin of a moving car. Speech and noise simulation based on de...
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ISBN:
(纸本)0780370414
The effectiveness of small microphone arrays for in car use is investigated. These arrays are designed for speech enhancing at noise background within the cabin of a moving car. Speech and noise simulation based on designed mathematical algorithm of sound field modeling within a car cavity is applied for predicting effectiveness of the spatial-time processingalgorithms. The mathematical model takes into account complicated cabin geometry, the difference of its sizes in. wavelength scale at low and high frequencies, frequency dependent sound absorption of the cabin surfaces and. distributed noise sources with their cross correlation. Theoretical estimates of the microphone arrays effectiveness and output simulated signals (for subjective estimation) are presented.
Consider the Hidden Markov model estimation problem where the realization of a single Markov chain is observed by a number of noisy sensors. The sensor scheduling problem for the resulting Hidden Markov model is as fo...
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ISBN:
(纸本)0780370414
Consider the Hidden Markov model estimation problem where the realization of a single Markov chain is observed by a number of noisy sensors. The sensor scheduling problem for the resulting Hidden Markov model is as follows: Design an optimal algorithm for selecting at each time instant, one of the many sensors to provide the next measurement. Each measurement has an associated measurement cost. The problem is to select an optimal measurement scheduling policy, so as to minimize a cost function of estimation errors and measurement costs. The problem of determining the optimal measurement policy is solved via stochastic dynamic programming. An optimal finite dimensional algorithm is presented along with numerical results.
The reliability of a recently introduced nonlinear estimation method for tomographic imaging is discussed in full detail. It is shown how a proper choice of the functional spaces to which unknown quantities belong and...
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The reliability of a recently introduced nonlinear estimation method for tomographic imaging is discussed in full detail. It is shown how a proper choice of the functional spaces to which unknown quantities belong and the exploitation of the expected properties of the object under test and of all the available a priori information positively affect robustness against false solutions of the inversion procedure. The developed arguments allow us to understand causes of possible false solutions, suggesting possible countermeasures. In particular, it is shown how the proposed approach allows us to achieve accurate and reliable reconstructions in a set of cases larger than the range of applicability of other "false solutions free" approaches. Numerical analyses confirm the validity of the approach and the effectiveness of developed inversion procedures through practical examples.
The problem of structure from motion (SFM) is to extract the three-dimensional model of a moving scene from a sequence of images. Most of the algorithms which work by fusing the two-frame depth estimates (observations...
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ISBN:
(纸本)0780370414
The problem of structure from motion (SFM) is to extract the three-dimensional model of a moving scene from a sequence of images. Most of the algorithms which work by fusing the two-frame depth estimates (observations) assume an underlying statistical model for the observations and do not evaluate the quality of the individual observations. However, in real scenarios, it is often difficult to justify the statistical assumptions. Also, outliers are present in any observation sequence and need to be identified and removed from the fusion algorithm. In this paper, we present a recursive fusion algorithm using Robbins-Monro stochastic approximation (RMSA) which takes care of both these problems to provide an estimate of the real depth of the scene point. The estimate converges to the true value asymptotically. We also propose a method to evaluate the importance of the successive observations by computing the Fisher information (FI) recursively. Though we apply our algorithm in the SFM problem by modeling of human face, it can be easily adopted to other data fusion applications.
Leafy spurge (Euphorbia esula L. sensu lato) is a perennial weed species common to the north-central United States and southern Canada. The plant is a foreign species toxic to cattle. Spurge infestation can reduce cat...
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Leafy spurge (Euphorbia esula L. sensu lato) is a perennial weed species common to the north-central United States and southern Canada. The plant is a foreign species toxic to cattle. Spurge infestation can reduce cattle carrying capacity by 50 to 75 percent [1]. University of Wyoming Entomology doctoral candidate vonny Barlow is conducting research in the area of biological control of leafy spurge via the Aphthona nigriscutis Foudras flea beetle. He is addressing the question of variability within leafy spurge and its potential impact on flea beetle herbivory. One component of Barlow's research consists of measuring the herbivory of leafy spurge plant specimens after introducing adult beetles. Herbivory is the degree of consumption of the plant's leaves and was measured in two different manners. First, Barlow assigned each consumed plant specimen a visual rank from 1 to 5. Second, imageprocessing techniques were applied to "before" and "after" images of each plant specimen in an attempt to more accurately quantify herbivory. Standardized techniques were used to acquire images before and after beetles were allowed to feed on plants for a period of 12 days. Matlab® was used as the imageprocessing tool. The imageprocessing algorithm allowed the user to crop the portion of the "before" image containing only plant foliage. Then Matlab cropped the "after" image with the same dimensions, converted the images from RGB to grayscale. The grayscale image was converted to binary based on a user defined threshold value. Finally, herbivory was computed based on the number of black pixels in the "before" and "after" images. The imageprocessing results were mixed. Although, this imageprocessing technique depends on user input and non-ideal images, the data is useful to Barlow's research and offers insight into better imaging systems and processingalgorithms.
This paper proposes a system estimating arbitrary 3-D human hand postures in real-time. Differently from most of the previous real-time system, it can accept not only predetermined hand signs but also arbitrary postur...
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ISBN:
(纸本)0769510744
This paper proposes a system estimating arbitrary 3-D human hand postures in real-time. Differently from most of the previous real-time system, it can accept not only predetermined hand signs but also arbitrary postures and it works in a monocular camera environment. The estimation is based on a 2-D image retrieval. More than 16000 possible hand appearances (silhouette contours) are first generated from a given 3-D shape model by rotating model joints and stored in an appearance database. Every appearance is tagged with its own joint angles which are used when the appearance was generated. B-v retrieving the appearance in the database well-matching to the input image contour, the joint angles of the input shape can be rapidly obtained. For robust matching, little difference between the appearances and the input is adjusted before matching considering shape deformation and quantization error in appearence samping. In order to achieve the real-time processing, the search area is reduced by using an adjacency map in the database. In the map, adjacent appearances having similar joint angles are connected with each other For each appearance, a neighborhood which consists of the adjacent appearances is defined. In each frame, the search area is limited to the neighborhood of the estimated appearance in the previous frame. The best candidate at one frame is sometimes wrong due to approximation errors, too rapid motions or ambiguities caused by self-occlusion. To prevent tracking failures, a fixed number of the well-matching appearances are saved at every frame, After the multiple neighborhoods of the saved appearances are merged, the unified neighborhood is searched for the estimate efficiently by Beam search. These algorithms are implemented on a PC cluster system consisting of 6 PCs (Pentium III 600 MHz) and real-time processing is achieved. The resulted posture estimates are shown by experimental examples.
The problem of image reconstruction is solved for a system of active multipositional sounding with following determination of the object image location on the reconstructed image. The Bayesian technique is used for sy...
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The problem of image reconstruction is solved for a system of active multipositional sounding with following determination of the object image location on the reconstructed image. The Bayesian technique is used for synthesis of the optimal algorithms of image reconstruction and determination of the object image parameters on an image. As a particular case, an example of image line reconstruction is considered with selection of a small-size target. Statistical modeling of the synthesized algorithms is carried out to estimate their normal operation.
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