A distributed automatic speech recognition (ASR) system is considered where features of the speech signal are extracted at the wireless terminal and transmitted to a centralized ASR server. An unequal error protection...
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ISBN:
(纸本)0780370414
A distributed automatic speech recognition (ASR) system is considered where features of the speech signal are extracted at the wireless terminal and transmitted to a centralized ASR server. An unequal error protection scheme is used for the quantized ASR feature stream. At the receiver, coherent demodulation is performed and the probability of error for each bit is computed using the Max-Log MAP algorithm [5]. A 'soft-feature' decoding strategy is introduced at the ASR server that uses the marginal distribution of only the reliable features during likelihood computation. Alternatively, the confidence of each feature is computed from the bit error probabilities and each feature in the probability computation is weighted as a function of the feature confidence. The performance of the proposed soft-feature algorithms is evaluated over typical cellular wireless channels and it is shown to reduce ASR error rate by over 50% for certain channels at a small additional computational cost.
Optical correlators using spatial light modulators in the filter plane have been discussed and presented for many years. In most cases, these devices are electrically addressed modulators and the filters are generated...
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ISBN:
(纸本)0819441856
Optical correlators using spatial light modulators in the filter plane have been discussed and presented for many years. In most cases, these devices are electrically addressed modulators and the filters are generated off-line in software. These filters can be tailored to fit the desired application but cannot be adjusted to account for real-time changes in the target appearance. In addition, building filters to account for all of the possible viewing configurations can strain the reference database and the memory storage capability of the system. Recently, a correlator architecture that used an optically addressed, multiple quantum well (MQW) spatial light modulator as the filter plane device was presented. The architecture is a modified vander Lugt correlator with and additional input modulator. The filter formed by the interference of the reference image beam and the reference beam is recorded on the MQW spatial light modulator. The recorded filter retains the full complex information as high-resolution film did years ago. Additionally, the filter can be updated simply by changing the pattern on the reference input modulator. The second input modulator is used to address this stored filter in - a normal correlator read-out configuration. The correlator has been completed and results will be presented as part of this paper.
The new MPEG-4 Audio standard provides two toolsets for synthetic Audio generation, Audio processing and multimedia content description called Structured Audio (SA) and BInary Format for Scenes (BIFS). Moving from a s...
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ISBN:
(纸本)0780370414
The new MPEG-4 Audio standard provides two toolsets for synthetic Audio generation, Audio processing and multimedia content description called Structured Audio (SA) and BInary Format for Scenes (BIFS). Moving from a systematic analysis of SA and from the implementation of an efficient SA decoder, this paper describes the design of a virtual DSP architecture able to exploit the data level parallelism contained in many typical audio processingalgorithms. The proposed virtual DSP architecture shows good performance on general purpose platforms and can be easily adapted and optimized for parallel superscalar devices. The porting and results on a v-LIW DSP device confirm the effectiveness and flexibility of the approach, particularly suitable for standalone embedded solutions.
The paper proposes a performance evaluation and comparison of recent ITU-T and ETSI voice activity detection algorithms. The comparison was made using both objective and psychoacoustic parameters, so as to have reliab...
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ISBN:
(纸本)0780370414
The paper proposes a performance evaluation and comparison of recent ITU-T and ETSI voice activity detection algorithms. The comparison was made using both objective and psychoacoustic parameters, so as to have reliable judgements that were close to subjective ones. A highly varied speech database was also set up to evaluate the extent to which vADs depend on language, the signal to noise ratio, or the power level.
Recent years have seen the development of signal denoising algorithms based on wavelet transform. It has been shown that thresholding the wavelet coefficients of a noisy signal allows to restore the smoothness of the ...
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ISBN:
(纸本)0780370414
Recent years have seen the development of signal denoising algorithms based on wavelet transform. It has been shown that thresholding the wavelet coefficients of a noisy signal allows to restore the smoothness of the original signal. However, wavelet denoising suffers of a main drawback : around discontinuities the reconstructed signal is smoothed, exhibiting pseudo-Gibbs phenomenon. We consider the problem of denoising piecewise smooth signals with sharp discontinuities. We propose to apply a traditional wavelet denoising method and to restore the denoised signal using a total variation minimization approach. This second step allows to remove the Gibbs phenomena and therefore to restore sharp discontinuities, while the other structures are preserved. The main innovation of our algorithm is to constrain the total variation minimization by the knowledge of the remaining wavelet coefficients. In this way, we make sure that the restoration process does not deteriorate the information that has been considered as significant in the denoising step. With this approach we substantially improve the performance of classical wavelet denoising algorithms, both in terms of SNR and in terms of visual artifacts.
In this paper a scheme for efficient system partitioning of computation in wireless sensor networks is presented. Local computation of the sensor data in wireless networks can be highly energy-efficient, because redun...
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ISBN:
(纸本)0780370414
In this paper a scheme for efficient system partitioning of computation in wireless sensor networks is presented. Local computation of the sensor data in wireless networks can be highly energy-efficient, because redundant communication costs can be reduced. It is important to develop energy-efficient signal processingalgorithms to be run at the sensor nodes. This paper presents a technique to optimize system energy by parallelizing computation through the network and by exploiting underlying hooks for power management. By parallelizing computation, the voltage supply level and clock frequency of the nodes can be lowered, which reduces energy dissipation. A 60% energy reduction for a sensor application of source localization is demonstrated. The results are generalized for finding optimal voltage and frequency operating points that lead to minimum system energy dissipation.
DSPs with dual memory banks offer high memory bandwidth, which is required for high-performance applications. However, such DSP architectures pose problems for C compilers, which are mostly not capable of partitioning...
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ISBN:
(纸本)0780370414
DSPs with dual memory banks offer high memory bandwidth, which is required for high-performance applications. However, such DSP architectures pose problems for C compilers, which are mostly not capable of partitioning program variables between memory banks. As a consequence, time-consuming assembly programming is required for an efficient coding of time-critical algorithms. This paper presents a new technique for automatic variable partitioning between memory banks in compilers, which leads to a higher utilization of available memory bandwidth in the generated machine code. We present experimental results obtained by integrating the proposed technique into an existing C compiler for the AMS Gepard, an industrial DSP core.
CDMA systems in multipath fading channels need to estimate channel parameters for coherent detection of the transmitted signals. In this paper we present a simple but effective channel estimation algorithm that can be...
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ISBN:
(纸本)0780370414
CDMA systems in multipath fading channels need to estimate channel parameters for coherent detection of the transmitted signals. In this paper we present a simple but effective channel estimation algorithm that can be incorporated into most types of multiuser receivers to obtain good detection performance. This technique uses a set of correlation filters to independently estimate each of the channel parameters. One advantage our method has over subspace-based algorithms for channel estimation is that it can estimate the channel parameters without phase or amplitude ambiguity. Simulation results demonstrating that our channel estimator is capable of tracking reasonably fast fading channels are also presented in the paper.
In this paper, we present a new technique to solve array pattern synthesis problems by using semidefinite programming. We first formulate (or reformulate) the array design problems into semidefinite programming proble...
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ISBN:
(纸本)0780370414
In this paper, we present a new technique to solve array pattern synthesis problems by using semidefinite programming. We first formulate (or reformulate) the array design problems into semidefinite programming problems, and then use the recently developed efficient numerical algorithms and software to compute the numerical solution of antenna array weights. Using this approach, we can directly solve not only the standard synthesis problems for nonuniform arrays, but also the synthesis problems for arrays having power restrictions and uncertainties. Numerical examples are presented to illustrate our approach.
Mathematical Morphology appears as a theory that can solve some drawbacks of the classical lineal imageprocessing. Linear filters generate a spatial distortion from initial image, what give as result that specific al...
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ISBN:
(纸本)0819443212
Mathematical Morphology appears as a theory that can solve some drawbacks of the classical lineal imageprocessing. Linear filters generate a spatial distortion from initial image, what give as result that specific algorithms are usually needed for each process with a complexity that can not be implemented in vLSI systems for Real Time imageprocessing. Mathematical Morphology is an alternative method to overcome the inherent drawbacks of the linear processing based on the comparison of an initial image with some well known geometric figures. In this paper we present the implementation of a specific processor that computes Mathematical Morphology (MM) basic operations. Using a clock frequency of 250 MHz this processor is able to handle real time 512x512 pixels video images. Mathematical Morphology allows the non-linear processing of images and it is based on Dilation and Erosion operations using a geometric figure called Structural Element (SE). More complex imageprocessing can be performed using these basic operations. In this implementation the structural element of 3x3 pixels was chosen. 0.6mum HGaAsIv standard cells technology, from vitesse Semiconductor Corporation, has been used achieving a logic level gate description with the possibility of migration to another technologies.
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