The Experts below are selected from a list of 365355 Experts worldwide ranked by ideXlab platform
Vinay A Vaishampayan - One of the best experts on this subject based on the ideXlab platform.
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asymmetric multiple description lattice vector Quantizers
IEEE Transactions on Information Theory, 2002Co-Authors: Suhas Diggavi, N J A Sloane, Vinay A VaishampayanAbstract:We consider the design of asymmetric multiple description lattice Quantizers that cover the entire spectrum of the distortion profile, ranging from symmetric or balanced to successively refinable. We present a solution to a labeling problem, which is an important part of the construction, along with a general design procedure. The high-rate asymptotic performance of the quantizer is also studied. We evaluate the rate-distortion performance of the quantizer and compare it to known information-theoretic bounds. The high-rate asymptotic analysis is compared to the performance of the quantizer.
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asymptotic analysis of multiple description Quantizers
IEEE Transactions on Information Theory, 1998Co-Authors: Vinay A Vaishampayan, J C BatlloAbstract:A high-rate analysis of multiple description Quantizers is presented for rth-power distortions and general source densities. Both, fixed-length and variable-length encoding of the quantizer indices are considered. Optimal companding functions are shown to be the same as for single-channel Quantizers. As compared to the bound of Ozarow (1980), a gap of 8.69 dB and 3.07 dB exists between the entropy-constrained and level-constrained cases, respectively, for a memoryless Gaussian source and r=2.
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design of multiple description scalar Quantizers
IEEE Transactions on Information Theory, 1993Co-Authors: Vinay A VaishampayanAbstract:The design of scalar Quantizers for communication systems that use diversity to overcome channel impairments is considered. The design problem is posed as an optimization problem and necessary conditions for optimality are derived. A design algorithm, a generalization of S.P. Lloyd's (1962) algorithm for quantizer design, is developed. Unlike a single channel scalar quantizer, the performance of a multiple description scalar quantizer is dependent on the index assignment. The problem of index assignment is addressed. Good index assignments, performance results, and sample quantizer designs are presented for a memoryless Gaussian source. Comparisons are made with rate distortion bounds for the multiple description problem. >
Toshiharu Sugie - One of the best experts on this subject based on the ideXlab platform.
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CDC - Stability analysis of quantized feedback systems including optimal dynamic Quantizers
2008 47th IEEE Conference on Decision and Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper characterizes the stability of quantized feedback systems which contains optimal dynamic Quantizers recently proposed by the authors. First, it is shown that the separation property of the quantizer-controller design, which is similar to the well-known separation property of the observer-controller design, holds in the quantized feedback systems. Next, based on this property, a necessary and sufficient condition for the stability is derived, where the stability is characterized by the poles/zeros of a linear feedback system to be quantized. Finally, we present suboptimal dynamic Quantizers for which the resulting quantized feedback systems are always stable.
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stability analysis of quantized feedback systems including optimal dynamic Quantizers
Conference on Decision and Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper characterizes the stability of quantized feedback systems which contains optimal dynamic Quantizers recently proposed by the authors. First, it is shown that the separation property of the quantizer-controller design, which is similar to the well-known separation property of the observer-controller design, holds in the quantized feedback systems. Next, based on this property, a necessary and sufficient condition for the stability is derived, where the stability is characterized by the poles/zeros of a linear feedback system to be quantized. Finally, we present suboptimal dynamic Quantizers for which the resulting quantized feedback systems are always stable.
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synthesis of optimal dynamic Quantizers for discrete valued input control
IEEE Transactions on Automatic Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper presents an optimal dynamic quantizer synthesis method for controlling linear time-invariant systems with discrete-valued input. The Quantizers considered here include dynamic feedback mechanism, for which we find quantizer parameters such that the system composed of a given linear plant and the quantizer is an optimal approximation of the linear plant in terms of the input-output relation. First, the performance of an arbitrarily given dynamic quantizer is analyzed, where we derive a closed form expression of the performance. Based on this result, it is shown that the quantizer design is reduced to a nonconvex optimization problem for which it is hard to obtain a solution in a direct way. We obtain a globally optimal solution, however, by taking advantage of a special structure of the problem which allows us to relax the original nonconvex problem. The resulting problem is easy to solve, so we provide a design method based on linear programming and derive an optimal structure of the dynamic Quantizers. Finally, the validity of the proposed method is demonstrated by numerical examples.
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optimal dynamic Quantizers for discrete valued input control
Automatica, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper discusses an optimal design problem of dynamic Quantizers for a class of discrete-valued input systems, i.e., linear time-invariant systems actuated by discrete-valued input signals. The Quantizers considered here are in the form of a linear difference equation, for which we find a quantizer such that the system composed of a given linear plant and the quantizer is an optimal approximation of the given linear plant in the sense of the input-output relation. First, we derive a closed form expression for the performance of a class of dynamic Quantizers. Next, based on the performance analysis, an optimal dynamic quantizer and its performance are provided. This result further shows that even for such discrete-valued input systems, a controller can be easily designed by the existing tools for the linear system design such as robust control theory. Finally, the relation among the optimal dynamic quantizer and two other Quantizers, i.e., the receding horizon quantizer and the @D@S modulator, is discussed.
Hamid Jafarkhani - One of the best experts on this subject based on the ideXlab platform.
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downlink non orthogonal multiple access with limited feedback
IEEE Transactions on Wireless Communications, 2017Co-Authors: Hamid JafarkhaniAbstract:In this paper, we analyze downlink non-orthogonal multiple access (NOMA) networks with limited feedback. Our goal is to derive appropriate transmission rates for rate adaptation and minimize outage probability of minimum rate for the constant-rate data service, based on distributed channel feedback information from receivers. We propose an efficient quantizer with variable-length encoding that approaches the best performance of the case where perfect channel state information is available everywhere. We prove that in the typical application with two receivers, the losses in the minimum rate and outage probability decay at least exponentially with the minimum feedback rate. We analyze the diversity gain and provide a sufficient condition for the quantizer to achieve the maximum diversity order. For NOMA with $K$ receivers where $K > 2$ , we solve the minimum rate maximization problem within an accuracy of $\epsilon $ in time complexity of $O\left ({K\log \frac {1}{\epsilon }}\right )$ , and then, we apply the previously proposed Quantizers for $K = 2$ to the case of $K > 2$ . Numerical simulations are presented to demonstrate the efficiency of our proposed Quantizers and the accuracy of the analytical results.
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downlink non orthogonal multiple access with limited feedback
arXiv: Information Theory, 2017Co-Authors: Hamid JafarkhaniAbstract:In this paper, we analyze downlink non-orthogonal multiple access (NOMA) networks with limited feedback. Our goal is to derive appropriate transmission rates for rate adaptation and minimize outage probability of minimum rate for the constant-rate data service, based on distributed channel feedback information from receivers. We propose an efficient quantizer with variable-length encoding that approaches the best performance of the case where perfect channel state information is available anywhere. We prove that in the typical application with two receivers, the losses in the minimum rate and outage probability decay at least exponentially with the minimum feedback rate. We analyze the diversity gain and provide a sufficient condition for the quantizer to achieve the maximum diversity order. For NOMA with $K$ receivers where $K > 2$, we find the maximum minimum rate within an accuracy of $\epsilon$ in time complexity of $O\left(K\log\frac{1}{\epsilon}\right)$, then, we apply the previously proposed Quantizers for $K = 2$ to $K > 2$. Numerical simulations are presented to demonstrate the efficiency of our proposed Quantizers and the accuracy of the analytical results.
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a systematic distributed quantizer design method with an application to mimo broadcast channels
Data Compression Conference, 2010Co-Authors: Erdem Koyuncu, Hamid JafarkhaniAbstract:We introduce a systematic distributed quantizer design method, called {\it{localization}}, in which, out of an existing centralized (global) quantizer, one synthesizes the distributed (local) quantizer using high-rate scalar quantization combined with entropy coding. The general localization procedure is presented, along with a practical application to a quantized beamforming problem for multiple-input multiple-output broadcast channels. For our particular application, not only localization provides high performance distributed Quantizers with very low feedback rates, but also reveals an interesting property of finite rate feedback schemes that might be of theoretical interest: For single-user multiple-input single-output systems, one can achieve the performance of almost any quantized beamforming scheme with an arbitrarily low feedback rate, when the transmitter power is sufficiently large.
Shunichi Azuma - One of the best experts on this subject based on the ideXlab platform.
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CDC - Stability analysis of quantized feedback systems including optimal dynamic Quantizers
2008 47th IEEE Conference on Decision and Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper characterizes the stability of quantized feedback systems which contains optimal dynamic Quantizers recently proposed by the authors. First, it is shown that the separation property of the quantizer-controller design, which is similar to the well-known separation property of the observer-controller design, holds in the quantized feedback systems. Next, based on this property, a necessary and sufficient condition for the stability is derived, where the stability is characterized by the poles/zeros of a linear feedback system to be quantized. Finally, we present suboptimal dynamic Quantizers for which the resulting quantized feedback systems are always stable.
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stability analysis of quantized feedback systems including optimal dynamic Quantizers
Conference on Decision and Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper characterizes the stability of quantized feedback systems which contains optimal dynamic Quantizers recently proposed by the authors. First, it is shown that the separation property of the quantizer-controller design, which is similar to the well-known separation property of the observer-controller design, holds in the quantized feedback systems. Next, based on this property, a necessary and sufficient condition for the stability is derived, where the stability is characterized by the poles/zeros of a linear feedback system to be quantized. Finally, we present suboptimal dynamic Quantizers for which the resulting quantized feedback systems are always stable.
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synthesis of optimal dynamic Quantizers for discrete valued input control
IEEE Transactions on Automatic Control, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper presents an optimal dynamic quantizer synthesis method for controlling linear time-invariant systems with discrete-valued input. The Quantizers considered here include dynamic feedback mechanism, for which we find quantizer parameters such that the system composed of a given linear plant and the quantizer is an optimal approximation of the linear plant in terms of the input-output relation. First, the performance of an arbitrarily given dynamic quantizer is analyzed, where we derive a closed form expression of the performance. Based on this result, it is shown that the quantizer design is reduced to a nonconvex optimization problem for which it is hard to obtain a solution in a direct way. We obtain a globally optimal solution, however, by taking advantage of a special structure of the problem which allows us to relax the original nonconvex problem. The resulting problem is easy to solve, so we provide a design method based on linear programming and derive an optimal structure of the dynamic Quantizers. Finally, the validity of the proposed method is demonstrated by numerical examples.
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optimal dynamic Quantizers for discrete valued input control
Automatica, 2008Co-Authors: Shunichi Azuma, Toshiharu SugieAbstract:This paper discusses an optimal design problem of dynamic Quantizers for a class of discrete-valued input systems, i.e., linear time-invariant systems actuated by discrete-valued input signals. The Quantizers considered here are in the form of a linear difference equation, for which we find a quantizer such that the system composed of a given linear plant and the quantizer is an optimal approximation of the given linear plant in the sense of the input-output relation. First, we derive a closed form expression for the performance of a class of dynamic Quantizers. Next, based on the performance analysis, an optimal dynamic quantizer and its performance are provided. This result further shows that even for such discrete-valued input systems, a controller can be easily designed by the existing tools for the linear system design such as robust control theory. Finally, the relation among the optimal dynamic quantizer and two other Quantizers, i.e., the receding horizon quantizer and the @D@S modulator, is discussed.
Michel Barlaud - One of the best experts on this subject based on the ideXlab platform.
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VCIP - Optimal nearly uniform scalar quantizer design for wavelet coding
Visual Communications and Image Processing 2002, 2002Co-Authors: C. Parisot, Marc Antonini, Michel BarlaudAbstract:Uniform scalar Quantizers are widely used in image coding. They are known to be optimum entropy constrained scalar Quantizers within the high resolution assumption. In this paper, we focus on the design of nearly uniform scalar Quantizers for high performance coding of wavelet coefficients whatever the bitrate is. Some codecs use uniform scalar Quantizers with a zero quantization bin size (deadzone) equal to two times the other quantization bin sizes (for example JPEG2000). We address the problem of deadzone size optimization using distortion rate considerations. The advantages of the proposed method are that the quantizer design is adapted to both the source statistics and the compression ratio. Our method is based on statistical information of the wavelet coefficients distribution. It provides experimental gains up to 0.19 dB.
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optimal nearly uniform scalar quantizer design for wavelet coding
Visual Communications and Image Processing, 2002Co-Authors: C. Parisot, Marc Antonini, Michel BarlaudAbstract:Uniform scalar Quantizers are widely used in image coding. They are known to be optimum entropy constrained scalar Quantizers within the high resolution assumption. In this paper, we focus on the design of nearly uniform scalar Quantizers for high performance coding of wavelet coefficients whatever the bitrate is. Some codecs use uniform scalar Quantizers with a zero quantization bin size (deadzone) equal to two times the other quantization bin sizes (for example JPEG2000). We address the problem of deadzone size optimization using distortion rate considerations. The advantages of the proposed method are that the quantizer design is adapted to both the source statistics and the compression ratio. Our method is based on statistical information of the wavelet coefficients distribution. It provides experimental gains up to 0.19 dB.
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distortion rate models for entropy coded lattice vector quantization
IEEE Transactions on Image Processing, 2000Co-Authors: P Raffy, Marc Antonini, Michel BarlaudAbstract:The increasing demand for real-time applications requires the use of variable-rate Quantizers having good performance in the low bit rate domain. In order to minimize the complexity of quantization, as well as maintaining a reasonably high PSNR ratio, we propose to use an entropy-coded lattice vector quantizer (ECLVQ). These Quantizers have proven to outperform the well-known EZW algorithm's performance in terms of rate-distortion tradeoff. We focus our attention on the modeling of the mean squared error (MSE) distortion and the prefix code rate for ECLVQ. First, we generalize the distortion model of Jeong and Gibson (1993) on fixed-rate cubic Quantizers to lattices under a high rate assumption. Second, we derive new rate models for ECLVQ, efficient at low bit rates without any high rate assumptions. Simulation results prove the precision of our models.
