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Exhaustive scheduling and retiming of digital signal processing systems

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL signal processing 1998年第7期45卷 821-838页

作者： Denk, TC Parhi, KK Lucent Technol Bell Labs Holmdel NJ 07733 USA Univ Minnesota Dept Elect & Comp Engn Minneapolis MN 55455 USA

Scheduling and retiming are important techniques used in the design of hardware and software implementations of digital signal processing algorithms. In this paper, techniques are developed for generating all scheduling and retiming solutions for a strongly connected data-flow graph, allowing a designer to explore the space of possible implementations. Formulations are developed for two scheduling problems. The first scheduling problem assumes a bit-parallel target architecture. The formulation for this problem is general because it considers retiming the dataflow graph as part of scheduling, and this formulation reduces to the retiming formulation as a special case. The second scheduling problem assumes a bit-serial target architecture. Based on these formulations, the conditions for a legal scheduling solution are derived, and a systematic technique is presented for exhaustively generating all legal scheduling solutions for a strongly connected data-flow graph. Since retiming is a special case of scheduling, this systematic technique can also be used for exhaustively generating all legal retiming solutions. A technique is also developed for exhaustively generating only those bit-parallel schedules which satisfy a given set of resource constraints, The techniques for exhaustively generating scheduling and retiming solutions are demonstrated for several filters. For example, we show that a simple filter such as the biquad has 224 possible retiming solutions for a latency of one time unit. We also show that a fifth-order wave digital elliptic filter has 4.7 million and 580 million scheduling solutions for iteration periods of 17 and 18, respectively.

关键词： data flow graphs high-level synthesis parallel architectures retiming scheduling signal processing very large scale integration

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VHDL token-based performance modeling for 2D and 3D infrared search and track processing

VHDL token-based performance modeling for 2D and 3D infrared...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Pauer, EK Pettigrew, MN Myers, CS Madisetti, VK Signal Proc Ctr Nashua NH 03061 USA

ISBN: (纸本)0819429163

This study develops and evaluates a new VHDL-based performance modeling capability for multiprocessor systems.* The framework for this methodology involved modeling the following system aspects: processor characterization, task modeling, network characterization, and data set size. Initially, all aspects are specified at an abstract) level, and eventually become specified at a detailed level through the process of verification and refinement of design assumptions. Processor characterization involves modeling the processor's speed, instruction set, and memory hierarchy. Task modeling is concerned with the execution time and instruction mix of software tasks within the system. Network characterization models bus protocols, topology, and bandwidths. Data set size refers to how much data is represented by the tokens used in the models. In this study, we applied and evaluated this methodology using both two-dimensional (2D) and three-dimensional (3D) infrared search and track (IRST) algorithms. Two different candidate processors were investigated: IBM PowerPC 604 and Texas Instruments TMS320C80. For the 2D IRST algorithm, the abstract and detailed performance modeling results were obtained far both processors using partitioned data and pipelined algorithmic approaches. For the 3D IRST algorithm, abstract performance models for pipelined and parallelized implementations on the PowerPC were developed. These models examined the feasibility of the implementations, the potential risk areas, and laid the groundwork for detailed performance modeling.

关键词： performance modeling VHDL IRST architectures simulation

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Invertible time-frequency representations

Invertible time-frequency representations

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Nelson, DJ Kenny, OP US Dept Def Ft George G Meade MD 20755 USA

ISBN: (纸本)0819429163

In this paper, we present a new class of representations of signals in the time-frequency (TF) plane. These representations are complex valued, linear, and satisfy reconstruction conditions in which the signal and its complex spectrum may be uniquely reconstructed from their TF representation. These surfaces are generalizations of one-dimensional linear transforms with which they share many properties.. The primary advantage of these representations is that the phase of the surface may be used to recover signal information which is not contained in real TF surfaces. Linearity guarantees that cross-terms normally associated with TF distributions do not exist in these representations. Several examples of invertible surfaces are presented, and it is demonstrated that these surfaces agree with normal intuition. Finally, a method, based on the phase gradient, is proposed as a method of modifying Fourier surfaces to produce representations which are more focused or more concentrated in time and frequency.

关键词： Time-Frequency signal reconstruction Fourier transform spectral phase instantaneous frequency group delay phase gradient

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A multivariate speech activity detector based on the syllable rate

A multivariate speech activity detector based on the syllabl...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Smith, D Townsend, J Nelson, DJ US Dept Def Ft George G Meade MD 20755 USA

ISBN: (纸本)0819429163

Computationally efficient algorithms which perform speech activity detection have significant potential economic and labor saving benefit, by automating an extremely tedious manual process. In many applications, it is desirable to extract intervals of speech which are bounded by segments of other signal types (fax/modem, music, static, dial tones, etc.). In the past, algorithms which successfully discriminate between speech and one specific other signal type have been developed. Frequently, these algorithms fail when the specific non-speech signal is replaced by a different non-speech signal. Little work has been done on combining such discriminators in order to solve the general speech vs. non-speech discrimination problem. Typically, several signal specific discriminators are blindly combined with predictable negative results. Moreover, when a large number of discriminators are involved, dimension reduction is achieved using Principal Components, which optimally compresses signal variance into the fewest number of dimensions. Unfortunately, these new coordinates are not necessarily optimal for discrimination. In this paper we apply graphical tools to determine a set of discriminators which produce excellent speech vs. non-speech clustering, thereby eliminating the guesswork in selecting good feature vectors. This cluster structure provides a basis for a general multivariate speech vs. non-speech discriminator, which compares very favorably with the TALKATIVE speech extraction algorithm.

关键词： signal processing

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Approximation by structured lower rank matrices

Approximation by structured lower rank matrices

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Chu, MT Funderlic, RE Plemmons, RJ N Carolina State Univ Dept Math Raleigh NC 27695 USA

ISBN: (纸本)0819429163

We consider two general procedures for constructing the nearest approximation of a given matrix by one with any lower rank and any linear structure. Nearness can be measured in any matrix norm. Structured low rank matrices arise in various applications, including image enhancement and model reduction. In practice, the empirical data collected in the matrix often either do not maintain the specified structure or do not induce the desirable rank. It is an important task to search for the nearest structured lower rank approximation of a given matrix. The techniques developed in this paper can easily be implemented for numerical computation. In particular, it is shown that the computations can be approached using efficient optimization packages. The special case of Toeplitz structure using the Frobenius matrix norm is discussed in detail to illustrate the ideas, and numerical tests are reported. The procedures developed herein can be generalized to consider a much broader range of approximation problems.

关键词： Matrices signal processing MATLAB Optimization (mathematics) Image enhancement Computer programming Computer science Fourier transforms Image processing Mathematics

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Efficient implementations of pipelined CORDIC based IIR digital filters using fast orthonormal μ-rotations

Efficient implementations of pipelined CORDIC based IIR digi...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Ma, J Parhi, KK Hekstra, GJ Deprettere, EF Univ Minnesota Dept ECE Minneapolis MN 55455 USA

ISBN: (纸本)0819429163

CORDIC based IIR digital filters are orthogonal filters whose internal computations consist of orthogonal transformations. These filters possess desirable properties for VLSI implementations such as regularity, local connection, low sensitivity to finite word-length implementation, and elimination of limit cycles. Recently, fine-grain pipelined CORDIC based IIR digital filter architectures which can perform the filtering operations at arbitrarily high sample rates at the cost of linear increase in hardware complexity have been developed. These pipelined architectures consist of only Givens rotations and a few additions which can be mapped onto CORDIC arithmetic based processors. However, in practical applications, implementations of Givens rotations using traditional CORDIC arithmetic are quite expensive. For example, for 16 bit accuracy, using floating point data format with 16 bit mantissa and 5 bit exponent, it will require approximately 20 pairs of shift-add operations for one Givens rotation. In this paper, we propose an efficient implementation of pipelined CORDIC based IIR digital filters based on fast orthonormal mu-rotations. Using this method, the Givens rotations are approximated by angles corresponding to orthonormal mu-rotations, which are based on the idea of CORDIC and can perform rotation with minimal number of shift-add operations. We present various methods of construction for such orthonormal mu-rotations. A significant reduction (over 76%) of the number of required shift-add operations is achieved. All types of fast rotations can be implemented as a cascade of only four basic types of shift-add stages. These stages can be executed on a modified floating-point CORDIC architecture, making the pipelined filter highly suitable for VLSI implementations.

关键词： orthogonal IIR digital filters pipelining approximate rotations orthonormal mu-rotations CORDIC architecture

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Some significant communications processing realized with adaptive Bragg gratings

Some significant communications processing realized with ada...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Upton, E Wickham, M Smith, M Hart, J Flynn, R Havstad, S Nachman, P TRW Co Inc Redondo Beach CA 90278 USA

ISBN: (纸本)0819429163

Higher data capacity demands and lower interference requirements in the wireless communications arena are exploiting higher carrier frequencies and wider modulation bandwidths. Circuitry which can perform intermediate frequency processing over these more demanding ranges is needed to provide complex signal processing without commercial penalties. Photonics technologies utilizing Bragg Grating signal processing (BGSP) can bridge the gap between the very high frequency RF millimeter wave integrated circuit (MIMIC) domains at the antenna interface and the CMOS digital signal processors at the base band frequency interface. The desirable benefits of multiple tap adaptive finite impulse response (FIR) and infinite impulse response (IIR) filters and equalizers are well known;however, they are usually the province of digital signal processing and force the sample rates prior to these processors to a higher overall system power consumption level. BGSP provides these functions with discrete taps and digital controls but at the bandwidths usually reserved for RF circuitry because the actual processing occurs at optical frequencies and at wave lengths which are compatible with integrated circuit technologies. The high performance benefits of photonic processing can be realized if the stability control of the Bragg grating is derived from the same metric which induces in photonics its sensitivity to drift. We will present a orthogonally coded tap modulation technique which stabilizes the transfer function of the signal processor and enables significant adaptive IF signal processing to be obtained with very low size, weight, and power. Our demonstration of a photonic proof-of-concept architecture is a reconfigurable multiple tap FIR filter that is dynamically controlled to perform low pass, high pass, band pass, and band stop filters operating over bandwidths of 3 GHz.

关键词： signal processing Fiber Bragg gratings Filtering (signal processing) Control systems Linear filtering Digital signal processing Optical filters Servomechanisms Modulators Electronic filtering

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New signal adaptive approach for the reduction of interference terms in quadratic time-frequency distributions

New signal adaptive approach for the reduction of interferen...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Nickel, RM Williams, WJ Univ Michigan Dept Elect Engn & Comp Sci Ann Arbor MI 48109 USA

ISBN: (纸本)0819429163

One of the key problems in high resolution (quadratic), time-varying spectral analysis is the suppression of interference terms which can obscure the true location of auto components in the resulting time-frequency distribution (TFD). Commonly used reduced interference distributions (RIDs) tackle the problem with a properly chosen two-dimensional low pass filter (kernel). A recently published(8) novel approach uses alternative means to achieve the desired goal. The idea of the new method is to obtain an estimate of the cross terms from a given prior distribution based on the magnitude and location of its negative components. The estimate is constructed via an iterative projection method that guarantees that the resulting distribution is positive and satisfies the marginals. Even though the marginals are usually a desirable property of TFDs in general, they can impose an undesirably strong constraint on positive TFDs in particular (Examples are given in this paper). For these cases it is thus beneficial to relax the marginals-constraint. In this paper we present a new method that does not require the incorporation of this constraint and thus leads to positive TFDs with reduced interference terms but without the restrictions due to the marginals.

关键词： positive time-frequency distributions cross-terms successive projections penalty functions

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Element accessed array radar processing

Element accessed array radar processing

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Wills, GD Rees, HD Skidmore, ID Def Evaluat & Res Agcy Malvern WR14 3PS Worcs England

ISBN: (纸本)0819429163

Digitising the signals from a phased array at the element level is becoming more practicable through advances in technology. Adaptive beamforming schemes such as a sample matrix inversion involve inverting a covariance matrix of dimension equal to the number of spatial channels. Since with an element digitised system there can be several thousand elements it becomes impractical to invert such large matrices. This paper presents a weight computation scheme for a fully digitised system. The clutter returns are firstly range gated and then the adaptive process is broken down into a smaller cascade of stages, or domains. Attenuation of the clutter is then achieved using a spatial Wiener filter in each domain. From a simulation of an airborne radar at a high pulse repetition frequency, examples are given of adapted beampatterns and clutter output doppler spectra within each domain. By choosing alias free domains, a clutter-free output is obtained for the sidelobe clutter scenario investigated. A comparison is then given with the performance of a 32 sub-array system. The sub-array system does not have the necessary control of the small scale order of the array weights to spatially null the clutter.

关键词： element level digitisation radar clutter subarrays

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Regularization of ill-posed problems using (symmetric) Cauchy-like preconditioners

Regularization of ill-posed problems using (symmetric) Cauch...

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SPIE Conference on advanced signal processing algorithms, architectures, and implementations VIII

作者： Kilmer, ME Northeastern Univ Dept Elect & Comp Engn Boston MA 02115 USA

ISBN: (纸本)0819429163

In certain applications, the discretization of two-dimensional integral equations can lead to systems involving matrices with block Toeplitz-Toeplitz block structure. Iterative Krylov subspace methods are sometimes employed to find regularized solutions to the related 2D discrete ill-posed problems;however, preconditioners which filter noise are needed to speed convergence to regularized solutions. We describe a preconditioning technique based on the Toeplitz-type structure of the matrix which generalizes the approaches in [1] and [2] to take advantage of symmetry and real arithmetic operations. We use fast sine transforms to transform the original system to a system whose matrix has partially reconstructible Cauchy-like blocks. The preconditioner is a block diagonal, rank m approximation to this matrix, with Cauchy-like blocks each augmented by an identity of appropriate dimension. We note that the initialization cost is in general less than that for the similar 2D preconditioner in [2] which does not take advantage of symmetry. Several examples are given which illustrate the success of our preconditioned methods.

关键词： regularization Toeplitz Cauchy-like minimal residual image processing deblurring

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