A CLASS OF LDPC CODE''''S CONSTRUCTION BASED ON AN ITERATIVE RANDOM METHOD

This letter gives a random construction for Low Density Parity Check (LDPC) codes, which uses an iterative algorithm to avoid short cycles in the Tanner graph. The construction method has great flexible choice in LDPC code's parameters including codelength, code rate, the least girth of the graph, the weight of column and row in the parity check matrix. The method can be applied to the irregular LDPC codes and strict regular LDPC codes. Systemic codes have many applications in digital communication, so this letter proposes a construction of the generator matrix of systemic LDPC codes from the parity check matrix. Simulations show that the method performs well with iterative decoding.     

Compensation of mass-based effects in component scaling on a hardware-in-the-loop test bench by virtual inertia

X-in-the Loop (XiL) enables component tests concerning the remaining system to support early validation in the context of frontloading. The system under test is connected with the physical or virtual remaining system. The performance variables of the bidirectional interactions must be adapted to the prototype, especially for testing a scaled prototype integrated into a remaining system. By applying a scaling, the bidirectional interactions between the test object and the remaining system can be considered in a scaled way. It is currently unclear how mass-based effects can be considered in the scaling model to reflect the behavior of unscaled systems.In this paper, the influence of mass-based effects on the adaptation of rotational quantities between interconnected systems is analyzed and compensated by virtual inertias to allow scaled component tests considering the remaining system. Using the example of a torque limiting clutch from a geared rotary actuator out of an aircraft, the influences of the rotational inertia of the drive shaft on the scaling are analyzed in a simulation study.The simulation shows an influence of the rotational inertia on the scaling and the system behavior if these effects are not considered in the scaling. The determining influence is taken into account in the scaling laws using adapted scaling laws by the integration of virtual inertia within the scaling.The results show that virtual inertia can be added to the scaling model to reflect mass-based effects in behavior. This enables simultaneous testing of powertrain components with different scaling in real-time.     

Theory of Periodic Dielect Waveguides

The propagation of electromagnetic waves along open periodic, dielectric waveguides is formulated here as a rigorous and exact boundary-value problem. The characteristic field solutions are shown to be of the surface-wave or leaky-wave type, depending on the ratio of periodicity to wavelength (d/lambda). The dispersion curves and the space-harmonic amplitudes of these fields are examined for both TE and TM modes. Specific numerical examples are given for the cases of holographic layers and for rectangularly corrugated gratings; these show the detailed behavior of the principal field components and the dependence of waveguiding and leakage characteristics on the physical parameters of the periodic configuration.     

Nonbinary LDPC Coding for Multicarrier Underwater Acoustic Communication

Recently, multicarrier modulation in the form of orthogonal frequency division multiplexing (OFDM) has been shown feasible for underwater acoustic communications via effective algorithms to handle the channel time-variability. In this paper, we propose to use nonbinary low density parity check (LDPC) codes to address two other main issues in OFDM: (i) plain (or uncoded) OFDM has poor performance in fading channels, and (ii) OFDM transmission has high peak to average power ratio (PAPR). We develop new methods to construct nonbinary regular and irregular LDPC codes that achieve excellent performance, match well with the underlying modulation, and can be encoded in linear time and in a parallel fashion. Based on the fact that the generator matrix of LDPC codes has high density, we further show how to reduce the PAPR considerably with minimal overhead. Experimental results confirm the excellent performance of the proposed nonbinary LDPC codes in multicarrier underwater acoustic communications.     

A CLASS OF LDPC CODE’S CONSTRUCTION BASED ON AN ITERATIVE RANDOM METHOD

This letter gives a random construction for Low Density Parity Check （LDPC） codes, which uses an iterative algorithm to avoid short cycles in the Tanner graph. The construction method has great flexible choice in LDPC code＇s parameters including codelength, code rate, the least girth of the graph, the weight of column and row in the parity check matrix. The method can be applied to the irregular LDPC codes and strict regular LDPC codes. Systemic codes have many applications in digital communication, so this letter proposes a construction of the generator matrix of systemic LDPC codes from the parity check matrix. Simulations show that the method performs well with iterative decoding.     

Serially-Concatenated Low-Density Generator Matrix (SCLDGM) Codes for Transmission Over AWGN and Rayleigh Fading Channels

Low density generator matrix (LDGM) codes are a particular class of low density parity check (LDPC) codes with very low encoding complexity. Single LDGM codes present high error-floors, which can be substantially reduced with the serial concatenation of two LDGM (SCLDGM) codes. We propose a technique to obtain good SCLDGM codes using extrinsic information transfer (EXIT) functions in a novel way. Although the optimization is performed for AWGN channels with binary signaling, the resulting codes are also optimal for AWGN and perfectly-interleaved Rayleigh fading channels with non-binary signaling and perfect CSI at reception, provided that Gray mapping is utilized. Optimized regular and irregular SCLDGM codes outperform heuristically-designed LDGM codes existing in the literature, and have a performance similar to or better than that of irregular repeat accumulate (IRA) codes.     

新型任意阶分抗逼近电路及新型标度方程

介绍并研究一类具有物理可实现性的描述分数算子有理迭代过程的非正则标度方程,提出几种新型分抗逼近电路,并用广义非正则标度方程描述。推广出基于未知参量m,n的一类非正则标度方程,并研究其描述的分数算子有理迭代过程的特性。置换已知分抗逼近电路中元件位置获得4种新的分抗逼近电路,并用相应的广义非正则标度方程描述。研究表明,广义非正则标度方程具有不同的近似解。最后,介绍广义非正则标度方程描述的阻抗函数代数迭代过程的优化方法,基于新型分抗逼近电路,提出几种具有高运算恒定性的任意阶标度分形分抗逼近电路设计方案。设计分数阶微电路仿真实验,验证新型分抗逼近电路的运算性能。     

Tailbiting codes: bounds and search results

Tailbiting trellis representations of linear block codes with an arbitrary sectionalization of the time axis are studied. The notations of regular and irregular tailbiting codes are introduced and their maximal state complexities are lower-bounded. The asymptotic behavior of the derived bound is investigated. Furthermore, for regular tailbiting codes the product state complexity is lower-bounded. Tables of new tailbiting trellis representations of linear block codes of rates 1/2, 1/3, and 1/4 are presented. Almost all found trellises are optimal in the sense of the new bound on the state complexity and for most codes with nonoptimal trellises there exist time-varying trellises which are optimal. Five of our newly found tailbiting codes are better than the previously known linear codes with the same parameters. Four of them are also superior to any previously known nonlinear code with the same parameters. Also, more than 40 other quasi-cyclic codes have been found that improve the parameter set of previously known quasi-cyclic codes     

Synchronization and complex oscillations in a two-ring system with phase control

Modes of dynamic behavior in a coupled system with phase control are studied. The system is intended for tracking estimation of a complex signal’s parameters. The case is considered when both subsystems individually exhibit both regular and chaotic dynamic states. The boundaries of the region where the system is switched to a tracking mode are determined, and scenarios for transformation of dynamic parameters when the system leaves this area are studied. Application of complex filters in the circuits controlling the subsystems and coupling via the control circuits is shown to enable excitation of various regular and chaotic non-synchronous modes.     

M-band compactly supported orthogonal symmetric interpolatingscaling functions

In many applications, wavelets are usually expected to have the following properties: compact support, orthogonality, linear-phase, regularity, and interpolation. To construct such wavelets, it is crucial designing scaling functions with the above properties. In two- and three-band cases, except for the Haar functions, there exists no scaling function with the above five properties. In M-band case (M⩾4), more free degrees available in design enable us to construct such scaling functions. A novel approach to designing such scaling functions is proposed. First, we extend the two-band Dubuc (1986) filters to the M-band case. Next, the M-band FIR regular symmetric interpolating scaling filters are parameterized, and then, M-band FIR regular orthogonal symmetric interpolating scaling filters (OSISFs) are designed via optimal selection of parameters. Finally, two family of four-band and five-band OSISFs and scaling functions are developed, and their smoothness are estimated     

High-performance simple-encoding generator-based systematic irregular LDPC codes and resulted product codes

Low-Density Parity-Check (LDPC) code is one of the most exciting topics among the coding theory community.It is of great importance in both theory and practical communications over noisy channels.The most advantage of LDPC codes is their relatively lower decoding complexity compared with turbo codes,while the disadvantage is its higher encoding complexity.In this paper,a new ap- proach is first proposed to construct high performance irregular systematic LDPC codes based on sparse generator matrix,which can significantly reduce the encoding complexity under the same de- coding complexity as that of regular or irregular LDPC codes defined by traditional sparse parity-check matrix.Then,the proposed generator-based systematic irregular LDPC codes are adopted as con- stituent block codes in rows and columns to design a new kind of product codes family,which also can be interpreted as irregular LDPC codes characterized by graph and thus decoded iteratively.Finally, the performance of the generator-based LDPC codes and the resultant product codes is investigated over an Additive White Gaussian Noise (AWGN) and also compared with the conventional LDPC codes under the same conditions of decoding complexity and channel noise.     

基于云模型移动对象行为识别算法评价

为了研究视频监控中异常行为识别算法鲁棒性、准确度和速度的评价方法,将采集图像序列移动对象运动类型等参数作为样本输入逆向云发生器,得到移动对象定性概念的定量表示:期望值Ex、熵En和超熵He。以这些参数作为基础模拟出移动对象行为参数表征。Ex,En和He输入正向云发生器,将每个移动对象设计成一个智能体,个体通过感知环境和自激励调整行为参数,产生多种行为表征参数,并用这些参数来评价行为识别算法。通过实验实现了多种行为表征参数的模拟,用这些参数评价了几种典型算法,实验结果表明评价方法切实可行。     

Evaluation of system performance by adding a fourth dimension to turbo code

Different forms of turbo codes (TCs) have already been used in the contemporary message transferring system for transmission of the protected information because of their astonishing bit error rate (BER) behavior. However, it suffers from poor “flattening effect” performance. To overcome this limitation, component encoders having higher memory elements or more number of component encoders may be considered. At the initial segment of this article, the proposal of binary 4‐dimensional turbo code (4D‐TC) with appropriate “generator polynomial” combination and suitable interleaver arrangement has been abridged in Third‐Generation Partnership Project standard. This is an amended form of 3‐dimensional turbo code where some part of the “parity bits” is re‐encoded by the third encoder, and rest part is re‐encoded by the fourth encoder consisting of single memory component. Afterwards, performance of the proposed structure has been assessed by varying block length, number of component encoders, puncturing rate, and channel condition. At the consequent segment, “constricted upper bound” on the BER performances of the 4D‐TC has been assessed by adopting an approach called simplified augmented state diagram. Moreover, an exhaustive analysis has been performed on the novel simplified augmented state diagram approach–based 4D‐TC by fluctuating several internal parameters of the code structure like generator polynomial combination, block length, puncturing rate, interleaver combination, and permeability rate. In this regard, the existing augmented state diagram approach has been considered for comparative analysis as well.     

Space Surface Parameters Determined from Fourier Transforms in Atomic Force Microscopy

A tabular analytic method for calculating space surface parameters of different materials is suggested. It uses Fourier transforms obtained with an atomic force microscope. Examples of calculation are given for periodic space structures and surfaces with different degrees of anisotropy and periodicity. It is shown that space parameters, namely, texture direction and texture direction index and also radial wavelength and radial wavelength index, allow anisotropy characterization and periodicity determination at a nanometer scale.     

Wavelet theory demystified

We revisit wavelet theory starting from the representation of a scaling function as the convolution of a B-spline (the regular part of it) and a distribution (the irregular or residual part). This formulation leads to some new insights on wavelets and makes it possible to rederive the main results of the classical theory - including some new extensions for fractional orders n a self-contained, accessible fashion. In particular, we prove that the B-spline component is entirely responsible for five key wavelet properties: order of approximation, reproduction of polynomials, vanishing moments, multiscale differentiation property, and smoothness (regularity) of the basis functions. We also investigate the interaction of wavelets with differential operators giving explicit time domain formulas for the fractional derivatives of the basis functions. This allows us to specify a corresponding dual wavelet basis and helps us understand why the wavelet transform provides a stable characterization of the derivatives of a signal. Additional results include a new peeling theory of smoothness, leading to the extended notion of wavelet differentiability in the L/sub p/-sense and a sharper theorem stating that smoothness implies order.     

Texture synthesis: textons revisited.

This paper introduces a technique for synthesizing natural textures, with emphasis on quasiperiodic and structural textures. Textures are assumed to be composed of three components, namely illumination, structure, and stochastic. The contribution of this work is that, in contrast to previous techniques, it proposes a joint approach for handling the texture's global illumination, irregular structure, and stochastic component which may be correlated to the other two components. Furthermore, the proposed technique does not produce verbatim copies in the synthesized texture. More specifically, a top-down approach is used for extraction of texture elements (textons) in which, in contrast to previous texton-based approaches, no assumptions regarding perfect periodicity are made. The structure itself can be modeled as a stochastic process. Consequently, textons are allowed to have irregular and nonidentical shapes. In the synthesis stage, a new nonregular textural structure is designed from the original one that defines the place holders for textons. We call such place holders empty textons (e-textons). The e-textons are filled in by a representative texton. Since e-textons do not have identical shapes, a texton shape-matching procedure is required. After adding the illumination to the structural component, a strictly localized version of a block sampling technique is applied to add the stochastic component. The block sampling technique combined with the addition of the illumination component provides a significant improvement in the appearance of synthesized textures. Results show that the proposed method is successful in synthesizing structural textures visually indistinguishable to the original. Moreover, the method is successful in synthesizing a variety of stochastic textures.     

Dark Soliton Transmission in Twin-Core Fiber

Dark soliton transmission is investigated by numerical simulation in twin-core fiber. It is shown that the energy exchange between two cores relates to initial relative phases and initial relative amplitudes of input dark solitons, it may be of regular and apparent period, irregular period, or non-period, and the influence factors on beat length are analysed.     

Nonrigid image registration in shared-memory multiprocessor environments with application to brains, breasts, and bees

One major problem with nonrigid image registration techniques is their high computational cost. Because of this, these methods have found limited application to clinical situations where fast execution is required, e.g., intraoperative imaging. This paper presents a parallel implementation of a nonrigid image registration algorithm. It takes advantage of shared-memory multiprocessor computer architectures using multithreaded programming by partitioning of data and partitioning of tasks, depending on the computational subproblem. For three different biomedical applications (intraoperative brain deformation, contrast-enhanced MR mammography, intersubject brain registration), the scaling behavior of the algorithm is quantitatively analyzed. The method is demonstrated to perform the computation of intra-operative brain deformation in less than a minute using 64 CPUs on a 128-CPU shared-memory supercomputer (SGI Origin 3800). It is shown that its serial component is no more than 2% of the total computation time, allowing a speedup of at least a factor of 50. In most cases, the theoretical limit of the speedup is substantially higher (up to 132-fold in the application examples presented in this paper). The parallel implementation of our algorithm is, therefore, capable of solving nonrigid registration problems with short execution time requirements and may be considered an important step in the application of such techniques to clinically important problems such as the computation of brain deformation during cranial image-guided surgery.     

Automatic Performance Setting for Dynamic Voltage Scaling

The emphasis on processors that are both low power and high performance has resulted in the incorporation of dynamic voltage scaling into processor designs. This feature allows one to make fine granularity tradeoffs between power use and performance, provided there is a mechanism in the OS to control that tradeoff. In this paper, we describe a novel software approach to automatically controlling dynamic voltage scaling in order to optimize energy use. Our mechanism is implemented in the Linux kernel and requires no modification of user programs. Unlike previous automated approaches, our method works equally well with irregular and multiprogrammed workloads. Moreover, it has the ability to ensure that the quality of interactive performance is within user specified parameters. Our experiments show that as a result of our algorithm, processor energy savings of as much as 75% can be achieved with only a minimal impact on the user experience.