一种自适应滤波中步长因子调节的算法

本文在研究时变信道的自适应匹配中,采用了多途信道的横向滤波器模型(MA模型),为求滤波器权系数应用的是最小均方误差滤波方法。在最小均方误差滤波中无论是采用最徒下降法(Steepst Descent Method),还是最小均方算法(LMS Algorithm),在叠代方程中都要引入步长因子μ.以往对μ的取值只推导出一个范围0<μ<1/λ_max,λ_max为采集信号自相关矩阵的最大本征值,且在叠代过程中是一个常数。但究竞取多大值?取小了自适应叠代方程收敛慢,取大了误差能量函数产生振荡,甚至发散。为寻找一种快速收敛的自适应滤波方法,以适应信道的时变特性时发现,对叠代步长因子μ作自适应调节,会使收敛速度有明显提高。     

基于LMS/SOLMS算法的时变多径水声信道估计方法

缓变信道下基于LMS算法的信道估计算法具有较好的跟踪性能,但对快变信道,LMS算法跟踪性能下降。SOLMS算法具有比LMS算法更好的跟踪性能,尤其是在快变的信道下。但由于SOLMS算法在收敛阶段的振荡性,这时收敛速度较LMS算法慢。本文提出一种收敛模式下用LMS算法获得信道的参数,收敛后则切换成SOLMS算法跟踪信道的变化的信道估计方法。新方法结合了LMS算法收敛快和SOLMS算法跟踪性能好的优点。对时变多径水声信道估计的计算机仿真实验证明了该方法的有效性。     

An adaptive filter-based method for robust, automatic detection and frequency estimation of whistles

This paper proposes an adaptive filter-based method for detection and frequency estimation of whistle calls, such as the calls of birds and marine mammals, which are typically analyzed in the time-frequency domain using a spectrogram. The approach taken here is based on adaptive notch filtering, which is an established technique for frequency tracking. For application to automatic whistle processing, methods for detection and improved frequency tracking through frequency crossings as well as interfering transients are developed and coupled to the frequency tracker. Background noise estimation and compensation is accomplished using order statistics and pre-whitening. Using simulated signals as well as recorded calls of marine mammals and a human whistled speech utterance, it is shown that the proposed method can detect more simultaneous whistles than two competing spectrogram-based methods while not reporting any false alarms on the example datasets. In one example, it extracts complete 1.4 and 1.8 s bottlenose dolphin whistles successfully through frequency crossings. The method performs detection and estimates frequency tracks even at high sweep rates. The algorithm is also shown to be effective on human whistled utterances.     

基于LMS自适应时延估计和FPGA的超声波测风系统研究

利用超声波传感器进行风速测量时,温度对超声波传播有很大影响,时延估计对超声波测风系统的精度起到很大的作用。本超声波测风系统为避免温度对风速测量中的影响,采用了基于时差法的测量原理,为了提高时延估计值的精度,提出了基于最小均方(LMS)自适应时延估计的测量方法,研制了以单片机Atmega128和现场可编程门阵列(FPGA)为核心的硬件系统。仿真和实际测试的结果表明,该超声波测风系统的时延估计值精确度较高,具有很高的应用价值。     

An automatic frequency domain modal parameter estimation algorithm

In this article, a frequency-domain modal parameter estimation method is proposed. The algorithm automatically separates physical poles from mathematical ones. An important issue in the automatization of the algorithm is the inclusion of noise information to estimate the standard deviations of the poles. These standard deviations are used (together with other features) as the inputs of a fuzzy clustering algorithm. The clustering algorithm then classifies the poles into the mathematical and physical ones. The method requires no user interaction, and a parameter is available quantifying the success of the classification.     

An adaptive step-size spectrum auction mechanism for two-tier heterogeneous networks

Recently, with the rapid growth of demands for wireless communications, dynamic spectrum allocation is one of the key technologies in cognitive radio networks to resolve the realistic problem of low utilization efficiency of spectrum. It mainly focuses on how the spectrum owner dynamically allocates idle spectrum to secondary users who have no licensed spectrum for communications. In this paper, a dynamic spectrum allocation model based on auction theory in a two-tier heterogeneous network is proposed, in which the primary users (PUs) are the sellers, the central processor (CP) auctioneer is the coordinator, and femtocell base station (FBS) as the buyer bids for the idle spectrum and act as a wireless access point that provides communication services for secondary users (SUs). Its basic process is as follows: the auctioneer gradually raises the spectrum price from the reserved price; each bidder decides whether participates in the purchase or not. It is characterized by distributed execution and low complexity which can reduce unnecessary information exchange between primary users or secondary users. Meanwhile it can enhance the utilization of spectrum and improve the efficiency of the auction by generate the incentive mechanism.     

An improved least square channel estimation algorithm for coherent optical OFDM system

This paper presents an improved processing added to conventional least square (LS) channel estimation to modify its performance for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. By testing selected limitation factors of the existing algorithms, the influence of our improved algorithm to the performance of CO-OFDM system were studied and compared with other published algorithms. The simulation results of the study demonstrated that the proposed approaches achieved better channel estimation performance and are considered as a more appropriate alternative for CO-OFDM system with the tradeoff between complexity and performance.     

An adaptive quarter-wave tube that uses the sliding-Goertzel algorithm for estimation of phase

This paper describes an adaptive quarter wave tube used to attenuate a tone from the exhaust noise of a large diesel engine. A sliding-Goertzel algorithm was used to calculate the phase angle of the transfer function between a microphone in the adaptive quarter wave tube and in the main exhaust duct. The control system adjusted the length of the adaptive quarter wave tube until the phase angle was −90° and caused the sound pressure level at the cylinder firing frequency in the exhaust duct to be minimized. The system was able to adapt to changes in engine speed, exhaust gas temperature, and load applied to the engine. The results demonstrate that the sliding-Goertzel algorithm can be used effectively to estimate the phase angle in an adaptive–passive acoustic control system.     

Color adjustment algorithm adapted to the spectral reflectance estimation method

We are developing a daily health monitoring system that uses mobile phones with cameras and analyzes physiological conditions from R, G, and B intensity levels. However, since it is affected by various imaging conditions of the image input, color correction is required for accurate health monitoring. Therefore, we developed and validated a colorcorrection algorithm to derive reliable color information by correcting the spectral reflectance using the Wiener estimation and a color chart.     

An NLMS algorithm with optimized preparatory step-size parameters for SQUID-based MCG data processing

We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magnetocardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting the adaptive parameter $\alpha $ to systematic optimum values in the course of the programmed procedure, the convergence is accelerated with a highest speed and the minimum steady-state error is obtained simultaneously. This algorithm may be applied to eliminate other non-steady relevant noises as well.     

利用先验估计自适应加窗的准静态超声弹性成像位移估计算法

准静态弹性成像技术是基于组织压缩前和压缩后超声回波射频信号进行组织运动重构的弹性成像技术。提出了一种基于先验估计的自适应窗函数算法,在位移估计过程中,使用已估计的临近窗的时延值作为先验信息,自动调整截取压缩后射频信号段的截取窗函数,提高了互相关运算所需的压缩前和压缩后信号段之间的相关性。仿真实验结果表明,该算法不仅大大提高了成像速度,而且提高了信噪比较低时的成像质量,同时该算法具有更宽的应变通带。     

A comparative study between LMS and PSO algorithms on the optical channel estimation for radio over fiber systems

In this paper the particle swarm optimization (PSO) and least mean square (LMS) algorithms are comparatively studied to estimate the optical communication channel parameters for radio over fiber systems. It is observed that especially in low noise one tap optical channels, the convergence of LMS algorithm is approximately same with PSO algorithm. On the other hand, as a communication medium, selecting high noisy fiber optical channels or free space optical channels; PSO reaches better mean square error values. The computational complexity which is one of the most important features for optimization algorithms has also been taken into account.     

An adaptive time delay estimati on algorithm based onquadratic weighting of the frequency domain

Time delay estimation (TDE) plays an important role in many engineering appli-cations. A new time delay estimation configuration, the quadratic weighting of the frequency domain adaptive TDE model, is put forward. The quadratic weighting of the frequency domainSCOT (Smoothed Coherence Transform) and ML (Maximum Likelihood) adaptive TDE algo-rithms are presented, respectively. The variance of the quadratic weighting of the frequency domain SCOT algorithm is derived. Then the proposed algorithms are applied in the TDE of helicopter passive acoustic location. The simulation results are presented which verify that the proposed algorithm has better performance in the low signal to noise ratio.     

An improved algorithm for in situ adaptive tabulation

In situ adaptive tabulation (ISAT) is a proven storage/retrieval method which efficiently provides accurate approximations to high-dimensional functions which are computationally expensive to evaluate. Previous applications of ISAT to computations of turbulent combustion have resulted in speed-ups of up to a thousand. In this paper, improvements to the original ISAT algorithm are described and demonstrated using two test problems. The principal improvements are in the table-searching strategies and the addition of an error checking and correction algorithm. Compared to an earlier version of ISAT, reductions in CPU time and storage requirements by factors of 2 and 5, respectively, are observed for the most challenging, 54-dimensional test problem.     

一种对加性噪声和信道函数联合补偿的模型估计方法

语音识别系统在面对实际环境中多变的加性噪声和信道差异的影响时性能急剧下降,抑制这些噪声和差异所造成的性能下降具有重要意义。作者提出了一种模型补偿算法,使用句子中的非语音段估计加性噪声,然后利用EM算法估计信道函数,从而在倒谱域上对失配的声学模型进行联合补偿。实验表明,相比基线系统,采用该算法的系统的平均性能相对提升幅度超过50%。算法可以动态跟踪环境的变化,性能表现优于一些传统的语音识别稳健性处理算法。     

An adaptive system for active cancellation of the acoustic field with an auxiliary identification channel

An adaptive system for active cancellation of a narrow-band random acoustic field with an auxiliary identification channel for modeling a time-dependent acoustic path is investigated. The stability criterion of the system is found. The active cancellation system proposed has been tested experimentally.Lobachevskii State University, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 196–201, March–April, 1995.     

改进的多输人多输出正交频分复用水声通信判决反馈信道估计算法

针对最小均方误差准则下(Minimum Mean Square Error,MMSE)判决反馈信道估计算法在多输入多输出正交频分复用(Multiple-input Multiple-output Orthogonal Frequency Division Multiplexing,MIMO-OFDM)低信噪比水声通信环境下存在误码遗传缺陷,提出了一种基于压缩感知理论的改进的MMSE判决反馈信道估计算法。通过结合浅海水声信道的稀疏性特点,利用编码校验后的信息与原始信息实现了对信道估计的判决反馈更新,采用匹配追踪算法改进MMSE判决反馈追踪信道估计技术,实现了抑制传统判决反馈信道估计算法在迭代更新及传递过程中存在的误码遗传的目的。仿真和水池实验结果证实:改进的MMSE判决反馈追踪信道估计算法不仅可以有效的抑制误码遗传,对抗突发噪声,跟踪信道的缓慢时变,同时大幅降低了导频占用率,提高了通信质量。     

A guide to using shadowing filters for forecasting and state estimation

Most traditional, and many modern, methods of state estimation have a number a failings when applied to high-dimensional and nonlinear systems. A promising new alternative that avoids many of these failings is a shadowing filter. An additional advantage of shadowing filters is that when combined with indistinguishable states they provide a consistent generalisation to the imperfect model scenario. This paper is a practical guide to implementing shadowing filters in nonlinear systems. It provides a detailed account of various tests and procedures to ensure successful implementation of a shadowing filter using gradient descent of indeterminism.     

An adaptive integrated rule-based algorithm for license plate localization

This paper addresses a license plate localization (LPL) algorithm for a complex background. Most of LPL algorithm works on restricted conditions, as well as on a principle of sequential elimination of blocks from image level to final LP candidate region. In most of algorithms, blocks are filtered out for not satisfying required LP features in a top-down approach and this may result in a poor efficiency in a complex scenario. The major steps of the proposed approach are adaptive edge mapping, saliency measure of edge based rules with confidence level estimation using fuzzy rules and final step for reassessment of decision by colour attributes filtering. The proposed algorithm is adaptive to across the country variations in LP standards, as well as it is tested on two data sets each one consisting of more than 700 images, set-1 being for good images while set-2 including only constrained images. The algorithm is tested for a low contrast due to overexposure or poor lighting, existence of multiple plates, variation in aspect ratio and compatible background conditions. It has been observed, that the performance degradation imposing complex condition is nominal.