Cochannel Interference in Partially Coherent Communication

Effects of cochannel interference and synchronization error of the carrier phase on the probability of error in binary communications are considered. Several bounds on the probability of error are proposed. The bounds are easy to compute and do not require complete statistical characterization of the errors. They turn out to be simple linear combinations of error probabilities with no cochannel interferences and no phase errors. Several illustrative examples are given which show that the bounds can be tight.     

Bounds on Probability of Error in Decision Feedback Equalizers

Evaluation of the probability of error in decision feedback equalizers is difficult due to the presence of a hard limiter in the feedback path. This paper derives the upper and lower bounds on the probability of a single error and multiple error patterns. The bounds are fairly tight. The bounds can also be used to select proper tap gains of the equalizer.     

线性分组码不可检错误概率新的下限

线性分组码的不可检错误概率是评价自动请求重传(ARQ)系统的重要参数。不可检错误概率的计算涉及码的重量分布,而大部分码的重量分布还不知道,因此,研究不可检错误概率的限显得非常重要。本文得到了GF()上(n,k)线性分组码不可检错误概率的两个新的下限,在一定程度上,改进了Wolf等人的结果。由于新的限与码的重量结构无关,因此可以方便地估计任何线性分组码的不可检错误概率。     

Angle measurement in the presence of mainbeam interference

The problem of reducing interference impinging on an antenna array when the sources lie in the main beam is addressed. Adaptive antenna arrays are incorporated to form adapted sum and difference beams in which the interference signals are suppressed. Monopulse error curves are then obtained, providing the necessary distortion correction curves across the entire mainbeam tracking angle region. New Cramer-Rao (C-R) bounds on the angle estimation error are derived with generalized assumptions on the signal amplitude and phase. The bounds previously derived by others are valid under different conditions. With these generalized assumptions on the signal characteristics, a Monte Carlo simulation is performed, based on the estimation procedure presented, to determine the angle estimation error. These errors are compared with the C-R bounds. Good performance is shown for sufficient S/N₀ and angular separation between the target and the interference sources     

Estimation of Time of Arrival for Rectangular Pulses

We consider the performance of the maximum likelihood estimator (MLE) for the time of arrival of a rectangular pulse in additive white Gaussian noise. Upper and lower bounds are derived for the mean square error. These bounds are tight for both medium and large energy-to-noise ratios.     

Bounds on the Probability of Error in Digitial Communications

A class of upper bounds and lower bounds on the probability of error in digital communications are derived. Several degrading factors like intersymbol interference, cochannel interference, inaccurate carrier synchronization, and incoherent detection can be considered in obtaining the bounds. Several examples are given and it is shown that many situations not considered so far can be put into the conceptual framework developed here.     

Performance Bounds for Continuous-time Filters in the Presence of Modeling Errors

We are concerned with obtaining bounds on the performance of Kalman-type, linear, continuous-time filters susceptible to modeling errors. Limiting the discussion to stationary performance, we obtain bounds on the performance index, the mean square error of estimates for suboptimal and optimal (Kalman) filters. The bounds are expressed in terms of the model matrices and the range of errors of the matrices. The results are useful to a designer in comparing the performance of a suboptimal filter with that of the optimal filter when he has information on the range of modeling errors. The tightness of the bounds is shown by an application of the results in the estimation of the motion of an aircraft carrier at sea.     

On Truncation Error Bounds for Sampling Representations of Band-Limited Signals

All sampling representations of band-limited signals involve infinite sums. The truncation error associated with a given representation is defined as the difference between the signal and an approximating sum utilizing a finite number of terms. In this paper truncation error is expressed as a contour integral for Lagrange interpolation, general Hermite interpolation, the Shannon series (cardinal series), the Fogel derivative series, and multidimensional sampling expansions. Truncation error bounds are obtained under various constraints on the signal magnitude, spectral smoothness, and energy content.     

Application of the Volterra Series to the Analysis and Design of an Angle Track Loop

A typical function of an angle tracking loop is to keep a radar antenna pointed at a target. The error in pointing is directly related to successful operation of the tracking device; therefore, its behavior is of interest. For a tracker with a general polynomial nonlinearity, an arbitrary initial pointing error, and a bounded deterministic input, a method is developed for finding upper bounds on the magnitude of the tracking error using Volterra series techniques. Convergence regions of the Volterra series are also obtained. Applications of these results are made to a second-order tracking device.     

Global node selection for localization in a distributed sensor network

This work considers the problem of selecting the best nodes for localizing (in the mean squared (MS) position error sense) a target in a distributed wireless sensor network. Each node consists of an array of sensors that are able to estimate the direction of arrival (DOA) to a target. Different computationally efficient node selection approaches that use global network knowledge are introduced. Performance bounds based on the node/target geometry are derived, and these bounds help to determine the necessary communication reach of the active nodes. The resulting geolocation performance and energy usage, based on communication distance, is evaluated for a decentralized extended Kalman filter (EKF) that is exploiting the different selection approaches.     

结构系统失效概率的近似分析

提出用一阶简单边界的上、下界来估计结构系统失效概率的近似公式。它考虑了结构系统失效模式之间的相关性但仅包含失效模式的一阶概率。算例表明,通常最大误差在5％以内,精度高而计算简便。     

Cryptographic Digital Communication

This paper reviews the fundamentals of cryptographic digital systems and defines and discusses the two basic types of ciphers. The remainder of this article examines the word and bit error rates in digital al communication systems with block or stream ciphers. Upper bounds and ensemble averages of the error rates are obtained for both ciphers. The effect of modulation type on the degradation in communication system performance caused by the addition of cryptography is analyzed. A comparison is made between block and stream ciphers with respect to their effects on degradation.     

Comments on "on Probability of Error in Decision Feedback Equalizer"

The above-mentioned paper [1] derives bounds on the error probability of a decision feedback equalizer (DFE) which are claimed to be significantly tighter than the earlier upper bound of [2]. Unfortunately, [1] makes an unsupportable assumption which reddars the conclusions incorrect. We show that valid bounds can be obtained by the methods of [1], but that for the numerical example of [2] , the resulting upper bound is never tighter than, and sometimes significantly weaker than, that derived in [2]. Similarly, a lower bound derived by the method of [1] is shown for the same numerical example to be very close to the error-free past lower bound previously known.     

Paired overbounding for nonideal LAAS and WAAS error distributions

A significant challenge in fielding space-based and ground-based augmentation systems (SBAS and GBAS) for GPS involves the validation of navigation integrity, which requires the establishment of error bounds for aircraft position. This paper introduces a new approach to validating position-domain integrity by using two-sided envelopes for each ranging source. This paired-bounding approach allows for error distributions of arbitrary form and thus improves on earlier integrity validation approaches restricted to zero-mean, symmetric, and unimodal distributions     

空天飞行器的鲁棒自适应模糊轨迹线性化控制

提出了鲁棒自适应模糊轨迹线性化控制(RAFTLC)方法并应用于空天飞行器(ASV)飞行控制系统设计.根据系统的先验知识, 设计出标称模糊系统对系统的未知干扰和不确定进行估计, 并通过鲁棒自适应控制项来克服标称模糊系统逼近误差和权值误差的影响.标称模糊系统逼近误差和权值误差的界在线调整.采用Lyapunov方法证明了闭环系统的所有信号一致最终有界.最后利用提出的控制方案设计了ASV飞行控制系统, 并在高超声速条件下进行了仿真验证.仿真结果表明了控制方案的有效性和鲁棒性.      

Bounds on Elevation Error Estimates of a Target in Multipath

The Cramer-Rao bound for an unbiased estimate of the elevation angle of a target in the presence of multipath is calculated for the symmetric (target and image symmetric about the elevation symmetry plane of antenna) and nonsymmetric cases for an antenna consisting of 21 elements. These bounds are compared to the maximum likelihood estimates and it is found that the rms error of the maximum likelihood estimate (which has a bias) is below the Cramer-Rao bound for unbiased estimates.     

Experimental study in adaptive tracking control

The authors describe an experimental study of adaptive pointing and tracking control for flexible spacecraft conducted on a complex ground experiment facility. The algorithm used is based on a multivariable direct model reference adaptive control law. Several experimental validation studies performed using this algorithm for vibration damping and robust regulation are extended by addressing the pointing and tracking problem. As is consistent with an adaptive control framework, the plant is assumed to be poorly known to the extent that only system level knowledge of its dynamics is available. Explicit bounds on the steady-state pointing error are derived as functions of the adaptive controller design parameters. It is shown that good tracking performance can be achieved in an experimental setting by adjusting adaptive controller design weightings according to the guidelines indicated by the analytical expressions for the error     

Comments on "Bounds on Probability of Error in Decision Feedback Equalizers"

In the above paper1 a technique was proposed to derive an upper bound on the error probability of a decision feedback equalizer. It involves decomposition of the probability density function of residual intersymbol interference and derivation of Chebyshev-type bounds on the error functionals over the decomposed functions. In this correspondence, we demonstrate that the technique is not applicable in general. The result is not a bound in many cases.     

基于切比雪夫多项式展开的转子动力特性区间分析

基于切比雪夫多项式展开,建立了转子系统临界转速和稳态响应区间分析方法,能在仅具有参数上下界的情况下获得结果分布区间。针对临界转速区间分析问题,将支承刚度、密度和弹性模量视为区间变量,建立转子系统固有频率的切比雪夫多项式表达式,最终获得临界转速区间,临界转速误差不超过0.07%。在固有特性分析基础上,应用切比雪夫方法求解转子系统的稳态响应,并由模态叠加原理对响应区间进行修正,解决了固有特性不确定性较大时稳态响应求解精度不足的问题。与蒙特卡洛插值结果相比,响应上界误差不超过8%。基于切比雪夫展开的非确定分析方法,不需修改原结构的振动微分方程。结果表明该方法结合商业有限元软件后,应用简单,并具有理想的精度。     

Digital Communication Systems in Impulsive Atmospheric Radio Noise

Analyses are presented of the performance of binary and M-ary coherent and noncoherent communication systems operating in the impulsive atmospheric radio noise environment. The receiver is usually a maximum likelihood detector for white Gaussian interference and therefore has the form of a parallel bank of matched filters followed by decision circuitry. By employing a Poisson or generalized Shot noise model for the impulsive noise with a suitable probability density function (pdf), closed-form expressions and bounds of error probabilities for M-ary noncoherent and coherent amplitude-shift keying (ASK), phase-shift keying (PSK), and frequency-shift keying (FSK) systems are obtained and the results discussed.