Class of cyclic-based estimators for frequency-offset estimation ofOFDM systems

We present a new class of blind cyclic-based estimators for carrier frequency-offset and symbol-timing error estimation of orthogonal frequency-division multiplexing (OFDM) systems. The proposed approach exploits the properties of the cyclic prefix subset to reveal the synchronization parameters in the likelihood function of the received vector. A new likelihood function for the joint timing and frequency-offset estimation is derived, which globally characterizes the estimation problem. The resulting probabilistic measure is used to develop three classes of unbiased estimators, namely, maximum-likelihood, minimum variance unbiased, and moment estimator. In comparison to the previously proposed methods, the proposed estimators in this study are computationally and statistically efficient, which makes the estimators more attractive for real-time applications. The performance of the estimators is assessed by simulation for an OFDM system     

动态系统参数与状态联邦双估计方法研究

本文提出了基于联邦滤波思想的参数和状态双估计模型及算法,给出了多传感器组合系统状态和参数信息分配原则,拓展了双估计及联邦卡尔曼滤波的使用范围.利用北斗/LORAN_C舰船航行实测数据,对双估计、联邦双估计等方法进行试验比较,实验表明,该方法提高了参数和状态估计的准确度.     

A First Step for an INL Spectral-Based BIST: The Memory Optimization

Integral non-linearity (INL) is the main static parameter of analog-to-digital converter. This paper presents a comparison between different INL test techniques based on INL estimation from the spectrum of the converted signal. The most common technique is based on polynomial fitting of the INL curve. This technique is well suited to the estimation of a smooth INL curve without sharp transitions. The new method described in the paper is based on a Fourier series expansion of the INL curve. We demonstrate that this new technique allows a more efficient INL estimation. The comparison between the two techniques has been realized thanks to a metrics that considers the uncertainty of production test measurements. Finally, we propose a first step of the study of implementation feasibility of the INL estimation technique. This study focus only on the optimization of required memory.     

基于MIMO—OFDM系统的信道估计算法分析

MIMO-OFDM技术是未来无线通信系统的研究热点。信道估计是估计出信道的时域或频域响应,对接收到的数据进行校正与恢复,是实现MIMO-OFDM系统优良的传输性能的重要环节。对MIMO-OFDM系统的多种信道估计算法进行了全面深入地探讨,重点分析和比较了基于LS和MMSE的非盲信道估计算法、盲信道估计算法和半盲信道估计算法,并提出了未来信道估计算法的研究方向。     

一种融合残差点信息的改进的多基线InSAR高程重建方法

针对不连续地形难以精确重建地形高程的问题,将干涉图残差点和相邻像素点差异比较相结合的坏点判断方法与基于全变分能量函数的最大后验估计算法结合起来,该文提出一种改进的多基线InSAR高程重建方法。该方法利用干涉图残差点和相邻像素点差异比较对不连续点计算原理的不同,对基于全变分能量函数的最大后验估计算法重建的预估地形高程图进行坏点判断,有效判断出高程图不连续点中由于噪声或计算误差引起的坏点,并对预估地形高程图中坏点进行适当加权更新获得最终估计的地形高程图。该文算法在保留基于全变分能量函数的最大后验估计算法简便的优点的同时提高了目标地形高程的估计精度。最后通过2种不同类型地形的仿真实验,表明该方法简单有效。     

煤矿井下OFDM系统信道估计算法研究及FPGA实现

OFDM技术具有良好的抗多径衰落能力,非常适合煤矿井下无线通信.针对煤矿井下复杂、随机的无线信道特性,在MATLAB环境下建立OFDM系统仿真模型,通过对不同的信道估计算法进行仿真、比较,选择了基于DCT的信道估计算法,并将此算法在FPGA硬件平台上实现.仿真结果表明,该算法是一种在煤矿井下无线信道环境中效果较理想的信道估计实现方案,具有较好的实用价值.     

天气和气象条件对移动mini-DOAS系统测量污染源排放的影响探讨

介绍了北京奥运前利用一套微型被动差分吸收光谱学(mini-DOAS)系统,测量和估算北京市石景山区1个点源和1个面源SO2排放量的实验,探讨了应用该系统测量和估算排放量过程中的重要影响因素,尤其是天气和气象条件的作用.研究发现: (1)测量应当在中尺度天气系统的稳定控制下进行,而天气系统调整阶段由于局地山谷风的干扰,不易获得可靠的测量结果;(2)在混合层高度低、近地面几百米风速小的情况下,可以获得更为准确的测量值;(3)在推算点源排放量时,应选择排放高度上的风速和风向.     

SVM multiregression for nonlinear channel estimation in multiple-input multiple-output systems

This paper addresses the problem of multiple-input multiple-output (MIMO) frequency nonselective channel estimation. We develop a new method for multiple variable regression estimation based on Support Vector Machines (SVMs): a state-of-the-art technique within the machine learning community for regression estimation. We show how this new method, which we call M-SVR, can be efficiently applied. The proposed regression method is evaluated in a MIMO system under a channel estimation scenario, showing its benefits in comparison to previous proposals when nonlinearities are present in either the transmitter or the receiver sides of the MIMO system.     

信道估计在OFDM中的应用

介绍了信道估计在OFDM中的应用,提出一种易于实现的MMSE算法,并对MMSE和LS的性能进行了比较,同时研究了它们的改进算法。结果表明改进算法有很好的性能,可以逼近理想估计。在系统的实现中有较好的参考价值。     

Performance Analysis of Received Signal Strength Fingerprinting Based Distributed Location Estimation System for Indoor WLAN

Location Estimation has become important for many applications of indoor wireless networks. Received Signal Strength (RSS) fingerprinting methods have been widely used for location estimation. Most of the location estimation system suffers with the problem of scalability and unavailability of all the access points at all the location for large site. The accuracy and response time of estimation are critical issues in location estimation system for large sites. In this paper, we have proposed a distributed location estimation method, which divide the location estimation system into subsystems. Our method partitions the input signal space and output location space into clusters on the basis of visibility of access points at various locations of the site area. Each cluster of input signal space together with output location subspace is used to learn the association between RSS fingerprint and their respective location in a subsystem. We have performed experimentation on two RSS dataset, which are gathered on different testbeds, and compared our results with benchmark RADAR method. Experimental results show that our method provide better results in terms of accuracy and response time in comparison to centralized systems, in which a single system is used for large site.     

On parameter estimation in long-code DS/CDMA systems: Cramer-Rao bounds and least-squares algorithms

The problem of parameter estimation in direct-sequence code division multiple access (DS/CDMA) systems employing long (aperiodic) spreading codes is considered. In particular, for an asynchronous network, the problem of estimating the amplitudes, phase offsets, propagation delays, and directions of arrival (DoAs) for the CDMA signals transmitted by the active users is examined. First, formulas are provided for the Cramer-Rao bound (CRB) on the error variance of any joint multiuser parameter estimation procedure exploiting a known training sequence. Further, least-squares adaptive algorithms are derived, which, based on the transmission of known pilot symbols, enable adaptive estimation of the parameters with a computational complexity that is only quadratic in the processing gain. In particular, the cases where either the parameters from all of the active users are to be estimated, or the relevant parameters of only one user are to be acquired (based on the knowledge of its spreading code and training sequence only), are considered. This study is completed by an analysis of the convergence properties of the proposed adaptive algorithms and by extensive computer simulation results illustrating the performance of the estimation procedures, also in comparison with the CRB, and the impact of the estimation errors on the performance of the linear minimum mean square error (LMMSE) multiuser detector.     

测量雷达的实时测角新方法

现代的测量雷达通常要对目标进行实时跟踪,因此必须实时、准确地估计出目标方位。该文针对测量雷达的特殊情况,利用高分辨DOA估计理论,提出了一种新的实时测角方法。和传统的基于比相原理的FFT法相比,在计算量基本保持不变的情况下,新方法在低信噪比时具有好得多的估计效果。     

一种时频变换OFDM系统的信道估计模型

在OFDM系统中,无线信道的准确估计很大程度上决定了系统的传输性能,提出了一种时频变换信道估计模型,并将它应用于自适应OFDM系统中的信道估计,通过与理想自适应系统相比较,研究了模型的性能以及信道估计的误差对于系统性能的影响。     

The estimation of stable distribution parameters from teletrafficdata

This article is concerned with the estimation of the parameters that describe a stable distribution from teletraffic data. Stable distributions are characterized by four parameters that can be estimated using a number of methods. This article provides an introduction to the stable distribution and a summary of some of the estimation techniques developed for them. It presents a comprehensive performance comparison between four techniques and a study of how these techniques can be applied to real data. The data under consideration is that expected on broadband digital networks     

On Blind Timing Acquisition and Channel Estimation for Wideband Multiuser DS-CDMA Systems

The problems of blind timing acquisition and channel estimation for DS-CDMA signals in multipath fading channels are investigated. Using only the spreading code of the desired user, methods based on QR decompositions are proposed. These methods perform comparably or even better than subspace based methods with an order lower complexity. Furthermore, the methods exhibit significantly more robustness to channel order mismatch. Based on the acquired timing information, channel estimation algorithms are also developed which are competitive with the previously proposed subspace based channel estimation algorithms. In addition, a channel order estimation algorithm is proposed for the scenario where the order is unknown. Performance of the proposed algorithms is evaluated through simulation and comparison to asymptotic Cramér-Rao bounds.     

统一系统误差建模及估计方法研究

随着科学的发展，多传感器融合技术在军用和民用的各个领域中应用越来越广泛，而系统误差的估计和校正是影响融合系统性能的关键因素之一。该文针对系统误差建模和估计中存在的如系统误差种类较多、现有误差模型通用性较差等问题，提出了一种较为通用的统一的系统误差模型，并对比分析了现有系统误差估计方法的性能与特点，通过仿真证明了所建模型的通用性和有效性。     

一种改进的OFDM水声通信频偏估计算法

在OFDM水声通信中,由于OFDM系统对频率偏差的敏感性和水声信道的复杂性,载波频偏估计显得尤为重要。本文首先研究了Song和M engali两种频偏估计算法,提出了一种改进的反馈重复频偏估计算法,该算法不仅保持了高精度,增大了估计范围,而且运算复杂度也较小。还在理想条件下对这种改进算法与以上两种算法进行了性能分析比较。此外,还在多径衰落的水声信道下对Song算法和改进方法进行了仿真比较。     

H.264/AVC运动估计算法的硬件结构研究

运动估计是H.264/AVC编码器的重要组成部分,其运算量占据了整个编码器计算时间的60%~90%。对H.264/AVC运动估计的几种快速搜索算法进行分析比较,并在此基础上提出先进的六边形搜索算法。给出运动估计快速搜索算法的一般硬件结构,并在此基础上提出具有流水线并行处理能力的先进六边形搜索算法的硬件结构。实验结果表明：该硬件结构系统工作频率能够达到109.06 MHz,完全能够满足高清视频实时应用的要求。     

Pel-recursive motion estimation algorithm

A new pel-recursive motion estimation algorithm for video coding applications is presented. The derivation of the algorithm is based on recursive least-squares estimation that minimises the mean-square prediction error. A comparison with the modified steepest-descent gradient estimation technique algorithm shows significant improvement in terms of mean-square prediction error performance