WCDMA系统的迭代信道估计研究

本文针对WCDMA系统非连续导频情况,研究了采用Turbo编码的迭代信道估计技术,提出了一种基于LMS算法自适应滤波的信道估计方法.对信道估计值采用不同滤波器方法:维纳滤波、滑动平均滤波、FIR滤波、LMS自适应滤波的性能进行了比较,同时采用基于代价函数的方法对迭代信道估计进行了分析.理论分析和仿真结果表明对迭代信道估计所得信道估计值进行滤波的方法能够提高信道估计的精度,从而降低接收机的误比特率.     

MIMO-OFDM系统中一种基于自适应滤波的信道估计方法

该文提出了一种适用于MIMO-OFDM系统的基于自适应滤波器的信道估计方法,此方法在不需要任何信道统计信息的前提下,通过自适应滤波的方法对时变信道状态参数进行即时跟踪与估计。仿真结果表明该文提出的基于自适应滤波的信道估计方法,相比于不考虑噪声的基于LS算法的信道估计方法,MSE和BER性能均有很大的提高。其中基于LMS滤波器的信道估计方法具有计算复杂度小的特点;而基于RLS的信道估计方法具有收敛速度快,MSE和BER性能均优于基于LMS方法的特点。     

MPSK调制系统中的自适应信道估计

本文研究了在MPSK调制方式下,不发送训练序列的商接判决自适应信道估计问题。为提高信道估计性能,提出采用软判决鉴相估值来调整加权最小均方(WLMS)和加权递归最小二乘(WRLS)自适应算法中的权值来进行信道估计,并研究了改进的软判决WRLS算法。结果表明,软判决加权LMS算法比一般LMS性能有很大提高,改进的软判决WRLS算法估计性能优于WRLS算法。     

基于RLS的MIMO OFDM自适应信道估计

依据最小均方误差准则提出了基于多相正交序列循环移位和基于重复相位旋转Chu两种训练序列设计方法,并给出了相应的最小二乘(RLS)自适应信道估计算法。首先用简单的LS算法对信道进行初步估计,然后采用RLS算法进行自适应滤波器提高信道估计的性能,最后,将滤波后得到的时域信道估计经过FFT变换为频域信道响应,并对OFDM数据符号进行频域均衡。与传统单一的信道估计技术相比,该方法具有较低的复杂度和较好的估计性能,仿真实验证明了该算法的有效性。     

OFDM系统自适应盲信道估计新方法

基于无线通信OFDM系统信道估计,提出了两种时域自适应盲估计方法。这些方法通过对极性(符号)LMS算法（SLMS）进行改进,改进算法有几方面优点,一是继承了极性LMS算法简单易实现的特性;二是解决了极性LMS收敛速度慢的缺点;最后结合自适应可变步长及步长调整策略,有效地提高了算法的估计性能。仿真给出了误差曲线以及归一化均方误差曲线,结果表明,和基于极性LMS盲估计方法相比,修正极性LMS和时变步长修正极性LMS盲估计方法均具有很快的收敛速度。由于采用了变步长技术,时变步长修正极性LMS盲估计方法具有更好的估计性能。      

一种基于LMS自适应滤波的互相关时延估计优化算法

在多站时差定位系统中使用基于LMS自适应滤波的互相关法进行时延估计时,若采用固定步长因子则会在收敛速度和稳态失调之间存在较大矛盾,从而影响时延估计精度。针对这一问题,文中提出了一种基于分段变步长LMS自适应滤波和希尔伯特差值的互相关时延估计优化算法。该方法首先采用分段变步长LMS自适应滤波对信号进行滤波处理,然后将滤波后的信号作互相关运算,最后通过希尔伯特差值法锐化相关函数的峰值,进一步提高时延估计精度。在相同条件下,文中模拟分析了不同算法的时延估计精度。实验结果表明,新的优化算法时延估计精度更高。在不同信噪比下,新方法相较传统时延估计方法精度提高了2.2%以上,具有良好的抗噪声性能。     

基于模糊规则的低轨卫星信道自适应估计算法

低轨卫星通信功率控制需要有对信道增益及时的估计,而由于低轨系统链路增益的时变特性使传统的信道估计方法性能受到限制.基于模糊滤波理论,提出一种在功率控制中使用的自适应LMS信道估计算法,根据分析模型和经验数据建立信道增益及其滑动均值大小的模糊集,利用LMS算法调整模糊隶属函数的参数,使算法具有对信道时变特性一定的适应性.仿真结果表明了算法的有效性.     

OFDM调制技术在低压电力线的自适应控制

通过改进传统LMS算法,提出了一种模糊推理的变步长自适应算法。该算法结合模糊推理对LMS算法的步长增益进行了改进,通过模糊推理把输入变量映射为合适的步长增益,从而提高了对信道估计值的精度。通过误差绝对值与均方误差值的比较,表明该算法所测得的信道值比传统的LMS算法信道值更接近真实值,说明该算法具有良好的估计性能。     

一种快速时变自适应信道估计盲方法

提出了一种新的信道估计最小均方(LMS)盲方法--时变步长理想加权判决信道估计盲方法.该方法通过对常规LMS算法进行改进,实现自适应跟踪信道特征变化;同时利用接收机判决误差信息函数作为权系数的理想加权判决,从而解决了常规LMS盲方法收敛速度慢、信道估计性能不高的缺点.仿真证明,对于不同的多普勒频移、时延扩展以及时间,该方法均表现出了比常规LMS方法更优的性能.同时,该方法还可用于航天、雷达等领域估计其他特征参数.     

一种基于LMS滤波的OFDM系统信道估计方法

提出了一种适用于OFDM系统的最小均方(LMS)滤波的信道估计算法,对发送序列中导频位置的信道响应进行LMS滤波,进一步得出所有子载波上的信道响应。仿真结果表明,该方法同基于离散傅里叶变换(DFT)的信道估计算法相比,改善了估计的均方误差(MSE)和误码率(BER)性能。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks