多用户检测算法及其性能分析

首先阐述了多用户检测的现状，并介绍了线性多用户检测算法、判决反馈检测器、盲多用户检测、盲多用户检测的子空间方法等几种主要的多用户检测技术．对几种多用户检测方法进行了误码率仿真分析，最后对多用户检测技术进行了展望．     

递推功率估值码分多址多用户检测器

在码分多址（ＣＤＭＡ）通信的多用户检测器中，存在多址于扰和Ｎｅａｒ－Ｆａｒ问题．对国、内外新近提出的几种多用户检测器进行了性能分析和比较．在未知信号功率情况下，提出一种性能较优的检测器──递推估计检测器（ＲＥＤ）；通过ＭｏｒｔｅＣａｒｌｏ模拟证明了当Ｎｅａｒ－Ｆａｒ问题严重时，ＲＥＤ检测器的抗Ｎｅａｒ－Ｆａｒ性能优于这几种多用户检测器，但用户之间的功率相差不大时，ＲＥＤ检测器的抗多址干扰能力比去相关判决反馈检测器稍差．     

一种基于天线阵列的判决反馈最小二乘盲多用户检测算法

提出了一种基于天线阵列的判决反馈最小二乘恒模盲多用户检测算法，称为DFB-LSCMA算法。首先用天线阵列中每根天线的均衡输出与期望用户波达方向(DOA)的共轭进行相关形成判决量，然后用检测器的输出与此判决分量的误差信息去调节多用户检测器的抽头系数。仿真结果表明，DFB-LSCMA算法比传统的LSCMA算法性能要好，特别在低信噪比下性能仍优于LSCMA。     

一种基于天线阵列的判决反馈最小二乘盲多用户检测算法 

提出了一种基于天线阵列的判决反馈最小二乘恒模盲多用户检测算法，称为DFBLSCMA算法。首先用天线阵列中每根天线的均衡输出与期望用户波达方向(DOA)的共轭进行相关形成判决量，然后用检测器的输出与此判决分量的误差信息去调节多用户检测器的抽头系数。仿真结果表明，DFBLSCMA算法比传统的LSCMA算法性能要好，特别在低信噪比下性能仍优于LSCMA。     

CDMA系统中多用户检测算法的研究

在DS-CDMA系统中,多用户检测技术是抗多址干扰和“远近效应”的有效方法,因此也成为了第三代移动通信的关键技术之一。文中通过仿真比较分析了传统检测器、最优检测器、解相关检测器、MMSE检测器、串行干扰抵消检测器、并行干扰抵消检测器和解相关判决反馈检测器等经典多用户检测器的误码率、渐近多用户有效性和抗远近能力,并从计算复杂度和所需的假定知识两个方面讨论了这些检测器的实现复杂度。     

基于分支定界算法的DS—CDMAUWB系统多用户检测技术研究

研究一种带预处理的检测器,利用预处理动态设定的门限值直接判决用户的比特数据信息,用以解决线性多用户检测器由于判决门限值固定而影响检测性能的问题;利用分支定界算法进行预处理可以得到全局最优解,将原有的多用户检测问题转变成较小规模的检测问题,以达到减少多址干扰、增加正确判决的概率以及降低系统检测误码率的目的．仿真实验结果表明：预处理后,系统检测正确判决的概率增大,误码率降低．     

分布式检测系统的反馈融合算法

通过分析分布式检测系统的工作原理，在原有并行反馈检测系统的基础上提出了一种新的局部检测器反馈融合算法．该算法利用检测器局部判决结果与数据融合中心融合结果的误差对检测器下一步判决门限进行修正，使各局部检测器可以根据所处的环境，采用不同的修正因子修正判决结果，避免了原有检测系统对所有局部检测器使用相同的修正因子所带来的系统性能损失，从而达到提高检测器检测概率的目的．仿真结果表明，该算法能有效提高系统的性能，对于慢起伏噪声信号具有良好的抑制作用，同时也指出了该算法的不足以及改进的方法。     

编码同步CDMA系统中的Turbo DFD多用户检测

Turbo处理方法可以充分利用编码冗余信息，因此自从提出以来在通信各个领域得到广泛采用。这一方法应用于多用户检测中时，则可从AKMMSE的判决反馈多用户检测器的近似概率密度出发，推导出编码符号的对数似然比信息，然后把该信息作为先验信息输入到采用修正BCJR算法信道解码器中。经信道解码输出的外部信息给多用户检测器进行干扰抵消。然后采用Turbo原理进行迭代，多次迭代后利用MAP解码算法得到解码符号。最后的仿真结果证明这种方法具有较高的效率和接近于单用户的性能。     

一种改进的递推最小二乘盲多用户检测算法

为提高基于递推最小二乘(RLS)算法的盲多址干扰抑制检测器的稳态输出性能，根据空间正交投影算法和自适应判决反馈控制算法，提出一种基于RLS算法的自适应判决反馈盲干扰抑制检测器，该检测器在启动阶段，等价为一种基于RLS准则的盲干扰抑制检测器，在稳态收敛阶段，等价为一种有训练数据的RLS干扰抑制检测器．既保持了最小输出能量(MOE)检测器的全局收敛性，又具有最小均方误差检测器高输出信干比的优点．计算机仿真结果表明，该检测器性能优于已有的基于MOE准则的检测器，且能应用于时变信道．     

多用户检测技术在光码分多址系统中的应用

在分析光码分多址（OCDMA）系统的多址复用光纤传输信道模型的同时，从最长似然检测的角度出发，推导了基于该模型的DCDMA最佳多用户检测器。该检测器可通过维特比（Viterbi）算法实现，在此基础之上，利用相关检测的原理，研究了一种较实用的次佳多用户检测器-多级检测器，在抑制多址干扰的同时，尽量降低检测器实现的复杂度，并分析了它对系统性能的影响，结果表明，由于传输环境的不同，DCDMA系统具有与无线CDMA系统不同的最佳多用户检测判决准则，而作为一种非线性多用户检测技术，多级检测器可以较理想地改善DCDMA系统的误码率性能。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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