多用户MIMO空分多址下行链路预编码算法研究

针对多输入多输出(MIMO)空分多址下行链路,每个接收天线看成独立的用户来分配波束,联合正交随机波束成形(ORBF)和迫零波束成形(ZFBF)实现了每用户配置多天线的预编码方法。为了降低计算复杂度,提出了联合线性结合技术的RBF-ZFBF的下行链路预编码方案。该方案利用ORBF确定初选用户,每个用户利用线性结合技术获得有效SINR,所选用户将使用线性结合方法获得的信道质量信息(CQI)和信道方向信息(CDI)反馈到基站,完成用户选择、波束选择和最终预编码。实验结果表明,该算法与每用户单天线方案相比,提高了系统吞吐量,证实了所提算法的有效性。     

一种智能天线MC-CDMA系统中的最小二乘恒模波束成形算法

提出了智能天线多载波CDMA系统中一种最小二乘恒模波束成形算法，它是在对多载波阵列接收信号进行恒模波束成形的同时，用已估信道参数对各个子载波上的信号进行合并（采用ORC、EGC或MRC），然后对合并后的信号进行判决，用判决后的信息和期望用户的扩频码重构各个子载波上的信号，最后用此重构信号与波束成形输出信号的差去控制波束成形器的抽头系数，从而提高了系统的性能．对这种波束成形算法与传统的最小二乘恒模波束成形算法进行了仿真比较，仿真结果表明，提出的束成形算法的误码性能优于传统的算法．     

分布式天线小区协作通信系统下行链路频谱效率的研究

针对多小区分布式天线系统中下行链路的干扰问题,提出将基站协作通信和分布式天线技术相结合,通过最大化最小的用户频谱效率,保证用户频谱效率的公平性.同时提出一种用户天线选择关闭算法,改进了传统的基站协作迫零波束成形技术在用户数接近最大值时频谱效率急剧下降的缺陷.仿真结果表明,采用分布式基站天线和用户天线选择技术的小区协作通信,可以获得更高的用户频谱效率.     

多天线系统特征波束成形技术中的功率分配算法

介绍了基于特征波束成形的多天线传输技术.针对特征波束成形技术与两种典型的多天线技术(空时编码和分层空时)相结合的系统,从提高系统传输性能出发,分别推导了在独立同分布衰落信道中,发射端已知信道相关矩阵信息的情况下,特征波束成形的功率分配算法.仿真和分析结果表明,在发射端已知信道信息有限的情况下,作者提出的方法能显著改善多天线传输系统的性能,并且在发射天线间存在相关性时,仍能改善系统的性能.     

结合接收波束成形的Tomlinson-Harashima预编码方法

给出了一种利用Tomlinson-Harashima预编码(Tomlinson-Harashima precoding,THP)结合接收波束成形的多用户多输入多输出系统的广播信道预编码方案。当移动台有多个接收天线时,基站采用迫零Tomlinson-Harashima预编码(zero-forcing THP,ZF-THP)消除多用户间干扰,同时每个移动台利用接收波束成形保证系统拥有最大和容量。进而分析了预编码时QR分解的2种最佳的排序方法,揭示出ZF-THP系统存在和容量最大和误码性能最优不能兼顾的问题,而提出方案作为一种有效折衷,比传统的未排序的ZF-THP系统具有更高的和容量与更好的误码率性能。     

有限反馈的联合波束成形和调度方案

提出一种基于有限反馈的联合波束成形和调度方案:用户利用一种结构化的码本对用户的信道方向信息(CDI)进行量化,采用一种低复杂度算法计算其最大的信号干扰信噪比(SINR),反馈给基站;基站根据接收到的反馈信息,按照和容量最大的准则选择出多个正交波束以及相应的多个用户.此方案不需考虑所有可能的用户子集,因此其复杂度仅随用户数呈线性增加.与Sharif等前人方案相比,该方案具有更高的吞吐量,避免了选择波束成形矢量时的用户冲突,基站不需要将波束成形矢量发给各个用户.     

预波束成形智能天线在GSM系统中的应用

将预波束成形的智能天线及SDMA技术应用到GSM系统的扩容问题当中,对几种在多径环境下行之有效的DOA算法性能进行了对比,依据精确的用户来向角识别,利用切比雪夫线阵对下行波束进行了优化设计,并在一个蜂窝扇区的同一时隙中同时处理两个用户,从而将系统容量扩充为原来的2倍．仿真验证了此种扩容方法的可行性．     

多入多出(MIMO)系统中的可变速率多用户分集技术

提出一种在MIMO系统中采用自适应调制实现可变速率多用户分集的方案。这种方案在仅需反馈子信道信噪比的条件下,最大化系统的总比特率。在发射端利用随机波束成形矩阵对发射信号进行波束成形,并根据‘灌水原理’对不同天线的发射信号进行功率分配;接受端对接收信号进行相应的线性处理后,估计出子信道的有效信噪比并将其反馈回发射端。发射端根据反馈的信噪比,采用比例调度算法选出期望用户。最后,在满足一定误码率的条件下,对期望用户的子信道进行自适应调制。仿真结果表明,当小区内的用户数足够多时,所提出的方案获得的系统吞吐量将收敛于在发射端使用特征波束成形矩阵的吞吐量。     

用于智能天线技术中的MMSE波束成形器

近年来，智能天线正受到越来越多的重视，它可以有效地提高移动通信系统的容量，改善系统的信噪比。智能天线的自适应波束成形中，有多种不同的自适应波速成形算法，在这里我们重点讨论使用MMSE算法的波束成形器，因为使用MMSE接收机在静态（或者恒参）信道中，MMSE接收机的性能比较好。文中首先简单介绍智能天线技术，然后通过对MMSE算法和MV算法，设定条件进行仿真对比，来阐述MMSE算法的优势和选择它的场合。     

CR系统中基于空分复用的上行链路设计

设计了多天线认知无线电系统上行信号处理算法.该算法考虑移动终端尺寸、复杂度方面的约束,由认知基站完成接收波束成形及干扰抑制,认知终端仅进行发射波束成形,降低了终端复杂度,便于系统实现.在此基础上提出基于空分复用的机会频谱接入方法,认知系统通过合理的天线配置,当无法获得空闲频谱资源时以空分复用方式完成通信,并且保证对授权...     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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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