电力线通信系统中广义频分复用技术频域调制的应用与性能分析

正交频分复用技术(orthogonal frequency division multiplex,OFDM)能够有效的消除电力线信道中的频率选择性干扰、脉冲噪声干扰以及多径时延等不良影响,已成为现有电力线通信系统(power line communication,PLC)物理层调制编码的主要技术手段。但OFDM技术仍存在因添加循环前缀(cyclic prefix,CP)导致的频谱利用率受限、高峰值功率比、严格正交性约束下的同步解调等问题。研究了一种广义频分复用技术(GFDM,generalized frequency division multiplex)在电力线通信中的低复杂度模型及其应用方案,采用非矩形脉冲成型滤波器组,降低了带外频谱泄露,通过数据帧中使用更少的CP,提高了频谱利用率。仿真结果表明,在正交性与同步解调要求较低的情况下,基于GFDM的PLC系统错误率(symbol error rate,SER)性能与正交的OFDM系统性能十分接近,且其带外功率泄露明显降低。     

非正交频分复用技术的研究

针对当今无线频谱稀缺的窘状,提出了一种非正交频分复用(Non-Orthogonal Frequency Division Multiplexing,NOFDM)的传输方案。与当今最为流行正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)相比,该方案在一定程度上提高了频谱效率。在接收端,进行最大似然检测。通过理论推导以及仿真证明了该方案的可行性。     

水下混叠广义频分复用多载波调制方法研究

为提高水声通信系统的频谱效率及误码率性能,将混叠的概念引入了广义频分复用技术(GFDM)中,提出了混叠广义频分复用(O-GFDM)新型多载波调制方案.O-GFDM的发送矩阵及接收矩阵不再是传统的方阵,通过混叠系数来改变矩阵形状,从而提高频谱效率.给出了O-GFDM系统方案模型,并比较了几种主要调制方案的频谱效率分析及水声信道下误码率性能.结果表明,O-GFDM相对于正交频分复用(OFDM)、滤波器组多载波(FBMC)和GFDM表现出了更好的误码率特性和频谱效率.     

基于OFDM的电力线远程路灯控制模块设计

低压电力线通信技术由于其成本低、可靠性高和组网快等优点,成为近年来的研究热点。正交频分复用(OFDM)技术因实现简单、频谱利用率高及较好的抗多径和脉冲干扰性能,成为电力线通信的主要技术之一。文章在分析了电力线和OFDM特性后,给出了用DSP芯片TMS320C6418和单片机PIC16F690实现的基于OFDM的电力线城市路灯控制模块的软硬件结构。     

基于GCS陪集分选降系统峰均比方法

降低正交频分复用系统(Orthogonal Frequency Division Multiplexing,OFDM)的峰均功率比是有效应用OFDM技术的关键。提出了一种有效降低信号峰均比的方法,大大减少了传统的降OFDM系统的峰均比计算复杂度。仿真结果表明新算法更好地降低了正交频分复用系统信号的峰均比。     

MIMO-OFDM混合系统干扰容限研究

通过对多输入多输出系统(MIMO)和正交频分复用技术(OFDM)原理的分析,研究了通信中数据高速传输与系统有限带宽之间的关系,分析了多输入多输出系统和正交频分复用技术的抗干扰性能,阐明了MIMO和OFDM混合系统具有较高的频谱利用率,是一种提高通信系统容量的有效方法.讨论了 MIMO系统信道容量与天线单元之间关系,对3种MIMO-OFDM系统的抗干扰性能进行了研究,系统采用时间、频率和空间3种分集相结合的方法,使MIMO-OFDM无线通信系统干扰容限增加,仿真结果验证了该方法是可行的.     

基于脉冲成型的降低FBMC系统峰均比方法

针对滤波器组多载波(FBMC:Filter Bank MultiCarrier)系统峰均比(PAPR:Peak to Average Power Ration)较高的问题,基于FBMC系统中原型滤波器及其多项结构,借鉴正交频分复用(OFDM:Orthogonal Frequency Division Multiplex...     

MIMO-OFDM混合系统干扰容限研究

通过对多输入多输出系统(MIMO)和正交频分复用技术(OFDM)原理的分析,研究了通信中数据高速传输与系统有限带宽之间的关系,分析了多输入多输出系统和正交频分复用技术的抗干扰性能,阐明了MIMO和OFDM混合系统具有较高的频谱利用率,是一种提高通信系统容量的有效方法。讨论了MIMO系统信道容量与天线单元之间关系,对3种MIMO-OFDM系统的抗干扰性能进行了研究,系统采用时间、频率和空间3种分集相结合的方法,使MIMO-OFDM无线通信系统干扰容限增加,仿真结果验证了该方法是可行的。     

低压电力线数据通信正交频分复用（OFDM）技术研究

正交频分复用技术利用相互正交的多个子载波传送信息,具有频谱利用率高、调制方式灵活、抗多径干扰等特点,已成为第四代移动通信系统的关键技术。本文介绍了正交频分复用（OFDM）系统的基本原理,并说明了低压电力线介质上,改进OFDM技术实现方法。     

浅析低压电力线通信中OFDM技术的应用

随着通信技术的发展,频带资源短缺与日益增加的使用者之间的矛盾日渐突出。提高频带利用率和开拓新的通信资源成为解决这一矛盾的研究重点。OFDM(Orthogonal Frequency Division Multiplexing)即正交频分复用技术,它以其抗多径,频带利用率高,易于实现等优点被普遍认为是低压电力线高速数据传输的理想通信方案。     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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