基于用户服务质量和能效的SCMA资源分配

为提高移动通信中用户服务质量(QoS:Quality of Service),解决系统总能效和用户服务质量不能兼顾的问题,以稀疏码多址接入(SCMA:Spare Code Multiple Access)下行链路为应用场景提出了一种基于用户服务质量和能效的资源分配方案,将系统的容量和能耗作为主要方向进行优化。使用贪婪算法对用户进行码本分配,采用丁克尔巴赫理论(GDA:Generalized Dinkelbach’s Algorithm)将其转化为一个凸优化问题进行迭代求解,以本次计算得出的用户最低服务速率作为下一轮运算的系统最低服务速度重复进行用户码本和能耗轮换计算,直到系统中用户最低通信速度变化低于预设值或达到最大运算次数为止,使系统的容量及能耗达到较好的情况。通过理论分析和仿真结果表明,所提出的SCMA分配方案能有效提升下行链路的用户的通信速率和系统能效。     

基于QoS驱动的多目标优化用户动态关联研究

为实现5G通信网络自组织、自优化发展,提出一种混合控制多目标优化用户动态关联算法。在满足用户服务质量和基站成本效益的需求下,同时考虑吞吐量、能耗、基站效用等因素,基于QoS需求实现用户和基站的动态关联,从而解决因用户动态变化带来的网络拥塞、资源浪费、负载增加等问题。并引入随机梯度下降算法优化传输功率,提高网络吞吐量与基站利用率。仿真结果表明,该算法在提高网络吞吐量和基站利用率的基础上能有效缓解基站负载不均衡现象。     

比例公平保证下的SCMA能效资源分配研究

在倡导绿色通信的背景下,基于能效的资源分配算法是近些年研究的热点。针对稀疏码多址接入(sparse code multiple access, SCMA)下行链路系统,以保障用户服务质量为前提,降低接入网能量损耗,给出一种比例公平保证下的能效资源分配方案。将用户的最小速率需求以及传输速率比值作为约束条件进行能效资源分配。通过2个阶段的码本分配,既满足各个用户不同的速率需求,又保证了用户之间的公平性;根据已得到的码本分配方案,利用二分法求得近似最优能效下的功率分配。实验结果表明,所给出的算法在保证用户速率比例公平的前提下,也能获得较好的能效性能。     

稀疏码多址接入系统中基于分层编码的多播资源分配算法

稀疏码多址接入(sparse code multiple access,SCMA)技术被认为是一种能有效提高频谱效率的技术。将稀疏码多址接入技术应用于无线多播通信中可以扩展多播系统的容量。对多播系统的容量进行了推导,采用分层编码技术应用在SCMA系统的多播传输中,使得系统容量不再受限于多播系统中最差用户的信道质量,采用资源分配算法来最大化多播系统容量。为了减少最优化问题的计算复杂度,又提出了快速次优化算法(fast suboptimal algorithm, FSA),该算法分为码本分配和功率分配2个阶段。仿真结果显示,提出的快速次优化算法在SCMA系统中的多播系统功效要优于正交频分多址接入(orthogonal frequency division multiple access, OFDMA)系统中的多播系统功效。并且,在SCMA系统和OFDMA系统中,提出算法的系统功效都要远优于传统多播(conventional multicast, CM)策略的系统功效。     

认知网中多时隙联合频谱感知和功率分配

为了降低认知无线网中认知用户对主用户的干扰,并为了最大化系统的认知吞吐量,提出了一种多时隙频谱感知和功率分配的联合优化方案。该方案将系统的每个帧分为若干个时隙,每个时隙分别进行频谱感知,通过合并每个时隙的感知结果,有效的提高了系统的检测精度,降低了系统的干扰概率。同时理论分析了感知时间与传输功率分配方案,发现两者都存在最优分配解,在约束认知用户检测概率与传输功率的基础上,将吞吐量描述为关于感知时间与功率的多约束优化问题,通过设计联合迭代算法对认知吞吐量进行了联合优化并获得了最优感知时间与最优传输功率分配。仿真结果表明,所提联合优化方案吞吐量性能最接近理论最优方案,并可通过牺牲部分吞吐量性能降低系统干扰概率,且复杂度较低。     

SCMA系统中基于能效的码本和功率分配机制

在倡导绿色通信的未来,如何提高能效、降低功耗将成为非常重要的问题.针对基于稀疏码多址接入技术的单小区多用户上行蜂窝移动通信系统,在保障用户服务质量(quality of service,QoS)需求的前提下,以最大化系统上行能效为目标,提出了一种资源分配机制,主要包括码本和功率的分配.为了降低基站的负荷,减小网络信令开...     

无人机辅助的蜂窝数据流量卸载及保密传输方案

为解决传统蜂窝网络中边缘用户上行通信链路质量较差且容易遭到窃听的问题,提出了一种移动无人机辅助的流量卸载和保密传输方案。首先根据空地视距信道特性,建立了基于接收信号强度阈值的信道接入机制,解决了用户传输模式选择问题;其次,根据空地信道接入时延、无人机飞行高度和速度,确定了任意时刻无人机链路的覆盖范围;然后,利用随机几何理论,给出了平均可达速率解析式和安全容量评估方法;最后,通过仿真实验验证所提方案和理论结果的有效性,并给出关键参数的最优化配置方案。仿真结果表明,与传统蜂窝网络相比,所提出的基于移动无人机的组网方案能够在保证用户公平性的基础上,使网络上行通信速率提高约40%,安全容量提高约70%。     

基于多目标粒子群算法的无人机通信三维位置部署及优化研究

考虑无人机作为临时基站与地面终端用户通信问题,文中研究了节点的三维部署及功率分配的优化问题,以提高系统的能效和用户的覆盖率。首先,考虑了无人机通信节点的三维位置部署和链路传播模型,构建了无人机通信系统模型,并提出了以能效和覆盖率为目标的优化问题。然后,采用多目标粒子群算法对该非线性规划问题进行有效求解,得到其最优解。最后,仿真结果表明,该方案不仅能提高无人机网络的能效和覆盖率,而且能实现优化的节点三维位置部署和功率分配。同时,所提出的多目标粒子群算法与随机算法、贪婪算法相比,可减少迭代次数,防止陷入局部最优解。     

利用地理位置的中继选择及功率分配

在协作多中继蜂窝系统下行链路中,提出根据中继节点地理位置和吞吐量增益联合选取中继节点参与移动用户和基站间的协作通信方案,并运用凸优化算法分配各节点功率.仿真结果表明:该方案不仅改善了用户的误码率,并且提高了系统吞吐量.     

认知无线电系统中联合优化资源分配算法

在认知无线电系统中,次用户能够利用感知到的已授权频段进行通信,只要其传输过程对主用户通信引起的干扰处于主用户可以忍受的程度之内。协作中继方案能够利用中继节点的传输来有效提高频谱的利用率,并增强了直接链路的传输能力。文中研究在一个三节点的认知无线电网络中基于协作中继传输时的资源分配问题,为了保证在认知用户对主用户干扰可容忍的前提下使得通信系统端到端的可达吞吐量最大,提出了一种联合优化功率分配和信道分配的方案。仿真结果显示,相对于单独进行功率分配或者信道分配情况下该方案能够有效提高认知无线电系统端到端的传输性能。     

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.     

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     

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