蜂窝中继网络中协作切换策略研究

传统蜂窝网络架构存在着不少缺陷,小区边缘用户的服务质量远差于靠近基站中心的用户。通过部署中继,并完善其切换算法,提出了在该蜂窝中继网络中基于中继协作的切换策略,且对小区内及小区间切换策略进行细化,这样可以更精确的选择接入站点。比较了传统切换与协作切换中的切换阻塞率以及切换次数,通过仿真证明基于中继协作的协作切换的切换阻塞率小于传统切换,且基站间切换次数也得到降低,减轻了基站的负担,使系统性能得到提升。     

基于业务自适应的LTE切换优化机制*

为了减少时延、增加数据传输率,根据业务自适应特征,引入两种触发切换需求,分别从测量控制、切换判决和切换执行三方面对3GPP规范的LTE切换过程加以改进。根据基站邻居列表缩小测量范围,使用层次分析法进行多参数切换判决,在终端与源基站保持连接时进行与目标基站的同步接入。仿真表明此优化机制减少了切换延时,增加了数据传输速率,并有效地提高了切换效率和全网利用率。     

TD_LTE系统中从Macrocell到Femtocell的切换研究

当用户从Femtocell切换到Macrocell时,可能存在不必要的切换,且3GPP协议推荐的切换流程可能会引起较大的DL SIT(DownLink Service Interruption Time)和包丢失率.为此,提出一种优化的切换方法,既可以减少不必要切换,又可实现无缝切换.即切换执行前首先判断是否为不必要切换,如果是不必要切换,则目标基站拒绝本次切换,且推荐一个候选切换小区.同时原目标小区和候选目标小区分别调整切换相关参数.否则允许本次切换,且当切换过程激活后,服务网关将数据同时发送给源小区和目标小区.仿真结果显示与标准3GPP方案相比,该方案可以大大减少DL SIT和数据包的丢失.     

基于用户分群的低轨卫星系统切换管理策略

低轨（LEO）卫星系统具有通信距离远、覆盖范围广等诸多优势,在应急通信、灾害预警等领域发挥着重要作用,尤其能有效弥补地面基站无法服务偏远山区、海洋等盲区的缺陷。然而,LEO卫星高速移动会导致用户终端频繁切换,同时在用户聚集场景下,用户群组并发切换将导致LEO卫星系统发生网络拥塞问题。为此,提出一种基于用户分群的多波束LEO卫星系统切换管理策略。建立多波束覆盖模型,基于该模型设计群组切换管理机制,在成员选择的过程中考虑切换触发时刻和最佳波束小区2个因素,将具有相似切换行为的用户分为一组,以此降低系统的信令开销。在此基础上,从分群处理、群组切换、资源释放3个方面设计完整的切换流程以及切换信令交互机制,并基于OPNET软件搭建LEO卫星系统仿真平台。测试结果表明,该策略能够简化切换管理过程中的重复操作,降低系统信令开销和平均切换时延,提高切换成功率,且用户聚集数目越多,其性能相对传统用户独立切换方案的提升效果越明显。     

基于参考信号接收功率预测和负载的切换算法

针对密集异构网络中用户更容易发生频繁切换的问题,提出了一种基于参考信号接收功率(Reference Signal Received Power,RSRP)预测和负载的自适应切换算法,它不仅从用户的角度考虑了RSRP,而且从网络的角度考虑了基站的负载,同时还针对切换过程中用户的移动性和信道的时变性对RSRP产生的影响,对RSRP进行预测,从而使用户切换到更加合适的目标基站。仿真结果表明,相比于当前的切换算法,所提的切换算法能够获得更低的中断概率和乒乓切换率以及更高的吞吐量。     

基于TTCN-3的异系统间小区切换的测试

对TD-LTE与TD-SCDMA系统间的小区切换问题进行了深入研究,设计了相应的测试流程,提出了一种基于TTCN-3的测试系统实现方案,完成了对TD-LTE与TD-SCDMA系统间小区切换的测试。     

LTE室内外异频互操作策略研究

针对中国电信LTE组网使用室内2.1G与室外1.8G异频组网策略下,室内外异频信号交叠覆盖及频繁切换影响用户感知的问题,通过研究不同的重选和切换策略,提出了使用邻区低优先级小区重选方案和A2+A5切换方案,避免了用户频繁异频切换和室内长期占用室外信号的现象,并提供相关小区重选和切换的参数优化具体设置,为优化LTE室内外频繁切换和重选提供了指导方案,使得网优工程师在对室内外异频互操作优化中可以根据现场环境快速完成优化,降低了现场优化的难度,实现用户感知快速提升.     

认知无线电网络中终端群的接入网切换算法

在集中式认知无线电网络中,认知用户终端需要首先接入次基站才能够进行网络通信,而认知无线电网络的特性也决定了,多个用户终端可能会因某主用户的出现或网络环境质量的恶化,而在某一时刻同时发出网络切换请求.他们之间由于缺少协调会造成某些次基站的拥堵以及用户终端的频繁网络切换.提出一种终端群接入网切换网络侧控制算法,通过核心网侧的网络切换控制器来实现次基站的负载均衡及认知终端群的公平切换.通过模拟仿真,我们发现相较于传统切换算法,本算法可以有效地均衡各次基站的负载,极大地提高网络的整体性能.     

一种移动IP的外部代理分层模型--Step-HMIP

现有的移动IP规范存在两个重要的性能问题：(1)通信对端和外地链路上的移动节点之间的三角路由问题;(2)移动节点在紧密耦合的小蜂窝基站间频繁切换时会增加网络负载并加重数据包的丢失．该文针对这两个问题进行研究,给出了一个基于基本移动IP规范的外部代理分层模型——Step-HMIP模型．在此模型中引入了一个新的实体——网关移动代理,用以实现优化路由和平滑切换的功能：在NS上建立了Step-HMIP的仿真模型,对模型的主要参数测试结果表明．Step—HMIP模型在对属地代理(HA)、固定的通信对端(如Web服务器和FTP服务器)和对网络层以上协议无需进行改动的情况下．以小的配置代价就可显著优化路由,降低属地代理的注册负载和稳定了切换时的数据传输率．     

一种TD-LTE与eHRPD系统重叠覆盖下的负载均衡算法

 针对3G的eHRPD和4G的TD-LTE移动通信系统进行混合组网时,每种网络制式下的小区在用户增多时都有可能过载,除了传统的与邻近小区进行基站的切换,还可以在不同制式之间进行垂直切换。本文以网络资源利用率为参考,对系统内的用户进行异系统垂直切换,从而使混合组网后的系统负载得到均衡。通过该整合系统的仿真,在保证无线链路丢失率不受显著影响前提下,该方法使得蜂窝小区的平均吞吐率有所提高,并能找到使得吞吐率最大时的最佳切换阈值。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。