An Efficient Dynamic Integration Middleware for Cyber-Physical Systems in Mobile Environments

Advances in information technologies have brought a wide variety of computing environments. In recent years, integrations of computational, networking, and physical elements in different environments tend to increase, so interoperability between heterogeneous computing elements has become a key area of research. A cyber-physical system (CPS) that has gained a lot of attention lately is a tight integration of the system’s computational and physical elements. The CPS technology builds on the older discipline of embedded systems, and CPS applications can be found in diverse industry sectors, such as smart home, health care, and transportation. There is a high possibility that a global CPS network that integrates different CPS networks appears in the near future. This paper proposes a CPS middleware framework that ensures interoperability and communication between heterogeneous components in a global CPS network. Through local and global communications, the proposed middleware makes mobile devices in different networks interoperable. It employs Internet Protocol version 6 (IPv6) and performs protocol conversion to communicate with devices using different protocols.     

Dynamic Video Transcoding in Mobile Environments

A transcoder with dynamic feedback addresses interactivity, packet loss, and client power constraints in mobile communication systems.     

动态环境下载波锁相跟踪环的信号级仿真

在接收信号载噪比一定的前提下,针对GPS软件接收机在不同运动状态下载波环跟踪的问题,仿真研究了不同环路的跟踪性能:在低加速度动态下采用2阶锁相环跟踪更佳,在高加速度动态下则应该采用3阶锁相环跟踪。通过仿真验证了环路的有效性。此外通过仿真发现当载噪比和滤波器噪声带宽一定的情况下,选择合适的预检测积分时间可以有利于载波跟踪。     

高动态条件下测控系统载波跟踪环路优化设计

航天测控系统中载波跟踪误差主要来源于热噪声和航天器动态应力,对载波跟踪环路的优化一般通过调整环路等效噪声带宽来实现.分析了航天测控系统中航天器的动态应力特性及环路跟踪误差特性,导出由载噪比和动态应力决定的环路最佳带宽表达式,提出一种通过环路自身状态估计载噪比和动态应力的方法,通过对载噪比和动态应力的实时估计实现对环路参数的实时调整.仿真结果表明,该算法在动态应力和载噪比时变的高动态场合可以实现稳定的载波跟踪,测量精度得到明显改善.     

Secure Transmission of Mobile Agent in Dynamic Distributed Environments

Huang et al. has recently proposed an efficient key management and access control scheme for mobile agent environments based on Elliptic Curve Cryptosystem (ECC). Although their scheme provides superior efficiency in comparison with the previous works, however some active attacks threaten its security. In this paper a new dynamic key management scheme based on ECC is proposed that is secure and also is efficient in computation cost. Analyzing the security criteria and performance confirms suitability of the proposed scheme for mobile agent environments.     

Optimal Training Sequence for MIMO Wireless Systems in Colored Environments

In this paper, we design the training signal for a multi-input multi-output (MIMO) communication system in a colored medium. We assume that the known channel covariance matrix (CM) is a Kronecker product of a transmit channel CM and a receive channel CM. Similarly, the CM of the additive Gaussian noise is modeled by a Kronecker product of a temporal CM and a spatial CM. We maximize the differential entropy gained by receiver for a limited energy budget for training at the transmitter. Using, singular value decomposition of the involved CMs, we turn this problem into a convex optimization problem. We prove that the left and right singular vectors of the optimal training matrix are eigenvectors of the channel transmit CM and the noise temporal CM. In general case, this problem can be solved numerically using efficient methods. The impact of the optimal training is more significant in environments with larger eigenvalue spread. The expression of the optimal solution is interesting for some specific cases. For uncorrelated receive channel, the optimal training looks like water filling, i.e., more training power must be invested on the directions which have more impact. For high signal-to-noise ratios (SNRs), any orthogonal training is optimal; this means that if large amount of energy is available, it must be invested uniformly in all directions. In low SNR scenarios where low amount of energy is available for channel training, all the energy must be allocated to the best mode of channel (which has the highest ratio of the received channel variance to the received noise power).     

Cluster Properties Investigated From a Series of Ultrawideband Double Directional Propagation Measurements in Home Environments

Results from double directional ultrawideband (UWB) channel sounding in a wooden house are described. The double directional channel sounder estimates directional information at both ends of the link, so that we can separate antenna directivity from the channel sounding results. We investigated the dominant propagation mechanisms by introducing cluster analyses. The detected propagation paths from the channel sounding were first classified into clusters in the angular-delay domain, and then properties of the clusters such as standard deviation of path positions, dynamic range of path power, and power distribution of clusters were derived. From the results, we discussed the similarities and differences between the measurement environment and the physical propagation phenomena. Finally, different types of scattering losses of the propagation paths were derived and modeled. The results from sounding and analysis contribute in the development of UWB propagation models and can be used in UWB propagation simulations     

泛在末梢环境下基于动态备用的业务应急机制

在移动自组织网络(MANET)组成的泛在末梢环境下,由于终端能力有限及网络拓扑的动态变化,无法保证持续高质量的异构业务。该文提出一种基于动态备用的业务应急机制,实现备用指标函数的构建和业务修复策略的设计,包括业务发现、业务选择和业务维护3个阶段。首先,该文综合终端个体能力、协同能力及终端移动性预测,抽象出备用指标函数模型。其次,针对业务选择阶段提出基于时间预测算法(TPA)来构建稳健的业务执行及备用的终端集合。再次,针对业务维护过程的失效,提出全局备用算法(GBA)来动态维持业务的持续性。最后,通过仿真表明在该机制作用下,业务中断次数少于基于动态监督器的业务恢复方法(DMBSRS)和冷备用业务替代策略(CBSRS)约30%~45%和14%~28%,在效益方面分别高于这两者约10%~40%和0%~25%,同时具有最小重启时间,由此证明该机制具有较优的效率。     

Service Parameter Exposure and Dynamic Service Negotiation in SDN Environments

Software-defined networking(SDN)is a generic term and one of the major interests of the telecoms industry(and beyond)over thepast two years.However,defining SDN is a somewhat controversial exercise.The claimed flexibility,as well as other presumed as-sets of SDN,should be carefully investigated.In particular,the use of SDN to dynamically provision network services suggests theintroduction of a certain level of automation in the overall network service delivery process,from service parameter negotiation todelivery and operation.This paper aims to clarify the SDN landscape and focuses on two main aspects of the SDN framework:net-work abstraction,and dynamic parameter exposure and negotiation.     

Adaptability and Dependability in Dynamic Environments: the Quasi-Synchronous Approach

The widespread of new communication and computation infrastructures creates the potential, and the desire, to build, in that environment, applications with every increasing requirements in what concerns dependability and real-time. However, the dynamic characteristics and type of synchronism usually present on that type of environment (weak synchronism) makes it difficult to achieve that goal. Obtaining cost-effective systems implies the existence of a high level of flexibility and adaptability. That adaptability needs to be done in a timely and safe way so as to not compromise application goals. The quasi-synchronous approach makes it possible to deal with this situation in an effective way. By restricting synchronism requirements to a small part of the system, we are able to obtain synchronous components that can be used to control and validate the other components operation. Timely detection of timing failures and periodic dissemination of control information, allow to build an environment able to support the development of applications offering the desired adaptability and dependability characteristics.     

Use and Disuse of Contextual Primes in Dynamic News Environments

This study reexamines the news priming effects of the 1991 Persian Gulf War. Suggesting an alternative approach to those used in previous studies, this study assesses individuals' use and disuse of a contextual prime (i.e., the air war) in dynamic news environments. With a short-term, quasi-experimental approach considering the air war as a prime stimulus, a path analysis suggests robust evidence of the short-term accessibility effects of priming. More importantly, as suggested in Martin's (1986) set/reset model, this study extends priming effects beyond the simple hydraulic patterns of accessibility effects. It reveals that both attitudes toward military action and attitudes toward a diplomatic solution were used in subsequent judgments of the president's job performance and handling of the war. The associations between attitudes toward a diplomatic solution and subsequent judgments were even stronger than those between attitudes toward military action and the same subsequent judgments, despite the clear prowar primes of news discourse in the air-war context. This pattern was more greatly intensified among those in the high news attention group than those in the low news attention group     

移动通信环境中多媒体服务的动态资源分配

由于需求的显著增加，产生了在移动通信环境中提供多媒体服务的问题。本文根据对支持多媒体服务的基站的系统要求，介绍一个动态资源分配方案，该方案可以为陆基和移动环境间的接口提供一个框架。     

Exploiting Varying Resource Requirements in Wavelet-based Applications in Dynamic Execution Environments

In the context of future dynamic applications, systems will exhibit unpredictably varying platform resource requirements. To deal with this, they will not only need to be programmable in terms of instruction set processors, but also at least partial reconfigurability will be required. In this context, it is important for applications to optimally exploit the memory hierarchy under varying memory availability. This article presents a mapping strategy for wavelet-based applications: depending on the encountered conditions, it switches to different memory optimized instantations or localizations, permitting up to 51% energy gains in memory accesses. Systematic and parameterized mapping guidelines indicate which localization should be selected when, for varying algorithmic wavelet parameters. The results have been formalized and generalized to be applicable to more general wavelet-based applications.     

从嵌入式系统角度研究交互电视Java应用(MHP)的设计

介绍了开发MHP Java应用及其所处的环境特点,探讨了MHP应用程序开发人员在设计MHP应用软件时应注意与考虑的基本问题.     

多主体系统中的动态服务匹配

本文研究了多主体系统的服务匹配问题,分析了目前服务描述语言CDL、SDL和LARKS等存在的不足,并结合Web服务、语义Web服务和Grid服务等特点,提出了一种带语义、继承以及支持协商机制的主体服务描述语言SDLSIN.在SDLSIN的基础上,本文重点研究了多主体系统中的动态服务匹配,提出了四种类型的服务匹配算法.最后,介绍了SDLSIN和服务匹配算法在多主体环境MAGE中的实现方法.     

Effective Location Based Services with Dynamic Data Management in Mobile Environments

With the proliferation of mobile computing technologies, location based services have been identified as one of the most promising target application. We classify mobile information service domains based on feature characteristics of the information sources and different patterns of mobile information access. By carefully examining the service requirements, we identify the dynamic data management problem that must be addressed for effective location based services in mobile environments. We then devise a general architecture and cost model for servicing both location independent and location dependent data. Based on the architecture and cost model, we propose a set of dynamic data management strategies that employs judicious caching, proactive server pushing and neighborhood replication to reduce service cost and improve response time under changing user mobility and access patterns. Detail behavior analysis helps us in precisely capturing when and how to apply these strategies. Simulation results suggest that different strategies are effective for different types of data in response to different patterns of movement and information access. Shiow-yang Wu is an associate professor of the Department of Computer Science and Information Engineering at National Dong Hwa University, Hualien, Taiwan, R.O.C. He received the BS and MS degrees in computer engineering from National Chiao Tung University, Hsinchu, Taiwan, ROC, and the PhD degree in computer science from the University of Texas at Austin in 1984, 1986, and 1995, respectively. His research interests include data/knowledge bases, mobile computing, distributed processing, intelligence information systems, and electronic commerce. Kun-Ta Wu was born in Taipei, Taiwan, R.O.C., in 1976. He received the B.S. degree in computer science from Soochow University, Taipei, Taiwan, R.O.C., in 1999 and the M.S. degree in computer science and information engineering from National Dong Hwa University, Hualien, Taiwan, R.O.C., in 2001. Currently, he is an Assistant Researcher in the Domestic Division at Science and Technology Information Center, National Science Council, R.O.C., as a member of Information Gathering and Analysis Group of National Information and Communication Security Taskforce. His research interests include mobile computing, wireless network and information security.     

正态随机噪声环境下遗传算法的动态适应度评价

在大量实际应用问题进化优化的适应度评价都受到了噪声的干扰.本文研究了正态随机噪声对适应度评价的影响机理,对比分析了正态随机噪声环境下不同适应度评价方法的性能.本文提出了一种多次评价一次采样的动态适应度评价方法,该方法在种群更新过程中,重新评价上一代种群,可以降低伪优个体（劣个体）的生存周期,抑制随机噪声对优胜劣汰机制的影响.实验结果也表明总采样次数相同的情况下,新方法的性能优于一次评价一次采样和一次评价多次采样方法.     

有零点二阶系统的动态性能分析

本文针对有零点的二阶系统,全面分析了零点对动态响应性能的影响,讨论了系统具有左半复平面实数或复数极点时对应的零点在负实轴或正实轴上四种情况,并推导了负实数零极点情况下产生超调的条件,准确地给出了不会产生超调的零点取值范围。结果表明:只有当系统具有实数极点时,恰当地配置一个负实数零点可以明显改善快速性,且不影响平稳性;对于其他情况,增加零点基本上都是弊大于利。     

Performance Analysis of Slotted Multichannel ALOHA Systems with Capture in Microcellular Environments

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