A multistage hierarchical distributed arbitration technique for priority-based real-time communication systems

ISO 11898 is a communication protocol based on the carrier sense multiple access with collision detection and arbitration on message priority (CSMA/CD+AMP) technique, which at present is largely used as a real-time network for industrial environments. Unfortunately, because of the peculiarities of the arbitration technique it adopts, it suffers from severe limitations on the maximum extension of the network, which cannot be overcome simply by means of improvements in the transceiver's technology as they depend on the limited propagation speed of the signals on the communication support. In this paper, a new kind of network is presented that features a behavior very similar to ISO 11898, but which achieves noticeably larger areas to be covered without having to reduce the bit rate. It relies on a tree topology and adopts a brand new multistage hierarchical distributed arbitration technique, which takes the increased propagation delays into account properly.     

一种基于分层结构的动态自适应QoS分布控制模型

针对目前IP网实施QoS控制的主要难点问题，本文提出了基于分层结构的动态自适应QoS分布控制模型。本模型借鉴了DiffServ模型中基于端结点的分布控制思想，采用动态自适应的流控机制，这使得本模型不仅具有可扩展性，而且对网络的动态性与异构性具有适应能力。此外，本模型还采用分层结构将基于网络技术、视频编码技术以及FEC容错技术QoS控制策略进行有机集成，在带宽受限的情况下能为媒体流传输提供较好的服务质量。本模型已成功地应用于多媒体同步实时授课系统RealClass中。     

分布式VoD系统的分级存储调度

提出了一种适于大规模分布式ＶｏＤ系统的分级存储调度算法。该算法建立在多队列的排队模型之上,使用上系统均衡方法及基于优先级的缓冲区管理算法,并提供了迁移等待时间的计算方法。通过仿真实验给出了缓冲区大小与业务量和节目驻留时间的关系,为ＶｏＤ分级存储系统的设计提供了依据。     

A method for coordinating the distributed transmission of imagery.

Distributed imaging using sensor arrays is gaining popularity among various research and development communities. A common bottleneck within such an imaging sensor network is the large resulting data load. In applications for which transmission power and/or bandwidth are constrained, this can drastically decrease the sensor network lifetime. We present an algorithm that efficiently exploits inter- and intrasensor correlation for the purpose of power-constrained distributed transmission of sensor-network imagery. Gains in network lifetime up to 114% are obtained when using the suggested algorithm with lossless compression. Our results also demonstrate that when lossy compression is employed, much larger gains are achieved. For example, when a normalized root-mean-squared error of 0.78% can be tolerated in the received measurements, the network lifetime increases by a factor of 2.8, as compared to the (optimized) lossless case.     

楼宇智能控制系统总线电缆的研制

介绍了楼宇智能控制系统总线电缆的特点、性能，并结合实际生产，讨论了总线电缆的设计、制造技术及关键工艺控制和试验。     

A hierarchical model for estimating the early reliability of complex systems

We describe a hierarchical Bayesian model for assessing the early reliability of complex systems, for which sparse or no system level failure data are available, except that which exists for comparable systems developed by different categories of manufacturers. Novel features of the model are the inclusion of a "quality" index to allow separate treatment for systems produced by "experienced" & "inexperienced" manufacturers. We show how this index can be employed to distinguish the behavior of systems produced by each category of manufacturer for the first few applications, with later pooling of outcomes from both categories of manufacturers after the first few uses (i.e., after inexperienced manufacturers gain experience). We demonstrate how this model, together with suitable informative priors, can reproduce the reliability growth in the modeled systems. Estimation of failure probabilities (and associated uncertainties) for early launches of new space vehicles is used to illustrate the methodology. Disclaimer-This paper is provided solely to illustrate how hierarchical Bayesian methods can be applied to estimate systems reliability (including uncertainties) for newly introduced complex systems with sparse or nonexistent system level test data. The example problem considered (i.e. estimating failure probabilities of new launch vehicles) is employed solely for illustrative purposes. The authors have made numerous assumptions & approximations throughout the document in order to demonstrate the central techniques. The specific methodologies, results, and conclusions presented in this paper are neither approved nor endorsed by the United States Air Force or the Federal Aviation Administration.     

一种等级化分布式时间同步算法

为了满足无线自组网中采用分布式TDMA组网所需的时间同步要求,提出了一种等级化分布式时间同步算法。该方法采用时间参考节点推选制度,实时更新参考节点,同时采用分层的时间等级和时间质量相结合使得在网的每个节点都能和自己周围最靠近时间参考点的节点进行对时同步,仿真实验结果表明,该方法能够提高同步精度,完全满足分布式TDMA无线自组网的时间同步要求。     

Editorial. Special section on intelligent distributed surveillance systems

This paper introduces a special section which discusses CCTV systems and video surveillance aspects.     

Mobile agents for remote control of distributed systems

A modern distributed industrial system, such as a power transmission system, consists of many sites distributed throughout a wide area. Each site contains a number of monitoring and control devices, also known as intelligent electronic devices, which perform various tasks including condition monitoring, control, and protection. However, apart from dedicated links to the control center for control purposes, substations are often connected by networks with relatively low bandwidth, which makes remote access to these devices for control or monitoring relatively difficult. Therefore, we propose the use of mobile agents for remote access to devices. In this paper, the advantages and disadvantages of the use of mobile agents are evaluated by means of a theoretical model and a series of experiments. The results suggest that for networks with high latency mobile agents may provide performance improvements over more conventional client-server systems.     

Efficient distributed power control for cellular mobile systems

Various distributed carrier-to-interference (C/I) balancing procedures have been developed to cope with implementational drawbacks of centralized power-control schemes. However, it would be inevitable for these distributed schemes to lose some system performance compared to a centralized one since they control their power level based on only the local C/I measurements. An efficient distributed power-control (DPC) scheme is proposed to maximize the system performance. A distributed C/I balancing algorithm is suggested, which converges fast and is robust to C/I estimation errors. A simple instability detection rule is also suggested to accelerate the balancing phase of DPC schemes. Numerical results indicate that our algorithm achieves improvements in terms of the outage probability as well as the algorithm speed. Robustness to the C/I measurement errors is also explored     

Fast handover solution for network-based distributed mobility management in intelligent transportation systems

The current IP mobility protocols are called centralized mobility management (CMM) solutions, in which all data traffic and management signaling messages must be forwarded to an anchor entity. In some vehicle scenarios, vehicles may move as a group from one roadside unit to another (i.e., after traffic lights or traffic jams). This causes data traffic and exchanged mobility messages to peak at the anchor entity and, consequently, affects the network performance. A new design paradigm aimed at addressing the anchor entity issue is called distributed mobility management (DMM); it is an IETF proposal that is still being actively discussed by the IETF DMM working group. Nevertheless, network-based DMM is designed based on the well-known network-based CMM protocol Proxy Mobile IPv6 (PMIPv6). There is no significant difference between network-based DMM and PMIPv6 in terms of handover latency and packet loss. Because vehicles change their roadside unit frequently in this context, the IP addresses of mobile users (MUs) require fast IP handover management to configure a new IP address without disrupting ongoing sessions. Thus, this paper proposes the Fast handover for network-based DMM (FDMM) based on the Fast Handover for PMIPv6 (PFMIPv6). Several modifications to PFMIPv6 are required to adapt this protocol to DMM. This paper specifies the necessary extensions to support the scenario in which an MU has old IP flows and hence has multiple anchor entities. In addition, the analytic expressions required to evaluate and compare the handover performance of the proposed FDMM and the IETF network-based DMM have been derived. The numerical results show that FDMM outperforms the IETF network-based DMM in terms of handover latency, session recovery and packet loss at the cost of some extra signaling.     

数字城市服务自适应访问控制模型

传统访问控制模型不适合数字城市异构、跨域、动态变化的特征,容易造成用户使用服务信息的泄露.本文在分析传统访问控制模型基础上,结合数字城市服务特点,设计了数字城市网络中细粒度访问控制模型,给出自适应访问控制策略及实施策略算法并对其性能进行了分析.分析结果表明该模型能够满足不断变化或扩展的动态安全需求,而且相比传统访问控制模型,性能也得到了提高.     

A programming model and system infrastructure for real-timesynchronization in distributed multimedia systems

One of the major requirements of distributed multimedia applications is the need to maintain often complex, real-time synchronization constraints. More specifically, it is necessary to be able to manage arbitrary intra- and inter-media synchronization across activities in the distributed environment. Furthermore, it is important that such developments are integrated into emerging object-oriented standards for distributed computing. This paper presents an object-oriented programming model and associated implementation to meet these requirements. The main concepts behind the proposed approach are, firstly, the use of reactive objects for real-time control and synchronization and, secondly, quality of service controlled bindings for predictable communication between objects. The flexibility of the approach is demonstrated by three contrasting examples of real-time synchronization. The implementation extends the real-time capabilities of the Chorus micro-kernel by introducing the concepts of rtports, rthandlers and quality of service controlled connections. The paper demonstrates how reactive objects and bindings are realized on this infrastructure     

A framework for building intelligent manufacturing systems

The paper describes a systematic approach to design and development of software for intelligent manufacturing systems. The approach is based on a multilevel, general object oriented model of intelligent systems. Current methods and software design and development tools for intelligent manufacturing systems either stress particular components of intelligence (e.g., high level domain expertise, or learning capabilities, or fuzziness of decisions), or their domain dependence (e.g., monitoring and control systems, or CAPP systems). It is usually difficult to make extensions of such methods and tools, nor is it easy to reuse their components in developing intelligent manufacturing systems. Considerable efforts are being dedicated to the development of interoperable software components, distributed object environments, and flexible and scalable applications to overcome some of these problems. The approach described in the paper starts with a well founded software engineering principle, making clear distinction between generic, low level intelligent software components, and domain-dependent, high level components of an intelligent manufacturing system. It is extensible and adjustable. It also suggests some steps toward design of future software development tools for intelligent manufacturing systems. Several intelligent systems have been developed using the approach. One of these systems, in the cement manufacturing domain, is briefly overviewed, illustrating how the approach is used in practice. Finally, some informal discussion on the performance and complexity of the approach is presented     

QOS distributed routing protocol for mobile ad-hoc wireless networks using intelligent packet carrying systems

The wireless network should provide high throughput and positive status and this paper suggest a system that supports real-time communications with excellence of service necessities for application based on wireless communications. In addition a hybrid network that interconnects both mobile networks and wireless networks. By inheriting the features of Solid Rocket Booster technology for mobile and wireless networks the race condition, and invalid condition problem has been solved. The number of packets received may vary based on the parameter like mobility, energy, memory, bandwidth, jamming and other parameter. In past years many algorithm has been proposed for increasing the probability of packet delivery but it’s still a challenge. This paper uses an algorithm called intelligent packet carrying systems; it provides a tracking mechanism that tracks nodes in rural places. The effectives and reability has been calculated and the results are obtained using OPNET simulator.     

Macrodiversity power control in hierarchical CDMA cellular systems

Hierarchical code division multiple access (CDMA) cellular systems, consisting of macrocells with underlying microcells, are studied. We seek power control schemes which will allow both hierarchical layers to share the same spectrum. For the reverse link, hierarchical maximal ratio combining (HMRC) is applied where each mobile station (MSs) is received and coherently combined by base stations (BSs) in both layers. For the forward link, selective transmit diversity (STD) is applied where each BS provides multiple transmit paths for MSs to choose. We show that both HMRC and STD are effective in hierarchical CDMA architectures. We conclude that hierarchical architectures are a viable solution for improving CDMA cellular system capacity, and a significant performance gain can be achieved without assigning disjoint spectrum between the layers, by utilizing macrodiversity schemes such as HMRC and STD     

Interprocessor communication in systems with distributed control

A multiprocessor communication technique, called Sub-Module Interface (SMI) because it enables exchange of information between telephony control units (submodules), was developed for a telephony switching system, thus realizing a distributed control philosophy. In addition to allowing any processor to communicate with any other processor in the system, a variety of devices attached to the SMI can also be accessed by the processors. This paper explains the philosophy and operation of this technique and, based on previous common control concepts in telephony, certain conflicts between these philosophies are noted.     

A hierarchical modulation for upgrading digital broadcast systems

A hierarchical modulation scheme is proposed to upgrade an existing digital broadcast system, such as satellite TV, or satellite radio, by adding more data in its transmission. The hierarchical modulation consists of a basic constellation, which is the same as in the original system, and a secondary constellation, which carries the additional data for the upgraded system. The upgraded system with the hierarchical modulation is backward compatible in the sense that receivers that have been deployed in the original system can continue receiving data in the basic constellation. New receivers can be designed to receive data carried in the secondary constellation, as well as those in the basic constellation. Analysis will be performed to show the tradeoff between bit rate of the data in secondary constellation and the penalty to the performance of receiving the basic constellation.     

基于IEC 61499分布式智能照明控制系统的设计

针对智能楼宇中重要的照明子系统,设计基于IEC 61499分布式智能照明控制系统。采用固高科技的ideabox3 PLC作为硬件,将一栋楼宇分层、分区域进行控制。利用网页技术实现操作友好的人机交互界面,通过Internet可以实现远程操作管理,通过不同的情景模式和充分利用自然光,节约了能源。智能照明控制系统不仅提供安逸舒适的工作环境,而且可以远程操作,便于管理,实现了集中管理、分布控制,也达到了理想的节能效果。     

一种电梯群组智能控制方式

讨论了电梯的智能控制方式，提出了一种基于神经网络控制方案，并结合具体实例分析了该智能控制方案的可行性与实用性。