Real-time dependable channels: customizing QoS attributes fordistributed systems

Communication services that provide enhanced Quality of Service (QoS) guarantees related to dependability and real time are important for many applications in distributed systems. This paper presents real-time dependable (RTD) channels, a communication-oriented abstraction that can be configured to meet the QoS requirements of a variety of distributed applications. This customization ability is based on using CactusRT, a system that supports the construction of middleware services out of software modules called micro-protocols. Each micro-protocol implements a different semantic property or property variant and interacts with other micro-protocols using an event-driven model supported by the CactusRT runtime system. In addition to RTD channels CactusRT and its implementation are described. This prototype executes on a cluster of Pentium PCs running the OpenGroup/RI MK 7.3 Mach real-time operating system and CORDS, a system for building network protocols based on the x-kernel     

Structuring communication software for quality-of-serviceguarantees

We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. We present and evaluate a QoS sensitive communication subsystem architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The architecture design is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. The proposed architecture features a process per channel model that associates a channel handler with each established channel. The model employed for handler execution is one of “cooperative” preemption, where an executing handler yields the CPU to a waiting higher priority handler at well defined preemption points. The architecture provides several configurable policies for protocol processing and overload protection. We present extensions to the admission control procedure for real time channels to account for cooperative preemption and overlap between protocol processing and link transmission at a sending host. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees on outgoing traffic while adhering to the stated design goals     

POETS: Process-oriented event-driven transaction systems

We present a high-level enterprise system architecture that closely models the domain ontology of resource and information flows in enterprises. It is:Process-orientedformal, user-definable specifications for the expected exchange of resources (money, goods, and services), notably contracts, are represented explicitly in the system state to reflect expectations on future events;Event-drivenevents denote relevant information about real-world transactions, specifically the transfer of resources and information between economic agents, to which the system reacts by matching against its portfolio of running processes/contracts in real time;Declarativeuser defined reporting functions can be formulated as declarative functions on the system state, including the representations of residual contractual obligations.We introduce the architecture and demonstrate how analyses of the standard reporting requirements for companies—the income statement and the balance sheet—can be used to drive the design of events that need registering for such reporting purposes. We then illustrate how the multi-party obligations in trade contracts (sale, purchase), including pricing and VAT payments, can be represented as formal contract expressions that can be subjected to analysis.To the best of our knowledge this is the first architecture for enterprise resource accounting that demonstrably maps high-level process and information requirements directly to executable specifications.     

Multiprocessor platform for partitioned real‐time systems

Two current trends in the real‐time and embedded systems are the multiprocessor architectures and the partitioning technology that enables several isolated applications with different criticality levels to share the same computer. This paper presents a real‐time platform for multiprocessor and partitioned systems, in which communication requirements are also considered. The paper describes the adaptation of MaRTE OS (a monoprocessor real‐time operating system) to the XtratuM hypervisor for the multiprocessor Intel x86 architecture. This adaptation makes two contributions to ease the development process of future mixed‐criticality applications: firstly, it integrates the hypervisor technology and the fully partitioned scheduling in a multiprocessor environment, and secondly, it provides the basis to interconnect partitioned and non‐partitioned applications via a homogeneous communication subsystem. Copyright © 2016 John Wiley & Sons, Ltd.     

Real‐time model predictive control based on dual gradient projection: Theory and fixed‐point FPGA implementation

This paper proposes a method to design robust model predictive control (MPC) laws for discrete‐time linear systems with hard mixed constraints on states and inputs, in case of only an inexact solution of the associated quadratic program is available, because of real‐time requirements. By using a recently proposed dual gradient‐projection algorithm, it is proved that the discrepancy of the optimal control law as compared with the obtained one is bounded even if the solver is implemented in fixed‐point arithmetic. By defining an alternative MPC problem with tightened constraints, a feasible solution is obtained for the original MPC problem, which guarantees recursive feasibility and asymptotic stability of the closed‐loop system with respect to a set including the origin, also considering the presence of external disturbances. The proposed MPC law is implemented on a field‐programmable gate array in order to show the practical applicability of the method. Copyright © 2016 John Wiley & Sons, Ltd.     

Real-time communication in multihop networks

Communication in real-time systems has to be predictable, because unpredictable delays in the delivery of messages can adversely affect the execution of tasks dependent on these messages. We develop a scheme for providing predictable interprocess communication in real-time systems with (partially connected) point-to-point interconnection networks, which provide guarantees on the maximum delivery time for messages. This scheme is based on the concept of a real-time channel, a unidirectional connection between source and destination. A real-time channel has parameters that describe the performance requirements of the source-destination communication, e.g., from a sensor station to a control site. Once such a channel is established, the communications subsystem guarantees that these performance requirements will be met. We concentrate on methods to compute guarantees for the delivery time of messages belonging to real-time channels. We also address problems associated with allocating buffers for these messages and develop a scheme that preserves delivery time guarantees     

ARMADA Middleware and Communication Services

Real-time embedded systems have evolved during the past several decades from small custom-designed digital hardware to large distributed processing systems. As these systems become more complex, their interoperability, evolvability and cost-effectiveness requirements motivate the use of commercial-off-the-shelf components. This raises the challenge of constructing dependable and predictable real-time services for application developers on top of the inexpensive hardware and software components which has minimal support for timeliness and dependability guarantees. We are addressing this challenge in the ARMADA project.ARMADA is set of communication and middleware services that provide support for fault-tolerance and end-to-end guarantees for embedded real-time distributed applications. Since real-time performance of such applications depends heavily on the communication subsystem, the first thrust of the project is to develop a predictable communication service and architecture to ensure QoS-sensitive message delivery. Fault-tolerance is of paramount importance to embedded safety-critical systems. In its second thrust, ARMADA aims to offload the complexity of developing fault-tolerant applications from the application programmer by focusing on a collection of modular, composable middleware for fault-tolerant group communication and replication under timing constraints. Finally, we develop tools for testing and validating the behavior of our services. We give an overview of the ARMADA project, describing the architecture and presenting its implementation status.     

无线网状网中基于TDMA模式的QoS路由策略

为支持无线网状网中具有服务质量（QoS）需求的实时应用,提出基于TDMA模式服务质量路由策略TD-MQR。对网络进行分层,提出新的链路指标值,在考虑链路容量和无线信道间干扰的基础上对网络的流量进行路由和调度。仿真表明,该协议能够对WMN中实时应用提供QoS保证。     

移动式地理信息系统体系结构的研究

随着地理信息技术,嵌入式技术以及无线通信技术的快速发展,移动地理信息系统已经成为GIS领域内研究热点之一。移动式地理信息系统使人们在任意时间任意地点都可以充分享受空间信息服务。主要提出了移动式地理信息系统的体系结构。这种体系结构可以提供丰富的地理信息服务,例如数字地图的现实,地理信息的查询等。基于这种体系结构,可以在不久的将来完全实现移动式地理信息系统。     

A methodology for digital real time simulation of dynamic systems using modern DSPs

The speedup factor in real time simulation of dynamic systems using multiprocessor resources depends on: the architecture of the multiprocessor system, type of interconnection between parallel processors, numerical methods and techniques used for discretization and task assignment and scheduling policy. The minimization of the number of processors needed for real time simulation requires the minimization of processors times for interprocessor communications and efficient scheduling policy. Therefore, this article presents a methodology for the real time simulation of dynamic systems including a new pre-emptive static assignment and scheduling policy. The advantages of applying digital signal processor with parallel architecture, for example TMS320C40, in real time simulation have been described. Some important issues in real time architectures necessary for efficient multiprocessor real time simulations, such as multiple I/O channels, concurrent I/O and CPU processing, direct high speed interprocessor communications, fast context switching, multiple busses, multiple memories, and powerful arithmetic units are inherent to this processor. These features minimize interprocessor communication time and maximize sustained CPU performance.     

A RESTful and semantic framework for data integration

Companies have to deal with huge amounts of heterogeneous information, usually stored in distributed datasets that make use of different data schemas. This topic is especially crucial for enterprises that deal with new and different kinds of business data as new services are provided; they need to be able to dynamically add new datasets with new schemas to their information systems. However, even though research efforts have been applied to deal with this integration problem, there is still a lack of practical approaches ready to be implemented for industrial cases. We present a web‐based architecture and system built upon ontologies and other semantic web techniques to cope with federation of business data in real time. The scenario used to demonstrate the utility of the architecture is composed of actual data of a telecom company. Results show that our solution is more suitable, efficient and practical than other works. Copyright © 2014 John Wiley & Sons, Ltd.     

信息网络的通信安全控制

通信安全控制能够实现网络信息的安全传输。为了满足不同层次的通信安全需要，必须提供不同的安全控制服务，建立完善的安全控制体系，运用集中与分层相结合的安全控制方式，并对通信协议进行安全扩展。除此之外，安全控制效果的检测与反馈也是保证控制系统稳定的重要环节。为此，从系统控制的角度，提出了网络通信的安全控制需求、控制体系、控制方式和异常行为检测分析模型，为具体实施通信安全控制奠定了理论基础。     

Real-time transport of MPEG video with a statistically guaranteedloss ratio in ATM networks

Unlike deterministic real-time communication in which excessive resources may be required for “absolute” performance guarantees, statistical real-time communication seeks to achieve both probabilistic performance guarantees and efficient resource sharing. This paper presents a framework for statistical real-time communication in ATM networks, providing delay-guaranteed transport of MPEG-coded video traffic with a statistically-guaranteed cell-loss ratio. Delay-guaranteed communication is achieved with a modified version of Traffic-Controlled Rate-Monotonic Priority Scheduling (TCRM). A set of statistical real-time channels that share similar traffic characteristics are multiplexed into a common macrochannel. Those statistical real-time channels which are multiplexed together share the resources of a macrochannel, and individual statistical real-time channels are given timeliness and probabilistic cell-loss guarantees. A macrochannel is serviced by the modified TCRM which improves link utilization and makes channel management simpler. Based on the analysis of an M/D/1/N queueing system, we propose a procedure for determining the transmission capacity of a macrochannel necessary to statistically guarantee a cell-loss ratio bound. Our extensive trace-driven simulation has shown the superiority of the proposed framework to the other approaches. The overall cell-loss ratios for multihop statistical real-time channels are shown to be smaller than the predetermined bounds, thus verifying our analytical results     

海洋监测系统实时数据采集及聚类分析的研究

针对海洋监测环境的要求,提出一种基于移动GSM/GPRS通信网络的无线海洋监测实时数据采集的架构。该架构利用移动网络的GSM短消息和GPRS数据包传输服务,保证了数据采集的实时性和可靠性。在此基础上,设计了一种新的基于熵的增量式模糊聚类算法,通过实施一系列改进策略,算法能有效地对实时数据进行聚类,在提高聚类的准确性的同时兼顾实时性。仿真实验结果表明提出的算法符合海洋实时监控的要求。     

宽带多媒体卫星通信系统QoS架构设计与仿真验证

为解决宽带卫星通信系统中多媒体业务QoS的保障问题,参考Diffserv模型建立了系统QoS架构,针对系统上行链路为多用户共享接入的特点,进行了星地一体化联合设计,其中星上资源动态分配算法基于联合自由/按需分配多址接入协议进行扩展,在用户终端采用两级排队调度策略,通过分级调度算法实现业务与系统QoS的映射.在此基础上搭建宽带多媒体卫星通信地面仿真验证系统,测试了业务传输性能.测试表明,本架构对实时多媒体业务的QoS可提供较好的保障,达到了现有系统的实测水平.     

分布实时系统中的点到点通信

本文给出了一种由点到点互连网络连接的实时系统通信方法,分析了通道建立过程,消息调度算法,缓冲预留方案,以及消息传递时间的计算模型,可提供确定性的消息传递延迟。     

A novel communication system approach for a Smart City based on the human nervous system

The massive introduction of internet, architect of the Internet of Thingsparadigm, was expected to facilitate the spread of people out of the urban spaces. However, the reality is that increasingly people are moving to cities, which generates many challenges for the cities of tomorrow. In this context, the Smart Cityconcept emerges, where Information and Communication Technologies have a key role. This situation has revealed an important issue that needs to be addressed: the lack of an ubiquitous communication architecture able to deal with the expected requirements of a SC. To this end, a wide review of the existing communication frameworks and city services have been performed, which showed that existing proposals are classical fixed ad-hocsolutions for very specific problems with no resilience and common thread. By rethinking the nature of cities and considering them as living organisms, it is possible to relate the nervous systems with the communication architecture of a city. Therefore, this work proposes a novel communication architecture, ubiquitous and resilient, inspired in the human nervous system by the definition of Smart Gateways, able to satisfy the needs of a real SCand adaptable to the growing and specific requirements of every single city. Additionally, the research also includes the simulation of the communication channel with different technologies.     

An economic market for the brokering of time and budget guarantees

Grids offer best effort services to users. Service level agreements offer the opportunity to provide guarantees upon services offered, in such a way that it captures the users' requirements, while also considering concerns of the service providers. This is achieved via a process of converging requirements and service cost values from both sides towards an agreement. This paper presents the intelligent scheduling for quality of service market‐oriented mechanism for brokering guarantees upon completion time and cost for jobs submitted to a batch‐oriented compute service. Web Services agreement (negotiation) is used along with the planning of schedules in determining pricing, ensuring that jobs become prioritised depending on their budget constraints. An evaluation is performed to demonstrate how market mechanisms can be used to achieve this, whilst also showing the effects that scheduling algorithms can have upon the market in terms of rescheduling. The evaluation is completed with a comparison of the broker's capabilities in relation to the literature. Copyright © 2014 John Wiley & Sons, Ltd.     

Statistical real-time channels on multiaccess bus networks

Real-time communication with performance guarantees is expected to become an important and necessary feature of future computer networks. In this paper, we present a scheme which can provide real-time communication services with both absolute and statistical performance guarantees on multiaccess bus networks for given input traffic characteristics and performance requirements. The proposed scheme reserves network bandwidth for real-time connections according to their needs. It also allows for independent addition and deletion of real-time connections while preserving existing guarantees. Our extensive simulation results for motion video communication have shown the proposed scheme to outperform the other well-known schemes