Techniques for enhancing real-time CORBA quality of service

End-to-end predictability of remote operations is essential for many fixed-priority distributed real-time and embedded (DRE) applications, such as command and control systems, manufacturing process control systems, large-scale distributed interactive simulations, and testbeam data acquisition systems. To enhance predictability, the Real-time CORBA specification defines standard middleware features that allow applications to allocate, schedule, and control key CPU, memory, and networking resources necessary to ensure end-to-end quality of service support. This paper provides two contributions to the study of Real-time CORBA middleware for DRE applications. First, we identify potential problems with ensuring predictable behavior in conventional middleware by examining the end-to-end critical code path of a remote invocation and identifying sources of unbounded priority inversions. Experimental results then illustrate how the problems we identify can yield unpredictable behavior in conventional middleware platforms. Second, we present design techniques for ensuring real-time quality of service in middleware. We show how middleware can be redesigned to use nonmultiplexed resources to eliminate sources of unbounded priority inversion. The empirical results in this paper are conducted using TAO, which is widely used and open-source DRE middleware compliant with the Real-time CORBA specification.     

A high-performance end system architecture for real-time CORBA

Many application domains (e.g., avionics, telecommunications, and multimedia) require real-time guarantees from the underlying networks, operating systems, and middleware components to achieve their quality of service (QoS) requirements. In addition to providing end-to-end QoS guarantees, applications in these domains must be flexible and reusable. Requirements for flexibility and reusability motivate the use of object-oriented middleware like the Common Object Request Broker Architecture (CORBA). However, the performance of current CORBA implementations is not yet suited for hard real-time systems (e.g., avionics) and constrained latency systems (e.g., teleconferencing). This article describes the architectural features and optimizations required to develop real-time ORB end systems that can deliver end-to-end QoS guarantees to applications. While some operating systems, networks, and protocols now support real-time scheduling, they do not provide integrated solutions. The main thrust of this article is that advances in real-time distributed object computing can be achieved only by systematically pinpointing performance bottlenecks; optimizing the performance of networks, ORB end systems, common services, and applications; and simultaneously integrating techniques and tools that simplify application development     

Channel islands in a reflective ocean: large-scale eventdistribution in heterogeneous networks

We discuss the design of a multicast event distribution service intended to support extremely large-scale event distribution. To date, event notification services have been limited in their scope due to limitations of the infrastructure. At the same time, Internet network and transport layer multicast services have seen limited deployment due to lack of user demand (with the exception of streaming services, e.g., on Sprint's US core network and in the Internet II). Research in active networks and reflective middleware suggests a way to resolve these two problems at one go. The goal of this article is to describe a reflective middleware system that integrates the network, transport, and distributed middleware services into a seamless whole. The system integrates this "low-level" technology into an event middleware system, suitable for telemetry, novel mobile network services, and other as yet unforeseen applications     

Context-aware middleware for pervasive elderly homecare

The growing aging population faces a number of challenges, including rising medical cost, inadequate number of medical doctors and healthcare professionals, as well as higher incidence of misdiagnosis. There is an increasing demand for a better healthcare support for the elderly and one promising solution is the development of a context-aware middleware infrastructure for pervasive health/wellness-care. This allows the accurate and timely delivery of health/medical information among the patients, doctors and healthcare workers through a widespread deployment of wireless sensor networks and mobile devices. In this paper, we present our design and implementation of such a Context-Aware Middleware for Pervasive Homecare (CAMPH). The middleware offers several key-enabling system services that consist of P2P-based context query processing, context reasoning for activity recognition and context-aware service management. It can be used to support the development and deployment of various homecare services for the elderly such as patient monitoring, location-based emergency response, anomalous daily activity detection, pervasive access to medical data and social networking. We have developed a prototype of the middleware and demonstrated the concept of providing a continuing-care to an elderly with the collaborative interactions spanning multiple physical spaces: person, home, office and clinic. The results of the prototype show that our middleware approach achieves good efficiency of context query processing and good accuracy of activity recognition.     

Mobile Web Middleware of NFC Context-Awareness Applications

With the development of wireless networks and mobile computing, more advanced applications with context-awareness and adaptability to their changing context are needed. However, building context-aware applications is difficult due to the lack of adequate infrastructure support. In this paper, a web middleware architecture for the development of context-awareness applications using near field communication （NFC） is proposed. Based on it, the efficient support for acquiring, interpreting, and accessing context is provided, and the user＇s quality of experience is improved. Moreover, a mobile web middleware for the testing and full realization of NFC context-awareness applications has been developed together with two application examples.     

Developing next-generation distributed applications with QoSenabled DPE middleware

This article describes how recent advances in distributed object computing middleware are enabling the creation of common quality-of-service capabilities that support next-generation distributed applications. DOC middleware helps to simplify and coordinate applications in order to leverage the underlying network and end-system QoS architectures more effectively. This article also describes a QoS-enabled middleware framework used to customize the CORBA audio/video streaming service for applications on multiple operating system platforms     

ActiVECOM: An inter-working framework for Corba and DCOM based on a generic protocol

The constant rising of networks and the decrease of computer system costs have enforced the development of distributed platforms. Microsoft dcom (distributed component object model) and omg (object management group) Corba (common object request broker architecture) are two major solutions to develop distributed applications. However, heterogeneity of these platforms is a fundamental problem which prevents applications to inter-work because they depend on their platform support. Then, each of them introduces its own functionality from several perspectives: they define distinct Idls (interface definition language), distinct system mechanisms (for instance, object binding is based either on object references or on interface binding handles) and distinct communication protocols: orpc (object remote procedure call) for dcom and hop (Internet inter-ORB protocol) for Corba. While the commonly used approaches are based on bridges or on parsers, we propose, in this paper, an alternative approach to enable inter-working between Corba and dcom applications. Actually, we present a model called “activecOM” which provides native interworking between Corba and Dcom. In particular, an original solution — called grip for generic remote invocation protocol — obtained by combination of hop and orpc internal protocol behaviours is described. The grip protocol inherits both the robustness of orpc and the simplicity of hop. It also preserves compatibility with those solutions and enables interoperability without the use of bridges.     

光纤接入发展展望

随着社会的进步和人们生活水平的提高,人们对带宽的需求也快速增长。以无源光网络（PON）技术为代表的光纤接入技术在全球获得了广泛的应用,在中国的发展最快,应用规模最大。但在发展过程中也遇到了诸如政策支持力度不够、高带宽应用缺乏、配套基础设施较落后、运维技术有待提升等困难。为了更好满足多业务承载对光接入网络带宽和服务质量（QoS）的需求,本文在对目前光纤接入现状分析的基础上,从技术标准、应用场景、产品形态、运维管理等4个方面对光纤接入的发展趋势进行了深入剖析,提出了下一代光纤接入的主要研究方向。     

Achieving service portability using self-adaptive data paths

There is a growing demand for service access through heterogeneous devices attached to diverse networks. For ease of deployment, it is crucial to provide application-level support for transparent roaming and ubiquitous service access. We discuss how to develop such a service infrastructure integrating a variety of telephony arid data services spanning diverse access networks reaching heterogeneous end devices. We describe our techniques for achieving goals of transparent network- and device-independent service access, as well as scalable and fault-tolerant access to composed service entities across the wide area using self-adaptive data paths. We evaluate our implementation through applications that require adaptation to end devices and resource variations. The applications include Universal Inbox, Interactive Voice Room Control, MP3 Jukebox access using a cell phone, and real-time video delivery to wireless clients     

Middleware to support sensor network applications

Current trends in computing include increases in both distribution and wireless connectivity, leading to highly dynamic, complex environments on top of which applications must be built. The task of designing and ensuring the correctness of applications in these environments is similarly becoming more complex. The unified goal of much of the research in distributed wireless systems is to provide higher-level abstractions of complex low-level concepts to application programmers, easing the design and implementation of applications. A new and growing class of applications for wireless sensor networks require similar complexity encapsulation. However, sensor networks have some unique characteristics, including dynamic availability of data sources and application quality of service requirements, that are not common to other types of applications. These unique features, combined with the inherent distribution of sensors, and limited energy and bandwidth resources, dictate the need for network functionality and the individual sensors to be controlled to best serve the application requirements. In this article, we describe different types of sensor network applications and discuss existing techniques for managing these types of networks. We also overview a variety of related middleware and argue that no existing approach provides all the management tools required by sensor network applications. To meet this need, we have developed a new middleware called MiLAN. MiLAN allows applications to specify a policy for managing the network and sensors, but the actual implementation of this policy is effected within MiLAN. We describe MiLAN and show its effectiveness through the design of a sensor-based personal health monitor.     

Developing distributed multimedia telecommunication applications

The emerging open services market transforms services into tradable goods. It involves users; customers; service, content, and middleware providers; and network operators. This market requires effective methods to: provide new services to meet niche market demands; support customized services; provide appropriate accounting and billing mechanisms; support personal and terminal mobility, and meet information interchange security requirements such as authorization, confidentiality, and integrity. Efficient processes will reduce investment risks and let us benefit from software and hardware product development advances. To meet these needs requires an appropriate infrastructure that supports the object oriented development of distributed multimedia telecommunication applications     

FORMI: Integrating Adaptive Fragmented Objects into Java RMI

Distributed object-oriented applications are commonly implemented atop middleware platforms such as CORBA, .NET Remoting, and Java remote method invocation (RMI). These platforms provide a simple mechanism to invoke methods of remote objects. Increasingly more applications are demanding nonfunctional properties such as fault tolerance, high availability, and adaptivity, which require extensions to distributed objects' basic interaction model. A fragmented-object model, such as the one Marc Shapiro proposed, can provide the required flexibility. It's far more generic and flexible than the traditional client-server approach. A fragmented object is a truly distributed object; it consists of multiple fragments located on multiple nodes. Such a model allows arbitrary partitioning of state and functionality on these fragments, and arbitrary internal interaction between fragments of a single object. We have investigated integrating a fragmented-object model into CORBA (AspectIX), which requires internal modifications to the CORBA object request broker. Our approach for transparently integrating fault-tolerant objects into .NET Remoting is also useful for seamlessly integrating fragmented objects. Our FORMI architecture integrates fragmented objects into Java RMI without requiring internal modifications to the RMI runtime     

A service-integrated sensor network middleware applied to industrial solutions of IoT related

With the deployment and application of Internet of Things, middleware for sensor network has become an increasingly important factor to facilitate the programmer task and bridge the gap between the applications and the underlying infrastructure. Most existing middleware for sensor networks lack attention for integrating services into a generic architecture and present inflexibility that make them useless in the context of industrial solutions of Internet of Things. To solve this problem, we proposed a new middleware deployment model and present layered and distributed architecture utilizing our “Ends to the Middle” approach. Actual application of middleware demonstrates that our proposed architecture is highly modular and efficient, offers good performance in complex application scenarios of Internet of Things.     

Issues in designing middleware for wireless sensor networks

Wireless sensor networks are being developed for a variety of applications. With the continuing advances in network and application design, appropriate middleware is needed to provide both standardized and portable system abstractions, and the capability to support and coordinate concurrent applications on sensor networks. In this article, we first identify several design principles for such middleware. These principles motivate a cluster-based lightweight middleware framework that separates application semantics from the underlying hardware, operating system, and network infrastructure. We propose a layered architecture for each cluster that consists of a cluster control layer and a resource management layer. Key design issues and related challenges within this framework that deserve further investigation are outlined. Finally, we discuss a technique for energy-efficient resource allocation in a single-hop cluster, which serves as a basic primitive for the development of the resource management layer.     

Object Request Brokers in Mobile Computing

The widespread use of wireless and mobile networks and devices requiresspecial programming techniques and solutions. The object request brokers ofmobile environments have to adopt these techniques and offer servicesdealing with the problems of mobility. Most of the existing object request brokers however were developed for fixed networks assuming reliable transport protocols (mostly TCP), while the mobile networks cannot offer high qualitytransport.In this paper we give an overview of the challenges and solutions in mobilecomputing and present our ORB(M) framework implementing services based onthe solutions. Extending the framework doesn't require the assistance of itsdevelopers, the user can implement application-specific semantic elementsand deploy various new methods bound to the process of remote invocation.The user can form arbitrary new invocation semantics based on these elementsand customise the invocation semantics used by a given method. Our newmobility-related semantic elements offer solutions to the challengesof mobility allowing the user to concentrate on theessential problems of the application and handling.     

Distributed policy processing in active‐service based infrastructures

More and more applications in the Internet are requiring an intelligent service infrastructure to provide customized services. In this paper, we present an infrastructure, which can transparently and effectively provide customized active‐services to end users and dynamically adapt to changing customized policies in large distributed heterogeneous environments. The infrastructure consists of two components: the policy agent and middleware box. Particularly, our technologies include: (1) Generic active‐service based infrastructure, where the policy agent can integrate policies requested by applications, and middleware boxes can transparently execute services and (2) Distributed policy processing in the middleware box. We study two policy partitioning schemes to achieve conflict‐free policies for distributed policy processing and guarantee the correctness of the policy execution. We conduct extensive performance evaluations on different schemes proposed. Our experimental results demonstrate that our policy partitioning schemes can effectively generate partition‐capable and conflict‐free policy sets. The evaluation results also show that distributed policy processing can achieve over 70% increase in performance/price ratio with proper assignment of the policy distribution degree compared to a purely centralized approach. Copyright © 2005 John Wiley & Sons, Ltd.     

CORBA异步消息的研究与实现

异步机制是构造大规模分布式系统必不可少的机制之一.作为一种典型的分布应用支撑平台,CORBA没有很好的解决异步机制问题,这限制了CORBA在一些领域的应用.如何在CORBA中提供异步通信支持,为上层应用提供异步通信支持成为研究的热点.本文提出一种CORBA异步消息模型Star-Async,该模型通过ReplyHandler对象实现应答处理、通过异常封装对象实现异常处理,通过基于修改抽象语法树的机制实现异步代码生成.在自主研制的分布对象中间件平台StarBus中实现了本文提出的Star-Async异步模型,实现和初步应用表明本文提出的异步消息模型为在CORBA中实现异步机制提供了一种有效的参考.     

信息对抗侦察系统开放架构计算环境

为提高信息对抗侦察系统的通用性和可重用性,快速适应信息对抗多种作战任务和作战平台,借鉴美国海军开放架构计算环境(OACE),从技术架构、基础设施、任务配置与中间件应用4个方面开展研究,构建了一种信息对抗侦察系统开放架构计算环境。能够基于通用计算平台实现侦察系统软硬件的分离,基于软件中间件实现侦察系统业务应用与计算技术的分离。通过仿真验证,信息对抗侦察系统开放架构计算环境能够支持侦察系统软硬件即插即用,满足其快速升级与灵活扩展需求。     

Evaluating meta-programming mechanisms for ORB middleware

Distributed object computing middleware, such as CORBA, COM+, and Java RMI, shields developers from many tedious and error-prone aspects of programming distributed applications. It is hard to evolve distributed applications after they are deployed, however, without adequate middleware support for meta-programming mechanisms, such as smart proxies, interceptors, and pluggable protocols. These mechanisms can help improve the adaptability of distributed applications by allowing their behavior to be modified without changing their existing software designs and implementations significantly. This article examines and compares common meta-programming mechanisms supported by DOC middleware. These mechanisms allow applications to adapt more readily to changes in requirements and runtime environments throughout their lifecycles. Some of these meta-programming mechanisms are relatively new, whereas others have existed for decades. This article provides a systematic evaluation of these mechanisms to help researchers and developers determine which are best suited to their application needs