As the software radio makes its transition from research to practice, it becomes increasingly important to establish provable properties of the software radio architecture on which product developers and service providers can base technology insertion decisions. Establishing provable properties requires a mathematical perspective on the software radio architecture. This paper contributes to that perspective by critically reviewing the fundamental concept of the software radio, using mathematical models to characterize this rapidly emerging technology in the context of similar technologies like programmable digital radios. The software radio delivers dynamically defined services through programmable processing capacity that has the mathematical structure of the Turing machine. The bounded recursive functions, a subset of the total recursive functions, are shown to be the largest class of Turing-computable functions for which software radios exhibit provable stability in plug-and-play scenarios. Understanding the topological properties of the software radio architecture promotes plug-and-play applications and cost-effective reuse. Analysis of these topological properties yields a layered distributed virtual machine reference model and a set of architecture design principles for the software radio. These criteria may be useful in defining interfaces among hardware, middleware, and higher level software components that are needed for cost-effective software reuse.

Software radio architecture: a mathematical perspective

Industrial automation platforms are experiencing a paradigm shift. New technologies are making their way in the area, including embedded real-time systems, standard local area networks like Ethernet, Wi-Fi and ZigBee, IP-based communication protocols, standard service oriented architectures (SOAs) and Web services. An automation system will be composed of flexible autonomous components with plug & play functionality, self configuration and diagnostics, and autonomic local control that communicate through standard networking technologies. However, the introduction of these new technologies raises important problems that need to be properly solved, one of these being the need to support real-time and quality-of-service (QoS) for real-time applications. This paper describes a SOA enhanced with real-time capabilities for industrial automation. The proposed architecture allows for negotiation of the QoS requested by clients from Web services, and provides temporal encapsulation of individual activities. This way, it is possible to perform an a priori analysis of the temporal behavior of each service, and to avoid unwanted interference among them. After describing the architecture, experimental results gathered on a real implementation of the framework (which leverages a soft real-time scheduler for the Linux kernel) are presented, showing the effectiveness of the proposed solution. The experiments were performed on simple case studies designed in the context of industrial automation applications.

/pdf/a-real-time-service-oriented-architecture-for-industrial-47ffrd2mtb.pdf

A Real-Time Service-Oriented Architecture for Industrial Automation

Next generation real-time systems will require greater flexibility and predictability than is commonly found in today's systems. These future systems include the space station, integrated vision/robotics/AI systems, collections of humans/robots coordinating to achieve common objectives (usually in hazardous environments such as undersea exploration or chemical plants), and various command and control applications. The Spring kernel is a research oriented kernel designed to form the basis of a flexible, hard real-time operating system for such applications. Our approach challenges several basic assumptions upon which most current real-time operating systems are built and subsequently advocates a new paradigm based on the notion of predictability and a method for on-line dynamic guarantees of deadlines. The Spring kernel is being implemented on a network of (68020 based) multiprocessors called SpringNet.

The spring kernel: a new paradigm for real-time operating systems

Two fundamental trends influence the way we conceive and construct new computing and information systems The first is that information technology of all forms is becoming highly commoditized ie, hardware and software artifacts are getting faster, cheaper, and better at a relatively predictable rate The second is the growing acceptance of a network-centric paradigm, where distributed applications with a range of quality of service (QoS) needs are constructed by integrating separate components connected by various forms of communication services The nature of this interconnection can range from 1 The very small and tightly coupled, such as avionics mission computing systems to 2 The very large and loosely coupled, such as global telecommunications systems The interplay of these two trends has yielded new architectural concepts and services embodying layers of middleware These layers are interposed between applications and commonly available hardware and software infrastructure to make it feasible, easier, and more cost effective to develop and evolve systems using reusable software Middleware stems from recognizing the need for more advanced and capable support–beyond simple connectivity–to construct effective distributed systems A significant portion of middleware-oriented R&D activities over the past decade have focused on 1 The identification, evolution, and expansion of our understanding of current middleware services in providing this style of development and 2 The need for defining additional middleware layers and capabilities to meet the challenges associated with constructing future network-centric systems These activities are expected to continue forward well into this decade to address the needs of next-generation distributed applications

/pdf/middleware-for-distributed-systems-evolving-the-common-5grike1xkb.pdf

Middleware for Distributed Systems Evolving the Common Structure for Network-centric Applications

One of the primary requirements in many cyber-physical systems (CPS) is that the sensor data derived from the physical world should be disseminated in a timely and reliable manner to all interested collaborative entities. However, providing reliable and timely data dissemination services is especially challenging for CPS since they often operate in highly unpredictable environments. Existing network middleware has limitations in providing such services. In this paper, we present a novel publish/subscribe-based middleware architecture called Real-time Data Distribution Service (RDDS). In particular, we focus on two mechanisms of RDDS that enable timely and reliable sensor data dissemination under highly unpredictable CPS environments. First, we discuss the semantics-aware communication mechanism of RDDS that not only reduces the computation and communication overhead, but also enables the subscribers to access data in a timely and reliable manner when the network is slow or unstable. Further, we extend the semantics-aware communication mechanism to achieve robustness against unpredictable workloads by integrating a control-theoretic feedback controller at the publishers and a queueing-theoretic predictor at the subscribers. This integrated control loop provides Quality-of-Service (QoS) guarantees by dynamically adjusting the accuracy of the sensor models. We demonstrate the viability of the proposed approach by implementing a prototype of RDDS. The evaluation results show that, compared to baseline approaches, RDDS achieves highly efficient and reliable sensor data dissemination as well as robustness against unpredictable workloads.

RDDS: A Real-Time Data Distribution Service for Cyber-Physical Systems

This paper describes the requirements for real-time extensions to the CORBA standard, which are being developed by the object management group's special Interest Group on Real-Time CORBA. The paper also surveys efforts that are developing Real-Time CORBA systems. It provides a more detailed description of the dynamic real-time CORBA system being developed at the US Navy's NRaD facilities and at the University of Rhode Island.

Real-time CORBA

Distributed real-time applications have presented the need to extend the Object Management Group‘s Common Object Request Broker Architecture (CORBA) standard to support real-time. This paper describes a Dynamic Real-Time CORBA system, which supports the expression and enforcement of end-to-end timing constraints as an extension to a commercial CORBA system. The paper also describes performance tests that demonstrate the system‘s ability to enforce expressed timing constraints.

Expressing and Enforcing Timing Constraints in a DynamicReal-Time CORBA System

This paper presents the affected set priority ceiling protocols (ASPCP) for concurrency control in real-time object-oriented systems. These protocols are based on a combination of semantic locking and priority ceiling techniques. This paper shows that the ASPCP protocols provide higher potential concurrency for object-oriented systems than existing priority ceiling protocols, while still bounding priority inversion and preventing deadlock.

/pdf/concurrency-control-in-real-time-object-oriented-systems-the-1sc09y1iyi.pdf

Concurrency control in real-time object-oriented systems: the affected set priority ceiling protocols

This paper shows how priority ceiling techniques can be added to object-based real-time semantic concurrency control. The resulting protocol provides more potential concurrency for real-time object-oriented databases than previous priority ceiling techniques, while alleviating priority inversion and deadlock problems of previous object-based semantic concurrency control techniques. It is also a natural extension of priority ceiling techniques to objects in general.

Towards Priority Ceilings in Object-Based Semantic Real-Time Concurrency Control.

Distributed real time applications have presented the need to extend the Object Management Group's (OMG) Common Object Request Broker Architecture (CORBA) standard to support real time. The OMG has formed a real time special interest group (RT SIG) to specify requirements for extending CORBA for real time. One of these requirements involves providing global scheduling of all executions to support end to end timing constraints in the real time CORBA system. The paper describes the design and implementation of a real time scheduling service for a Dynamic Real Time CORBA system.

/pdf/a-scheduling-service-for-a-dynamic-real-time-corba-system-1h864s9h42.pdf

A scheduling service for a dynamic real-time CORBA system

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