Gleichstellungs-News : Nr. 14

Many embedded systems with real-time requirements demand minimal jitter and low communication end-to-end latency for its communication networks. The time-triggered paradigm, adopted by many real-time protocols, was designed to cope with these demands. A cost-efficient way to implement this paradigm is to synthesize a static schedule that indicates the transmission times of all the time-triggered frames such that all requirements are met. Synthesizing this schedule can be seen as a bin-packing problem, known to be NPcomplete, with complexity driven by the number of frames. In the last years, requirements on the amount of data being transmitted and the scalability of the network have increased. A solution was proposed, adapting real-time switched Ethernet to benefit from its high bandwidth. However, it added more complexity in computing the schedule, since every frame is distributed over multiple links. Tools like Satisfiability Modulo Theory solvers were able to cope with the added complexity and synthesize schedules of industrial size networks. Despite the success of such tools, applications are appearing requiring embedded systems with even more complex networks. In the future, real-time embedded systems, such as large factory automation or smart cities, will need extremely large hybrid networks, combining wired and wireless communication, with schedules that cannot be synthesized with current tools in a reasonable amount of time. With this in mind, the first thesis goal is to identify the performance limits of Satisfiability Modulo Theory solvers in schedule synthesis. Given these limitations, the next step is to define and develop a divide and conquer approach for decomposing the entire scheduling problem in smaller and easy solvable subproblems. However, there are constraints that relate frames from different subproblems. These constraints need to be treated differently and taken into account at the start of every subproblem. The third thesis goal is to develop an approach that is able to synthesize schedules when different frame constraints related to different subproblems are inter-dependent. Last, is to define the requirements that the integration of wireless communication in hybrid networks will bring to the schedule synthesis and how to cope with the increased complexity. We demonstrate the viability of our approaches by means of evaluations, showing that our method is capable to synthesize schedules of hundred of thousands of frames in less than 5 hours.RetNe

A Modeling and Verification Approach to the Design of Distributed IMA Architectures Using TTEthernet

AbstractIntegrated Modular Avionics (IMA) architectures complemented with Time-Triggered Ethernet (TTEthernet) provides a strong platform to support the design and deployment of distributed avionic software systems. The complexity of the design and continuous integration of such systems can be managed using a model-based methodology. In this paper, we build on top of our extension of the AADL modeling language to model TTEthernet-based distributed systems and leverage model transformations to enable undertaking the verification of the system models produced with this methodology. In particular, we propose to transform the system models to a model suitable for a simulation with DEVS. We illustrate the proposed approach using an example of a navigation and guidance system and we use this example to show the verification of the contention-freedom property of TTEthernet schedule

A Time-Triggered Constraint-Based Calculus for Avionic Systems

The Integrated Modular Avionics (IMA) architec- ture and the Time-Triggered Ethernet (TTEthernet) network have emerged as the key components of a typical architecture model for recent civil aircrafts. We propose a real-time constraint-based calculus targeted at the analysis of such concepts of avionic embedded systems. We show our framework at work on the modelisation of both the (IMA) architecture and the TTEthernet network, illustrating their behavior by the well-known Flight Management System (FMS)

Knowledge Representation Concepts for Automated SLA Management

Outsourcing of complex IT infrastructure to IT service providers has increased substantially during the past years. IT service providers must be able to fulfil their service-quality commitments based upon predefined Service Level Agreements (SLAs) with the service customer. They need to manage, execute and maintain thousands of SLAs for different customers and different types of services, which needs new levels of flexibility and automation not available with the current technology. The complexity of contractual logic in SLAs requires new forms of knowledge representation to automatically draw inferences and execute contractual agreements. A logic-based approach provides several advantages including automated rule chaining allowing for compact knowledge representation as well as flexibility to adapt to rapidly changing business requirements. We suggest adequate logical formalisms for representation and enforcement of SLA rules and describe a proof-of-concept implementation. The article describes selected formalisms of the ContractLog KR and their adequacy for automated SLA management and presents results of experiments to demonstrate flexibility and scalability of the approach.Comment: Paschke, A. and Bichler, M.: Knowledge Representation Concepts for Automated SLA Management, Int. Journal of Decision Support Systems (DSS), submitted 19th March 200

A modeling and verification approach to the design of distributed IMA architectures using TTEthernet

ABSTRACT: Integrated Modular Avionics (IMA) architectures complemented with Time-Triggered Ethernet (TTEthernet) provides a strong platform to support the design and deployment of distributed avionic software systems. The complexity of the design and continuous integration of such systems can be managed using a model-based methodology. In this paper, we build on top of our extension of the AADL modeling language to model TTEthernet-based distributed systems and leverage model transformations to enable undertaking the verification of the system models produced with this methodology. In particular, we propose to transform the system models to a model suitable for a simulation with DEVS. We illustrate the proposed approach using an example of a navigation and guidance system and we use this example to show the verification of the contention-freedom property of TTEthernet schedule

Exploring Alternatives to use Master/Slave Full Duplex Switched Ethernet for Avionics Embedded Applications

The complexity of distributed real-time systems, including military embedded applications, is increasing due to an increasing number of nodes, their functionality and higher amounts of exchanged data. This higher complexity imposes major development challenges when nonfunctional properties must be enforced. On the other hand, the current military communication networks are a generation old and are no longer effective in facing such increasingly complex requirements. A new communication network, based on Full Duplex Switched Ethernet and Master/slave approach, has been proposed previously. However, this initial approach is not efficient in terms of network bandwidth utilization. In this paper we propose two new alternative approaches that can use the network bandwidth more efficiently. In addition we provide a preliminary qualitative assessment of the three approaches concerning different factors such as performance, scalability, complexity and flexibility