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Title Schedulability-Driven Reliability Optimization of FlexRay Communications
Author Ma, Xiaojun
Supervisor Pop, Paul (Computer Science and Engineering, Department of Informatics and Mathematical Modeling, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2008
Abstract Currently, more and more real-time systems are implemented on distributed architectures in order to meet reliability, functional, and performance constraints. Communications in such systems can be triggered either dynamically, in response to an event (event-driven), or statically, at predetermined moments in time (time-driven). A large consortium of automotive manufacturers and suppliers has recently proposed a protocol called FlexRay, which allows the sharing of the bus among event-driven (ET) and time-driven (TT) messages, thus offering the advantages of both TT and ET worlds. FlexRay will very likely become the de-facto standard for in-vehicle communications. While the importance of FlexRay has been quickly recognized, analysis and optimization approaches for the protocol have not been available until recently. FlexRay will be used more and more in safety-critical applications, where message transmission has to be reliable. There are several approaches to increase message transmission reliability, such as hardware replication of the communication channels, replication of messages, message retransmission and information redundancy. FlexRay provides two channels, A and B (which could potentially be used for hardware redundancy), information redundancy in terms of cyclic redundancy checks (CRCs), but does not provide message acknowledgement. With the increasing integration of electronic functions in vehicles, we begin to see several classes of applications that have differing criticality levels. In this thesis we consider three types of messages, with increasing levels of criticality: (1) soft messages, for which we would like to maximize their quality of service (QoS), (2) hard messages for which we guarantee their deadlines and (3) critical messages, which not only have to meet their deadlines, but also have to tolerate one fault during their transmission. We have proposed an optimization approach based on integer linear programming (ILP), which is able to configure the FlexRay protocol parameters such that for a given application, the critical messages are fault-tolerant and meet their deadlines, the deadlines for hard messages are satisfied, and the QoS for soft messages is maximized. The proposed method has been evaluated using several case-studies.
Series IMM-M.Sc.-2008-31
Fulltext
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Admin Creation date: 2008-03-28    Update date: 2008-07-15    Source: dtu    ID: 211874    Original MXD