The recent research effort towards defining new communication solutions  to guarantee high availability level with limited cabling costs and complexity  has renewed the interest in ring-based networks. This topology has been recently used for industrial and embedded applications , with the implementation of many Real Time Ethernet (RTE) profiles. A relevant issue for such networks is handling cyclic dependencies to prove timing predictability, a key requirement for safety-critical systems , e. g., avionics and automotive. To deal with the performance evaluation of such networks, most relevant existing techniques are based on the Network Calculus framework, and consists in analyzing locally the delay upper bound in each crossed node, resulting in pessimistic end-to-end delay bounds. To overcome this limitation, an enhanced global timing analysis , accounting the flow serialization phenomena along the flow path , is proposed in this paper to improve the delay bounds tightness. The main contribution consists in defining and proving a closed form formula of the guaranteed end-to-end service curve of any flow of interest crossing a FIFO ring-based network. An extensive analysis of such a proposal has been conducted regarding the tightness of delay bounds and its impact on the system performance, in terms of system scalability and resource-efficiency . Results highlight the proposed approach efficiency to compute tight delay bounds , in comparison with conventional timing analysis and in reference with a worst-case delay lower bound .
The recent research effort towards defining new communication solutions for cyber-physical systems (CPS), to guarantee high availability level with limited cabling costs and complexity , has renewed the interest in ring-based networks. This topology has been recently used for various networked cyber-physical systems (Net-CPS), e.g., avionics and automotive , with the implementation of many Real Time Ethernet (RTE) profiles. A relevant issue for such networks is to prove timing predictability, a key requirement for safety-critical systems . We are interested in this paper in event-triggered ring-based networks, which guarantee high resource utilization efficiency and (re)configuration flexibility, at the cost of increasing the timing analysis complexity. The implementation of such a communication scheme on top of a ring topology actually induces cyclic dependencies, in comparison to time-triggered solutions. To cope with this arising issue of cyclic dependencies, only few techniques have been proposed in the literature, mainly based on Network Calculus framework, and consist in analyzing locally the delay upper bound in each crossed node, resulting in pessimistic end-to-end delay bounds. Hence, the main contribution in this paper is enhancing the delay bounds tightness of such networks, through an innovative global analysis based on Network Calculus , accounting the flow serialization phenomena along the flow path . An extensive analysis of such a proposal is conducted herein regarding the accuracy of delay bounds and its impact on the system performance, i.e., scalability and resource-efficiency ; and the results highlight its outperformance , in comparison to conventional methods .
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