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 .
Tightening performance bounds of ring networks with cyclic dependencies is still an open problem in the literature. In this paper, we tackle such a challenging issue based on Network Calculus . First, we review the conventional timing approaches in the area and identify their main limitations, in terms of delay bounds pessimism. Afterwards, we have introduced a new concept called Pay Multiplexing Only at Convergence points (PMOC) to overcome such limitations. PMOC considers the flow serialization phenomena along the flow path , by paying the bursts of interfering flows only at the convergence points. The guaranteed endto- end service curves under such a concept have been defined and proved for mono-ring and multiple-ring networks, as well as under Arbitrary and Fixed Priority multiplexing. A sensitivity analysis of the computed delay bounds for mono and multiple-ring networks is conducted with respect to various flow and network parameters, and their tightness is assessed in comparison with an achievable worst-case delay. A noticeable enhancement of the delay bounds, thus network resource efficiency and scalability, is highlighted under our proposal with reference to conventional approaches. Finally, the efficiency of the PMOC approach to provide timing guarantees is confirmed in the case of a realistic avionics application .
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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
Tightening performance bounds of ring networks with cyclic dependencies is still an open problem in the literature. In this paper, we tackle such a challenging issue
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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
. First, we review the conventional timing approaches in the area and identify their main limitations, in terms of delay bounds pessimism. Afterwards, we have introduced a new concept called Pay Multiplexing Only at Convergence points (PMOC) to overcome such limitations. PMOC considers
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. An extensive analysis of such a proposal is conducted herein regarding the accuracy of delay bounds
, by paying the bursts of interfering flows only at the convergence points. The guaranteed endto- end service curves under such a concept have been defined and proved for mono-ring
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its impact on the system performance, i. e., scalability and resource-efficiency; and the results highlight its outperformance, in comparison to conventional methods
multiple-ring networks, as well as under Arbitrary and Fixed Priority multiplexing. A sensitivity analysis of the computed delay bounds for mono and multiple-ring networks is conducted with respect to various flow and network parameters, and their tightness is assessed in comparison with an achievable worst-case delay. A noticeable enhancement of the delay bounds, thus network resource efficiency and scalability, is highlighted under our proposal with reference to conventional approaches. Finally, the efficiency of the PMOC approach to provide timing guarantees is confirmed in the case of a realistic avionics application