Abuteir, Mohammed

System-of-systems (SoS) have recently been used in several applications and scenarios in the field of safety, defense, and healthcare. In an SoS environment, the entire system is divided into sub-systems, which provides more flexibility and reduces the management cost of the entire system. SoS have been widely used in healthcare monitoring services, where patients are provided with medical sensors that send their medical measurements to a remote unit for further processing and decision-making. These sensors communicate with an access point using the wireless channel, which gives patients flexibility in mobility and makes the monitoring system more convenient and comfortable. However, sending data over the wireless channel presents several challenges, such as contention between the different sensors in accessing the channel and the bit errors associated with the noisy wireless channel. In this paper, an SoS healthcare monitoring framework is proposed, where a wireless communication protocol is proposed that addresses the sensors’ node network access contention and mitigates the bit errors of the communication channel by providing forward error correction bits to the transmitted packets. In addition, the protocol takes into consideration the sensors’ importance and criticality, such that more important sensors are given more network access time and more error correction bits, which in turn results in a robust transmission process with low transmission delay. The simulation results show the proposed wireless communication protocol’s effectiveness in lowering the packet loss, giving higher priority and having higher throughput for the more critical sensors.

In many domains such as avionics, industrial control, or healthcare there is an increasing trend to mixed-criticality systems, where applications of different importance and criticality are implemented on a shared computing platform. The major requirement of such a system is a modular safety case where each application is certified to the respective assurance level. A mixed-criticality architecture for networked multi-core chips with real-time support, fault isolation and security is missing in the state-of-the-art. In this dissertation, we advance the state-of-the-art by providing solutions to research gaps towards such an architecture for networked multi-core chips, which include the architecture models, selective fault-tolerance concepts, scheduling techniques, and a simulation framework. The foundations for this integration are mechanisms for temporal and spatial partitioning, to ensure that applications of different criticality levels are protected so they cannot influence each other. We establish temporal partitioning using autonomous temporal control based on a time-triggered schedule containing the instants of all message exchanges with respect to a global time base. The predetermined instants of the periodic messages improve predictability and enable rigorous error detection and fault isolation. The time-triggered schedules facilitate managing the complexity of fault-tolerance and analytical dependability models. In addition, we use network bandwidth partitioning to support different timing models (i.e., periodic, sporadic and aperiodic traffic). We introduce an architectural model for mixed-criticality systems based on networked multi-core chips, which describes both the physical system structure as well as a logical system structure of the application. Another contribution of the dissertation is a selective fault-tolerance concept for mixed-criticality systems. One of the key features of existing fault-tolerant communication protocols such as ac{TTEthernet} and ARINC 664 is providing redundant channels for the communication between nodes over multiple independent network components. The data flows between the nodes are protected against the failure of any network component such as a link or a switch. However, the main drawback of replicated networks in large systems is the extra cost, in particular, if the networks provide their services for non safety-critical subsystems alongside with the critical subsystems. We introduce a novel system architecture supporting redundancy in mixed-criticality systems based on a ring topology, which fulfills the requirements of high-critical systems while also being economically suitable for low-critical systems. The main characteristic of the proposed architecture is fault isolation so that a failure of a low-critical subsystem cannot reach subsystems of higher criticality. Moreover, the proposed architecture supports the delivery of messages with bounded delays and bounded jitter. Based on these contributions, we address the scheduling algorithms for large scale mixed-criticality systems where different criticality levels of the subsystem as well as high numbers of nodes and applications lead to a steady increase of the complexity of scheduling the events associated with such systems. The architecture models have also been evaluated using a simulation framework. This simulation framework is established for hierarchical mixed-criticality systems based on networked multi-core chips. Additionally, this framework is used to verify the proposed scheduling algorithms. This evaluation is accompanied by analytical models of end-to-end communication for different criticality levels.

Abuteir, Mohammed

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