Sharif Digital Repository

Abstract: Fault tolerance in computing systems often depends on the precision of fault detection methods, significantly impacting overall reliability. Classic fault tolerance methods, like task replication, struggle to achieve certain reliability targets with imperfect fault detection, which, unlike perfect detection mechanisms, imposes minimal system overheads. Addressing this, our paper introduces Dynamic Task Replication (DTR), a general fault tolerance technique that dynamically determines the number of replicas at runtime to overcome the limitations of classical task replication. Our primary contribution, Optimal Dynamic Task Replication (ODTR), optimizes DTR for a given task, aiming to... 

Cyber-Physical Systems, including embedded systems, have become essential components of various applications in modern life. Due to this fact, cyber-physical and embedded systems must be reliable, safe, and meet timing constraints. Task replication is an effective approach to improve reliability and safety, but it may violate the real-time constraints of the executing tasks and aggravate the aging effects of the system due to elevating the on-chip temperature. Moreover, since embedded systems have time, reliability, power, and thermal constraints, the appropriate number of replicas should be determined to handle the extra overheads. Existing works determine the number of replicas at design... 

Cloud computing has provided a suitable platform for processing and storing Internet of Things data over the last few decades by establishing data centers with high processing power. Today, with the rise of real-time processing applications in the Internet of Things, such as voice assistants, smart health controls, and self-driving cars, the number of real-time tasks has increased rapidly; this is despite the fact that cloud servers cannot meet the deadline constraint due to physical distance delays. To address this challenge, Fog computing has been introduced. By moving computational and storage resources closer to the edge of the network, fog computing enables executing real-time tasks... 

With the increasing development of Internet of Things (IoT) devices, issues such as establishing effective communication, optimizing energy consumption, ensuring reliability and improving the quality of services provided by these devices become more and more complex and critical challenges. With the introduction of fog computing model by Cisco in 2012, some of these challenges were successfully managed. Fog computing is a distributed computing paradigm that acts as a middle layer between cloud data centers and IoT-based devices/sensors. By distributing computing resources closer to edge devices, fog computing enables real-time data processing and analysis. However, one of the key aspects in...