Due to increased on-chip power density, multi-core systems face various thermal issues. In particular, exceeding a certain threshold temperature can reduce the system's performance and reliability. Therefore, when designing a real-time application with non-deterministic workload, the designer has to be aware of the maximum possible temperature of the system. This paper proposes an analytic method to calculate an upper bound on the worst-case peak temperature of a real-time system with multiple cores generated under all possible scenarios of task executions. In order to handle a broad range of uncertainties, task arrivals are modeled as periodic event streams with jitter and delay. Finally, the proposed method is applied to a multi-core ARM platform and our results are validated in various case studies.

In this paper, we propose a reliability optimization technique for low earth orbit (LEO) satellite systems that operate in highly varying temperatures. In the proposed technique, we harden the target satellite on-board computer considering two common reliability threats, soft-error and hard-error, at the same time. Based on an existing fault-tolerant scheduling, we show how the reliability and lifetime of the system can be quantified with respect to a given error handling policy. Then, using these models, we perform extensive reliability analyses and optimizations of the hardening degree for different functional safety requirements. We implemented the proposed technique in a widely adopted real-time operating system (RTOS), Real-Time Executive for Multiprocessor Systems (RTEMS), working on a real satellite on-board computer system, GR712RC. The proposed technique enables efficient explorations of the trade-off between the soft-error reliability (failure rate), hard-error reliability (expected lifetime), and other resource utilization indicators, like power consumption or CPU utilization. In particular, the proposed technique could be successfully utilized to co-optimize the lifetime and fault-tolerance concerning the unique ambient temperature profile of LEO satellites.

Thanks to their higher performance compared to conventional batteries, lithium-ion (Li-ion) batteries have recently become popular as a power source in many electronic systems. However, Li-ion batteries are known to suffer from an aging issue: the available capacity is gradually degraded as the operation goes by. The impact of aging is particularly critical to satellite systems where no maintenance is available after the initial deployment. Recently, a real-time scheduling framework was proposed to decelerate the aging of Li-ion batteries. However, this framework simply relies on the fact that the elevated temperature results in a worse lifespan of the battery. In contrast to this, in this paper, we argue that the reduced temperature may actually cause an adverse effect in the battery lifetime when considering satellite environments. To evidently demonstrate this anomaly, we extend an open-source Li-ion battery aging simulator to consider the temperature-dependent aging characteristics of the Li-ion batteries. Then, a couple of alternative scheduling policies that better suit the target satellite systems are evaluated in the simulator in comparison with the existing scheduling policies. Our simulation results show that the existing scheduling method, which does not consider the satellite temperature environments, rather deteriorates the lifespan of battery and the proposed scheduling technique can extend the lifespan by up to 65.51%.