TY - CHAP A1 - Krämer, Stefan A1 - Raab, Peter A1 - Mottok, Jürgen A1 - Racek, Stanislav T1 - Reliability analysis of real-time scheduling by means of stochastic simulation T2 - 2012 International Conference on Applied Electronics (AE 2012), Pilsen, Czech Republic, 5 - 7 September 2012 N2 - We present a simulation-based approach to reliability analysis combined with a schedulability analysis of software intensive embedded real-time systems. In such a system not only does the software execution have to be hardened against soft errors, e.g., by means of coded processing or diverse execution, but also the real-time requirements have still to be met in the presence of such error to guarantee a safe operation of the system. For that reason, the influence regarding the real-time characteristics of a given sporadic error with a certain error rate is analyzed by means of a Monte Carlo simulation. Different safety design patterns are introduced and compared. Furthermore, the impact on the schedulability of an embedded system is discussed. Y1 - 2012 SP - 151 EP - 156 ER - TY - CHAP A1 - Raab, Peter A1 - Racek, Stanislav A1 - Krämer, Stefan A1 - Mottok, Jürgen T1 - Reliability of Task Execution during Safe Software Processing T2 - 15th Euromicro Conference on Digital System Design, Cesme, Turkey N2 - This paper presents the reliability evaluation of task execution during safe software processing. The standard method of duplication in a safety-critical application can also be applied for tasks in a software system. But in addition to this, there is also the possibility for coded task processing to increase the reliability and availability of software. The presented analysis covers the reliability analysis of a single, a duplicated and a coded task by the technique of continuous time Markov processes. Markov processes are often used for the reliability evaluation of safety-critical systems. We introduce a method to describe the execution time of tasks by means of enhanced Markov models and their solution by numerical methods. KW - reliability analysis KW - continuous-time Markov process KW - error probability KW - Erlang-distribution Y1 - 2012 U6 - https://doi.org/10.1109/DSD.2012.110 SP - 84 EP - 89 ER - TY - JOUR A1 - Raab, Peter A1 - Krämer, Stefan A1 - Mottok, Jürgen T1 - Reliability of data processing and fault compensation in unreliable arithmetic processors, Microprocessors and Microsystems JF - Microprocessors and Microsystems N2 - In logical circuits, like arithmetic operations in a processor system, arbitrary faults become a more tremendous aspect in future. Modern manufacturing processes lead to less reliability and higher vulnerability of software execution to soft-errors. The correctness of certain results is important especially for safety–critical applications whose reliability depends on the fault-free execution of each single instruction and the dependencies between them. The more complex a software is the more unreliable the outcome is. But, there is a contrary effect. If the probability for multiple faults increases, there is also the chance that two faults compensate each other and the result is correct again. This paper presents the basic ideas for such a reliability evaluation of a software's data flow with arbitrary soft-errors and the effect of fault compensation. Further, this evaluation provides a possibility to compare different implementations of a data flow with respect to the reliability. This is shown by the comparison of two different error codes as alternatives for coded data processing. Y1 - 2016 U6 - https://doi.org/10.1016/j.micpro.2015.07.014 VL - 40 IS - Februar SP - 102 EP - 112 PB - Elsevier ER - TY - CHAP A1 - Krämer, Stefan A1 - Mottok, Jürgen A1 - Racek, Stanislav T1 - Proportionate fair based multicore scheduling for fault tolerant multicore real-time systems T2 - International Conference on Electrical and Information Technologies (ICEIT), 25-27 March 2015, Marakesch, Morocco N2 - In this paper we present a scheduling approach for safety critical, fault tolerant, multicore real-time embedded systems. For this kind of systems, not only the correctness of a computed result but also the strict adherence to timing requirements of computation is essential to avoid any kind of damage. To react to unpredictable, arbitrary hardware faults suitable error detection mechanisms have to be applied. The caused error itself and the detection and correction have great impact on the system's timing behavior. To still keep the real-time requirements, the used scheduling algorithm has to ensure maximum flexibility to disturbances of the timing. The group of Proportionate Fair (Pfairness) multicore scheduling algorithms has been proven to create an optimal schedule in polynomial time. The contribution of this paper is a Pfair-based algorithm that uses tight coupling between the error detection mechanisms and the scheduler of the real-time operating system to establish a loop-back connection. KW - Multicore processing KW - Time factors KW - Safety KW - Schedules KW - Scheduling algorithms KW - Real-time systems Y1 - 2015 U6 - https://doi.org/10.1109/EITech.2015.7162952 SP - 88 EP - 93 ER - TY - CHAP A1 - Seidl, M. A1 - Krämer, Stefan A1 - Mottok, Jürgen T1 - Improving the reliability of an embedded real-time system by applying coded processing T2 - 4th Applied Research Conference, 5th July 2014, Ingolstadt Y1 - 2014 SN - 978-3-8440-2875-1 SP - 70 EP - 74 PB - Shaker CY - Aachen ER - TY - CHAP A1 - Mucha, Matthias A1 - Mottok, Jürgen A1 - Krämer, Stefan T1 - Estimation of Worst Case Response Time Boundaries in Multi-Core Real-Time Systems T2 - 2017 International Conference on Applied Electronics (AE), 5-6 Sept. 2017, Pilsen N2 - We address a novel probabilistic approach to estimate the Worst Case Response Time boundaries of tasks. Multi-core real-time systems process tasks in parallel on two or more cores. Tasks in our contribution may preempt other tasks, block tasks with semaphores to access global shared resources, or migrate to another core. The depicted task behavior is random. The shape of collected response times of a task within a processing time is multimodal. Extreme Value approaches need unimodal response time distributions to estimate the Worst Case Response Time of tasks. The new proposed method derives a set of three task set shapes from the source task set. It is used to minimize the uncertainty of random task behavior by maximizing the coverage of possible Worst Case Response Times. The case study evaluates the new proposed estimation method by the use of dynamically generated random tasks with varying task properties. Y1 - 2017 SN - 978-80-261-0641-8 U6 - https://doi.org/10.23919/ae.2017.8053598 SN - 1803-7232 SP - 1 EP - 6 PB - IEEE ER -