Event count automata: A state-based model for stream processing systems

10.1109/RTSS.2005.21Proceedings - Real-Time Systems Symposium-PRSY

Lightweight modeling of complex state dependencies in stream processing systems

10.1109/RTAS.2009.27Proceedings of the IEEE Real-Time and Embedded Technology and Applications Symposium, RTAS195-20

A multi-mode real-time calculus

10.1109/RTSS.2008.47Proceedings - Real-Time Systems Symposium59-69PRSY

Composing functional and state-based performance models for analyzing heterogeneous real-time systems

10.1109/RTSS.2007.46Proceedings - Real-Time Systems Symposium343-352PRSY

Video quality driven buffer sizing via frame drops

10.1109/RTCSA.2011.49Proceedings - 17th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 20111319-32

Opaque analysis for resource sharing in compositional real-time systems

In this paper we propose opaque analysis methods to integrate dependent real-time components into hierarchical fixed-priority scheduled systems. To arbitrate mutually exclusive resource access between components, we consider two existing protocols: HSRP - comprising overrun with and without payback - and SIRAP. An opaque analysis allows to postpone the choice of a synchronization protocol until component integration time. First, we identify the sources of pessimism in the existing analysis techniques and we conclude that both protocols assume different models in their local analysis. In particular, the compositional analysis for overrun with payback (OWP) is not opaque and is pessimistic. The latter makes OWP expensive compared to its counter part without a payback mechanism (ONP). This paper presents an opaque and less pessimistic OWP analysis. Secondly, SIRAP requires more timing information to perform a task-level schedulability analysis. In many practical situations, however, detailed timing characteristics of tasks are hard to obtain. We introduce an opaque analysis for SIRAP using the analysis of ONP to reduce the required timing information during the local analysis. We show that the analysis for ONP cannot deem systems schedulable which are infeasible with SIRAP. The SIRAP analysis may therefore reduce the required system resources of a component by sacrificing the choice for an arbitrary synchronization protocol at system integration time

Arrival curves for real-time calculus: the causality problem and its solutions

Abstract. The Real-Time Calculus (RTC) [16] is a framework to analyze heterogeneous real-time systems that process event streams of data. The streams are characterized by pairs of curves, called arrival curves, that express upper and lower bounds on the number of events that may arrive over any specified time interval. System properties may then be computed using algebraic techniques in a compositional way. A wellknown limitation of RTC is that it cannot model systems with states and recent works [7, 1, 13, 11] studied how to interface RTC curves with statebased models. Doing so, while trying, for example to generate a stream of events that satisfies some given pair of curves, we faced a causality problem [14]: it can be the case that, once having generated a finite prefix of an event stream, the generator deadlocks, since no extension of the prefix can satisfy the curves anymore. When trying to express the property of the curves with state-based models, one may face the same problem. This paper formally defines the problem on arrival curves, and gives algebraic ways to characterize causal pairs of curves, i.e. curves for which the problem cannot occur. Then, we provide algorithms to compute a causal pair of curves equivalent to a given curve, in several models. These algorithms provide a canonical representation for a pair of curves, which is the best pair of curves among the curves equivalent to the ones they take as input.

BSN simulator: Optimizing application using system level simulation

10.1109/BSN.2009.22Proceedings - 2009 6th International Workshop on Wearable and Implantable Body Sensor Networks, BSN 20099-1

Fast and accurate simulation of biomonitoring applications on a wireless body area network

10.1109/ISSMDBS.2008.4575039Proc. 5th Int. Workshop on Wearable and Implantable Body Sensor Networks, BSN2008, in conjunction with the 5th Int. Summer School and Symp. on Medical Devices and Biosensors, ISSS-MDBS 2008145-14