Papers by Liesbeth Steffens
For Consumer Terminals Quality-Of-Service Resource Management
Execution of video algorithms on programmable platforms is limited by the available resources. A ... more Execution of video algorithms on programmable platforms is limited by the available resources. A novel approach with scalable algorithms and run-time control of output quality and resource usage can transcend such limitations.
Rtcsa 2008: 14th Ieee International Conference on Embedded and Real-Time Computing Systems and Applications - Proceedings, 2008
The convergence of application domains in new systemson-chip (SoC) results in systems with many a... more The convergence of application domains in new systemson-chip (SoC) results in systems with many applications with a mix of soft and hard real-time requirements. To reduce cost, resources, such as memories and interconnect, are shared between applications. However, resource sharing introduces interference between the sharing applications, making it difficult to satisfy their real-time requirements. Existing arbiters do not efficiently satisfy the requirements of applications in SoCs, as they either couple rate or allocation granularity to latency, or cannot run at high speeds in hardware with a low-cost implementation. The contribution of this paper is an arbiter called Credit-Controlled Static-Priority (CCSP), consisting of a rate regulator and a static-priority scheduler. The rate regulator isolates applications by regulating the amount of provided service in a way that decouples allocation granularity and latency. The static-priority scheduler decouples latency and rate, such that low latency can be provided to any application, regardless of the allocated rate. We show that CCSP belongs to the class of latency-rate servers and guarantees the allocated rate within a maximum latency, as required by hard real-time applications. We present a hardware implementation of the arbiter in the context of a DDR2 SDRAM controller. An instance with six ports running at 200 MHz requires an area of 0.0223 mm 2 in a 90 nm CMOS process.
QoS-Based Resource Management for Ambient Intelligence
Ambient Intelligence: Impact on Embedded Sytem Design, 2003
QoS-based Resource Management for Ambient Intelligence Clara M. Otero Perez, Liesbeth Steffens, P... more QoS-based Resource Management for Ambient Intelligence Clara M. Otero Perez, Liesbeth Steffens, Peter van der Stok and Sjir van Loo Philips Research Laboratories Eindhoven, Eindhoven, The Netherlands {clara. otero. perez, liesbeth. steffens, peter. van. der. stok, ...
Abstract:,The convergence of application domains,in new systems-on-chip results in
Resource Reservation and Service Contract
Real-Time Systems, 2005
Video processing in software is often characterized by highly fluctuating, contentdependent proce... more Video processing in software is often characterized by highly fluctuating, contentdependent processing times, and a limited tolerance for deadline misses. We present an approach that allows close-to-average-case resource allocation to a single video processing task, based on asynchronous, scalable processing, and QoS adaptation. The QoS adaptation balances different QoS parameters that can be tuned, based on user-perception experiments: picture quality, deadline misses, and quality changes. We model the balancing problem as a discrete stochastic decision problem, and propose two solution strategies, based on a Markov decision process and reinforcement learning, respectively. We enhance both strategies with a compensation for structural (non-stochastic) load fluctuations. Finally, we validate our approach by means of simulation experiments, and conclude that both enhanced strategies perform close to the theoretical optimum.
Journal of Scheduling, 2000
In this paper, we present a simple recursive equation and an iterative procedure to determine the... more In this paper, we present a simple recursive equation and an iterative procedure to determine the best-case response times of periodic tasks under fixed-priority preemptive scheduling and arbitrary phasings. The approach is of a similar nature as the one used to determine worst-case response times (Joseph and Pandya, 1986) in the sense that where a critical instant is considered to determine the latter, we base our analysis on an optimal instant. Such an optimal instant occurs when all higher priority tasks have a simultaneous release that coincides with the completion of an execution of the task under consideration. The resulting recursive equation closely resembles the one for worst-case response times. The iterative procedure is illustrated by means of a small example. Next, we apply the best-case response times to analyze jitter in distributed multiprocessor systems. To this end, we discuss the effect of the best-case response times on completion jitter, as well as the effect of release jitter on the best-case response times. The newly derived best-case response times generally result in tighter bounds on jitter, in turn leading to tighter worst-case response time bounds.
On-the-fly garbage collection: an exercise in cooperation
Communications of the ACM, 1978
8. HoIn, BKP Determining lightness from an image. Comptr. Graphics and Image Processing 3, 4(Dec.... more 8. HoIn, BKP Determining lightness from an image. Comptr. Graphics and Image Processing 3, 4(Dec. 1974), 277-299. 9. Huffman, DA Impossible objects as nonsense sentences. In Machine Intelligence 6, B. Meltzer and D. Michie, Eds., Edinburgh U. Press, Edinburgh, 1971, pp. ...
Virtual platform: An approach to manage temporal complexity
www-users.cs.york.ac.uk
Page 1. Virtual platform: An approach to manage temporal complexity Clara M. Otero Pérez, Liesbet... more Page 1. Virtual platform: An approach to manage temporal complexity Clara M. Otero Pérez, Liesbeth Steffens and Sjir van Loo Philips Research Laboratories Eindhoven (PRLE) { clara.otero.perez, liesbeth.steffens, sjir.van.loo}@philips.com ...
Many applications utilize deeply embedded sensors and actuators that are tightly coupled with the... more Many applications utilize deeply embedded sensors and actuators that are tightly coupled with the physical environment in order to perform their functionality. Sensor, actuators and embedded computation resources used for implementing such systems usually exhibit regular local configurations, while the global structure of the subsystems is either not fixed a priori and can change at runtime or is not known. Examples include systems that use many randomly distributed sensing boards, each one having a fixed structure of computation resources and sensing devices, to autonomously detect events and take proper actions. This paper discusses the requirements of the aforementioned systems, their advantages and the issues involved in developing them. Specifically we focus on dynamic adaptation of the system as a particular feature of such systems. This feature is discussed in depth in a collaborative and dynamically adaptive object tracking system that has been built in our lab as the experimental framework of this study. We exploit reconfigurable hardware devices embedded in a number of networked cameras in order to achieve our goal. We justify the need for dynamic adaptation of the system through scenarios and applications. Experimental results on a set of scenes advocate the fact that our system works effectively for different scenario of events through reconfiguration. Comparing results with non-adaptive implementations verify the fact that our approach improves system's robustness to scene variations and outperforms the traditional implementations.
Method of Running an Algorithm and a Scalable Programmable Processing Device
Method of Running a Media Application and a Media System with Job Control
A Method to Assist in the Predictability of Open and Flexible Systems Using Video Analysis
Processing a Media Signal on a Media System
Processing a Media Signal in a Media System to Prevent Overload
Method of and system for withdrawing budget from a blocking task
Method of and system for determining a best-case response time of a periodic task
Method for operating a real-time multimedia terminal in a QoS manner
In this paper, we present QoS control challenges for multimedia consumer terminals based on an ap... more In this paper, we present QoS control challenges for multimedia consumer terminals based on an application execution model and a QoS resource management framework. In the context of this framework, we briefly recapitulate earlier work aimed at QoS control for high-quality video processing. By relaxing a number of assumptions in that work, and by considering the work in relation to the framework and the applied video algorithms, new control challenges are identified.
In this paper, we present a simple recursive equation to determine the best-case response times o... more In this paper, we present a simple recursive equation to determine the best-case response times of periodic tasks under fixed-priority preemptive scheduling and arbitrary phasings. The approach is of a similar nature to the one used to determine worst-case response times, in the sense that, where a critical instant is considered to determine the latter, we base our analysis on an optimal instant, in which all higher priority tasks have a simultaneous release that coincides with the bestcase completion of the task under consideration. The resulting recursive equation closely resembles the one for worst-case response times, apart from a term ¢ 1 difference, and the fact that the bestcase response times are approached from above. The resulting iterative procedure is illustrated by means of a small example. Finally, we discuss the effect of the best-case response times on completion jitter, as well as the effect of release jitter on the best-case response times.
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Papers by Liesbeth Steffens