Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601356
T. Tan, W. Hsu
Scheduling multimedia applications is not straightforward. The deterministic techniques in hard real-time scheduling, though applicable, are not absolutely necessary and instead result in very conservative execution. Current real-time scheduling research does not properly address the problem of scheduling under overload and nondeterministic situations. In this paper, we introduce a more representative task model for multimedia applications. We describe the use of a frequency parameter, associated with the tasks, which can serve to regulate execution during degradation (when the system is overloaded). We also analyze the worst case CPU bounds for scheduling using frequency and show the possibility of utilization, /spl Sigma/c/p>1 under certain conditions. We conduct experiments to see the performance of the model and best-effort frequency-based scheduling under extreme and variable conditions, where modeling fails.
{"title":"Scheduling multimedia applications under overload and non-deterministic conditions","authors":"T. Tan, W. Hsu","doi":"10.1109/RTTAS.1997.601356","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601356","url":null,"abstract":"Scheduling multimedia applications is not straightforward. The deterministic techniques in hard real-time scheduling, though applicable, are not absolutely necessary and instead result in very conservative execution. Current real-time scheduling research does not properly address the problem of scheduling under overload and nondeterministic situations. In this paper, we introduce a more representative task model for multimedia applications. We describe the use of a frequency parameter, associated with the tasks, which can serve to regulate execution during degradation (when the system is overloaded). We also analyze the worst case CPU bounds for scheduling using frequency and show the possibility of utilization, /spl Sigma/c/p>1 under certain conditions. We conduct experiments to see the performance of the model and best-effort frequency-based scheduling under extreme and variable conditions, where modeling fails.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134105846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601347
Minsoo Ryu, Seongsoo Hong, M. Saksena
This paper presents a control theoretic approach to optimizing end-to-end timing constraints subject to the performance requirements and the schedulability constraint of a real-time control system. The control performance is specified in terms of control output responses such as steady state error maximum overshoot, settling time, and rise time; and the end-to-end timing constraints include loop processing periods and input-to-output latency. Our approach includes a generic real-time controller model on which our analysis is performed, and a heuristic optimization algorithm which derives end-to-end timing constraints. We apply the approach to the design of an embedded real-time controller and validate it through an experimental study using simulation. Our approach contributes to both the control and real-time areas: (1) it allows control engineers to take into consideration the effect of scheduling latency and sampling periods at the early stage of system design; and (2) it makes it possible to streamline the design of real-time control systems, since temporal requirements are derived in an automatic manner. Our approach can be effectively used with the period calibration method as its front-end.
{"title":"Streamlining real-time controller design: From performance specifications to end-to-end timing constraints","authors":"Minsoo Ryu, Seongsoo Hong, M. Saksena","doi":"10.1109/RTTAS.1997.601347","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601347","url":null,"abstract":"This paper presents a control theoretic approach to optimizing end-to-end timing constraints subject to the performance requirements and the schedulability constraint of a real-time control system. The control performance is specified in terms of control output responses such as steady state error maximum overshoot, settling time, and rise time; and the end-to-end timing constraints include loop processing periods and input-to-output latency. Our approach includes a generic real-time controller model on which our analysis is performed, and a heuristic optimization algorithm which derives end-to-end timing constraints. We apply the approach to the design of an embedded real-time controller and validate it through an experimental study using simulation. Our approach contributes to both the control and real-time areas: (1) it allows control engineers to take into consideration the effect of scheduling latency and sampling periods at the early stage of system design; and (2) it makes it possible to streamline the design of real-time control systems, since temporal requirements are derived in an automatic manner. Our approach can be effectively used with the period calibration method as its front-end.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130566994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601349
D. Clarke, Insup Lee
We present a framework for testing timing constraints of real-time systems. Our tests are automatically derived from specifications of minimum and maximum allowable delays between input/output events in the execution of a system. Our test derivation scheme uses a graphical specification formalism for timing constraints, and the real-time process algebra Algebra of Communicating Shared Resources (ACSR) for representing tests and process models. The use of ACSR to describe test sequences has two main advantages. First, tests can be applied to an ACSR model of the software system within the ACSR semantic framework for model validation purposes. Second, ACSR has concise notation and a precise semantics that will facilitate the translation of real-time tests into a software test language for software validation purposes. The major benefit of our approach is that it can be used to validate a design specification which has too many states for exhaustive state space exploration based analysis. As an illustration of this benefit, we describe the case study of using the automatic derivation of tests from timing specifications for the analysis of the Philips Audio Control Protocol.
{"title":"Automatic test generation for the analysis of a real-time system: Case study","authors":"D. Clarke, Insup Lee","doi":"10.1109/RTTAS.1997.601349","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601349","url":null,"abstract":"We present a framework for testing timing constraints of real-time systems. Our tests are automatically derived from specifications of minimum and maximum allowable delays between input/output events in the execution of a system. Our test derivation scheme uses a graphical specification formalism for timing constraints, and the real-time process algebra Algebra of Communicating Shared Resources (ACSR) for representing tests and process models. The use of ACSR to describe test sequences has two main advantages. First, tests can be applied to an ACSR model of the software system within the ACSR semantic framework for model validation purposes. Second, ACSR has concise notation and a precise semantics that will facilitate the translation of real-time tests into a software test language for software validation purposes. The major benefit of our approach is that it can be used to validate a design specification which has too many states for exhaustive state space exploration based analysis. As an illustration of this benefit, we describe the case study of using the automatic derivation of tests from timing specifications for the analysis of the Philips Audio Control Protocol.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124873672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601352
V. Wolfe, L. DiPippo, Gregory Cooper, Russell Johnston, Peter Kortmann, B. Thuraisingham
This paper describes the requirements for real-time extensions to the CORBA standard, which are being developed by the object management group's special Interest Group on Real-Time CORBA. The paper also surveys efforts that are developing Real-Time CORBA systems. It provides a more detailed description of the dynamic real-time CORBA system being developed at the US Navy's NRaD facilities and at the University of Rhode Island.
{"title":"Real-time CORBA","authors":"V. Wolfe, L. DiPippo, Gregory Cooper, Russell Johnston, Peter Kortmann, B. Thuraisingham","doi":"10.1109/RTTAS.1997.601352","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601352","url":null,"abstract":"This paper describes the requirements for real-time extensions to the CORBA standard, which are being developed by the object management group's special Interest Group on Real-Time CORBA. The paper also surveys efforts that are developing Real-Time CORBA systems. It provides a more detailed description of the dynamic real-time CORBA system being developed at the US Navy's NRaD facilities and at the University of Rhode Island.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124324114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601353
Sue Nagy, Azer Bestavros
The use of admission control and overload management techniques in real-time systems has been shown to result in improved system performance-in terms of maximizing the value-added to the system by those transactions committing on time-in comparison to systems which do not employ such techniques. Continuing with our research in hard deadline Real-Time DataBase (RTDB) systems, we investigate the challenges associated with soft deadline transactions and describe a number of admission control and overload management techniques as well as scheduling algorithms appropriate for such systems.
{"title":"Admission control for soft-deadline transactions in ACCORD","authors":"Sue Nagy, Azer Bestavros","doi":"10.1109/RTTAS.1997.601353","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601353","url":null,"abstract":"The use of admission control and overload management techniques in real-time systems has been shown to result in improved system performance-in terms of maximizing the value-added to the system by those transactions committing on time-in comparison to systems which do not employ such techniques. Continuing with our research in hard deadline Real-Time DataBase (RTDB) systems, we investigate the challenges associated with soft deadline transactions and describe a number of admission control and overload management techniques as well as scheduling algorithms appropriate for such systems.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125347900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601342
Ping Xuan, S. Sen, O. González, J. Fernández-Conde, K. Ramamritham
The demand for efficient scalable and cost effective mobile information access systems is rapidly growing. Radiofrequency broadcast plays a major role in mobile computing, and there is a need to provide service models for broadcasting information according to mobile users' needs. The authors present a model called broadcast on demand (BoD), which provides timely broadcasts according to requests from users. Compared to static broadcast, this approach has a different emphasis: it is based on a demand driven framework, aimed at satisfying the temporal constraints of the requests, and uses scheduling techniques at the server side to utilize the limited bandwidth dynamically and efficiently. Several broadcast transmission scheduling policies for BoD are examined. The study indicates that EDF-based policies combined with batching of requests achieve good performance. The results show that BoD is successful in satisfying the temporal constraints of the requests and is a viable service model for wireless broadcast stations.
{"title":"Broadcast on demand: efficient and timely dissemination of data in mobile environments","authors":"Ping Xuan, S. Sen, O. González, J. Fernández-Conde, K. Ramamritham","doi":"10.1109/RTTAS.1997.601342","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601342","url":null,"abstract":"The demand for efficient scalable and cost effective mobile information access systems is rapidly growing. Radiofrequency broadcast plays a major role in mobile computing, and there is a need to provide service models for broadcasting information according to mobile users' needs. The authors present a model called broadcast on demand (BoD), which provides timely broadcasts according to requests from users. Compared to static broadcast, this approach has a different emphasis: it is based on a demand driven framework, aimed at satisfying the temporal constraints of the requests, and uses scheduling techniques at the server side to utilize the limited bandwidth dynamically and efficiently. Several broadcast transmission scheduling policies for BoD are examined. The study indicates that EDF-based policies combined with batching of requests achieve good performance. The results show that BoD is successful in satisfying the temporal constraints of the requests and is a viable service model for wireless broadcast stations.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126877790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601323
Yi Ye, J. Hou
Given an ATM network topology, the link capacity, and the traffic characteristics, we consider the problem of laying out virtual paths over an ATM network to facilitate the timely transmission of isochronous message streams. Specifically, we characterize each message stream in a message stream set with the real-time channel model, and propose a VP layout scheme that determines a near-optimal VP layout which is capable to provide deterministic delay bound desired for each message stream. Such a VP layout is obtained by reserving as minimal bandwidth on each physical link as possible. We then analytically derive and devise all the component procedures in the proposed scheme in detail. We also present simulation results to illustrate the effectiveness of the proposed VP layout scheme.
{"title":"On laying out virtual paths for real-time message streams in ATM networks","authors":"Yi Ye, J. Hou","doi":"10.1109/RTTAS.1997.601323","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601323","url":null,"abstract":"Given an ATM network topology, the link capacity, and the traffic characteristics, we consider the problem of laying out virtual paths over an ATM network to facilitate the timely transmission of isochronous message streams. Specifically, we characterize each message stream in a message stream set with the real-time channel model, and propose a VP layout scheme that determines a near-optimal VP layout which is capable to provide deterministic delay bound desired for each message stream. Such a VP layout is obtained by reserving as minimal bandwidth on each physical link as possible. We then analytically derive and devise all the component procedures in the proposed scheme in detail. We also present simulation results to illustrate the effectiveness of the proposed VP layout scheme.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124592815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601350
M. Brockmeyer, F. Jahanian, C. Heitmeyer, Elly Winner
This paper describes MTSim, an extensible, customizable simulation platform for the Modechart toolset (MT). MTSim provides support for "plugging in" user-defined viewers useful an simulating system behavior in different ways, including application-specific ways. MTSim also supports full user participation in the generation of simulations by allowing users to inject events into the execution trace. Moreover, MTSim provides monitoring and assertion checking of execution traces and the invocation of user-specified handlers upon assertion violation. This paper also introduces a MTSim component called WebSim, a suite of simulation tools for MT, and an an application-specific component of MTSim, which displays the cockpit of an F-18 aircraft and models its bomb release function.
{"title":"A flexible, extensible simulation environment for testing real-time specifications","authors":"M. Brockmeyer, F. Jahanian, C. Heitmeyer, Elly Winner","doi":"10.1109/RTTAS.1997.601350","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601350","url":null,"abstract":"This paper describes MTSim, an extensible, customizable simulation platform for the Modechart toolset (MT). MTSim provides support for \"plugging in\" user-defined viewers useful an simulating system behavior in different ways, including application-specific ways. MTSim also supports full user participation in the generation of simulations by allowing users to inject events into the execution trace. Moreover, MTSim provides monitoring and assertion checking of execution traces and the invocation of user-specified handlers upon assertion violation. This paper also introduces a MTSim component called WebSim, a suite of simulation tools for MT, and an an application-specific component of MTSim, which displays the cockpit of an F-18 aircraft and models its bomb release function.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117149144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601344
S. Goddard
Real-time signal processing applications are commonly designed using a data flow software architecture. The author attempts to understand fundamental real-time properties of such an architecture-the Navy's coarse-grain processing graph method (PGM). By applying recent results in real-time scheduling theory to the subset of PGM employed by the ARPA RASSP Synthetic Aperture Radar benchmark application, he identifies inherent real-time properties of nodes in a PGM data flow graph, and demonstrates how these properties can be exploited to perform useful and important system-level analyses such as schedulability analysis, end-to-end latency analysis, and memory requirements analysis. More importantly, he develops relationships between properties such as latency and buffer bounds and show how one may be traded-off for the other. The results assume only the existence of a simple EDF scheduler and thus can be easily applied in practice.
{"title":"Analyzing the real-time properties of a dataflow execution paradigm using a synthetic aperture radar application","authors":"S. Goddard","doi":"10.1109/RTTAS.1997.601344","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601344","url":null,"abstract":"Real-time signal processing applications are commonly designed using a data flow software architecture. The author attempts to understand fundamental real-time properties of such an architecture-the Navy's coarse-grain processing graph method (PGM). By applying recent results in real-time scheduling theory to the subset of PGM employed by the ARPA RASSP Synthetic Aperture Radar benchmark application, he identifies inherent real-time properties of nodes in a PGM data flow graph, and demonstrates how these properties can be exploited to perform useful and important system-level analyses such as schedulability analysis, end-to-end latency analysis, and memory requirements analysis. More importantly, he develops relationships between properties such as latency and buffer bounds and show how one may be traded-off for the other. The results assume only the existence of a simple EDF scheduler and thus can be easily applied in practice.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"298 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121455101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-06-09DOI: 10.1109/RTTAS.1997.601351
T. Savor, R. Seviora
Software supervision is an approach to automatic detection of software failures. A software supervisor observes the inputs and outputs of a target system. It uses a model of correct behavior, derived from the target system's requirements specification. Discrepancies between specified and observed behaviors are reported as failures. The tradeoff between the computational complexity of supervision and the latency of failure reporting is discussed in this paper. Supervisor computational complexity can be significantly reduced at the expense of increased failure reporting latency. For applications such as software testing, this is a practical tradeoff. Such a supervisor is called an out-of-time supervisor. This paper describes the data, flows, algorithms, operation and evaluation of an out-of-time supervisor for communicating finite state machine based requirements specifications. A prototype supervisor was used to monitor the operation a small telephone exchange control program. For a failure reporting latency equal to the worst-case response time of the target system, a reduction in computational complexity of several orders of magnitude was measured.
{"title":"An approach to automatic detection of software failures in real-time systems","authors":"T. Savor, R. Seviora","doi":"10.1109/RTTAS.1997.601351","DOIUrl":"https://doi.org/10.1109/RTTAS.1997.601351","url":null,"abstract":"Software supervision is an approach to automatic detection of software failures. A software supervisor observes the inputs and outputs of a target system. It uses a model of correct behavior, derived from the target system's requirements specification. Discrepancies between specified and observed behaviors are reported as failures. The tradeoff between the computational complexity of supervision and the latency of failure reporting is discussed in this paper. Supervisor computational complexity can be significantly reduced at the expense of increased failure reporting latency. For applications such as software testing, this is a practical tradeoff. Such a supervisor is called an out-of-time supervisor. This paper describes the data, flows, algorithms, operation and evaluation of an out-of-time supervisor for communicating finite state machine based requirements specifications. A prototype supervisor was used to monitor the operation a small telephone exchange control program. For a failure reporting latency equal to the worst-case response time of the target system, a reduction in computational complexity of several orders of magnitude was measured.","PeriodicalId":448474,"journal":{"name":"Proceedings Third IEEE Real-Time Technology and Applications Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127449954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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