Date of Award

Summer 1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Computer Science

Committee Director

Ravi Mukkamala

Committee Member

Kurt Maly

Committee Member

Hussein Abdel-Wahab

Committee Member

Larry W. Wilson

Committee Member

John W. Stoughton

Abstract

The number and complexity of applications that run in real-time environments have posed demanding requirements on the part of the real-time system designer. It has now become important to accommodate the application complexity at early stages of the design cycle. Further, the stringent demands to guarantee task deadlines (particularly in a hard real-time environment, which is the assumed environment in this thesis) have motivated both practioners and researchers to look at ways to analyze systems prior to run-time. This thesis reports a new perspective to analyzing real-time systems that in addition to ascertaining the ability of a system to meet task deadlines also qualifies these guarantees. The guarantees are qualified by a measure (called the scaling factor) of the systems ability to continue to provide these guarantees under possible changes to the tasks. This measure is shown to have many applications in the design (task execution time estimation), development (portability and fault tolerance) and maintenance (scalability) of real-time systems. The measure is shown to bear relevance in both uniprocessor and distributed (more generally referred to as end-to-end) real-time systems.

However, the derivation of this measure in end-to-end systems requires that we solve a fundamental (very important, yet unsolved) problem--the end-to-end schedulability problem. The thesis reports a solution to the end-to-end schedulability problem which is based on a solution to another fundamental problem relevant to single-component real-time systems (a uniprocessor system is a special instance of such a system). The problem of interest here is the schedulability of a set of tasks with arbitrary arrival times, that run on a single component. The thesis presents an optimal solution to this problem. One important consequence of this result (besides serving as a basis for the end-to-end schedulability problem) is its applicability to tbe classical approach to real-time scheduling, viz., static scheduling. The final contribution of the thesis comes as an application of the results to the area of real-time communication. More specifically, we report a heuristic approach to the problem of admission control in real-time traffic networks. The heuristic is based on the scaling factor measure.

DOI

10.25777/8gjd-0b49

ISBN

9780591048735

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