III B.E. (Computer Engg.)

VII SEMESTER

7CP6.4 REAL -TIME SYSTEMS

1.   INTRODUCTION TO REAL-TIME APPLICATIONS: Digital control-sampled data systems, compels control-law computations, High-level control -control hierarchy, guidance and control, real- time command and control. Signal processing "Processing Bandwidth demands, Radar system. Real-time data bases and Multimedia application.

2.   HARD VERSUS SOFT REAL TIME SYSTEMS: Jobs and. processors. Release times, deadlines and timing constraints. Hard and soft timing constraints - Hard timings constraints and temporal Quality-of-Service quarantines. Hard real-time systems -reasons for timing guarantee requirement and examples of hard timing constraints. Soft real-time systems.

3.    A REFERENCE MODEL OF REAL-TIME SYSTEMS: Processors and resources. Temporal parameters of real-time workload -fixed, jittered, sporadic release times and execution time. Periodic task. Model -periods, execution times and phases of periodic tasks, A periodic and sporadic tasks. Precedence graph and data dependency. Temporal dependency, AND/OR precedence constraints, conditional branches and pipeline relationship. Functional Parameters-preemptively and criticality of jobs, optional execution, laxity type and laxity function. Resource par.m1eters of jobs and parameters of resources -pre-emptive of resources and resource graph. Scheduling hierarchy -Scheduler and schedules; Feasibility optimality and performance measures; Interaction among schedulers.

4.    COMMONLY USED APPROACHES TO REAL-TIME SCHEDULING: Clock-Driven approach; Weighted round-robin approach; priority driven approach. Dynamic versus static systems. Effective release times and deadlines. Optimality of EDF and LST algorithms. Non optimality of EDF and LST algorithms. Challenges validating timing constraints and their performance. Off-line versus on-line scheduling.

5. CLOCK-DRIVEN SCHEDULING: Assumptions for scheduling. Static and timer-driven scheduler. General structure of cyclic schedules-frame major cycles, frame size constraints and job slices. Cyclic executives. Improving the average response time of aperiodic jobs -slack stealing and average response time. Scheduling sporadic jobs -acceptance test, EDF scheduling of the accepted jobs, implementation of acceptance test and optimality of cyclic EDF algorithm.

Recommended Books:

1.      W.S. Liu Real Time Systems, Pearson Education Asia.

2.      Raymond A. Buhr -Introduction to Real-Time Systems, Pearson education Asia.

3.      Alan Bums Real Time Systems and Programming Languages, Pearson Education.