Electrical & Computer Engineering Research Works

Permanent URI for this collectionhttp://hdl.handle.net/1903/1658

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    A New Quality of Service Metric for Hard/Soft Real-Time Applications
    (IEEE, 2003-04) Hua, Shaoxiong; Qu, Gang
    Real-time applications often have mixed hard and soft deadlines, can be preempted subject to the cost of context switching or the restart of computation, and have various data dependency. The simple but widely used task completion ratio, as the Quality of Service (QoS) metric, does not capture these characteristics and can not reflect user perceived QoS well. In this paper, we propose a new quantitative QoS metric, which is based on task completion ratio but differentiates hard and soft deadlines and models data dependency as well. Basically, it assigns different weights to hard and soft deadline tasks, penalizes late soft task completion, and measures the tasks affected by any dropped tasks. We apply popular online schedulers, such as EDF (earliest deadline first), FCFS (first come first serve), and LETF (least execution time first), on a set of simulated MPEG movies at the frame level and for each application compare the new QoS measurement, traditional completion ratio with the “real” completion ratio which considers the number of correctly decoded frames and has been mapped to the user perceived QoS well. Experimental results show that our proposed QoS metric can reflect real life QoS much better than the traditional one.
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    Power Optimization of Variable-Voltage Core-Based Systems
    (IEEE, 1998-06) Hong, Inki; Kirovski, Darko; Qu, Gang; Potkonjak, Miodrag; Srivastava, Mani B.
    The growing class of portable systems, such as personal computing and communication devices, has resulted in a new set of system design requirements, mainly characterized by dominant importance of power minimization and design reuse. The energy efficiency of systems-on-a-chip (SOC) could be much improved if one were to vary the supply voltage dynamically at run time. We develop the design methodology for the lowpower core-based real-time SOC based on dynamically variable voltage hardware. The key challenge is to develop effective scheduling techniques that treat voltage as a variable to be determined, in addition to the conventional task scheduling and allocation. Our synthesis technique also addresses the selection of the processor core and the determination of the instruction and data cache size and configuration so as to fully exploit dynamically variable voltage hardware, which results in significantly lower power consumption for a set of target applications than existing techniques. The highlight of the proposed approach is the nonpreemptive scheduling heuristic, which results in solutions very close to optimal ones for many test cases. The effectiveness of the approach is demonstrated on a variety of modern industrial-strength multimedia and communication applications.
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    Power Optimization of Variable Voltage Core-Based Systems
    (IEEE, 1999-12) Hong, Inki; Kirovski, Darko; Qu, Gang; Potkonjak, Miodrag; Srivastava, Mani B.
    The growing class of portable systems, such as personal computing and communication devices, has resulted in a new set of system design requirements, mainly characterized by dominant importance of power minimization and design reuse. The energy efficiency of systems-on-a-chip (SOC) could be much improved if one were to vary the supply voltage dynamically at run time. We develop the design methodology for the lowpower core-based real-time SOC based on dynamically variable voltage hardware. The key challenge is to develop effective scheduling techniques that treat voltage as a variable to be determined, in addition to the conventional task scheduling and allocation. Our synthesis technique also addresses the selection of the processor core and the determination of the instruction and data cache size and configuration so as to fully exploit dynamically variable voltage hardware, which results in significantly lower power consumption for a set of target applications than existing techniques. The highlight of the proposed approach is the nonpreemptive scheduling heuristic, which results in solutions very close to optimal ones for many test cases. The effectiveness of the approach is demonstrated on a variety of modern industrial strength multimedia and communication applications.