Electrical & Computer Engineering Research Works
Permanent URI for this collectionhttp://hdl.handle.net/1903/1658
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Item Power Minimization under QoS Constraints(IEEE, 2002-04) Wong, Jennifer L.; Qu, Gang; Potkonjak, MiodragQoS has been often addressed in multimedia, video, and networking research communities, but rarely in the design community. Our goal is to introduce the first system design technique for comprehensive quality-of-service (QoS) low power synthesis. Specifically, we study how to efficiently exploit the trade-o between the system cost and energy consumption in real-time systems that address packet-based multimedia transmission and processing. We first introduce a system of techniques that minimizes energy consumption of stream-oriented applications under two main QoS metrics: latency and synchronization. Speci cally, we study how multiple voltages can be used to simultaneously satisfy hardware requirements and minimize power consumption, while preserving the requested level of QoS, in this case satisfying latency and synchronization requirements. We have developed a provably optimal polynomial time o -line algorithm for multiple volt- age scheduling of single and multiple processes. The o -line algorithm provides lower bounds on achievable power minimization and can be used as a starting point for the development and evaluation of an on-line approach. The effectiveness of the algorithm is demonstrated on a number of multimedia benchmarks.Item Exploring the Probabilistic Design Space of Multimedia Systems(IEEE, 2003-06) Hua, Shaoxiong; Qu, Gang; Bhattacharyya, Shuvra S.In this paper, we propose the novel concept of probabilistic design for multimedia systems and a methodology to quickly explore such design space at an early design stage. The probabilistic design is motivated by the challenge of how to design, but not over-design, multimedia embedded systems while systematically incorporating such application’s performance requirements, uncertainties in execution time, and tolerance for reasonable execution failures. Our goal is to bridge the gap between real-time analysis and embedded software implementation for rapid and economic (multimedia) system prototyping. Our method takes advantage of multimedia system’s unique features mentioned above to relax the rigid hardware requirements for software implementation and eventually avoid over-designing the system.Item INTRODUCING THE CONCEPT OF DESIGN REUSE INTO UNDERGRADUATE DIGITAL DESIGN CURRICULUM(IEEE, 2003-06) Qu, GangIntellectual property (IP) reuse based system design is becoming an industry standard recently. However, current educational system is not effective in the training of engineers who design by reuse and design for reuse. In this paper, we report our experience at the University of Maryland at College Park (UMCP) in introducing the concept of design reuse into the introductory digital logic design course. We present a practical curriculum innovation plan, which does not increase the teaching load or sacrifices the current curriculum significantly, to implement this idea. Our teaching experience show that students learn the basics of design reuse and enjoy doing IP-based design.Item Design Space Exploration for Energy-Efficient Secure Sensor Network(IEEE, 2002-07) Yuan, Lin; Qu, GangWe consider two of the most important design issues for distributed sensor networks in the battlefield: security for communication in such hostile terrain; and energy efficiency because of battery’s limited capacity and the impracticality of recharging. Communication security is normally provided by encryption, i.e., data are encrypted before transmission and will be decrypted first on reception. We exploit the secure sensor network design space for energy efficiency by investigating different microprocessors coupled with various public key algorithms. We propose a power control mechanism for sensors to operate at an energy-efficient fashion using the newly developed dynamical voltage scaling (DVS) technique. In particular, we consider multiple voltage processors and insert additional information into the communication channel to guide the selection of proper voltages for data decryption/encryption and processing in order to reduce the total computational energy consumption. We experiment several encryption standards on a broad range of embedded processors and simulate the behavior of the sensor network to show that the sensor’s lifetime can be extended substantially.Item System Synthesis of Synchronous Multimedia Applications(IEEE, 1999-11) Qu, Gang; Mesarina, Malena; Potkonjak, MiodragModern system design is being increasingly driven by applications such as multimedia and wireless sensing and communications, which all have intrinsic quality of service (QoS) requirements, such as throughput, error-rate, and resolution. One of the most crucial QoS guarantees that the system has to provide is the timing constraints among the interacting media (synchronization) and within each media (latency). We have developed the first framework for systems design with timing QoS guarantees, latency and synchronization. In particular, we address how to design system-on-chip with minimal silicon area to meet timing constraints. We propose the two-phase design methodology. In the first phase, we select an architecture which facilitates the needs of synchronous low latency applications well. In the second phase, for a given processor configuration, we use our new scheduler in such a way that storage requirements are minimized. We have develop scheduling algorithms that solve the problem optimally for a-priori specified applications. The algorithms have been implemented and their effectiveness demonstrated on a set of simulated MPEG streams from popular movies.Item What is the Limit of Energy Saving by Dynamic Voltage Scaling?(IEEE, 2001-11) Qu, GangDynamic voltage scaling (DVS) is a technique that varies the supply voltage and clock frequency based on the computation load to provide desired performance with the minimal amount of energy consumption. It has been demonstrated as one of the most effective low power system design techniques, in particular for real time systems. Previously, there are works on both ends of the DVS systems: the ideal variable voltage system which can change its voltage with no physical constraints, and the multiple voltage system which has a number of discrete voltages available simultaneously. In this paper, we study the DVS systems between these two extreme cases. We consider systems that can vary the operating voltage dynamically under various real-life physical constraints. Based on the system’s different behavior during voltage transition, we define the feasible DVS system and the practical DVS system. We build mathematical model to analyze the potential of DVS on energy saving for these different systems. Finally, we simulate the behavior of a secure wireless communication networks with DVS systems. The results show that DVS results in energy reduction from 36% to 79%, and the real life DVS systems can be very close to the ideal system in energy saving.Item Achieving Utility Arbitrarily Close to the Optimal with Limited Energy(IEEE, 2000-07) Qu, Gang; Potkonjak, MiodragEnergy is one of the limited resources for modern systems, especially the battery-operated devices and personal digi- tal assistants. The backlog in new technologies for more powerful battery is changing the traditional system design philosophies. For example, due to the limitation on battery life, it is more realistic to design for the optimal benefit from limited resource rather than design to meet all the applica- tions' requirement. We consider the following problem: a system achieves a certain amount of utility from a set of applications by providing them certain levels of quality of service (QoS). We want to allocate the limited system re- sources to get the maximal system utility. We formulate this utility maximization problem, which is NP-hard in gen- eral, and propose heuristic algorithms that are capable of finding solutions provably arbitrarily close to the optimal. We have also derived explicit formulae to guide the alloca- tion of resources to actually achieve such solutions. Simu- lation shows that our approach can use 99.9% of the given resource to achieve 25.6% and 32.17% more system utilities over two other heuristics, while providing QoS guarantees to the application program.Item Power Minimization using System-Level Partitioning of Applications with Quality of Service Requirements(1999-11) Qu, Gang; Potkonjak, MiodragDesign systems to provide various quality of service (QoS) guarantees has received a lot of attentions due to the increasing popularity of real-time multimedia and wireless communication applications. Meanwhile, low power consumption is always one of the goals for system design, especially for battery-operated systems. With the design trend of integrating multiple processor cores and memory on a single chip, we address the problem of how to partition a set of applications among processors, such that all the individual QoS requirements are met and the total energy consumption is minimized. We exploit the advantages provided by the variable voltage design methodology to choose the voltage for each application on the same processor optimally for this purpose. We also discuss how to partition applications among the processors to achieve the same goal. We formulate the problem on an abstract QoS model and present how to allocate resources (e.g., CPU time) and determine the voltage profile for every single processor. Experiments on media benchmarks have also been studied.Item Energy Minimization of System Pipelines Using Multiple Voltages(IEEE, 1999-05) Qu, Gang; Kirovski, Darko; Potkonjak, Miodrag; Srivastava, Mani B.Modem computer and communication system design has to consider the timing constraints imposed by communication and system pipelines, and minimize the energy consumption. We adopt the recent proposed model for communication pipeline latency[23] and address the problem of how to minimize the power consumption in system-level pipelines under the latency constraints by selecting supply voltage for each pipeline stage using the variable voltage core-based system design methodology[l 11. We define the problem, solve it optimally under realistic assumptions and develop algorithms for power minimization of system pipeline designs based on our theoretical results. We apply this new approach on the 4- stage Myrinet GAM pipeline, with the appropriate voltage profiles, we achieve 93.4%, 91.3% and 26.9% power reduction on three pipeline stages over the traditional design.Item Energy Minimization with Guaranteed Quality of Service(IEEE, 2000-07) Qu, Gang; Potkonjak, Potkonjak; Copyright © 2000 IEEE. Reprinted from ACM/IEEE International Symposium on Low Power Electronics and Dsign. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Maryland's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.Quality of service (QoS) is one of the key features for new Internet-based multimedia and other applications. Mean- while, energy remains as a big concern for systems that per- form such applications. We address the issue of combining system design concerns and QoS requirements to design systems that can deliver QoS guarantees. In this paper, we discuss how to satisfy QoS requirements and minimize the system's energy consumption. Specifically, we consider the following problem: Given a set of applications each specifying its required amount of computation and service time, how we allocate CPU time and determine the voltage profile on a variable voltage system, such that all the applications' requirements are satisfied and the system's total energy con- sumption is minimized. We optimally solve several basic cases and propose a dynamic programming procedure for the general case. Simulation shows that the new approach saves 38.75% energy over the system shut-down technique.