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61
Managing Distributed UPS Energy for Effective Power Capping in Data Centers
"... Power over-subscription can reduce costs for modern data centers. However, designing the power infrastructure for a lower operating power point than the aggregated peak power of all servers requires dynamic techniques to avoid high peak power costs and, even worse, tripping circuit breakers. This wo ..."
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Cited by 22 (4 self)
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Power over-subscription can reduce costs for modern data centers. However, designing the power infrastructure for a lower operating power point than the aggregated peak power of all servers requires dynamic techniques to avoid high peak power costs and, even worse, tripping circuit breakers. This work presents an architecture for distributed per-server UPSs that stores energy during low activity periods and uses this energy during power spikes. This work leverages the distributed nature of the UPS batteries and develops policies that prolong the duration of their usage. The specific approach shaves 19.4 % of the peak power for modern servers, at no cost in performance, allowing the installation of 24 % more servers within the same power budget. More servers amortize infrastructure costs better and, hence, reduce total cost of ownership per server by 6.3%. 1
Detailed models for sensor network simulations and their impact on network performance
- Proc. of ACM International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM
, 2004
"... Recent trends in sensor network simulation can be divided between less flexible but accurate emulation based approach and more generic but less detailed network simulator models. We offer an approach with the flexibility of network simulators and provides the accuracy comparable to emulation based a ..."
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Cited by 16 (3 self)
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Recent trends in sensor network simulation can be divided between less flexible but accurate emulation based approach and more generic but less detailed network simulator models. We offer an approach with the flexibility of network simulators and provides the accuracy comparable to emulation based approaches. We describe the design and architecture of sensor network simulator which provides a rich suite of following models: sensing stack to model wave and diffusion based sensor channels, an accurate battery model, processor power consumption model, energy consumption model and sensor network based traffic model. We also present our study on the effects of detailed modeling on the performance of higher layer protocols. We describe the impact of using accurate models for battery, processor power consumption and traffic models on the network layer statistics as network lifetime and availability, throughput and routing overhead. Our results show there is high sensitivity of model accuracy on network and application level statistics. In extreme cases we have noticed an inversion of results with our accurate models as compared with previous generation of abstract models.
System-wide energy minimization for real-time tasks: Lower bound and approximation
- In Proceedings of ICCAD
, 2006
"... We present a dynamic voltage scaling (DVS) technique that minimizes system-wide energy consumption for both periodic and sporadic tasks. It is known that a system consists of processors and a number of other components. Energy-aware processors can be run in different speed levels; components like me ..."
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Cited by 12 (3 self)
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We present a dynamic voltage scaling (DVS) technique that minimizes system-wide energy consumption for both periodic and sporadic tasks. It is known that a system consists of processors and a number of other components. Energy-aware processors can be run in different speed levels; components like memory and I/O subsystems and network interface cards can be in a standby state when they are active but idle. Processor energy optimization solutions are not necessarily efficient from the perspective of systems. Current system-wide energy optimization studies are often limited to periodic tasks with heuristics in getting approximated solutions. In this paper, we develop an exact dynamic programming algorithm for periodic tasks on processors with practical discrete speed levels. The algorithm determines the lower bound of energy expenditure in pseudo-polynomial time. An approximation algorithm is proposed to provide performance guarantee with a given bound in polynomial running time. Because of their time efficiency, both the optimization and approximation algorithms can be adapted for online scheduling of sporadic tasks with irregular task releases. We prove that system-wide energy optimization for sporadic tasks is NP-hard in the strong sense. We develop (pseudo-) polynomial-time solutions by exploiting its inherent properties.
A novel design of adaptive reconfigurable multiple battery for power-aware embedded networked sensing systems
- In GLOBECOM’12
, 2012
"... Abstract — Battery-powered embedded networked sensing sys-tems become more and more pervasive with the fast-paced deployment of various remote sensing applications. How to prolong the battery operating time is one of the most challenging areas in the design and development of these sensing systems d ..."
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Cited by 11 (1 self)
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Abstract — Battery-powered embedded networked sensing sys-tems become more and more pervasive with the fast-paced deployment of various remote sensing applications. How to prolong the battery operating time is one of the most challenging areas in the design and development of these sensing systems due to the fact that the battery operation is much more dynamic and complex than considered, which is derived from its application and its internal structure (multiple hardwired series/parallel cells) to produce a specific voltage and capacity. Current research on prolonging the battery operating time is mainly focusing on the low-power hardware and energy-efficient network protocol designs, and simply treats the battery as a passive two-terminal energy source. In this paper, we will propose a novel adap-tive, proactive, and reconfigurable multicell battery design for supporting power-aware hardware and energy-efficient network protocols for embedded networked systems, which provides a whole new perspective to look at the energy problems of battery-powered embedded networked sensing systems. A theoretical modeling of the proposed design is provided, and simulation results show that the proposed design can significantly enhance the energy performance, especially for low voltage and low discharge current scenarios. I.
Battery optimization vs energy optimization: which to choose and when
- Proc. of IEEE/ACM Intl. Conf. on Computer-Aided Design (ICCAD
, 2005
"... Abstract — Batteries are non-ideal energy sources – minimizing the energy consumption of a battery-powered system is not equivalent to maximizing its battery life. We propose an alternative interpretation of a previously proposed battery model, which indicates that the deviation from ideal behavior ..."
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Cited by 11 (0 self)
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Abstract — Batteries are non-ideal energy sources – minimizing the energy consumption of a battery-powered system is not equivalent to maximizing its battery life. We propose an alternative interpretation of a previously proposed battery model, which indicates that the deviation from ideal behavior is due to the buildup of “unavailable charge” during the discharge process. Previously, battery-aware task scheduling algorithms and power management policies have been developed, which try to reduce the unavailable charge at the end of a given workload. However, they do not account for the occurrence of rest periods (user enforced, naturally occurring, or due to finite load horizon), which are present in a variety of workloads. We first obtain an analytical bound on the recovery time of a battery as a function of the extent of recovery. Then, we shown that the effect of the rest periods is to reduce the improvement of battery-charge optimizing techniques over traditional energy-optimizing techniques. Under certain conditions, the policy that only minimizes energy consumption can actually achieve a longer battery lifetime than a battery-aware policy. A formal criterion based on the recovery time is proposed to choose between a candidate battery-aware policy and a candidate energy-aware policy. We also model the battery discharge process as a Linear Time Invariant system and obtain the frequency response of a battery. This is then used to study the effect of task granularity on the improvement achieved by battery-aware task scheduling. It was observed that the response time of typical batteries are of the order of seconds to several minutes. This, along with the charge recovery effect, was seen to cause battery-aware task scheduling methods to become ineffective for both very fine-grained (less than 10 ms) and very coarse-grained (greater than 30 min) task granularities. I.
S.: Performance Optimal Processor Throttling Under Thermal Constraints
- In: CASES ’07: Proceedings of the 2007 International Conference on Compilers, Architecture, and Synthesis for Embedded Systems
, 2007
"... We derive analytically, the performance optimal throttling curve for a processor under thermal constraints for a given task sequence. We found that keeping the chip temperature constant requires an exponential speed curve. Earlier works that propose constant throttling only keep the package/case tem ..."
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Cited by 10 (1 self)
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We derive analytically, the performance optimal throttling curve for a processor under thermal constraints for a given task sequence. We found that keeping the chip temperature constant requires an exponential speed curve. Earlier works that propose constant throttling only keep the package/case temperature constant, and are hence suboptimal. We develop high-level thermal and power models that are simple enough for analysis, yet account for important effects like the power-density variation across a chip (hotspots), leakage dependence on temperature (LDT), and differing thermal characteristics of the silicon die and the thermal solution. We use a piecewiselinear approximation for the exponential leakage dependence on temperature, and devise a method to remove the circular dependency between leakage power and temperature. To solve the multitask speed control problem, we first solve analytically, the single task problem with a constraint on the final package temperature using optimal control theory. We then find the optimum final package temperature of each task by dynamic programming. We compared the total execution time of several randomly generated task sequences using the optimal control policy against a constant speed throttling policy, and found significantly smaller total execution times. We compared the thermal profiles predicted by the proposed high-level thermal model to that of the Hotspot thermal model, and found them to be in good agreement.
Battery Power Efficiency of PPM and FSK in Wireless Sensor Networks
"... Abstract — As sensor nodes are typically powered by nonrenewable batteries, energy efficiency is a critical factor in wireless sensor networks (WSNs). Orthogonal modulations appropriate for the energy-limited WSN setup have been investigated under the assumption that batteries are linear and ideal, ..."
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Cited by 9 (0 self)
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Abstract — As sensor nodes are typically powered by nonrenewable batteries, energy efficiency is a critical factor in wireless sensor networks (WSNs). Orthogonal modulations appropriate for the energy-limited WSN setup have been investigated under the assumption that batteries are linear and ideal, but their effectiveness is not guaranteed when more realistic nonlinear battery models are considered. In this paper, based on a general model that integrates typical WSN transmission and reception modules with realistic battery models, we derive two battery power-conserving schemes for two M-ary orthogonal modulations, namely pulse position modulation (PPM) and frequency shift keying (FSK), both tailored for WSNs. Then we analyze and compare the battery power efficiency of PPM and FSK over various wireless channel models. Our results reveal that FSK is more power-efficient than PPM in sparse WSNs, while PPM may outperform FSK in dense WSNs. We also show that in sparse WSNs, the power advantage of FSK over PPM is no more than 3dB; whereas in very dense WSNs, the power advantage of PPM over FSK can be much more significant as the constellation size M increases. Index Terms — Wireless sensor networks (WSN), pulse position modulation (PPM), frequency shift keying (FSK), battery power efficiency, fading I.
An Efficient Dynamic Task Scheduling Algorithm for Battery Powered
- DVS Systems” In: Asia and South Pacific Design Automation Conference (ASP-DAC
, 2005
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Hypoenergy: Hybrid supercapacitorbattery power-supply optimization for energy efficiency
- in DATE
, 2011
"... Abstract—This paper presents HypoEnergy, a framework for extending the hybrid battery-supercapacitor power supply life-time. HypoEnergy combines high energy density and reliable workload supportability of an electrochemical battery with high power density and high number of recharge cycles of superc ..."
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Cited by 8 (2 self)
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Abstract—This paper presents HypoEnergy, a framework for extending the hybrid battery-supercapacitor power supply life-time. HypoEnergy combines high energy density and reliable workload supportability of an electrochemical battery with high power density and high number of recharge cycles of supercapacitors. The lifetime optimizations consider nonlinear battery characteristics and supercapacitors ’ charging overhead. HypoEnergy-KI studies the hybrid supply lifetime optimization for a preemptively known workload and for one ideal superca-pacitor. We show a mapping of HypoEnergy-KI to the multiple-choice knapsack problem and use dynamic programming to address the problem. HypoEnergy-KN considers the optimization for the known workload but in the case of having a nonideal supercapacitor bank that leaks energy. Evaluations on iPhone load measurements demonstrate the efficiency and applicability of the HypoEnergy framework in extending the system’s lifetime. I.
A Survey of Software Based Energy Saving Methodologies for Handheld Wireless Communication Devices
"... Abstract — Advances in computing hardware, communications technologies, and novel multimedia applications are spurring the development of smart phones and personal digital assistants. There is world-wide accessibility to 2G, 3G, and Wi-Fi networks. Some examples of well-known wireless handheld devic ..."
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Cited by 5 (0 self)
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Abstract — Advances in computing hardware, communications technologies, and novel multimedia applications are spurring the development of smart phones and personal digital assistants. There is world-wide accessibility to 2G, 3G, and Wi-Fi networks. Some examples of well-known wireless handheld devices are BlackBerry, iPhone, iPad, iPod, and Kindle. On the one hand, small size and light weight are their attractive features for high mobility and accessibility. On the other hand, the same features impose significant constraints on their processing, memory, and energy storage capabilities, thereby limiting the device’s general functionalities and availabilty. User expectations in terms of performance from handheld devices are ever increasing. In addition to performance expectations, the requirement of portability imposes severe constraints on size and weight of a handheld system. Consequently, batteries too are small and light, and, therefore, the system energy budget is severely limited. The amount of energy in a fully charged battery is one of the most important resources of a handheld system, and battery lifetime is one of the most important characteristics. Unfortunately, improvements in energy density of batteries have not kept pace with the advancements in microelectronics technology. Therefore, reserachers have proposed novel architectures, strategies, methodologies, and techniques to make handheld devices energy efficient. In this paper, we study the results published in about 200 reserach papers to have a comprehensive understanding of the various approaches to make handheld devices energy efficient. We present our study in the form of 12 cohesive sections that include the following topics: smart batteries, energy-efficient graphical user interface design, the concept of a sleep mode to save energy, power efficient communication, proxy assisted energy saving, source-level power control, transport control protocol based energy saving, upperlevel power management, virtual memory on the network, programming and compilation techniques, integrated power management, and energy estimation models. I.
