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Showing papers on "Efficient energy use published in 2001"


Proceedings ArticleDOI
23 Apr 2001
TL;DR: This paper proposes a formal classification of sensor networks, based on their mode of functioning, as proactive and reactive networks, and introduces a new energy efficient protocol, TEEN (Threshold sensitive Energy Efficient sensor Network protocol) for reactive networks.
Abstract: Wireless sensor networks are expected to find wide applicability and increasing deployment in the near future. In this paper, we propose a formal classification of sensor networks, based on their mode of functioning, as proactive and reactive networks. Reactive networks, as opposed to passive data collecting proactive networks, respond immediately to changes in the relevant parameters of interest. We also introduce a new energy efficient protocol, TEEN (Threshold sensitive Energy Efficient sensor Network protocol) for reactive networks. We evaluate the performance of our protocol for a simple temperature sensing application. In terms of energy efficiency, our protocol has been observed to outperform existing conventional sensor network protocols.

2,423 citations


Proceedings ArticleDOI
16 Jul 2001
TL;DR: A randomized algorithm where coordinators rotate with time is given, demonstrating how localized node decisions lead to a connected, capacity-preserving global topology.
Abstract: This paper presents Span, a power saving technique for multi-hop ad hoc wireless networks that reduces energy consumption without significantly diminishing the capacity or connectivity of the network. Span builds on the observation that when a region of a shared-channel wireless network bag a sufficient density of nodes, only a small number of them need be on at any time to forward traffic for active connections.Span is a distributed, randomized algorithm where nodes make local decisions on whether to sleep, or to join a forwarding backbone as a coordinator. Each node bases its decision on an estimate of how many of its neighbors will benefit from it being awake, and the amount of energy available to it. We give a randomized algorithm where coordinators rotate with time, demonstrating how localized node decisions lead to a connected, capacity-preserving global topology.Improvement in system lifetime due to Span increases as the ratio of idle-to-sleep energy consumption increases, and increases as the density of the network increases. For example, our simulations show that with a practical energy model, system lifetime of an 802.11 network in power saving mode with Span is a factor of two better than without. Span integrates nicely with 802.11—when run in conjunction with the 802.11 power saving mode, Span improves communication latency, capacity, and system lifetime.

1,854 citations


Proceedings ArticleDOI
16 Jul 2001
TL;DR: This work proposes an adaptive rate control mechanism aiming to support media access control in sensor networks and finds that such a scheme is most effective in achieving the authors' fairness goal while being energy efficient for both low and high duty cycle of network traffic.
Abstract: We study the problem of media access control in the novel regime of sensor networks, where unique application behavior and tight constraints in computation power, storage, energy resources, and radio technology have shaped this design space to be very different from that found in traditional mobile computing regime. Media access control in sensor networks must not only be energy efficient but should also allow fair bandwidth allocation to the infrastructure for all nodes in a multihop network. We propose an adaptive rate control mechanism aiming to support these two goals and find that such a scheme is most effective in achieving our fairness goal while being energy efficient for both low and high duty cycle of network traffic.

1,068 citations


Proceedings ArticleDOI
16 Jul 2001
TL;DR: This work proposes a physical layer driven approach to designing protocols and algorithms for wireless microsensor networks that have extremely long lifetimes and shows how to reduce energy consumption of non-ideal hardware through physical layer aware algorithms and protocols.
Abstract: The potential for collaborative, robust networks of microsensors has attracted a great deal of research attention. For the most part, this is due to the compelling applications that will be enabled once wireless microsensor networks are in place; location-sensing, environmental sensing, medical monitoring and similar applications are all gaining interest. However, wireless microsensor networks pose numerous design challenges. For applications requiring long-term, robust sensing, such as military reconnaissance, one important challenge is to design sensor networks that have long system lifetimes. This challenge is especially difficult due to the energy-constrained nature of the devices. In order to design networks that have extremely long lifetimes, we propose a physical layer driven approach to designing protocols and algorithms. We first present a hardware model for our wireless sensor node and then introduce the design of physical layer aware protocols, algorithms, and applications that minimize energy consumption of the system. Our approach prescribes methods that can be used at all levels of the hierarchy to take advantage of the underlying hardware. We also show how to reduce energy consumption of non-ideal hardware through physical layer aware algorithms and protocols.

1,059 citations


Journal ArticleDOI
TL;DR: A comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack of wireless networks is presented.
Abstract: Wireless networking has witnessed an explosion of interest from consumers in recent years for its applications in mobile and personal communications. As wireless networks become an integral component of the modern communication infrastructure, energy efficiency will be an important design consideration due to the limited battery life of mobile terminals. Power conservation techniques are commonly used in the hardware design of such systems. Since the network interface is a significant consumer of power, considerable research has been devoted to low-power design of the entire network protocol stack of wireless networks in an effort to enhance energy efficiency. This paper presents a comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack.

958 citations


Journal ArticleDOI
TL;DR: It is argued that power-aware methodology uses an embedded microoperating system to reduce node energy consumption by exploiting both sleep state and active power management.
Abstract: We propose an OS-directed power management technique to improve the energy efficiency of sensor nodes. Dynamic power management (DPM) is an effective tool in reducing system power consumption without significantly degrading performance. The basic idea is to shut down devices when not needed and wake them up when necessary. DPM, in general, is not a trivial problem. If the energy and performance overheads in sleep-state transition were negligible, then a simple greedy algorithm that makes the system enter the deepest sleep state when idling would be perfect. However, in reality, sleep-state transitioning has the overhead of storing processor state and turning off power. Waking up also takes a finite amount of time. Therefore, implementing the correct policy for sleep-state transitioning is critical for DPM success. It is argued that power-aware methodology uses an embedded microoperating system to reduce node energy consumption by exploiting both sleep state and active power management.

747 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present two important expansions of the single-service model in order to show the potential relevance of the rebound effect to ecological economics, and also provide a strong argument for the introduction of energy taxes.

687 citations


Journal ArticleDOI
TL;DR: The model can be used to simulate scenarios, which can add new information to the discussion of future, sustainable agricultural production and supplement the Intergovernmental Panel on Climate Change manual to quantify fossil energy use and subsequent carbon dioxide emissions from agriculture.

483 citations


Proceedings ArticleDOI
22 Apr 2001
TL;DR: A lazy online algorithm that varies transmission times according to backlog and is shown to be more energy efficient than a deterministic schedule that guarantees stability for the same range of arrival rates is devised.
Abstract: The paper considers the problem of minimizing the energy used to transmit packets over a wireless link via lazy schedules that judiciously vary packet transmission times. The problem is motivated by the following key observation: in many channel coding schemes, the energy required to transmit a packet can be significantly reduced by lowering the transmission power and transmitting the packet over a longer period of time. However, information is often time-critical or delay-sensitive and transmission times cannot be made arbitrarily long. We therefore consider packet transmission schedules that minimize energy subject to a deadline or a delay constraint. Specifically, we obtain an optimal offline schedule for a node operating under a deadline constraint. An inspection of the form of this schedule naturally leads us to an online schedule which is shown, through simulations, to be energy-efficient. Finally, we relax the deadline constraint and provide an exact probabilistic analysis of our offline scheduling algorithm. We then devise a lazy online algorithm that varies transmission times according to backlog and show that it is more energy efficient than a deterministic schedule that guarantees stability for the same range of arrival rates.

371 citations


Proceedings ArticleDOI
30 Sep 2001
TL;DR: This work proposes and evaluates a power control loop, similar to those commonly found in cellular CDMA networks, for ad-hoc wireless networks, and shows that it reduces energy consumption per transmitted byte and increases overall throughput by 15%.
Abstract: Mobile ad-hoc networking involves peer-to-peer communication in a network with a dynamically changing topology. Achieving energy efficient communication in such a network is more challenging than in cellular networks since there is no centralized arbiter such as a base station that can administer power management. We propose and evaluate a power control loop, similar to those commonly found in cellular CDMA networks, for ad-hoc wireless networks. We use a comprehensive simulation infrastructure consisting of group mobility, group communication and terrain blockage models. A major focus of research in ad-hoc wireless networking is to reduce energy consumption because the wireless devices are envisioned to have small batteries and be incapable of energy scavenging. We show that this power control loop reduces energy consumption per transmitted byte by 10-20%. Furthermore, we show that it increases overall throughput by 15%.

365 citations


Journal ArticleDOI
TL;DR: The Probe series of post-occupancy studies had reported individually on 16 buildings and compared their energy performance and carbon emissions (for technical performance and occupant satisfaction, see papers 2 and 4 in this issue).
Abstract: By early 1999, the Probe series of post-occupancy studies had reported individually on 16 buildings. This paper compares their energy performance and carbon emissions (for technical performance and occupant satisfaction, see papers 2 and 4 in this issue). All but one building (which paradoxically used the least energy of Probe's air-conditioned offices) claimed to be energy efficient, but achieved performance ranged from excellent to below average. Across the sample, there was a factor of six in carbon dioxide emissions per unit floor area, and even more per occupant. The air-conditioned buildings tended to use the most energy: they usually contained more equipment, were more intensively occupied, but also usually ran more liberally and wastefully – as did more complex systems generally. Often complication seemed to have been added before the fundamentals had been made efficient. Design objectives were also frustrated by poor airtightness, control problems, unintended consequences, a dearth of energy mana...

Journal ArticleDOI
TL;DR: It is demonstrated that the incorporation of energy considerations into multicast algorithms can, indeed, result in improved energy efficiency.
Abstract: In this paper we address the problem of multicasting in ad hoc wireless networks from the viewpoint of energy efficiency. We discuss the impact of hte wireless medium on the multicasting problem and the fundamental trade-offs that arise. We propose and evaluate several algorithms for defining multicast trees for session (or connection-oriented) traffic when transceiver resources are limited. The algorithms select the relay nodes and the corresponding transmission power levels, and achieve different degrees of scalability and performance. We demonstrate that the incorporation of energy considerations into multicast algorithms can, indeed, result in improved energy efficiency.

Journal ArticleDOI
TL;DR: A detailed electrochemical battery model and a simple stochastic model that captures the fundamental behavior of the battery are presented and results indicate that the proposed battery management techniques improve system performance no matter which parameters values are chosen to characterize the cells' behavior.
Abstract: A challenging aspect of mobile communications consists in exploring ways in which the available run time of terminals can be maximized. We present a detailed electrochemical battery model and a simple stochastic model that captures the fundamental behavior of the battery. The stochastic model is then matched to the electrochemical model and used to investigate battery management techniques that may improve the energy efficiency of radio communication devices. We consider an array of electrochemical cells. Through simple scheduling algorithms, the discharge from each cell is properly shaped to optimize the charge recovery mechanism, without introducing any additional delay in supplying the required power. Then, a battery management scheme, which exploits knowledge of the cells' state of charge, is implemented to achieve a further improvement in the battery performance. In this case, the discharge demand may be delayed. Results indicate that the proposed battery management techniques improve system performance no matter which parameters values are chosen to characterize the cells' behavior.

Journal ArticleDOI
TL;DR: In this article, the authors present scenarios for a Clean Energy Future, which assess how energy-efficient and clean energy technologies can address key energy and environmental challenges facing the US, and conclude that policies exist that can significantly reduce oil dependence, air pollution, carbon emissions, and inefficiencies in energy production and end-use systems.

Book
22 Jan 2001
TL;DR: Theories of knowledge and practice are discussed in this article, where the authors propose a framework for energy-aware research in buildings and present a case study of an office building with solar energy.
Abstract: Part I. Introduction 1. Environmental sociology and energy efficiency 2. Engaging with energy and buildings 3. Science, knowledge and practice Part II. Building Research Environments 4. Defining energy research 5. Comparing research environments: i. Close communities ii. Co-ordinated contractors iii. Contracting knowledge iv. Networking expertise 6. Positioning energy efficiency 7. Changing research environments Part III. Energy Knowledges 8. Constructing conventions 9. Abstracting knowledge: capturing solar energy 10. Building knowledge: demonstrations and case studies 11. Replicating knowledges: i. Design Tools ii. Case studies 12. Converging conventions Part IV. Theories of Knowledge and Practice 13. Theories of technical change: i. Barriers to energy efficiency ii. Leaping the barriers 14. Changing course 15. Following energy efficiency Part V. The Politics of Insulation 16. Conventional explanations 17. Culture of energy conservation: i. Denmark ii. Sweden iii. France iv. The European insulation industry 18. Filling the gap: i. First fillings 1959-1974 ii. Curbing the cowboys 1975-1981 iii. Foam fears 1981-1983 iv. Fibre Wars 1984-1992 19. Government, industry and consumer interaction Part VI. Organising Design: Housing and Energy Efficiency 20. Best practice and decision-making 21. Contexts of action: i. Shifting associations ii. Local pressures iii. Private dilemmas 22. Context, change and choice Part VII. Developing Interests: Office Buildings and Barriers 23. Property relationships: i. Investing and exchanging ii. Nesting and using iii. Globalising design 24. Fluctuating priorities Part VIII. Conclusions 25. Understanding energy efficiency 26. Technical convergence, cultural diversity 27. Reconstructing research

Journal ArticleDOI
01 Mar 2001
TL;DR: In this article, a sectoral approach was employed, with the supply side examined in terms of themain energy sources, while final demand was separated into four energy end-use groups: the domestic, service, industrial and transport sectors.
Abstract: The exergy method has been used to analyse changes in the structure of the UK energy system over a period of more than 30 years from 1965. A sectoral approach was employed, with the supply side examined in terms of themain energy sources, while final demand was separated into four energy end-use groups: the domestic, service, industrial and transport sectors. Estimates of sector-weighted or ‘lumped’ parameters, such as exergy efficiencies, were obtained from the particular characteristics of each sector. These were employed to determine the exergetic ‘improvement potential’ for critical elements of the energy system. Electricity generation together with final energy demand in the domestic sector and in transport are shown to account for nearly 80 per cent of the Second Law improvement potential. This poor thermodynamic performance is principally due to exergy losses in combustion and heat transfer processes associated with power generation, space heating and main transport modes. The results of th...

Proceedings ArticleDOI
Flavius Gruian1
06 Aug 2001
TL;DR: In this article, the authors propose an approach to reduce energy consumption of hard real-time tasks with fixed priorities assigned in a rate-monotonic or deadline-constrained manner.
Abstract: Addresses scheduling for reduced energy of hard real-time tasks with fixed priorities assigned in a rate monotonic or deadline monotonic manner. The approach described can be exclusively implemented in the RTOS. It targets energy consumption reduction by using both on-line and off-line decisions, taken both at task level and at task-set level. We consider sets of independent tasks running on processors with dynamic voltage supplies (DVS). Taking into account the real behavior of a realtime system, which is often better than the worst case, our methods employ stochastic data to derive energy efficient schedules. The experimental results show that our approach achieves more important energy reductions than other policies from the same class.

Proceedings ArticleDOI
06 Aug 2001
TL;DR: Several energy minimization techniques derived from the unique properties of a practical short range asymmetric microsensor system are presented, including energy efficient modulation schemes, appropriate multiple access protocols, and a fast turn-on transmitter architecture.
Abstract: Wireless microsensor systems are used in a variety of civil and military applications. Such microsensors are required to operate for years from a small energy source. To minimize the energy dissipation of the sensor node, RF front-end circuitry must be designed based on system level optimization of the entire network. This paper presents several energy minimization techniques derived from the unique properties of a practical short range asymmetric microsensor system. These include energy efficient modulation schemes, appropriate multiple access protocols, and a fast turn-on transmitter architecture.


Proceedings ArticleDOI
22 Jun 2001
TL;DR: This paper presents a technique to determine voltage settings for a variable voltage processor that utilizes a fixed priority assignment to schedule jobs and produces the minimum constant voltage needed to feasibly schedule the entire job set.
Abstract: Energy consumption has become an increasingly important consideration in designing many real-time embedded systems. Variable voltage processors, if used properly, can dramatically reduce such system energy consumption. In this paper, we present a technique to determine voltage settings for a variable voltage processor that utilizes a fixed priority assignment to schedule jobs. Our approach also produces the minimum constant voltage needed to feasibly schedule the entire job set. Our algorithms lead to significant energy saving compared with previously presented approaches.

01 Jan 2001
Abstract: Author(s): Cowan, John | Abstract: The International Performance Measurement and Verification Protocol (MVP) provides an overview of current best practice techniques available for verifying results of energy efficiency, water efficiency, and renewable energy projects. It may also be used by facility operators to assess and improve facility performance. Energy conservation measures (ECMs) covered herein include fuel saving measures, water efficiency measures, load shifting and energy reductions through installation or retrofit of equipment, and/or modification of operating procedures. The IPMVP is not intended to prescribe contractual terms between buyers and sellers of efficiency services, although it provides guidance on some of these issues. Once other contractual issues are decided, this document can help in the selection of the measurement a verification (MaV) approach that best matches: i) project costs and savings magnitude, ii) technology-specific requirements, and iii) risk allocation between buyer and seller, i.e., which party is responsible for installed equipment performance and which party is responsible for achieving long term energy savings. Two dimensions of ECM performance verification are addressed in this document: Savings determination technique using available data of suitable quality and disclosure of data and analysis enabling one party to perform saving determinations while another verifies it.

Proceedings ArticleDOI
30 Sep 2001
TL;DR: This work considers energy consumption reduction, under guaranteed quality of service, as a main objective in system design, in systems on chips that can be designed and produced in five to ten years from today.
Abstract: We consider systems on chips (SoCs) that will be designed and produced in five to ten years from today, with gate lengths in the range 50-100nm. We address the distinguishing features of a design methodology that aims at achieving reliable designs under the limitations of the interconnect technology. Specifically, we consider energy consumption reduction, under guaranteed quality of service (QoS), as a main objective in system design.

Proceedings ArticleDOI
28 Oct 2001
TL;DR: This paper focuses on an energy efficient TDMA protocol, power aware clustered TDMA (PACT), that adapts the duly cycle to the user traffic, and shows significant improvement in energy saving and network lifetime.
Abstract: In this paper we present a novel TDMA scheme for a large population of sensors interconnected by a wireless multihop network. Applications of this wireless sensor network include battlefield surveillance, space exploration and condition based monitoring. Key characteristics of this system are the large number of sensor nodes and the need to rely on battery operation for a long period of time. Since communication is a major consumer of energy, low power communication protocols play a critical role in wireless sensor networks and have significant impact on the overall energy dissipation of these networked systems. This paper focuses on an energy efficient TDMA protocol, power aware clustered TDMA (PACT), that adapts the duly cycle to the user traffic. In other words, the radio is powered off if the network is inactive. Moreover, we apply passive clustering to take advantage of the redundant dense topology and prolong the lifetime of the entire network even further. At a given time, only a subset of network nodes (i.e., cluster heads and gateways) participates in the communication. The role of cluster heads and gateways is rotated according to their energy levels. The clustering requires no explicit control messages and therefore incurs negligible energy overhead. Using the proposed protocol, simulation and analytical results show significant improvement in energy saving and network lifetime.

Patent
16 Aug 2001
TL;DR: In this paper, the authors present an approach that enables a facility (home, business or industrial site) to optimize the consumption of energy in that facility by using a power accounting server to predict when the rates for using the energy will be the least expensive for a particular task or to operate a particular appliance.
Abstract: The present invention enables a facility (home, business or industrial site) to optimize the consumption of energy in that facility. In this invention, the power companies that supply energy provide information to its client facilities on the cost and availability of energy from that company on a real-time basis. Each client facility would have a power accounting server. These servers store this and process this information to predict when the rates for using the energy will be the least expensive for a particular task or to operate a particular appliance. A homeowner (client facility) for example can program appliances such as a dishwasher or laundry machine to turn on when the cost of energy is below a particular threshold price. The present invention has the capability to receive characteristics about a particular appliance, generate a list of energy consumption options for that particular product at a particular time period and select and implement the most efficient energy supply option. This invention can also enable a client facility that generates energy to efficiently use the generated energy and sell any excess energy to another end user or to other energy consumers.

Patent
10 Sep 2001
TL;DR: In this paper, the authors describe a system where the existing proliferation of standard electrical junction boxes in a typical home or building implement a form of biofeedback for home energy, increasing user awareness and enabling more effective and efficient energy usage.
Abstract: A system is described where the existing proliferation of standard electrical junction boxes in a typical home or building implement a form of “Bio-Feedback for Home Energy”, increasing user awareness and enabling more effective and efficient energy usage. Energy-related information is gathered by way of EMAC (Energy Monitoring And Control) points typically installed at standard electrical junction boxes used for power plug receptacles and wall switches. In addition to being visually displayed at the point of energy use or measurement, energy-related information—electrical and thermal—is typically communicated through a powerline or wireless data link to a centrally located intelligent device where it is monitored, analyzed, profiled, viewed, and also used for energy-related control functions. Energy consumption can be alternately displayed in terms of cost-per-time. Energy monitoring may be also added at the electrical breaker box to supplement distributed EMAC points.

Proceedings ArticleDOI
01 Dec 2001
TL;DR: An integrated algorithm to control both architectural adaptation and DVS targeted to multimedia applications is developed and evaluated and it is found that while less aggressive architectures reduce energy for fixed frequency hardware, with DVS, more aggressive architectures are often more energy efficient.
Abstract: General-purpose processors are expected to be increasingly employed for multimedia workloads on systems where reducing energy consumption is an important goal. Researchers have proposed the use of two forms of hardware adaptation - architectural adaptation and dynamic voltage (and frequency) scaling or DVS - to reduce energy. This paper develops and evaluates an integrated algorithm to control both architectural adaptation and DVS targeted to multimedia applications. It also examines the interaction between the two forms of adaptation, identifying when each will perform better in isolation and when the addition of architectural adaptation will benefit DVS. Our adaptation control algorithm is effective in saving energy and exploits most of the available potential. For the applications and systems studied, DVS is consistently better than architectural adaptation in isolation. The addition of architectural adaptation to DVS benefits some applications, but not all. Finally, in a seemingly counter-intuitive result, we find that while less aggressive architectures reduce energy for fixed frequency hardware, with DVS, more aggressive architectures are often more energy efficient.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the concept of low energy building, examined how urban density might affect building energy design in high density cities, and discussed the strategies for low-energy building design in densely populated areas.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated the feasibility and viability of widening the use of WACS by the provision of centralized, district-wide water supply systems, which include seawater supply systems for once-through condenser cooling or for making up of water losses at cooling towers, and district cooling systems.

Journal ArticleDOI
TL;DR: In this paper, the authors used QUICKcontrol, a software tool, to perform the complex and fully integrated building, HVAC and control simulations, which was used to determine the comfort enhancement and energy saving potential with new control strategies for the Human Science Building at the University of Pretoria.

Journal ArticleDOI
Max Åhman1
01 Nov 2001-Energy
TL;DR: In this paper, the authors considered the technical potential concerning the energy efficiency attainable for vehicles with alternative powertrains within 10-20 years and compared the potential improvement in conventional vehicles with internal combustion engines (ICEVs).