Energy Harvesting Sensor Nodes: Survey and Implications
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paper_title: Energy-efficient communication protocol for wireless microsensor networks

paper_content:

Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.
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paper_title: Directed diffusion: a scalable and robust communication paradigm for sensor networks

paper_content:

Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.
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paper_title: The case for multi--tier camera sensor networks

paper_content:

In this position paper, we examine recent technology trends that have resulted in a broad spectrum of camera sensors, wireless radio technologies, and embedded sensor platforms with varying capabilities. We argue that future sensor applications will be hierarchical with multiple tiers, where each tier employs sensors with different characteristics. We argue that multi-tier networks are not only scalable, they offer a number of advantages over simpler, single-tier unimodal networks: lower cost, better coverage, higher functionality, and better reliability. However, the design of such mixed networks raises a number of new challenges that are not adequately addressed by current research. We discuss several of these challenges and illustrate how they can be addressed in the context of SensEye, a multi-tier video surveillance application that we are designing in our research group.
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paper_title: On k-coverage in a mostly sleeping sensor network

paper_content:

Sensor networks are often desired to last many times longer than the active lifetime of individual sensors. This is usually achieved by putting sensors to sleep for most of their lifetime. On the other hand, event monitoring applications require guaranteed k-coverage of the protected region at all times. As a result, determining the appropriate number of sensors to deploy that achieves both goals simultaneously becomes a challenging problem. In this paper, we consider three kinds of deployments for a sensor network on a unit square--a √n × √n grid, random uniform (for all n points), and Poisson (with density n). In all three deployments, each sensor is active with probability p, independently from the others. Then, we claim that the critical value of the function npπ r2/ log(np) is 1 for the event of k-coverage of every point. We also provide an upper bound on the window of this phase transition. Although the conditions for the three deployments are similar, we obtain sharper bounds for the random deployments than the grid deployment, which occurs due to the boundary condition. In this paper, we also provide corrections to previously published results. Finally, we use simulation to show the usefulness of our analysis in real deployment scenarios.
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paper_title: Wireless sensor networks for habitat monitoring

paper_content:

We provide an in-depth study of applying wireless sensor networks to real-world habitat monitoring. A set of system design requirements are developed that cover the hardware design of the nodes, the design of the sensor network, and the capabilities for remote data access and management. A system architecture is proposed to address these requirements for habitat monitoring in general, and an instance of the architecture for monitoring seabird nesting environment and behavior is presented. The currently deployed network consists of 32 nodes on a small island off the coast of Maine streaming useful live data onto the web. The application-driven design exercise serves to identify important areas of further work in data sampling, communications, network retasking, and health monitoring.
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paper_title: Integrated coverage and connectivity configuration in wireless sensor networks

paper_content:

An effective approach for energy conservation in wireless sensor networks is scheduling sleep intervals for extraneous nodes, while the remaining nodes stay active to provide continuous service. For the sensor network to operate successfully, the active nodes must maintain both sensing coverage and network connectivity. Furthermore, the network must be able to configure itself to any feasible degrees of coverage and connectivity in order to support different applications and environments with diverse requirements. This paper presents the design and analysis of novel protocols that can dynamically configure a network to achieve guaranteed degrees of coverage and connectivity. This work differs from existing connectivity or coverage maintenance protocols in several key ways: 1) We present a Coverage Configuration Protocol (CCP) that can provide different degrees of coverage requested by applications. This flexibility allows the network to self-configure for a wide range of applications and (possibly dynamic) environments. 2) We provide a geometric analysis of the relationship between coverage and connectivity. This analysis yields key insights for treating coverage and connectivity in a unified framework: this is in sharp contrast to several existing approaches that address the two problems in isolation. 3) Finally, we integrate CCP with SPAN to provide both coverage and connectivity guarantees. We demonstrate the capability of our protocols to provide guaranteed coverage and connectivity configurations, through both geometric analysis and extensive simulations.
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paper_title: Deploying a wireless sensor network on an active volcano

paper_content:

Augmenting heavy and power-hungry data collection equipment with lighten smaller wireless sensor network nodes leads to faster, larger deployments. Arrays comprising dozens of wireless sensor nodes are now possible, allowing scientific studies that aren't feasible with traditional instrumentation. Designing sensor networks to support volcanic studies requires addressing the high data rates and high data fidelity these studies demand. The authors' sensor-network application for volcanic data collection relies on triggered event detection and reliable data retrieval to meet bandwidth and data-quality demands.
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paper_title: PRESTO: A Predictive Storage Architecture for Sensor Networks

paper_content:

We describe PRESTO, a predictive storage architecture for emerging large-scale, hierarchical sensor networks. In contrast to existing techniques, PRESTO is a proxy-centric architecture, where tethered proxies balance the need for interactive querying from users with the energy optimization needs of the remote sensors. The main novelty in this work lies in extensive use of predictive techniques that are a natural fit to the correlated behavior of the physical world. PRESTO exploits technology trends in storage to build an architecture that emphasizes archival at remote sensors and intelligent caching at proxies. The system also addresses user needs for querying such sensor networks by exposing a unified, easy to use data abstraction across numerous proxies and remote sensors.
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paper_title: Versatile low power media access for wireless sensor networks

paper_content:

We propose B-MAC, a carrier sense media access protocol for wireless sensor networks that provides a flexible interface to obtain ultra low power operation, effective collision avoidance, and high channel utilization. To achieve low power operation, B-MAC employs an adaptive preamble sampling scheme to reduce duty cycle and minimize idle listening. B-MAC supports on-the-fly reconfiguration and provides bidirectional interfaces for system services to optimize performance, whether it be for throughput, latency, or power conservation. We build an analytical model of a class of sensor network applications. We use the model to show the effect of changing B-MAC's parameters and predict the behavior of sensor network applications. By comparing B-MAC to conventional 802.11-inspired protocols, specifically SMAC, we develop an experimental characterization of B-MAC over a wide range of network conditions. We show that B-MAC's flexibility results in better packet delivery rates, throughput, latency, and energy consumption than S-MAC. By deploying a real world monitoring application with multihop networking, we validate our protocol design and model. Our results illustrate the need for flexible protocols to effectively realize energy efficient sensor network applications.
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paper_title: Sensor networks for smart roads

paper_content:

This paper proposes the use of a wireless sensor network of "cat's eye" augmented with embedded processing, communication, and sensing capabilities to monitor vehicle behaviour on augmented roads. The primary goal of the system is to provide drivers with early warning of potentially dangerous situations that may arise. The focus of the paper is on the software architecture needed and the technical challenges to be overcome in order to support this and related applications.
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paper_title: An energy-efficient MAC protocol for wireless sensor networks

paper_content:

This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s.
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paper_title: Design of a wireless sensor network platform for detecting rare, random, and ephemeral events

paper_content:

We present the design of the extreme scale mote, a new sensor network platform for reliably detecting and classifying, and quickly reporting, rare, random, and ephemeral events in a large-scale, long-lived, and ret askable manner. This new mote was designed for the ExScal project which seeks to demonstrate a 10,000 node network capable of discriminating civilians, soldiers and vehicles, spread out over a 10 km/sup 2/ area, with node lifetimes approaching 1,000 hours of continuous operation on two AA alkaline batteries. This application posed unique functional, usability, scalability, and robustness requirements which could not be met with existing hardware, and therefore motivated the design of a new platform. The detection and classification requirements are met using infrared, magnetic, and acoustic sensors. The infrared and acoustic sensors are designed for low-power continuous operation and include asynchronous processor wakeup circuitry. The usability and scalability requirements are met by minimizing the frequency and cost of human-in-the-loop operations during node deployment, activation, and verification through improvements in the user interface, packaging, and configurability of the platform. Recoverable retasking is addressed by using a grenade timer that periodically forces a system reset. The key contributions of this work are a specific design point and general design methods for building sensor network platforms to detect exceptional events.
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paper_title: X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor networks

paper_content:

In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this “low power listening” approach is simple, asynchronous, and energy-efficient, the long preamble introduces excess latency at each hop, is suboptimal in terms of energy consumption, and suffers from excess energy consumption at nontarget receivers. X-MAC proposes solutions to each of these problems by employing a shortened preamble approach that retains the advantages of low power listening, namely low power communication, simplicity and a decoupling of transmitter and receiver sleep schedules. We demonstrate through implementation and evaluation in a wireless sensor testbed that X-MAC’s shortened preamble approach significantly reduces energy usage at both the transmitter and receiver, reduces per-hop latency, and offers additional advantages such as flexible adaptation to both bursty and periodic sensor data sources.
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paper_title: A backup routing with wireless sensor network for bridge monitoring system

paper_content:

This paper proposed and implemented an efficient and reliable backup scheme for bridge monitoring system. It is mainly using the wireless sensor network (WSN) to gather the related environment parameters, and transmitting the numerical data to the gateway through multiple-hop relay, and then it further stores data in the back-end database for the professional monitoring staffs to analyze and study. The proposed backup scheme could to ameliorate the inconvenience to add or remove sensor nodes in an existing wired bridge monitoring network. Final, the feasibility of the proposed scheme is verified by experimental results.
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paper_title: Brimon: a sensor network system for railway bridge monitoring

paper_content:

Railway systems are critical in many regions, and can consist of several tens of thousands of bridges, being used over several decades. It is critical to have a system to monitor the health of these bridges and report when and where maintenance operations are needed. This paper presents BriMon, a wireless sensor network based system for such monitoring. The design of BriMon is driven by two important factors: application requirements, and detailed measurement studies of several pieces of the architecture. In comparison with prior bridge monitoring systems and sensor network prototypes, our contributions are three-fold. First, we have designed a novel event detection mechanism that triggers data collection in response to an oncoming train. Next, BriMon employs a simple yet effective multi-channel data transfer mechanism to transfer the collected data onto a sink located on the moving train. Third, the BriMon architecture is designed with careful consideration of the interaction between the multiple requisite functionalities such as time synchronization, event detection, routing, and data transfer. Based on a prototype implementation, this paper also presents several measurement studies to show that our design choices are indeed quite effective.
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paper_title: Estimating clock uncertainty for efficient duty-cycling in sensor networks

paper_content:

Radio duty cycling has received significant attention in sensor networking literature, particularly in the form of protocols for medium access control and topology management. While many protocols have claimed to achieve significant duty-cycling benefits in theory and simulation, these benefits have often not translated into practice. The dominant factor that prevents the optimal usage of the radio in real deployment settings is time uncertainty between sensor nodes which results in overhead in the form of long packet preambles, guard bands, and excessive control packets for synchronization. This paper proposes an uncertainty-driven approach to duty-cycling, where a model of long-term clock drift is used to minimize the duty-cycling overhead. First, we use long-term empirical measurements to evaluate and analyze in-depth the interplay between three key parameters that influence long-term synchronization: synchronization rate, history of past synchronization beacons, and the estimation scheme. Second, we use this measurement-based study to design a rate-adaptive, energy-efficient long-term time synchronization algorithm that can adapt to changing clock drift and environmental conditions, while achieving application-specific precision with very high probability. Finally, we integrate our uncertainty-driven time synchronization scheme with the BMAC medium access control protocol, and demonstrate one to two orders of magnitude reduction in transmission energy consumption with negligible impact on packet loss rate.
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paper_title: The Tenet architecture for tiered sensor networks

paper_content:

Most sensor network research and software design has been guided by an architectural principle that permits multi-node data fusion on small-form-factor, resource-poor nodes, or motes. We argue that this principle leads to fragile and unmanageable systems and explore an alternative. The Tenet architecture is motivated by the observation that future largescale sensor network deployments will be tiered, consisting of motes in the lower tier and masters, relatively unconstrained 32-bit platform nodes, in the upper tier. Masters provide increased network capacity. Tenet constrains multinode fusion to the master tier while allowing motes to process locally-generated sensor data. This simplifies application development and allows mote-tier software to be reused. Applications running on masters task motes by composing task descriptions from a novel tasklet library. Our Tenet implementation also contains a robust and scalable networking subsystem for disseminating tasks and reliably delivering responses.We show that a Tenet pursuit-evasion application exhibits performance comparable to a mote-native implementation while being considerably more compact.
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paper_title: Perpetual environmentally powered sensor networks

paper_content:

Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.
---
paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
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paper_title: Design, Modeling, and Capacity Planning for Micro-solar Power Sensor Networks

paper_content:

This paper describes a systematic approach to building micro-solar power subsystems for wireless sensor network nodes. Our approach composes models of the basic pieces - solar panels, regulators, energy storage elements, and application loads - to appropriately select and size the components. We demonstrate our approach in the context of a microclimate monitoring project through the design of the node, micro-solar subsystem, and network, which is deployed in a challenging, deep forest setting. We evaluate our deployment by analyzing the effects of the range of solar profiles experienced across the network.
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paper_title: Design considerations for solar energy harvesting wireless embedded systems

paper_content:

Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery nonidealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
---
paper_title: Parasitic power harvesting in shoes

paper_content:

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.
---
paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
---
paper_title: AmbiMax: Autonomous Energy Harvesting Platform for Multi-Supply Wireless Sensor Nodes

paper_content:

AmbiMax is an energy harvesting circuit and a supercapacitor based energy storage system for wireless sensor nodes (WSN). Previous WSNs attempt to harvest energy from various sources, and some also use supercapacitors instead of batteries to address the battery aging problem. However, they either waste much available energy due to impedance mismatch, or they require active digital control that incurs overhead, or they work with only one specific type of source. AmbiMax addresses these problems by first performing maximum power point tracking (MPPT) autonomously, and then charges supercapacitors at maximum efficiency. Furthermore, AmbiMax is modular and enables composition of multiple energy harvesting sources including solar, wind, thermal, and vibration, each with a different optimal size. Experimental results on a real WSN platform, Eco, show that AmbiMax successfully manages multiple power sources simultaneously and autonomously at several times the efficiency of the current state-of-the-art for WSNs
---
paper_title: Human Powered Wearable Computing

paper_content:

Batteries add size, weight, and inconvenience to present-day mobile computers. This paper explores the possibility of harnessing the energy expended during the user's everyday actions to generate power for his or her computer, thus eliminating the impediment of batteries. An analysis of power generation through leg motion is presented in depth, and a survey of other methods such as generation by breath or blood pressure, body heat, and finger and limb motion is also presented.
---
paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
---
paper_title: Parasitic power harvesting in shoes

paper_content:

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.
---
paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
---
paper_title: Human Powered Wearable Computing

paper_content:

Batteries add size, weight, and inconvenience to present-day mobile computers. This paper explores the possibility of harnessing the energy expended during the user's everyday actions to generate power for his or her computer, thus eliminating the impediment of batteries. An analysis of power generation through leg motion is presented in depth, and a survey of other methods such as generation by breath or blood pressure, body heat, and finger and limb motion is also presented.
---
paper_title: Perpetual environmentally powered sensor networks

paper_content:

Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.
---
paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
---
paper_title: A survey of energy harvesting sources for embedded systems

paper_content:

Historically, batteries have been the source of energy for most mobile, embedded and remote system applications. Now, with ubiquitous computing requirements in the fields of embedded systems, wireless sensor networks and low- power electronics such as MEMS devices, an alternative source of energy is required. Also with the limited capacity of finite power sources and the need for supplying energy for a lifetime of a system, there is a requirement for self- powered devices. The process of extracting energy from the surrounding environment is termed as energy harvesting. Energy harvesting, which originated from the windmill and water wheel, is widely being considered as a low- maintenance solution for a wide variety of applications. There are various forms of energy that can be scavenged, like thermal, mechanical, solar, acoustic, wind, and wave. This paper serves as a survey for identifying the sources of energy harvesting based on various technical papers available in the public domain.
---
paper_title: Design, Modeling, and Capacity Planning for Micro-solar Power Sensor Networks

paper_content:

This paper describes a systematic approach to building micro-solar power subsystems for wireless sensor network nodes. Our approach composes models of the basic pieces - solar panels, regulators, energy storage elements, and application loads - to appropriately select and size the components. We demonstrate our approach in the context of a microclimate monitoring project through the design of the node, micro-solar subsystem, and network, which is deployed in a challenging, deep forest setting. We evaluate our deployment by analyzing the effects of the range of solar profiles experienced across the network.
---
paper_title: Design considerations for solar energy harvesting wireless embedded systems

paper_content:

Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery nonidealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
---
paper_title: Parasitic power harvesting in shoes

paper_content:

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.
---
paper_title: Remote area wind energy harvesting for low-power autonomous sensors

paper_content:

A growing demand for deployment of autonomous sensors and sensor networks is leading to a subsequent increase in the demand for localized, independent energy harvesting capabilities for each node. In this paper, a method of remote area wind energy harvesting is presented, with a focus on an anemometer-based solution. By utilizing the motion of the anemometer shaft to turn a compact alternator, small amounts of power can be harvested from otherwise unavailable sources. Energy harvested is converted to battery potential via a pulsed buck-boost converter operating in discontinuous conduction mode (DCM). It is found that maintaining a constant input resistance at the input port of the converter biases the alternator to operate at its peak power point over a wide range of wind speeds. Results show that power harvesting capability using the discussed alternator and power converter solution are in the range of tens to hundreds of microwatts up to approximately one milliwatt. This power is passed to the central system batteries, providing a trickle-charge. As a result, sensor nodes incorporating this harvesting solution have an increased field lifetime. High overall efficiency is maintained over a wide range of potential wind speeds, with little impact on anemometer measurement accuracy.
---
paper_title: AmbiMax: Autonomous Energy Harvesting Platform for Multi-Supply Wireless Sensor Nodes

paper_content:

AmbiMax is an energy harvesting circuit and a supercapacitor based energy storage system for wireless sensor nodes (WSN). Previous WSNs attempt to harvest energy from various sources, and some also use supercapacitors instead of batteries to address the battery aging problem. However, they either waste much available energy due to impedance mismatch, or they require active digital control that incurs overhead, or they work with only one specific type of source. AmbiMax addresses these problems by first performing maximum power point tracking (MPPT) autonomously, and then charges supercapacitors at maximum efficiency. Furthermore, AmbiMax is modular and enables composition of multiple energy harvesting sources including solar, wind, thermal, and vibration, each with a different optimal size. Experimental results on a real WSN platform, Eco, show that AmbiMax successfully manages multiple power sources simultaneously and autonomously at several times the efficiency of the current state-of-the-art for WSNs
---
paper_title: Human Powered Wearable Computing

paper_content:

Batteries add size, weight, and inconvenience to present-day mobile computers. This paper explores the possibility of harnessing the energy expended during the user's everyday actions to generate power for his or her computer, thus eliminating the impediment of batteries. An analysis of power generation through leg motion is presented in depth, and a survey of other methods such as generation by breath or blood pressure, body heat, and finger and limb motion is also presented.
---
paper_title: A backup routing with wireless sensor network for bridge monitoring system

paper_content:

This paper proposed and implemented an efficient and reliable backup scheme for bridge monitoring system. It is mainly using the wireless sensor network (WSN) to gather the related environment parameters, and transmitting the numerical data to the gateway through multiple-hop relay, and then it further stores data in the back-end database for the professional monitoring staffs to analyze and study. The proposed backup scheme could to ameliorate the inconvenience to add or remove sensor nodes in an existing wired bridge monitoring network. Final, the feasibility of the proposed scheme is verified by experimental results.
---
paper_title: Perpetual environmentally powered sensor networks

paper_content:

Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.
---
paper_title: Wireless sensor networks for habitat monitoring

paper_content:

We provide an in-depth study of applying wireless sensor networks to real-world habitat monitoring. A set of system design requirements are developed that cover the hardware design of the nodes, the design of the sensor network, and the capabilities for remote data access and management. A system architecture is proposed to address these requirements for habitat monitoring in general, and an instance of the architecture for monitoring seabird nesting environment and behavior is presented. The currently deployed network consists of 32 nodes on a small island off the coast of Maine streaming useful live data onto the web. The application-driven design exercise serves to identify important areas of further work in data sampling, communications, network retasking, and health monitoring.
---
paper_title: Deploying a wireless sensor network on an active volcano

paper_content:

Augmenting heavy and power-hungry data collection equipment with lighten smaller wireless sensor network nodes leads to faster, larger deployments. Arrays comprising dozens of wireless sensor nodes are now possible, allowing scientific studies that aren't feasible with traditional instrumentation. Designing sensor networks to support volcanic studies requires addressing the high data rates and high data fidelity these studies demand. The authors' sensor-network application for volcanic data collection relies on triggered event detection and reliable data retrieval to meet bandwidth and data-quality demands.
---
paper_title: Design, Modeling, and Capacity Planning for Micro-solar Power Sensor Networks

paper_content:

This paper describes a systematic approach to building micro-solar power subsystems for wireless sensor network nodes. Our approach composes models of the basic pieces - solar panels, regulators, energy storage elements, and application loads - to appropriately select and size the components. We demonstrate our approach in the context of a microclimate monitoring project through the design of the node, micro-solar subsystem, and network, which is deployed in a challenging, deep forest setting. We evaluate our deployment by analyzing the effects of the range of solar profiles experienced across the network.
---
paper_title: A backup routing with wireless sensor network for bridge monitoring system

paper_content:

This paper proposed and implemented an efficient and reliable backup scheme for bridge monitoring system. It is mainly using the wireless sensor network (WSN) to gather the related environment parameters, and transmitting the numerical data to the gateway through multiple-hop relay, and then it further stores data in the back-end database for the professional monitoring staffs to analyze and study. The proposed backup scheme could to ameliorate the inconvenience to add or remove sensor nodes in an existing wired bridge monitoring network. Final, the feasibility of the proposed scheme is verified by experimental results.
---
paper_title: Brimon: a sensor network system for railway bridge monitoring

paper_content:

Railway systems are critical in many regions, and can consist of several tens of thousands of bridges, being used over several decades. It is critical to have a system to monitor the health of these bridges and report when and where maintenance operations are needed. This paper presents BriMon, a wireless sensor network based system for such monitoring. The design of BriMon is driven by two important factors: application requirements, and detailed measurement studies of several pieces of the architecture. In comparison with prior bridge monitoring systems and sensor network prototypes, our contributions are three-fold. First, we have designed a novel event detection mechanism that triggers data collection in response to an oncoming train. Next, BriMon employs a simple yet effective multi-channel data transfer mechanism to transfer the collected data onto a sink located on the moving train. Third, the BriMon architecture is designed with careful consideration of the interaction between the multiple requisite functionalities such as time synchronization, event detection, routing, and data transfer. Based on a prototype implementation, this paper also presents several measurement studies to show that our design choices are indeed quite effective.
---
paper_title: Perpetual environmentally powered sensor networks

paper_content:

Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.
---
paper_title: Design of an RFID-Based Battery-Free Programmable Sensing Platform

paper_content:

This paper presents the wireless identification and sensing platform (WISP), which is a programmable battery-free sensing and computational platform designed to explore sensor-enhanced radio frequency identification (RFID) applications. WISP uses a 16-bit ultralow-power microcontroller to perform sensing and computation while exclusively operating from harvested RF energy. Sensors that have successfully been integrated into the WISP platform to date include temperature, ambient light, rectified voltage, and orientation. The microcontroller encodes measurements into an electronic product code (EPC) Class 1 Generation 1 compliant ID and dynamically computes the required 16-bit cyclical redundancy checking (CRC). Finally, WISP emulates the EPC protocol to communicate the ID to the RFID reader. To the authors' knowledge, WISP is the first fully programmable computing platform that can operate using power transmitted from a long-range (UHF) RFID reader and communicate arbitrary multibit data in a single response packet.
---
paper_title: Everlast: long-life, supercapacitor-operated wireless sensor node

paper_content:

This paper describes a supercapacitor-operated, solar-powered wireless sensor node called Everlast. Unlike traditional wireless sensors that store energy in batteries, Everlast's use of supercapacitors enables the system to operate for an estimated lifetime of 20 years without any maintenance. The novelty of this system lies in the feed-forward, pulse-frequency modulated (PFM) converter and open-circuit solar voltage method for maximum power point tracking (MPPT), enabling the solar cell to efficiently charge the supercapacitor and power the node. Experimental results show that Everlast can achieve low power consumption, long operational lifetime, and high transmission rates, something that traditional sensor nodes cannot achieve simultaneously and must trade-off.
---
paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
---
paper_title: An 0.9 x 1.2", Low Power, Energy-Harvesting System with Custom Multi-Channel Communication Interface

paper_content:

Presented is a self-powered computing system, Sunflower, that uses a novel combination of a PIN photodiode array, switching regulators, and a supercapacitor, to provide a small footprint renewable energy source. The design provides software-controlled power-adaptation facilities, for both the main processor and its peripherals. The system's power consumption is characterized, and its energy-scavenging efficiency is quantified with field measurements under a variety of weather conditions.
---
paper_title: Adaptive Duty Cycling for Energy Harvesting Systems

paper_content:

Harvesting energy from the environment is feasible in many applications to ameliorate the energy limitations in sensor networks. In this paper, we present an adaptive duty cycling algorithm that allows energy harvesting sensor nodes to autonomously adjust their duty cycle according to the energy availability in the environment. The algorithm has three objectives, namely (a) achieving energy neutral operation, i.e., energy consumption should not be more than the energy provided by the environment, (b) maximizing the system performance based on an application utility model subject to the above energy-neutrality constraint, and (c) adapting to the dynamics of the energy source at run-time. We present a model that enables harvesting sensor nodes to predict future energy opportunities based on historical data. We also derive an upper bound on the maximum achievable performance assuming perfect knowledge about the future behavior of the energy source. Our methods are evaluated using data gathered from a prototype solar energy harvesting platform and we show that our algorithm can utilize up to 58% more environmental energy compared to the case when harvesting-aware power management is not used.
---
paper_title: Design considerations for solar energy harvesting wireless embedded systems

paper_content:

Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery nonidealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
---
paper_title: Getting Things Done on Computational RFIDs with Energy-Aware Checkpointing and Voltage-Aware Scheduling

paper_content:

Computational RFIDs (CRFIDs) provide flexible, general-purpose computation on a microcontroller via energy that is harvested and stored in capacitors rather than batteries. Our contributions include a definition of CRFIDs, a framework for energy management in CRFIDs, and the preliminary design of Mementos, a medley of compile-time and run-time techniques to achieve effective forward progress of computation on CRFIDs by using energy-aware computational checkpoints and voltage-aware program reordering that maintains program semantics. Our preliminary measurements indicate that Mementos will enable CRFIDs to complete long-running computations despite constant interruptions to power.
---
paper_title: Parasitic power harvesting in shoes

paper_content:

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.
---
paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
---
paper_title: Remote area wind energy harvesting for low-power autonomous sensors

paper_content:

A growing demand for deployment of autonomous sensors and sensor networks is leading to a subsequent increase in the demand for localized, independent energy harvesting capabilities for each node. In this paper, a method of remote area wind energy harvesting is presented, with a focus on an anemometer-based solution. By utilizing the motion of the anemometer shaft to turn a compact alternator, small amounts of power can be harvested from otherwise unavailable sources. Energy harvested is converted to battery potential via a pulsed buck-boost converter operating in discontinuous conduction mode (DCM). It is found that maintaining a constant input resistance at the input port of the converter biases the alternator to operate at its peak power point over a wide range of wind speeds. Results show that power harvesting capability using the discussed alternator and power converter solution are in the range of tens to hundreds of microwatts up to approximately one milliwatt. This power is passed to the central system batteries, providing a trickle-charge. As a result, sensor nodes incorporating this harvesting solution have an increased field lifetime. High overall efficiency is maintained over a wide range of potential wind speeds, with little impact on anemometer measurement accuracy.
---
paper_title: Revisiting Smart Dust with RFID Sensor Networks

paper_content:

We argue that sensing and computation platforms that leverage RFID technology can realize “smart-dust” applications that have eluded the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags to wireless sensor networks. We describe sample applications suited to the space between existing sensor networks and RFID. We highlight the research challenges in realizing RSNs such as the use of intermittent power and RFID protocols suited to sensor queries.
---
paper_title: AmbiMax: Autonomous Energy Harvesting Platform for Multi-Supply Wireless Sensor Nodes

paper_content:

AmbiMax is an energy harvesting circuit and a supercapacitor based energy storage system for wireless sensor nodes (WSN). Previous WSNs attempt to harvest energy from various sources, and some also use supercapacitors instead of batteries to address the battery aging problem. However, they either waste much available energy due to impedance mismatch, or they require active digital control that incurs overhead, or they work with only one specific type of source. AmbiMax addresses these problems by first performing maximum power point tracking (MPPT) autonomously, and then charges supercapacitors at maximum efficiency. Furthermore, AmbiMax is modular and enables composition of multiple energy harvesting sources including solar, wind, thermal, and vibration, each with a different optimal size. Experimental results on a real WSN platform, Eco, show that AmbiMax successfully manages multiple power sources simultaneously and autonomously at several times the efficiency of the current state-of-the-art for WSNs
---
paper_title: Human Powered Wearable Computing

paper_content:

Batteries add size, weight, and inconvenience to present-day mobile computers. This paper explores the possibility of harnessing the energy expended during the user's everyday actions to generate power for his or her computer, thus eliminating the impediment of batteries. An analysis of power generation through leg motion is presented in depth, and a survey of other methods such as generation by breath or blood pressure, body heat, and finger and limb motion is also presented.
---
paper_title: Systems for human-powered mobile computing

paper_content:

This article outlines several projects aimed at generating electrical energy by passively tapping a variety of human body sources and activities. After summarizing different energy harvesting modalities and techniques, I spotlight work done in my research group at the MIT media laboratory, including a system that scavenges electricity from the forces exerted on a shoe during walking. This system uses a flexible piezoelectric foil stave to harness sole-bending energy and a reinforced PZT dimorph to capture heel-strike energy. The piezoelectric generators drive a battery-less, active RF tag, which transmits a short-range wireless ID while walking, thereby enabling location based services and active environments. Other systems that we have developed are also discussed, including a battery-less pushbutton that can send an RF ID code with a single push, sensor nodes that harvest mobility rather than energy, and power management schemes that exploit sensor diversity to achieve energy efficiency.
---
paper_title: Perpetual environmentally powered sensor networks

paper_content:

Environmental energy is an attractive power source for low power wireless sensor networks. We present Prometheus, a system that intelligently manages energy transfer for perpetual operation without human intervention or servicing. Combining positive attributes of different energy storage elements and leveraging the intelligence of the microprocessor, we introduce an efficient multi-stage energy transfer system that reduces the common limitations of single energy storage systems to achieve near perpetual operation. We present our design choices, tradeoffs, circuit evaluations, performance analysis, and models. We discuss the relationships between system components and identify optimal hardware choices to meet an application's needs. Finally we present our implementation of a real system that uses solar energy to power Berkeley's Telos Mote. Our analysis predicts the system will operate for 43 years under 1% load, 4 years under 10% load, and 1 year under 100% load. Our implementation uses a two stage storage system consisting of supercapacitors (primary buffer) and a lithium rechargeable battery (secondary buffer). The mote has full knowledge of power levels and intelligently manages energy transfer to maximize lifetime.
---
paper_title: Telos: enabling ultra-low power wireless research

paper_content:

We present Telos, an ultra low power wireless sensor module ("mote") for research and experimentation. Telos is the latest in a line of motes developed by UC Berkeley to enable wireless sensor network (WSN) research. It is a new mote design built from scratch based on experiences with previous mote generations. Telos' new design consists of three major goals to enable experimentation: minimal power consumption, easy to use, and increased software and hardware robustness. We discuss how hardware components are selected and integrated in order to achieve these goals. Using a Texas Instruments MSP430 microcontroller, Chipcon IEEE 802.15.4-compliant radio, and USB, Telos' power profile is almost one-tenth the consumption of previous mote platforms while providing greater performance and throughput. It eliminates programming and support boards, while enabling experimentation with WSNs in both lab, testbed, and deployment settings.
---
paper_title: Everlast: long-life, supercapacitor-operated wireless sensor node

paper_content:

This paper describes a supercapacitor-operated, solar-powered wireless sensor node called Everlast. Unlike traditional wireless sensors that store energy in batteries, Everlast's use of supercapacitors enables the system to operate for an estimated lifetime of 20 years without any maintenance. The novelty of this system lies in the feed-forward, pulse-frequency modulated (PFM) converter and open-circuit solar voltage method for maximum power point tracking (MPPT), enabling the solar cell to efficiently charge the supercapacitor and power the node. Experimental results show that Everlast can achieve low power consumption, long operational lifetime, and high transmission rates, something that traditional sensor nodes cannot achieve simultaneously and must trade-off.
---
paper_title: An 0.9 x 1.2", Low Power, Energy-Harvesting System with Custom Multi-Channel Communication Interface

paper_content:

Presented is a self-powered computing system, Sunflower, that uses a novel combination of a PIN photodiode array, switching regulators, and a supercapacitor, to provide a small footprint renewable energy source. The design provides software-controlled power-adaptation facilities, for both the main processor and its peripherals. The system's power consumption is characterized, and its energy-scavenging efficiency is quantified with field measurements under a variety of weather conditions.
---
paper_title: Design, Modeling, and Capacity Planning for Micro-solar Power Sensor Networks

paper_content:

This paper describes a systematic approach to building micro-solar power subsystems for wireless sensor network nodes. Our approach composes models of the basic pieces - solar panels, regulators, energy storage elements, and application loads - to appropriately select and size the components. We demonstrate our approach in the context of a microclimate monitoring project through the design of the node, micro-solar subsystem, and network, which is deployed in a challenging, deep forest setting. We evaluate our deployment by analyzing the effects of the range of solar profiles experienced across the network.
---
paper_title: Long-duration solar-powered wireless sensor networks

paper_content:

This paper discusses hardware design principles for long-term solar-powered wireless sensor networks. We argue that the assumptions and principles appropriate for long-term operation from primary cells are quite different from the solar power case with its abundant energy and regular charging cycles. We present data from a long-term deployment that illustrates the use of solar energy and rechargeable batteries to achieve 24x7 operation for over two years, since March 2005.
---
paper_title: Design considerations for solar energy harvesting wireless embedded systems

paper_content:

Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery nonidealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
---
paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
---
paper_title: AmbiMax: Autonomous Energy Harvesting Platform for Multi-Supply Wireless Sensor Nodes

paper_content:

AmbiMax is an energy harvesting circuit and a supercapacitor based energy storage system for wireless sensor nodes (WSN). Previous WSNs attempt to harvest energy from various sources, and some also use supercapacitors instead of batteries to address the battery aging problem. However, they either waste much available energy due to impedance mismatch, or they require active digital control that incurs overhead, or they work with only one specific type of source. AmbiMax addresses these problems by first performing maximum power point tracking (MPPT) autonomously, and then charges supercapacitors at maximum efficiency. Furthermore, AmbiMax is modular and enables composition of multiple energy harvesting sources including solar, wind, thermal, and vibration, each with a different optimal size. Experimental results on a real WSN platform, Eco, show that AmbiMax successfully manages multiple power sources simultaneously and autonomously at several times the efficiency of the current state-of-the-art for WSNs
---
paper_title: An energy-efficient MAC protocol for wireless sensor networks

paper_content:

This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s.
---
paper_title: Hardware design experiences in ZebraNet

paper_content:

The enormous potential for wireless sensor networks to make a positive impact on our society has spawned a great deal of research on the topic, and this research is now producing environment-ready systems. Current technology limits coupled with widely-varying application requirements lead to a diversity of hardware platforms for different portions of the design space. In addition, the unique energy and reliability constraints of a system that must function for months at a time without human intervention mean that demands on sensor network hardware are different from the demands on standard integrated circuits. This paper describes our experiences designing sensor nodes and low level software to control them. In the ZebraNet system we use GPS technology to record fine-grained position data in order to track long term animal migrations [14]. The ZebraNet hardware is composed of a 16-bit TI microcontroller, 4 Mbits of off-chip flash memory, a 900 MHz radio, and a low-power GPS chip. In this paper, we discuss our techniques for devising efficient power supplies for sensor networks, methods of managing the energy consumption of the nodes, and methods of managing the peripheral devices including the radio, flash, and sensors. We conclude by evaluating the design of the ZebraNet nodes and discussing how it can be improved. Our lessons learned in developing this hardware can be useful both in designing future sensor nodes and in using them in real systems.
---
paper_title: Active sensing platform for wireless structural health monitoring

paper_content:

This paper presents SHiMmer, a wireless platform for sensing and actuation that combines localized processing with energy harvesting to provide long-lived structural health monitoring. The life-cycle of the node is significantly extended by the use of super-capacitors for energy storage instead of batteries. During this period the node is expected to work completely maintenance-free. The node is capable of harvesting up to 780 J per day. This makes it completely self- sufficient while employed in real structural health monitoring applications. Unlike other sensor networks that periodically monitor a structure and route information to a base station, our device acquires the data and processes it locally after being radio-triggered by an external agent. The localized processing allows us to avoid issues due to network congestion. Our experiments show that its 32- bits computational core can run at 100 MIPS for 15 minutes daily.
---
paper_title: Hardware design experiences in ZebraNet

paper_content:

The enormous potential for wireless sensor networks to make a positive impact on our society has spawned a great deal of research on the topic, and this research is now producing environment-ready systems. Current technology limits coupled with widely-varying application requirements lead to a diversity of hardware platforms for different portions of the design space. In addition, the unique energy and reliability constraints of a system that must function for months at a time without human intervention mean that demands on sensor network hardware are different from the demands on standard integrated circuits. This paper describes our experiences designing sensor nodes and low level software to control them. In the ZebraNet system we use GPS technology to record fine-grained position data in order to track long term animal migrations [14]. The ZebraNet hardware is composed of a 16-bit TI microcontroller, 4 Mbits of off-chip flash memory, a 900 MHz radio, and a low-power GPS chip. In this paper, we discuss our techniques for devising efficient power supplies for sensor networks, methods of managing the energy consumption of the nodes, and methods of managing the peripheral devices including the radio, flash, and sensors. We conclude by evaluating the design of the ZebraNet nodes and discussing how it can be improved. Our lessons learned in developing this hardware can be useful both in designing future sensor nodes and in using them in real systems.
---
paper_title: Long-duration solar-powered wireless sensor networks

paper_content:

This paper discusses hardware design principles for long-term solar-powered wireless sensor networks. We argue that the assumptions and principles appropriate for long-term operation from primary cells are quite different from the solar power case with its abundant energy and regular charging cycles. We present data from a long-term deployment that illustrates the use of solar energy and rechargeable batteries to achieve 24x7 operation for over two years, since March 2005.
---
paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
---
paper_title: Parasitic power harvesting in shoes

paper_content:

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.
---
paper_title: Human Powered Wearable Computing

paper_content:

Batteries add size, weight, and inconvenience to present-day mobile computers. This paper explores the possibility of harnessing the energy expended during the user's everyday actions to generate power for his or her computer, thus eliminating the impediment of batteries. An analysis of power generation through leg motion is presented in depth, and a survey of other methods such as generation by breath or blood pressure, body heat, and finger and limb motion is also presented.
---
paper_title: Design of an RFID-Based Battery-Free Programmable Sensing Platform

paper_content:

This paper presents the wireless identification and sensing platform (WISP), which is a programmable battery-free sensing and computational platform designed to explore sensor-enhanced radio frequency identification (RFID) applications. WISP uses a 16-bit ultralow-power microcontroller to perform sensing and computation while exclusively operating from harvested RF energy. Sensors that have successfully been integrated into the WISP platform to date include temperature, ambient light, rectified voltage, and orientation. The microcontroller encodes measurements into an electronic product code (EPC) Class 1 Generation 1 compliant ID and dynamically computes the required 16-bit cyclical redundancy checking (CRC). Finally, WISP emulates the EPC protocol to communicate the ID to the RFID reader. To the authors' knowledge, WISP is the first fully programmable computing platform that can operate using power transmitted from a long-range (UHF) RFID reader and communicate arbitrary multibit data in a single response packet.
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paper_title: A Compact, Wireless, Self-Powered Pushbutton Controller

paper_content:

We describe a compact piezoelectric pushbutton and associated minimal circuitry that is able to wirelessly transmit a digital ID code to the immediate region (e.g., 50-100 foot radius) upon a single button push, without the need of batteries or other energy sources. Such devices have the potential of enabling controls and interfaces to be introduced into interactive environments without requiring any wiring, optical/acoustic lines of sight, or batteries.
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paper_title: Getting Things Done on Computational RFIDs with Energy-Aware Checkpointing and Voltage-Aware Scheduling

paper_content:

Computational RFIDs (CRFIDs) provide flexible, general-purpose computation on a microcontroller via energy that is harvested and stored in capacitors rather than batteries. Our contributions include a definition of CRFIDs, a framework for energy management in CRFIDs, and the preliminary design of Mementos, a medley of compile-time and run-time techniques to achieve effective forward progress of computation on CRFIDs by using energy-aware computational checkpoints and voltage-aware program reordering that maintains program semantics. Our preliminary measurements indicate that Mementos will enable CRFIDs to complete long-running computations despite constant interruptions to power.
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paper_title: Remote area wind energy harvesting for low-power autonomous sensors

paper_content:

A growing demand for deployment of autonomous sensors and sensor networks is leading to a subsequent increase in the demand for localized, independent energy harvesting capabilities for each node. In this paper, a method of remote area wind energy harvesting is presented, with a focus on an anemometer-based solution. By utilizing the motion of the anemometer shaft to turn a compact alternator, small amounts of power can be harvested from otherwise unavailable sources. Energy harvested is converted to battery potential via a pulsed buck-boost converter operating in discontinuous conduction mode (DCM). It is found that maintaining a constant input resistance at the input port of the converter biases the alternator to operate at its peak power point over a wide range of wind speeds. Results show that power harvesting capability using the discussed alternator and power converter solution are in the range of tens to hundreds of microwatts up to approximately one milliwatt. This power is passed to the central system batteries, providing a trickle-charge. As a result, sensor nodes incorporating this harvesting solution have an increased field lifetime. High overall efficiency is maintained over a wide range of potential wind speeds, with little impact on anemometer measurement accuracy.
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paper_title: Revisiting Smart Dust with RFID Sensor Networks

paper_content:

We argue that sensing and computation platforms that leverage RFID technology can realize “smart-dust” applications that have eluded the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags to wireless sensor networks. We describe sample applications suited to the space between existing sensor networks and RFID. We highlight the research challenges in realizing RSNs such as the use of intermittent power and RFID protocols suited to sensor queries.
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paper_title: Versatile low power media access for wireless sensor networks

paper_content:

We propose B-MAC, a carrier sense media access protocol for wireless sensor networks that provides a flexible interface to obtain ultra low power operation, effective collision avoidance, and high channel utilization. To achieve low power operation, B-MAC employs an adaptive preamble sampling scheme to reduce duty cycle and minimize idle listening. B-MAC supports on-the-fly reconfiguration and provides bidirectional interfaces for system services to optimize performance, whether it be for throughput, latency, or power conservation. We build an analytical model of a class of sensor network applications. We use the model to show the effect of changing B-MAC's parameters and predict the behavior of sensor network applications. By comparing B-MAC to conventional 802.11-inspired protocols, specifically SMAC, we develop an experimental characterization of B-MAC over a wide range of network conditions. We show that B-MAC's flexibility results in better packet delivery rates, throughput, latency, and energy consumption than S-MAC. By deploying a real world monitoring application with multihop networking, we validate our protocol design and model. Our results illustrate the need for flexible protocols to effectively realize energy efficient sensor network applications.
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paper_title: AmbiMax: Autonomous Energy Harvesting Platform for Multi-Supply Wireless Sensor Nodes

paper_content:

AmbiMax is an energy harvesting circuit and a supercapacitor based energy storage system for wireless sensor nodes (WSN). Previous WSNs attempt to harvest energy from various sources, and some also use supercapacitors instead of batteries to address the battery aging problem. However, they either waste much available energy due to impedance mismatch, or they require active digital control that incurs overhead, or they work with only one specific type of source. AmbiMax addresses these problems by first performing maximum power point tracking (MPPT) autonomously, and then charges supercapacitors at maximum efficiency. Furthermore, AmbiMax is modular and enables composition of multiple energy harvesting sources including solar, wind, thermal, and vibration, each with a different optimal size. Experimental results on a real WSN platform, Eco, show that AmbiMax successfully manages multiple power sources simultaneously and autonomously at several times the efficiency of the current state-of-the-art for WSNs
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paper_title: Pacemakers and Implantable Cardiac Defibrillators: Software Radio Attacks and Zero-Power Defenses

paper_content:

Our study analyzes the security and privacy properties of an implantable cardioverter defibrillator (ICD). Introduced to the U.S. market in 2003, this model of ICD includes pacemaker technology and is designed to communicate wirelessly with a nearby external programmer in the 175 kHz frequency range. After partially reverse-engineering the ICD's communications protocol with an oscilloscope and a software radio, we implemented several software radio-based attacks that could compromise patient safety and patient privacy. Motivated by our desire to improve patient safety, and mindful of conventional trade-offs between security and power consumption for resource-constrained devices, we introduce three new zero-power defenses based on RF power harvesting. Two of these defenses are human-centric, bringing patients into the loop with respect to the security and privacy of their implantable medical devices (IMDs). Our contributions provide a scientific baseline for understanding the potential security and privacy risks of current and future IMDs, and introduce human-perceptible and zero-power mitigation techniques that address those risks. To the best of our knowledge, this paper is the first in our community to use general-purpose software radios to analyze and attack previously unknown radio communications protocols.
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paper_title: Eco: an ultra-compact low-power wireless sensor node for real-time motion monitoring

paper_content:

Eco is an ultra-compact wireless sensor node. Only 648 mm/sup 3/ in volume and weighing under 1.6 grams, Eco was initially designed to monitor the spontaneous motion of preterm infants over 2.4 GHz radio links at the maximum data rate of 1 Mbps. The compact form factor and low power consumption also make Eco nodes highly suitable for many other applications, including medicine, environmental monitoring, new computer-human interface, and ambient intelligence. This paper describes the hardware and software designs of the second generation Eco nodes and the host interface. We also present an evaluation and comparison against other popular sensor nodes in the similar class.
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paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
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paper_title: An environmental energy harvesting framework for sensor networks

paper_content:

Energy constrained systems such as sensor networks can increase their usable lifetimes by extracting energy from their environment. However, environmental energy will typically not be spread homogeneously over the spread of the network. We argue that significant improvements in usable system lifetime can be achieved if the task allocation is aligned with the spatio-temporal characteristics of energy availability. To the best of our knowledge, this problem has not been addressed before. We present a distributed framework for the sensor network to adaptively learn its energy environment and give localized algorithms to use this information for task sharing among nodes. Our framework allows the system to exploit its energy resources more efficiently, thus increasing its lifetime. These gains are in addition to those from utilizing sleep modes and residual energy based scheduling mechanisms. Performance studies for an experimental energy environment show up to 200% improvement in lifetime.
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paper_title: A Data Gathering Scheme for Environmental Energy-Based Wireless Sensor Networks

paper_content:

Prolongation of network lifetime is one of the most important issues of sensor networks. EEHF (Environmental Energy Harvesting Framework) is a framework that includes a data gathering scheme and estimates the energy gained from the environment by using the periodicity of environmental power. Thus, sensor nodes can use environmental energy efficiently and the network lifetime is extended. However, since the accuracy of the estimation depends on the length of the period, and the data gathering scheme used in EEHF does not take environmental energy into consideration, this method has room for improvement. In this paper, we propose a more accurate and adaptive energy estimation method that does not depend on the length of the period, and a data gathering scheme that is optimized for the environmental energy-based sensor network, in order to prolong the lifetime of environmental energy-based sensor networks.
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paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
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paper_title: Adaptive Duty Cycling for Energy Harvesting Systems

paper_content:

Harvesting energy from the environment is feasible in many applications to ameliorate the energy limitations in sensor networks. In this paper, we present an adaptive duty cycling algorithm that allows energy harvesting sensor nodes to autonomously adjust their duty cycle according to the energy availability in the environment. The algorithm has three objectives, namely (a) achieving energy neutral operation, i.e., energy consumption should not be more than the energy provided by the environment, (b) maximizing the system performance based on an application utility model subject to the above energy-neutrality constraint, and (c) adapting to the dynamics of the energy source at run-time. We present a model that enables harvesting sensor nodes to predict future energy opportunities based on historical data. We also derive an upper bound on the maximum achievable performance assuming perfect knowledge about the future behavior of the energy source. Our methods are evaluated using data gathered from a prototype solar energy harvesting platform and we show that our algorithm can utilize up to 58% more environmental energy compared to the case when harvesting-aware power management is not used.
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paper_title: Power management in energy harvesting sensor networks

paper_content:

Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.
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paper_title: Adaptive Control of Duty Cycling in Energy-Harvesting Wireless Sensor Networks

paper_content:

Increasingly many wireless sensor network deployments are using harvested environmental energy to extend system lifetime. Because the temporal profiles of such energy sources exhibit great variability due to dynamic weather patterns, an important problem is designing an adaptive duty-cycling mechanism that allows sensor nodes to maintain their power supply at sufficient levels (energy neutral operation) by adapting to changing environmental conditions. Existing techniques to address this problem are minimally adaptive and assume a priori knowledge of the energy profile. While such approaches are reasonable in environments that exhibit low variance, we find that it is highly inefficient in more variable scenarios. We introduce a new technique for solving this problem based on results from adaptive control theory and show that we achieve better performance than previous approaches on a broader class of energy source data sets. Additionally, we include a tunable mechanism for reducing the variance of the node's duty cycle over time, which is an important feature in tasks such as event monitoring. We obtain reductions in variance as great as two-thirds without compromising task performance or ability to maintain energy neutral operation.
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paper_title: A survey on power control issues in wireless sensor networks

paper_content:

A vehicle suspension assembly for tandem drive axles has a suspension system for each axle. Each suspension system incorporates two lower torque beams on each side of the vehicle and a single central upper torque rod. A central hanger is mounted between the two axles. The lower torque beams are pivotally connected between the hanger and an axle seat. A straddle bracket connects the axle to the axle seat in a hinged fashion. The upper central torque rod is connected between the upper side of the axle housing and the chassis. The lower torque beams act as a parallelogram to stabilize the axle seat. They also act together with a portion of the axle seat as a composite lower torque rod cooperating with the upper torque rod to stabilize the axle.
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paper_title: Priority-based Routing for Solar-Powered Wireless Sensor Networks

paper_content:

Rapid advances in wireless sensor networks require routing protocols which can accommodate new types of power source and data of differing priorities. We describe a priority-based geographical routing scheme based on a solar-cell energy model. It exploits an algorithm (APOLLO) that periodically and locally determines the topological knowledge range of each node, based on an estimated energy budget for the following period which includes the current energy, the predicted energy consumption, and the energy expected from the solar cell. The second algorithm (PISA) runs on each node and uses its knowledge range to determine a route which meets the objectives of each priority level in terms of path delay and energy consumption. These algorithms maximize scalability and minimize memory requirements by employing a localized geographical routing method which only uses information about a node and its adjacent neighbors
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paper_title: Adaptive power management in energy harvesting systems

paper_content:

Recently, there has been a substantial interest in the design of systems that receive their energy from regenerative sources such as solar cells. In contrast to approaches that attempt to minimize the power consumption we are concerned with adapting parameters of the application such that a maximal utility is obtained while respecting the limited and time-varying amount of available energy. Instead of solving the optimization problem on-line which may be prohibitively complex in terms of running time and energy consumption, we propose a parameterized specification and the computation of a corresponding optimal on-line controller. The efficiency of the new approach is demonstrated by experimental results and measurements on a sensor node.
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paper_title: Directed diffusion: a scalable and robust communication paradigm for sensor networks

paper_content:

Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.
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paper_title: Performance aware tasking for environmentally powered sensor networks

paper_content:

Performance Aware Tasking for Environmentally Powered Sensor Networks Aman Kansal, Dunny Potter and Mani B Srivastava Department of Electrical Engineering University of California, Los Angeles Los Angeles, CA, USA kansal,dpotter,mbs @ee.ucla.edu ABSTRACT The use of environmental energy is now emerging as a feasible en- ergy source for embedded and wireless computing systems such as sensor networks where manual recharging or replacement of bat- teries is not practical. However, energy supply from environmental sources is highly variable with time. Further, for a distributed sys- tem, the energy available at its various locations will be different. These variations strongly inﬂuence the way in which environmental energy is used. We present a harvesting theory for determining per- formance in such systems. First we present a model for characteriz- ing environmental sources. Second, we state and prove two harvest- ing theorems that help determine the sustainable performance level from a particular source. This theory leads to practical techniques for scheduling processes in energy harvesting systems. Third, we present our implementation of a real embedded system that runs on solar energy and uses our harvesting techniques. The system adjusts its performance level in response to available resources. Fourth, we propose a localized algorithm for increasing the perfor- mance of a distributed system by adapting the process scheduling to the spatio-temporal characteristics of the environmental energy in the distributed system. While our theoretical intuition is based on certain abstractions, all the scheduling methods we present are motivated solely from the experimental behavior and resource con- straints of practical sensor networking systems. 1. INTRODUCTION Several prototypes and research efforts have demonstrated the usefulness of sensor networks [1, 2, 3] for a wide variety of ap- plications spanning defense [4], education [5, 6], science [7, 8], to arts and entertainment [9]. However, energy supply still remains one of the open challenges in such systems because unfettered de- ployment rules out traditional wall socket supplies and batteries with acceptable form factor and cost constraints do not yield the lifetimes desired by most applications. One method to improve the battery lifetime of such systems is to supplement the battery supply with environmental energy. Sev- eral technologies exist to extract energy from the environment such as solar, thermal, optical and kinetic energy, vibrational [10, 11, 12, 13, 14, 15]. However, system level methods to efﬁciently ex- ploit these resources for optimal performance are lacking. Sensor networks are expected to be deployed for several mission critical tasks and operate unattended for extended durations. This makes performance awareness crucial. Environmental sources are highly variable. A key concern then is ensuring a desired level of perfor- mance even as the source varies. In distributed systems, not only does the energy source vary in time, but also the energy available at different locations, and thus at different nodes of the sensor net- work differs. Energy consumption at different nodes may not be uniform either. In this situation, the performance can be improved by scheduling tasks according to the spatio-temporal characteris- tics of energy availability. The problem then, is to ﬁnd schedul- ing mechanisms which can adapt the performance to the available energy proﬁle. We address the problems mentioned above, both analytically and in experiments on our custom designed harvesting hardware. Categories and Subject Descriptors C.2.4 [Computer Systems Organization]: Computer Communi- cation Networks—Distributed Systems; C.4 [Computer Systems Organization]: Performance of Systems; G.m [Mathematics of Computing]: Miscellaneous General Terms Performance, Theory, Algorithms, Experimentation 1.1 Contributions of this paper This paper makes several contributions towards achieving a sus- tainable performance in systems using energy harvesting facilities. First, we develop an analytically tractable characterization for en- ergy sources that can be used for deriving performance bounds. This is a very ﬂexible model which can handle a wide variety of en- ergy sources ranging from natural ones like solar energy to robotic energy delivery. Next, we propose a harvesting theory that helps to determine performance levels given the energy source classiﬁcation. This theory aims to answer questions such as the following. What is the minimum latency for a particular application in a given energy environment? What performance level can a system achieve if it must survive eternally (until its hardware gets outdated or dam- aged) from environmental sources? What additional resources may be needed if a particular quality of service must be achieved? The Keywords energy harvesting, process scheduling, performance guarantees Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proﬁt or commercial advantage and that copies bear this notice and the full citation on the ﬁrst page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior speciﬁc permission and/or a fee. SIGMETRICS/Performance’04 June 12-16, 2004, New York, NY, USA. Copyright 2004 ACM 1-58113-873-3/04/0006 ...$5.00.
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paper_title: Harvesting aware power management for sensor networks

paper_content:

Energy harvesting offers a promising alternative to solve the sustainability limitations arising from battery size constraints in sensor networks. Several considerations in using an environmental energy source are fundamentally different from using batteries. Rather than a limit on the total energy, harvesting transducers impose a limit on the instantaneous power available. Further, environmental energy availability is often highly variable and a deterministic metric such as residual battery capacity is not available to characterize the energy source. The different nodes in a sensor network may also have different energy harvesting opportunities. Since the same end-user performance may be achieved using different workload allocations at multiple nodes, it is important to adapt the workload allocation to the spatio-temporal energy availability profile in order to enable energy-neutral operation of the network. This paper describes power management techniques for such energy harvesting sensor networks. Platform design considerations as well as power scaling techniques at the node-level and network-level are described.
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paper_title: Energy aware routing for low energy ad hoc sensor networks

paper_content:

The recent interest in sensor networks has led to a number of routing schemes that use the limited resources available at sensor nodes more efficiently. These schemes typically try to find the minimum energy path to optimize energy usage at a node. In this paper we take the view that always using lowest energy paths may not be optimal from the point of view of network lifetime and long-term connectivity. To optimize these measures, we propose a new scheme called energy aware routing that uses sub-optimal paths occasionally to provide substantial gains. Simulation results are also presented that show increase in network lifetimes of up to 40% over comparable schemes like directed diffusion routing. Nodes also burn energy in a more equitable way across the network ensuring a more graceful degradation of service with time.
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paper_title: Utilizing solar power in wireless sensor networks

paper_content:

Sensor networks are designed especially for deployment in adverse and non-accessible areas without a fixed infrastructure. Therefore, energy conservation plays a crucial role for these networks. We propose to utilize solar power in wireless sensor networks, establishing a topology where, changing over time, some nodes can receive and transmit packets without consuming the limited battery resources. We propose and evaluate two protocols that perform solar-aware routing. The presented simulation results show that both protocols provide significant energy savings when utilizing solar power. The paper shows that incorporating the solar status of nodes in the routing decision is feasible and results in reduced overall battery consumption.
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paper_title: Maximizing the Lifetime of Wireless Sensor Networks through Optimal Single-Session Flow Routing

paper_content:

Wireless sensor networks are becoming increasingly important in recent years due to their ability to detect and convey real-time, in-situ information for many civilian and military applications. A fundamental challenge for such networks lies in energy constraint, which poses a performance limit on the achievable network lifetime. We consider a two-tier wireless sensor network and address the network lifetime problem for upper-tier aggregation and forwarding nodes (AFNs). Existing flow routing solutions proposed for maximizing network lifetime require AFNs to split flows to different paths during transmission, which we call multisession flow routing solutions. If an AFN is equipped with a single transmitter/receiver pair, a multisession flow routing solution requires a packet-level power control at the AFN so as to conserve energy, which calls for considerable overhead in synchronization among the AFNs. In this paper, we show that it is possible to achieve the same optimal network lifetime by power control on a much larger timescale with the so-called single-session flow routing solutions, under which the packet-level power control and, thus, strict requirement on synchronization are not necessary. We also show how to perform optimal single-session flow routing when the bit-rate of composite flows generated by AFNs is time-varying, as long as the average bit-rate can be estimated
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paper_title: Online power-aware routing in wireless Ad-hoc networks

paper_content:

This paper discusses online power-aware routing in large wireless ad-hoc networks for applications where the message sequence is not known. We seek to optimize the lifetime of the network. We show that online power-aware routing does not have a constant competitive ratio to the off-line optimal algorithm. We develop an approximation algorithm called max-min zP min that has a good empirical competitive ratio. To ensure scalability, we introduce a second online algorithm for power-aware routing. This hierarchical algorithm is called zone-based routing. Our experiments show that its performance is quite good.
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paper_title: Low-Latency Geographic Routing for Asynchronous Energy-Harvesting WSNs

paper_content:

Research on data routing strategies for wireless sensor networks (WSNs) has largely focused on energy efficiency. However rapid advances in WSNs require routing protocols which can accommodate new types of energy source and data of requiring short end-to-end delay. In this paper, we describe a duty-cycle-based low-latency geographic routing for asynchronous energy-harvesting WSNs. It uses an algorithm (D-APOLLO) that periodically and locally determines the topological knowledge range and duty-cycle of each node, based on an estimated energy budget for each period which includes the currently available energy, the predicted energy consumption, and the energy expected from the harvesting device. This facilitates a low latency routing scheme which considers both geographic and duty-cycle information about the neighbors of a node, so that data can be routed efficiently and delivered to the sink as quickly as possible. Simulation results confirm that our routing scheme can deliver data to the sink with high reliability and low latency.
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paper_title: X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor networks

paper_content:

In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this “low power listening” approach is simple, asynchronous, and energy-efficient, the long preamble introduces excess latency at each hop, is suboptimal in terms of energy consumption, and suffers from excess energy consumption at nontarget receivers. X-MAC proposes solutions to each of these problems by employing a shortened preamble approach that retains the advantages of low power listening, namely low power communication, simplicity and a decoupling of transmitter and receiver sleep schedules. We demonstrate through implementation and evaluation in a wireless sensor testbed that X-MAC’s shortened preamble approach significantly reduces energy usage at both the transmitter and receiver, reduces per-hop latency, and offers additional advantages such as flexible adaptation to both bursty and periodic sensor data sources.
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paper_title: A survey of multicast routing protocols for mobile Ad-Hoc networks

paper_content:

A Mobile Ad-hoc NETwork (MANET) is composed of Mobile Nodes (MNs) without any infrastructure. MNs selforganize to form a network over radio links. In this environment, multicast routing protocols are faced with the challenge of producing multi-hop routing under host mobility and bandwidth constraint. Multicast routing plays a significant role in MANETs. In recent years, various multicast routing protocols with distinguishing feature have been newly proposed. In order to provide a comprehensive understanding of these multicast routing protocols designed for MANETs and pave the way for the further research, a survey of the multicast routing protocols is discussed in detail in this paper. Qualitatively, based on their primary multicast routing selection principle, we show that all these protocols could be placed under one of two broad routing selection categories: multicast routing based on application independence and multicast routing based on application dependence.
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paper_title: Low-latency routing for energy-harvesting sensor networks

paper_content:

This paper presents low-latency routing strategies that take account of energy-harvesting sensor nodes in wireless sensor networks. Currently, in the case of tree-based network connectivity, 'lazy' nodes with a long interval between computational activities may slow down communication if deployed along a routing path. To cope with this problem, we suggest a random graph in which a node may have multiple parent nodes, thus allowing a choice of path to the sink node. We also propose three path selection schemes for the network topology on the basis of (a) the cost of a single hop from the current node, (b) the cost of two hops, and (c) the cost of a single hop plus a cost estimate for the remainder of the path to the sink, respectively. The proposed strategies are shown to outperform the existing routing algorithm for a tree-structured energy-harvesting sensor network.
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paper_title: Priority-based Routing for Solar-Powered Wireless Sensor Networks

paper_content:

Rapid advances in wireless sensor networks require routing protocols which can accommodate new types of power source and data of differing priorities. We describe a priority-based geographical routing scheme based on a solar-cell energy model. It exploits an algorithm (APOLLO) that periodically and locally determines the topological knowledge range of each node, based on an estimated energy budget for the following period which includes the current energy, the predicted energy consumption, and the energy expected from the solar cell. The second algorithm (PISA) runs on each node and uses its knowledge range to determine a route which meets the objectives of each priority level in terms of path delay and energy consumption. These algorithms maximize scalability and minimize memory requirements by employing a localized geographical routing method which only uses information about a node and its adjacent neighbors
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paper_title: Energy-efficient communication protocol for wireless microsensor networks

paper_content:

Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.
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paper_title: A design framework and taxonomy for hybrid routing protocols in mobile Ad Hoc networks

paper_content:

Routing protocols for mobile ad hoc networks can be classified into two categories: topological routing and geographic routing. Hybrid routing protocols that take advantage of both schemes have attracted a lot of attention recently. This article provides a systematic survey of these hybrid routing protocols. We first analyze the three types of routing information used in the hybrid routing protocols, namely, topological information, geographic information, and hierarchy information. Then, based on a review of the representative hybrid routing protocols, we summarize the three design options for hybrid routing protocols, namely, radius of the routing zone (1, k, or D), geographic information (position or position plus partition), and routing structure (flat or hierarchical). Finally, we propose a three-dimensional design framework that can accommodate well all of the existing hybrid routing protocols. The framework also helps find the unexplored design space, motivating the design of new hybrid routing protocols.
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paper_title: Steady and fair rate allocation for rechargeable sensors in perpetual sensor networks

paper_content:

Renewable energy enables sensor networks with the capability to recharge and provide perpetual data services. Due to low recharging rates and the dynamics of renewable energy such as solar and wind power, providing services without interruptions caused by battery runouts is non-trivial. Most environment monitoring applications require data collection from all nodes at a steady rate. The objective of this paper is to design a solution for fair and high throughput data extraction from all nodes in presence of renewable energy sources. Specifically, we seek to compute the lexicographically maximum data collection rate for each node, such that no node will ever run out of energy. We propose a centralized algorithm and an asynchronous distributed algorithm that can compute the optimal lexicographic rate assignment for all nodes. The centralized algorithm jointly computes the optimal data collection rate for all nodes along with the flows on each link, while the distributed algorithm computes the optimal rate when the routes are pre-determined. We prove the optimality for both the centralized and the distributed algorithms, and use a testbed with 155 sensor nodes to validate the distributed algorithm.
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paper_title: An evaluation of multi-resolution storage for sensor networks

paper_content:

Wireless sensor networks enable dense sensing of the environment, offering unprecedented opportunities for observing the physical world. Centralized data collection and analysis adversely impact sensor node lifetime. Previous sensor network research has, therefore, focused on in network aggregation and query processing, but has done so for applications where the features of interest are known a priori. When features are not known a priori, as is the case with many scientific applications in dense sensor arrays, efficient support for multi-resolution storage and iterative, drill-down queries is essential.Our system demonstrates the use of in-network wavelet-based summarization and progressive aging of summaries in support of long-term querying in storage and communication-constrained networks. We evaluate the performance of our linux implementation and show that it achieves: (a) low communication overhead for multi-resolution summarization, (b) highly efficient drill-down search over such summaries, and (c) efficient use of network storage capacity through load-balancing and progressive aging of summaries.
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paper_title: Energetic sustainability of environmentally powered wireless sensor networks

paper_content:

Environmentally-powered wireless sensor networks (WSNs) exploit renewable energy sources to make the lifetime of sensor nodes theoretically unlimited. This perspective requires a paradigm shift in the design of energy-aware WSNs: Instead of maximizing the lifetime under given energy constraints, we need to maximize the workload that can be sustained by a given distribution of environmental power. This paper formulates the maximum energetically sustainable workload problem (MESW) and we shows that it can be cast into an instance of a modified max-flow problem
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paper_title: Data-aggregation techniques in sensor networks: a survey

paper_content:

Wireless sensor networks consist of sensor nodes with sensing and com- munication capabilities. We focus on data-aggregation problems in energy- constrained sensor networks. The main goal of data-aggregation algorithms is to gather and aggregate data in an energy efficient manner so that net- work lifetime is enhanced. In this article we present a survey of data-aggre- gation algorithms in wireless sensor networks. We compare and contrast different algorithms on the basis of performance measures such as lifetime, latency, and data accuracy. We conclude with possible future research directions.
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paper_title: A Data Gathering Scheme for Environmental Energy-Based Wireless Sensor Networks

paper_content:

Prolongation of network lifetime is one of the most important issues of sensor networks. EEHF (Environmental Energy Harvesting Framework) is a framework that includes a data gathering scheme and estimates the energy gained from the environment by using the periodicity of environmental power. Thus, sensor nodes can use environmental energy efficiently and the network lifetime is extended. However, since the accuracy of the estimation depends on the length of the period, and the data gathering scheme used in EEHF does not take environmental energy into consideration, this method has room for improvement. In this paper, we propose a more accurate and adaptive energy estimation method that does not depend on the length of the period, and a data gathering scheme that is optimized for the environmental energy-based sensor network, in order to prolong the lifetime of environmental energy-based sensor networks.
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paper_title: A survey of clustering schemes for mobile ad hoc networks

paper_content:

Clustering is an important research topic for mobile ad hoc networks (MANETs) because clustering makes it possible to guarantee basic levels of system performance, such as throughput and delay, in the presence of both mobility and a large number of mobile terminals. A large variety of approaches for ad hoc clustering have been presented, whereby different approaches typically focus on different performance metrics. This article presents a comprehensive survey of recently proposed clustering algorithms, which we classify based on their objectives. This survey provides descriptions of the mechanisms, evaluations of their performance and cost, and discussions of advantages and disadvantages of each clustering scheme. With this article, readers can have a more thorough and delicate understanding of ad hoc clustering and the research trends in this area.
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paper_title: Adaptive Control of Duty Cycling in Energy-Harvesting Wireless Sensor Networks

paper_content:

Increasingly many wireless sensor network deployments are using harvested environmental energy to extend system lifetime. Because the temporal profiles of such energy sources exhibit great variability due to dynamic weather patterns, an important problem is designing an adaptive duty-cycling mechanism that allows sensor nodes to maintain their power supply at sufficient levels (energy neutral operation) by adapting to changing environmental conditions. Existing techniques to address this problem are minimally adaptive and assume a priori knowledge of the energy profile. While such approaches are reasonable in environments that exhibit low variance, we find that it is highly inefficient in more variable scenarios. We introduce a new technique for solving this problem based on results from adaptive control theory and show that we achieve better performance than previous approaches on a broader class of energy source data sets. Additionally, we include a tunable mechanism for reducing the variance of the node's duty cycle over time, which is an important feature in tasks such as event monitoring. We obtain reductions in variance as great as two-thirds without compromising task performance or ability to maintain energy neutral operation.
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paper_title: Energetic sustainability of routing algorithms for energy-harvesting wireless sensor networks

paper_content:

A new class of wireless sensor networks that harvest power from the environment is emerging because of its intrinsic capability of providing unbounded lifetime. While a lot of research has been focused on energy-aware routing schemes tailored to battery-operated networks, the problem of optimal routing for energy harvesting wireless sensor networks (EH-WSNs) has never been explored. The objective of routing optimization in this context is not extending network lifetime, but maximizing the workload that can be autonomously sustained by the network. In this work we present a methodology for assessing the energy efficiency of routing algorithms for networks whose nodes drain power from the environment. We first introduce the energetic sustainability problem, then we define the maximum energetically sustainable workload (MESW) as the objective function to be used to drive the optimization of routing algorithms for EH-WSNs. We propose a methodology that makes use of graph algorithms and network simulations for evaluating the MESW starting from a network topology, a routing algorithm and a distribution of the environmental power available at each node. We present a tool flow implementing the proposed methodology and we show comparative results achieved on several routing algorithms. Experimental results highlight that routing strategies that do not take into account environmental power do not provide optimal results in terms of workload sustainability. Using optimal routing algorithms may lead to sizeable enhancements of the maximum sustainable workload. Moreover, optimality strongly depends on environmental power configurations. Since environmental power sources change over time, our results prompt for a new class of routing algorithms for EH-WSNs that are able to dynamically adapt to time-varying environmental conditions.
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paper_title: On k-coverage in a mostly sleeping sensor network

paper_content:

Sensor networks are often desired to last many times longer than the active lifetime of individual sensors. This is usually achieved by putting sensors to sleep for most of their lifetime. On the other hand, event monitoring applications require guaranteed k-coverage of the protected region at all times. As a result, determining the appropriate number of sensors to deploy that achieves both goals simultaneously becomes a challenging problem. In this paper, we consider three kinds of deployments for a sensor network on a unit square--a √n × √n grid, random uniform (for all n points), and Poisson (with density n). In all three deployments, each sensor is active with probability p, independently from the others. Then, we claim that the critical value of the function npπ r2/ log(np) is 1 for the event of k-coverage of every point. We also provide an upper bound on the window of this phase transition. Although the conditions for the three deployments are similar, we obtain sharper bounds for the random deployments than the grid deployment, which occurs due to the boundary condition. In this paper, we also provide corrections to previously published results. Finally, we use simulation to show the usefulness of our analysis in real deployment scenarios.
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paper_title: AN ADAPTIVE ENERGY EFFICIENT MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS

paper_content:

Sensor networks are deployed in remote locations with limited processor capabilities, memory capacities, and battery supplies. Wireless Sensor Networks (WSN) detects environmental information with sensors in remote settings. One problem facing WSNs is the inability to resupply power to these energy-constrained devices due to their remoteness. Therefore to extend a WSN's effectiveness, the lifetime of the network must be increased by making them as energy efficient as possible. An energy-efficient medium access control (MAC) can boost a WSN's lifetime. This paper focuses on a protocol stack solution that deals with MAC layer, that minimizes the energy consumption and delay required to transmit packets across the network. It is based on Sensor Medium Access Control (S-MAC) called Adaptive SMAC protocol designed for sensor networks. It enables low duty cycle operation in a multi-hop network and common sleep schedules to reduce control overhead and enable traffic adaptive wakeup. To reduce control overhead and latency, introduces coordinated sleeping among neighboring nodes. It is a contention based protocol based on CSMA/CA mechanism. This protocol is simulated in NS-2 and performance evaluated using various topologies under various traffic conditions. In addition with this we tried to improve the energy efficiency of Adaptive SMAC with the help of a new design called Adaptive Cross MAC protocol
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paper_title: Integrated coverage and connectivity configuration in wireless sensor networks

paper_content:

An effective approach for energy conservation in wireless sensor networks is scheduling sleep intervals for extraneous nodes, while the remaining nodes stay active to provide continuous service. For the sensor network to operate successfully, the active nodes must maintain both sensing coverage and network connectivity. Furthermore, the network must be able to configure itself to any feasible degrees of coverage and connectivity in order to support different applications and environments with diverse requirements. This paper presents the design and analysis of novel protocols that can dynamically configure a network to achieve guaranteed degrees of coverage and connectivity. This work differs from existing connectivity or coverage maintenance protocols in several key ways: 1) We present a Coverage Configuration Protocol (CCP) that can provide different degrees of coverage requested by applications. This flexibility allows the network to self-configure for a wide range of applications and (possibly dynamic) environments. 2) We provide a geometric analysis of the relationship between coverage and connectivity. This analysis yields key insights for treating coverage and connectivity in a unified framework: this is in sharp contrast to several existing approaches that address the two problems in isolation. 3) Finally, we integrate CCP with SPAN to provide both coverage and connectivity guarantees. We demonstrate the capability of our protocols to provide guaranteed coverage and connectivity configurations, through both geometric analysis and extensive simulations.
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paper_title: A survey, classification and comparative analysis of medium access control protocols for ad hoc networks

paper_content:

Recent technological advances in wireless communications offer new opportunities and challenges for wireless ad hoc networking. In the absence of the fixed infrastructure that characterizes traditional wireless networks, control and management of wireless ad hoc networks must be distributed across the nodes, thus requiring carefully designed medium access control (MAC) layer protocols. In this article we survey, classify, and analyze 34 MAC layer protocols for wireless ad hoc networks, ranging from industry standards to research proposals. Through this analysis, six key features emerge: (1) channel separation and access; (2) topology; (3) power; (4) transmission initiation; (5) traffic load and scalability; and (6) range. These features allow us to characterize and classify the protocols, to analyze the tradeoffs produced by different design decisions, and to assess the suitability of various design combinations for ad hoc network applications. The classification and the tradeoff analysis yield design guidelines for future wireless ad hoc network MAC layer protocols.
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paper_title: RI-MAC: a receiver-initiated asynchronous duty cycle MAC protocol for dynamic traffic loads in wireless sensor networks

paper_content:

The problem of idle listening is one of the most significant sources of energy consumption in wireless sensor nodes, and many techniques have been proposed based on duty cycling to reduce this cost. In this paper, we present a new asynchronous duty cycle MAC protocol, called Receiver-Initiated MAC (RI-MAC), that uses receiver-initiated data transmission in order to efficiently and effectively operate over a wide range of traffic loads. RI-MAC attempts to minimize the time a sender and its intended receiver occupy the wireless medium to find a rendezvous time for exchanging data, while still decoupling the sender and receiver's duty cycle schedules. We show the performance of RI-MAC through detailed ns-2 simulation and through measurements of an implementation in TinyOS in a testbed of MICAz motes. Compared to the prior asynchronous duty cycling approach of X-MAC, RI-MAC achieves higher throughput, packet delivery ratio, and power efficiency under a wide range of traffic loads. Especially when there are contending flows, such as bursty traffic or transmissions from hidden nodes, RI-MAC significantly improves throughput and packet delivery ratio. Even under light traffic load for which X-MAC is optimized, RI-MAC achieves the same high performance in terms of packet delivery ratio and latency while maintaining comparable power efficiency.
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paper_title: RT-Link: A global time-synchronized link protocol for sensor networks

paper_content:

For real-time wireless communication in industrial control, surveillance and inventory tracking, we propose RT-Link, a time-synchronized link protocol. RT-Link provides predictable lifetime for battery-operated embedded nodes, bounded end-to-end delay across multiple hops, and collision-free operation. We investigate the use of hardware-based time-synchronization for infrastructure nodes by using an AM carrier-current radio for indoors and atomic clock receivers for outdoors. Mobile nodes are synchronized via in-band software synchronization within the same framework. Through the design and deployment of RT-Link, we identify three key observations: (a) Hardware-based global time-synchronization is a robust and scalable option to in-band software-based techniques. (b) Achieving global time-synchronization is both economical and convenient for indoor and outdoor deployments. (c) RT-Link achieves a practical lifetime of over 2 years. By analysis and simulation, we show that RT-Link outperforms energy-efficient low-power-listen CSMA protocols in terms of node lifetime and end-to-end latency. The protocol supports flexible services such as on-demand end-to-end rate control and logical topology control. We implemented RT-Link on the CMU FireFly sensor platform as a link layer running on the Nano-RK real-time sensor OS. We also discuss deployment experiences using RT-Link in a coal mine safety application.
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paper_title: Versatile low power media access for wireless sensor networks

paper_content:

We propose B-MAC, a carrier sense media access protocol for wireless sensor networks that provides a flexible interface to obtain ultra low power operation, effective collision avoidance, and high channel utilization. To achieve low power operation, B-MAC employs an adaptive preamble sampling scheme to reduce duty cycle and minimize idle listening. B-MAC supports on-the-fly reconfiguration and provides bidirectional interfaces for system services to optimize performance, whether it be for throughput, latency, or power conservation. We build an analytical model of a class of sensor network applications. We use the model to show the effect of changing B-MAC's parameters and predict the behavior of sensor network applications. By comparing B-MAC to conventional 802.11-inspired protocols, specifically SMAC, we develop an experimental characterization of B-MAC over a wide range of network conditions. We show that B-MAC's flexibility results in better packet delivery rates, throughput, latency, and energy consumption than S-MAC. By deploying a real world monitoring application with multihop networking, we validate our protocol design and model. Our results illustrate the need for flexible protocols to effectively realize energy efficient sensor network applications.
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paper_title: An energy-efficient MAC protocol for wireless sensor networks

paper_content:

This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s.
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paper_title: X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor networks

paper_content:

In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this “low power listening” approach is simple, asynchronous, and energy-efficient, the long preamble introduces excess latency at each hop, is suboptimal in terms of energy consumption, and suffers from excess energy consumption at nontarget receivers. X-MAC proposes solutions to each of these problems by employing a shortened preamble approach that retains the advantages of low power listening, namely low power communication, simplicity and a decoupling of transmitter and receiver sleep schedules. We demonstrate through implementation and evaluation in a wireless sensor testbed that X-MAC’s shortened preamble approach significantly reduces energy usage at both the transmitter and receiver, reduces per-hop latency, and offers additional advantages such as flexible adaptation to both bursty and periodic sensor data sources.
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Title: Energy Harvesting Sensor Nodes: Survey and Implications

Section 1: INTRODUCTION
Description 1: Introduce the concept of sensor networks and discuss the challenges and limitations associated with battery-powered sensor nodes. Introduce energy harvesting as a solution and outline the contributions and structure of the paper.

Section 2: ENERGY HARVESTING SENSOR NODES
Description 2: Describe the definition, importance, and general mechanisms of energy harvesting for sensor nodes. Present the major components: energy sources, harvesting architectures, and the load.

Section 3: Energy Harvesting Architectures
Description 3: Detail the two main types of architectures, Harvest-Use and Harvest-Store-Use, and discuss their features and applications.

Section 4: Sources of Harvestable Energy
Description 4: Explain the various types of ambient energy sources and human power sources, detailing their controllability, predictability, and general characteristics.

Section 5: Energy Conversion Mechanisms
Description 5: Describe the methods by which energy from different sources is converted into electrical energy for sensor nodes, including solar panels, piezo-electric materials, and wind turbines.

Section 6: Storage Technologies
Description 6: Discuss the various storage technologies, with a focus on batteries (Lithium-ion, NiMH) and super-capacitors, their characteristics, advantages and disadvantages.

Section 7: ENERGY HARVESTING SENSOR NODES AND APPLICATIONS
Description 7: Provide examples of sensor nodes using different energy harvesting methods (solar, human power, wind, RF), and review specific applications of these technologies.

Section 8: IMPLICATIONS ON SENSOR NETWORK SYSTEMS AND SOLUTIONS
Description 8: Discuss the impact of energy harvesting on sensor network design, focusing on optimizing lifetime and performance. Explain concepts like energy neutral operation, performance adaptation, and the effects on routing, clustering, data collection, and other network-level design considerations.

Section 9: CONCLUSIONS
Description 9: Summarize the potential of energy harvesting for addressing the challenge of finite energy in sensor networks, recapping the main findings and suggesting directions for future research.