Browsing by Subject "Wireless sensor networks"
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Item Acknowledgment Strategies for Efficient Asymmetric Routing in Energy Harvesting Wireless Sensor Networks(2013-05) Gade, Tejaswi; Lim, Sunho; Youn, EunseogEnergy conservation has been a primary concern in wireless sensor networks (WSNs), where long-term operations are often required in hard-reach environments. Due to unavoidable batteries replacement or replenishment, diverse energy harvesting techniques have been integrated with WSNs to overcome limited battery power and extend the network lifetime. However, variable transmission power levels caused by non-uniform energy harvesting rates can lead to asymmetric links. In this document, we propose weighted and lazy acknowledgment schemes and their combination to efficiently route sensory data to a sink over asymmetric links. The weighted acknowledgment (WACK) can differentiate multiple paths between data source and the sink by assigning multiplicative weights on the paths. The lazy acknowledgment (LACK) can assure reverse path by waiting for extended communication range. An asymmetric link aware backoff mechanism is also proposed to avoid data contention and collision. We compare the proposed schemes through extensive simulation experiments and their results indicate that the proposed acknowledgment strategies can be a viable approach in energy harvesting WSNs.Item An adaptive gossip protocol for improving communication performance in wireless sensor networks(2012-05) Murali, Deepika; Lim, Sunho; Lopez-Benitez, NoeA Wireless Sensor Network (WSN) consists of a set of battery-powered devices (later in short, nodes) equipped with sensing, computing, and communicating capabilities, and it is rapidly integrated with various real-world applications in civil and military environments. Due to the limited amount of battery energy, however, a great deal of research efforts has been devoted on developing energy efficient techniques in the WSNs. In this thesis, we propose an Adaptive Gossip Protocol (AGP) to improve the communication performance in terms of packet delivery ratio, packet latency, and energy consumption under the energy-constrained WSNs. In the proposed AGP, a node decides whether it should participate in the communication based on a gossiping probability. If the node participates in the communication, it judiciously selects a set of candidate nodes for forwarding. Otherwise, the node decides whether it should sleep based on a sleeping probability. Here, gossiping probability is determined by the number of neighbor nodes but sleeping probability is determined by both the number of neighbor nodes and remaining of battery energy. We build a discrete-event driven simulator using CSIM20 and compare the proposed scheme with conventional flooding and simple gossiping techniques. Extensive performance study shows that the proposed scheme can save the energy consumption up to 12% and reduce the packet latency 5 times in comparison to flooding and gossiping techniques. The proposed scheme also shows the competitive packet delivery ratio, and thus it is a viable approach for WSNs.Item An energy harvesting aware data dissemination strategy for energy rechargeable wireless sensor networks(2012-08) Gosavi, Amit; Lim, Sunho; Lakhani, GopalA wireless sensor network (WSN) is often deployed in a harsh or hard-reach area and is required to operate for a long period time to collect and route sensed information. Since each sensor node (later node) is battery-powered, prudent energy-efficient mechanisms have been proposed to extend the network life-time. However, recharging (or replacing) battery is ultimately unavoidable. In this thesis, we consider energy harvesting (or scavenging) with environmental energy sources, such as solar, wind, or vibration. Then we extend the original sensor protocols for information via negotiation (SPIN) and propose an energy harvesting aware data dissemination strategy for energy rechargeable wireless sensor networks, called Green-SPIN. In Green-SPIN, each node intermittently harvests energy and judiciously changes its communication range. We compare the performance of three data dissemination schemes as a function of number of nodes and the communication range through extensive simulation: Flooding, SPIN with broadcast (SPIN-BC), SPIN with reliability (SPIN-RL), and Green-SPIN. Our simulation results indicate that the proposed scheme achieves more data dissemination rate than the SPIN-RL in the low node density and short communication range. Compared to Flooding and SPIN-BC, both proposed scheme and SPIN-RL show two times higher data dissemination rate. The proposed scheme also shows competitive performance with SPIN-RL in high node density and extended communication range. In addition, the proposed scheme transmits similar number of data packets with the SPIN-RL.Item Design of an electromagnetic vibration energy harvester for structural health monitoring of bridges employing wireless sensor networks(2011-08) Dierks, Eric Carl; Wood, Kristin L.; Crawford, Richard H.Energy harvesting is playing an increasingly important role in supplying power to monitoring and automation systems such as structural health monitoring using wireless sensor networks. This importance is most notable when the structures to be monitored are in rural, hazardous, or limited access environments such as busy highway bridges where traffic would be greatly disrupted during maintenance, inspection, or battery replacement. This thesis provides an overview of energy harvesting technologies and details the design, prototyping, testing, and simulation of an energy harvester which converts the vibrations of steel highway bridges into stored electrical energy through the use of a translational electromagnetic generator, to power a wireless sensor network for bridge structural health monitoring. An analysis of bridge vibrations, the use of nonlinear and linear harvester compliance, resonant frequency tuning, and bandwidth widening to maximize the energy harvested is presented. The design approach follows broad and focused background research, functional analysis, broad and focused concept generation and selection, early prototyping, parametric modeling and simulation, rapid prototyping with selective laser sintering, and laboratory testing with replicated bridge vibration. The key outcomes of the work are: a breadth of conceptual designs, extensive literature review, a prototype which harvests an average of 80µW under bridge vibration, a prototype which provides quick assembly, mounting and tuning, and the conclusion that a linear harvester out performs a nonlinear harvester with stiffening magnetic compliance for aperiodic vibrations such as those from highway bridges.Item Design, testing, and implementation of WiSeMote: A wireless sensor network for structural health monitoring(2012-05) Hoover, Davis; Karp, Tanja; Rice, Jennifer A.; Li, ChangzhiMuch research has been done toward the realization of wireless sensor networks (WSN's) that can detect damage by aggregating information in a distributed manner from civil structures. These networks are still bound by system limitations such as limited battery power, low processor speeds, and limited radio transmission throughput. While many systems have been presented that have the ability to practically perform damage detection with their limited resources, there still exists room for improvement in power consumption, noise immunity, and utilization of network resources. This research presents the WiSeMote: a new wireless sensor node and base station that improves upon the power consumption and noise immunity of existing systems. Performance characterization test results are shown for communication, time synchronization, noise immunity, and data quality. Furthermore, this research takes an existing strategy for damage detection and analyzes it from the perspective of our new sensor platform. This new strategy is also implemented on the WiSeMote in a more resource efficient manner. Improvements in power consumption, external memory usage, and processing time are made possible through a novel parallel processing strategy for real-time calculation.Item Innovative energy harvesting technology for wireless bridge monitoring systems(2011-08) Weaver, Jason Michael; Wood, Kristin L.; Crawford, Richard H.; Seepersad, Carolyn C.; Wilson, Preston; Wood, SharonEnergy harvesting is a promising and evolving field of research capable of supplying power to systems in a broad range of applications. In particular, the ability to gather energy directly from the environment without human intervention makes energy harvesting an excellent option for powering autonomous sensors in remote or hazardous locations. This dissertation examines the possibility of using energy harvesting in new and innovative ways to power wireless sensor nodes placed in the substructures of highway bridges for structural health monitoring. Estimates for power requirements are established, using a wireless sensor node from National Instruments as an example system. Available power in a bridge environment is calculated for different energy sources, including solar radiation, wind, and vibration from traffic. Feasibility of using energy harvesting in such an application is addressed for both power availability and cost as compared with grid power or primary batteries. An in-depth functional analysis of existing energy-harvesting systems is also presented, with insights into where innovation would be most beneficial in future systems. Finally, the development of a suite of complementary energy-harvesting devices is described. Because conditions on bridges may vary, multiple solutions involving different energy domains are desired, with the end user able to select the harvester most appropriate for the specific installation. Concept generation techniques such as mind-mapping and 6-3-5 (C-Sketch) are used to produce a wide variety of concepts, from which several promising concept variants are selected. The continued development for one concept, which harvests vibration using piezoelectric materials, is described. Analytical modeling is presented for static and dynamic loading, as well as predicted power generation. Two proof-of-concept prototypes are built and tested in laboratory conditions. Through the development of this prototype, it is shown that the example wireless sensor node can successfully be powered through energy harvesting, and insights are shared concerning the situations where this and other energy harvesters would be most appropriate.