Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 125-129).

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 84-86). Also available via World Wide Web.

Includes bibliographical references (p. 45-47).

This dissertation shows that with simple programming abstractions, network-wide resource coordination is efficient and useful for programming embedded sensor networks. Existing systems have focused primarily on managing resources for individual nodes, but a sensor network is not merely a collection of nodes operating independently: it must coordinate behavior across multiple nodes to achieve high efficiency. We need tools that can enable system-wide coordination at a higher level of abstraction than what exists today. We present three core contributions. The first is a service called IDEA that enables networkwide energy management for sensor networks. It unites energy monitoring, load modeling, and distributed state sharing into a single service that facilitates distributed decision making. Using simulation and testbed results, we show that IDEA enables improvements in network lifetime of up to 35% over approaches that do not consider energy distribution. Our second contribution is Karma, a system for coordinating insect-sized robotic microaerial vehicle (MAV) swarms, an emerging class of mobile sensor networks. Karmas system architecture simplifies the functionality of an individual MAV to a sequence of sensing and actuation commands called behaviors. Each behavior has an associated progress function, a measure of how much of that behavior has been completed. Programming is done by composing behaviors which are coordinated using input from the progress functions. Through simulation and testbed experiments, we demonstrate Karma applications can run on limited resources, are robust to individual MAV failure, and adapt to changes in the environment. Our final contribution is Simbeeotic, a testbed for MAV coordination algorithms. MAV sensors must be codesigned with the software and coordination algorithms that depend on them. This requires a testbed capable of simulating sensors to evaluate them before actual hardware is available and the ability to test with real flight dynamics for accurate control evaluation. In addition, simulation should be able to scale to hundreds or thousands of MAVs at a reduced level of fidelity in order to test at scale. We demonstrate that Simbeeotic provides the appropriate level of fidelity to evaluate prototype systems while maintaining the ability to test at scale. / Engineering and Applied Sciences

Τα Ασύρματα Δίκτυα Αισθητήρων (Wireless Sensor Networks, WSN) αποτελούν σήμερα ένα πολλά υποσχόμενο πεδίο έρευνας στον τομέα των ασύρματων επικοινωνιών. Ωστόσο, λόγω κάποιων από τις ιδιαιτερότητές τους, οι κόμβοι ενός WSN υπόκεινται σε λειτουργικούς και σχεδιαστικούς περιορισμούς, που δημιουργούν νέες προκλήσεις και αντικείμενα έρευνας με σκοπό τη βελτιστοποίηση της απόδοσης του δικτύου. Ένα τέτοιο αντικείμενο έρευνας αποτελεί και η συνδεσιμότητα του συνολικού δικτύου, μια έννοια καθοριστική για τη δυνατότητα επικοινωνίας μεταξύ των κόμβων και ανταλλαγής πληροφοριών επί της παρατηρούμενης διεργασίας. Η χρησιμότητα των WSN σε συνδυασμό με την απαίτηση για συνδεσιμότητα αποτέλεσαν το σημείο εκκίνησης για την παρούσα διπλωματική εργασία. Ποιο συγκεκριμένα, επιχειρήθηκε η μεγιστοποίηση της περιοχής επικοινωνιακής κάλυψης σε ένα WSN αλλά και του αριθμού των επικοινωνούντων κόμβων. Η ιδιαιτερότητα της έρευνας εντοπίζεται στη χρήση του Δείκτη Ισχύος Ληφθέντος Σήματος (RSSI) για την εξαγωγή συμπερασμάτων για τη συνδεσιμότητα του δικτύου. Υλοποιήθηκε συνεπώς ένα WSN, αποτελούμενο από ένα ζευγάρι κόμβων αποστολέας-παραλήπτης, των οποίων η επικοινωνία βασίζεται στο πρότυπο της IEEE 802.15.4. Στόχος της πειραματικής διαδικασίας αποτέλεσε η μέτρηση (στην μεριά του παραλήπτη) του RSSI και ο υπολογισμός του ποσοστού των επιτυχώς ληφθέντων πακέτων για την επικοινωνία μεταξύ αποστολέα-παραλήπτη, μεταβάλλοντας την προγραμματιζόμενη ισχύ εκπομπής του αποστολέα αλλά και τη θέση του παραλήπτη σε μια δεδομένη περιοχή ενδιαφέροντος. Από το στάδιο αυτό της πειραματικής διαδικασίας προέκυψε η περιοχή επικοινωνιακής κάλυψης ενός κόμβου για τα διάφορα προγραμματιζόμενα επίπεδα ισχύος εκπομπής. Τα αποτελέσματα αυτά συνέβαλαν στην ανάπτυξη αλγορίθμου βελτιστοποίησης της συνδεσιμότητας του δικτύου, με βάση τον οποίο αναζητήθηκε η μέγιστη επικοινωνιακή κάλυψη του δικτύου και ο μέγιστος αριθμός ζευγών επικοινωνούντων κόμβων. / Wireless Sensor Networks consist a new research domain in the field of wireless communications. However, they are under many constraints, whisch open new research in this field. One such field consitutes connectivity in Wireless Sensor Networks, which was the stimulus of this Diploma Thesis. The initial goal was the extraction of the maximization of the connunication range of the network and of the number of the nodes tha communicate. The parsticularity of the reserch is the m,easurement of the Received Signal Strength. We deployed tow nodes in the area of interest and measured this indicator. Then the results wereused in an algorithm for the optimization of the communication range and the number of communicating nodes in the network.

Wireless sensor networks are the collection of wireless nodes that are deployed to monitor certain phenomena of interest. Once the node takes measurements it transmits to a base station over a wireless channel. The base station collects data from all the nodes and do further analysis. To save energy, it is often useful to build clusters, and the head of each cluster communicates with the base station. Initially, we do the simulation analysis of the Zigbee networks where few nodes are more powerful than the other nodes. The results show that in the mobile heterogeneous sensor networks, due to phenomenon orphaning and high cost of route discovery and maintenance, the performance of the network degrades with respect to the homogeneous network. The core of this thesis is to empirically analyze the sensor network. Due to its resource constraints, low power wireless sensor networks face several technical challenges. Many protocols work well on simulators but do not act as we expect in the actual deployments. For example, sensors physically placed at the top of the heap experience Free Space propagation model, while the sensors which are at the bottom of the heap have sharp fading channel characteristics. In this thesis, we show that impact of asymmetric links in the wireless sensor network topology and that link quality between sensors varies consistently. We propose two ways to improve the performance of Link Quality Indicator (LQI) based algorithms in the real asymmetric link sensor networks. In the first way, network has no choice but to have some sensors which can transmit over the larger distance and become cluster heads. The number of cluster heads can be given by Matérn Hard-Core process. In the second solution, we propose HybridLQI which improves the performance of LQI based algorithm without adding any overhead on the network. Later, we apply theoretical clustering approaches in sensor network to real world. We deploy Matérn Hard Core Process and Max-Min cluster Formation heuristic on real Tmote nodes in sparse as well as highly dense networks. Empirical results show clustering process based on Matérn Hard Core Process outperforms Max-Min Cluster formation in terms of the memory requirement, ease of implementation and number of messages needed for clustering. Finally, using Absorbing Markov chain and measurements we study the performance of load balancing techniques in real sensor networks.

Vystyti mikrosensorinio tinklo duomenų perdavimą racionalaus maršrutizavimo sistemoje. Minimizuoti perdavimų skaičių, sudarant bevielį mikrosensorinį tinklą. Taip pat, trumpinti skaičiavimo procesus, kai mazgai turi atlikti racionalų maršrutizavimą. Bevielio mikrosensorinio tinklo trumpiausio kelio radimas turi būti paprastai realizuojamas ir skaičiuojamas. / In this paper it is described a method of creation of the shortest path algorithm for wireless sensor networks. Algorithm computes optimal shortest path and works on any wireless sensor networks topology. One of the limitations of wireless sensor nodes is their inherent limited energy resource. The limited available energy of sensor nodes is mainly problem making communication and computational processing. An energy efficient routing protocol can limit the number of nodes transmissions and the computational complexity of finding the shortest routing path. In the experimental part, the correct functionality of the algorithm is evaluated and the results are analized.

This thesis presents two main achievements. The first is a novel link-layer encryption protocol for wireless sensor networks. The protocol design aims to reduce energy consumption by reducing security-related communication overhead. This is done by merging security-related data of consecutive packets. The merging is based on simple mathematical operations. It helps to reduce energy consumption by eliminating the requirement to transmit security-related fields in the packet. The protocol is named the Compact Security Protocol and is referred to as C-Sec. In addition to energy savings, the C-Sec protocol also includes a unique security feature of hiding the packet header information. This feature makes it more difficult to trace the flow of wireless communication, and helps to minimize the effect of replay attacks. The C-Sec protocol is rigorously tested and compared with well-known related protocols. Performance evaluations demonstrate that C-Sec protocol outperforms other protocols in terms of energy savings. The protocol is evaluated with respect to other performance metrics including queuing delay and error probability. The C-Sec operation requires fast encryption, which leads to a second major contribution: The SN-Sec, a 32-bit RISC secure wireless sensor platform with hardware cryptographic primitives. The security vulnerabilities in current WSNs platforms are scrutinized and the main approaches to implementing their cryptographic primitives are compared in terms of security, time, and energy efficiency. The SN-Sec secures these vulnerabilities and provides more time and energy efficiency. The choice of cryptographic primitives for SN-Sec is based on their compatibility with the constrained nature of WSNs and their security. The AES implementation has the best data-path and S-Box design in the literature. All SHA family members are implemented and compared to choose the most compatible with WSN constraints. An efficient elliptic-curve processor design is proposed. It has the least mathematical operations compared to elliptic-curve processors proposed for WSNs in the literature. It also exploits parallelism among mathematical operations to compute elliptic-curve point multiplication with minimal amount of clock cycles. SN-Sec is implemented using VHDL. Experimental results using synthesis for Spartan-6 low-power FPGA shows that the proposed design has very reasonable computational time and energy consumption.

Complex Network Topologies (CNTs)–network holes and cuts–often occur in practical WSN deployments. Many researchers have acknowledged that CNTs adversely affect the performance of location-based routing and proposed various CNT- aware location-based routing protocols. However, although they aim to address practical issues caused by CNTs, many proposed protocols are either based on idealistic assumptions, require too much resources, or have poor performance. Additionally, proposed protocols are designed only for a single routing primitive–either unicast, multicast, or convergecast. However, as recent WSN applications require diverse traffic patterns, the need for an unified routing framework has ever increased. In this dissertation, we address these main weaknesses in the research on location- based routing. We first propose efficient algorithms for detecting and abstracting CNTs in the network. Using these algorithms, we present our CNT-aware location- based unicast routing protocol that achieves the guaranteed small path stretch with significantly reduced communication overhead. We then present our location-based multicast routing protocol that finds near optimal routing paths from a source node to multicast member nodes, with efficient mechanisms for controllable packet header size and energy-efficient recovery from packet losses. Our CNT-aware convergecast routing protocol improves the network lifetime by identifying network regions with concentrated network traffic and distributing the traffic by using the novel concept of virtual boundaries. Finally, we present the design and implementation details of our unified routing framework that seamlessly integrates proposed unicast, multicast, and convergecast routing protocols. Specifically, we discuss the issues regarding the implementation of our routing protocols on real hardware, and the design of the framework that significantly reduces the code and memory size to fit in a resource constrained sensor mote. We conclude with a proactive solution designed to cope with CNTs, where mobile nodes are used for “patching” CNTs to restore the network connectivity and to optimize the network performance.

Recent years have witnessed a tremendous amount of research in the field of wireless sensor networks (WSNs) due to their numerous real-world applications in environmental and habitat monitoring, fire detection, object tracking, traffic controlling, industrial and machine-health control and monitoring, enemy-intrusion in military battlefields, and so on. However, reducing energy consumption of individual sensors in such networks and obtaining the expected standard of quality in the solutions provided by them is a major challenge. In this thesis, we investigate several problems in WSNs, particularly in the areas of broadcasting, routing, target monitoring, self-protecting networks, and topology control with an emphasis on minimizing and balancing energy consumption among the sensors in such networks. Several interesting theoretical results and bounds have been obtained for these problems which are further corroborated by extensive simulations of most of the algorithms. These empirical results lead us to believe that the algorithms may be applied in real-world situations where we can achieve a guarantee in the quality of solutions with a certain degree of balanced energy consumption among the sensors. / Thesis (Ph.D, Computing) -- Queen's University, 2010-04-27 10:19:39.03