Advances in micro-sensor and wireless technology enable small but smart sensors to be developed for wide range environment-monitor applications. Since Sensor nodes only have limited power capacity and are difficult to recharge, how to prolong network lifetime is an important issue in wireless sensor networks design. Several topology control algorithms have been proposed to maintain the connectivity of wireless sensor network and reduce the energy consumption. Multi-hop Infrastructure Network Architecture (MINA) is a kind of Multi-layer Architecture for WSN topology, which utilizes hundred of sensors to transmit data to a sink. This architecture partitions sensor nodes into layers based on their distances (calculated by hop count) to BS. In this way, the node connected to more nodes will relay more data for other nodes. This make the node exhaust its battery power quickly and thus reduces the network lifetime. This study proposes an Efficient Energy Time-Slot Allocation (EETA) scheme which distributes time slots in accordance with the energy of neighbor nodes and the number of neighbor nodes. In addition, this work also devises an adaptive time slot size to reduce data packet drop in case when the node buffer is full. The simulation results show that the EETA performs better than the MINA in terms of network lifetime.

Τα κυψελικά αυτόματα (ΚΑ) αποτελούν την εξιδανίκευση ενός φυσικού συστήματος όπου ο χώρος και ο χρόνος είναι διακριτοί και οι φυσικές ποσότητες λαμβάνουν μόνο ένα πεπερασμένο σύνολο τιμών. Τα κυψελικά αυτόματα αποτελούνται από ένα πλέγμα με διακριτούς πανομοιότυπους κόμβους. Κάθε σημείο-κόμβος του πλέγματος χαρακτηρίζεται από μία τιμή η οποία δεν είναι αυθαίρετη, αλλά λαμβάνεται από ένα συγκεκριμένο σύνολο ‘επιτρεπτών’ ακέραιων τιμών. Οι τιμές αυτών των κόμβων του πλέγματος εξελίσσονται από τη μία χρονική στιγμή στην άλλη σύμφωνα με προκαθορισμένους τοπικούς κανόνες. Η συνολική δομή αποτελεί ένα μοντέλο παράλληλου υπολογισμού. ΄Οταν η απλή δομή του μοντέλου επαναλαμβάνεται, προκύπτουν πολύπλοκα πρότυπα που μπορούν να προσομοιώσουν ποικίλα πολύπλοκα φυσικά φαινόμενα και συστήματα. Χρησιμοποιούμε τα κυψελικά αυτόματα για να προσομοιώσουμε έναν αλγόριθμο ελέγχου τοπολογίας για ασύρματα δίκτυα αισθητήρων. Τα ασύρματα δίκτυα αισθητήρων αποτελούνται από ένα μεγάλο αριθμό διασκορπισμένων αισθητήρων-κόμβων που λειτουργούν με μπαταρίες. Σκοπός του προβλήματος ελέγχου τοπολογίας σε ασύρματα δίκτυα αισθητήρων είναι η επιλογή κατάλληλου υποσυνόλου κόμβων ικανών να παρακολουθούν μια περιοχή με στόχο τη μικρότερη δυνατή κατανάλωση ενέργειας και ως εκ τούτου την επέκταση της διάρκειας ζωής του δικτύου. / Cellular automata (CA) are an idealization of a physical system where space and time are discrete and the physical quantities take only a finite set of values. Cellular automata consist of a regular grid of identical cells-nodes. Each node is characterized by a non arbitrary value selected by a specific set of appropriate integers. The values of the nodes change over time according to predefined localized rules. The overall structure can be viewed as a parallel processing device. This simple structure when iterated several times produces complex patterns displaying the potential to simulate different sophisticated natural phenomena. We use cellular automata for simulating a topology control algorithm in Wireless Sensor Networks (WSNs). WSNs are composed of a large number of distributed sensor nodes operating on batteries; the objective of the topology control problem in WSNs is to select an appropriate subset of nodes able to monitor a region at a minimum energy consumption cost thus extending the network lifetime.

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Wireless sensor networks (WSNs) is a virtual layer in the paradigm of the Internet of Things (IoT). It inter-relates information associated with the physical domain to the IoT drove computational systems. WSN provides an ubiquitous access to location, the status of different entities of the environment, and data acquisition for long-term IoT monitoring. Since energy is a major constraint in the design process of a WSN, recent advances have led to project various energy-efficient protocols. Routing of data involves energy expenditure in considerable amount. In recent times, various heuristic clustering protocols have been discussed to solve the purpose. This article is an improvement of the existing stable election protocol (SEP) that implements a threshold-based cluster head (CH) selection for a heterogeneous network. The threshold maintains uniform energy distribution between member and CH nodes. The sensor nodes are also categorized into three different types called normal, intermediate, and advanced depending on the initial energy supply to distribute the network load evenly. The simulation result shows that the proposed scheme outperforms SEP and DEEC protocols with an improvement of 300% in network lifetime and 56% in throughput.

Context: Wireless Sensor Networks (WSN) are applied to collect information by distributed sensor nodes (anchors) that are usually in fixed positions. Localization (estimating the location of objects) of moving sensors, devices or people which recognizes the location’s information of a moving object is one of the essential WSN services and main requirement. To find the location of a moving object, some of algorithms are based on RSSI (Received Signal Strength Indication). Since very accurate localization is not always feasible (cost, complexity and energy issues) requirement, RSSI-based method is a solution. This method has two specific features: it does not require extra hardware (cost and energy aspects) and theoretically RSSI is a function of distance. Objectives: In this thesis firstly, we develop an RSSI-based localization algorithm (server side application) to find the position of a moving object (target node) in different situations. These situations are defined in different experiments so that we observe and compare the results (finding accurate positioning). Secondly, since RSSI characteristic is highly related to the environment that an experiment is done in (moving, obstacles, temperature, humidity …) the importance and contribution of “environmental condition” in the empirical papers is studied. Methods: The first method which is a common LR (Literature Review) is carried out to find out general information about localization algorithms in (WSN) with focus on the RSSI-based method. This LR is based on papers and literature that are prepared by the collaborating company, the supervisor and also ad-hoc search in scientific IEEE database. By this method as well as relevant information, theoretical algorithm (mathematical function) and different effective parameters of the RSSI-based algorithm are defined. The second method is experimentation that is based on development of the mentioned algorithm (since experiment is usually performed in development, evaluation and problem solving research). Now, because we want to compare and evaluate results of the experiments with respect to environmental condition effect, the third method starts. The third method is SMS (Systematic mapping Study) that essentially focuses on the contribution of “environmental condition” effect in the empirical papers. Results: The results of 30 experiments and their analyses show a highly correlation between the RSSI values and environmental conditions. Also, the results of the experiments indicate that a direct signal path between a target node and anchors can improve the localization’s accuracy. Finally, the experiments’ results present that the target node’s antenna type has a clear effect on the RSSI values and in consequence distance measurement error. Our findings in the mapping study reveal that although there are a lot of studies about accuracy requirement in the context of the RSSI-based localization, there is a lack of research on the other localization requirements such as performance, reliability and stability. Also, there are a few studies which considered the RSSI localization in a real world condition. Conclusion: This thesis studies various localization methods and techniques in WSNs. Then, the thesis focuses on the RSSI-based localization by implementing one algorithm and analyzing the experiments’ results. In our experiments, we mostly focus on environmental parameters that affect localization’s accuracy. Moreover, we indicate some areas of research in this context which need more studies.

The concept of wireless sensor network (WSN) is where tiny devices (sensor nodes), positioned fairly close to each other, are used for sensing and gathering data from its environment and exchange information through wireless connections between these nodes (e.g. sensor nodes distributed through out a bridge for monitoring the mechanical stress level of the bridge continuously). In order to easily deploy a relatively large quantity of sensor nodes, the sensor nodes are typically designed for low price and small size, thereby causing them to have very limited resources available (e.g. energy, processing power). Over the years, different security (cryptographic) primitives have been proposed and refined aiming at utilizing modern processor’s power e.g. 32-bit or 64-bit operation, architecture such as MMX (Multi Media Extension) and etc. In other words, security primitives have targeted at high-end systems (e.g. desktop or server) in software implementations. Some hardware-oriented security primitives have also been proposed. However, most of them have been designed aiming only at large message and high speed hashing, with no power consumption or other resources (such as memory space) taken into considerations. As a result, security mechanisms for ultra-low power (<500µW) devices such as the wireless sensor nodes must be carefully selected or designed with their limited resources in mind. The objective of this project is to provide implementations of security primitives (i.e. encryption and authentication) suitable to the WSN environment, where resources are extremely limited. The goal of the project is to provide an efficient building block on which the design of WSN secure routing protocols can be based on, so it can relieve the protocol designers from having to design everything from scratch. This project has provided three main contributions to the WSN field.  Provides analysis of different tradeoffs between cryptographic security strength and performances, which then provide security primitives suitable for the needs in a WSN environment. Security primitives form the link layer security and act as building blocks for higher layer protocols i.e. secure routing protocol.  Implements and optimizes several security primitives in a low-power microcontroller (TI MSP430F1232) with very limited resources (256 bytes RAM, 8KB flash program memory). The different security primitives are compared according to the number of CPU cycles required per byte processed, specific architectures required (e.g. multiplier, large bit shift) and resources (RAM, ROM/flash) required. These comparisons assist in the evaluation of its corresponding energy consumption, and thus the applicability to wireless sensor nodes.  Apart from investigating security primitives, research on various security protocols designed for WSN have also been conducted in order to optimize the security primitives for the security protocols design trend. Further, a new link layer security protocol using optimized security primitives is also proposed. This new protocol shows an improvement over the existing link layer security protocols. Security primitives with confidentiality and authenticity functions are implemented in the TinyMote sensor nodes from the Technical University of Vienna in a wireless sensor network. This is to demonstrate the practicality of the designs of this thesis in a real-world WSN environment. This research has achieved ultra-low power security primitives in wireless sensor network with average power consumption less than 3.5 µW (at 2 second packet transmission interval) and 700 nW (at 5 second packet transmission interval). The proposed link layer security protocol has also shown improvements over existing protocols in both security and power consumption. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

Interactive digital art installations are fundamentally enabled by hardware and software. Through a combination of these elements an interactive experience is con- structed. The first half of this thesis discusses the technical complexity associated with design and implementation of digital interactive installation. A system, dreamIO, is proposed for mediating this complexity through providing wireless building blocks for creating interactive installations. The technical details–both hardware and software– of this system are outlined. Measurements of the system are presented followed by analysis and discussion of the real world impact of this data. Finally, a discussion of future improvements is presented. The second half of this thesis examines an example interactive installation, Trans- code, which uses the proposed system as the building block for the piece. The piece is presented as evidence for the value of the proposed system and as a work of art in it’s own right. The use of the dreamIO system is detailed followed by a discussion of the interactivity and aesthetic form of the work. The purposes of these specific design choices are then presented. Finally, the work is analyzed through a combination of Relational Aesthetics and Cybernetics. / Graduate

Master’s thesis in the first part focuses on the effectiveness of communication in the selection of reference nodes during the anchor-free localization in WSN. In this part two anchor-free localization algorithms AFL and CRP are explored. Knowledge learned on the selection of reference nodes and communication complexities of these algorithms are used in the second part. The second part is aimed at eliminating weaknesses in communication and subsequently proposed a new algorithm for selection of references. The principle of the newly proposed algorithm CASRU (Centralized Algorithm for Selection of Reference Nodes) is based on the principle of CRP. CASRU algorithm builds logical tree structure and then filters the communication through it. New algorithm achieves much greater success in the selection in randomly distributed networks while reducing the amount of communication load.

Nowadays, wireless sensor network (WSN) is becoming popular in various fields of different industries along with the rapid development of hardware and software. Whereas more and more WSN applications come into use has make it difficult for consumers especially those who do not have professional knowledge to use. So it is urgently necessary and significant to offer services which do not need professional knowledge to satisfy consumers’ requirements from the users’ point of view. Therefore, service oriented architecture (SOA) is introduced as a method to do our research from the users’ point of view. After asimple overall introduction of WSN which include the system architecture, hardware, software and supported technologies, we pay our emphasis on the power consumption modeling for WSN and get some formulations following the operation cycle. Last but not least, SOA method is analyzed and some SOA based WSN applications are introduced as examples to further understand of SOA based WSN for readers.

Wireless sensor networks (WSNs) groups specialized transducers that provide sensing services to Internet of Things (IoT) devices with limited energy and storage resources. Since replacement or recharging of batteries in sensor nodes is almost impossible, power consumption becomes one of the crucial design issues in WSN. Clustering algorithm plays an important role in power conservation for the energy constrained network. Choosing a cluster head (CH) can appropriately balance the load in the network thereby reducing energy consumption and enhancing lifetime. This paper focuses on an efficient CH election scheme that rotates the CH position among the nodes with higher energy level as compared to other. The algorithm considers initial energy, residual energy, and an optimum value of CHs to elect the next group of CHs for the network that suits for IoT applications, such as environmental monitoring, smart cities, and systems. Simulation analysis shows the modified version performs better than the low energy adaptive clustering hierarchy protocol by enhancing the throughput by 60%, lifetime by 66%, and residual energy by 64%.