Τα ασύρματα δίκτυα αισθητήρων αποτελούν μια νέα κατηγορία δικτύων υπολογιστών. Αποτελούνται από ένα μεγάλο πλήθος υπολογιστικών κόμβων μικροσκοπικού μεγέθους, εφοδιασμένων με πλήθος αισθητήρων και μονάδων ελέγχου. Σκοπός τους είναι η επίτευξη μιας δύσκολης, για τα δεδομένα του κάθε κόμβου, αποστολής μέσω της συνεργασίας μεταξύ όλων των κόμβων του δικτύου. Τα δίκτυα αυτά αντιμετωπίζονται με μεγάλο ενδιαφέρον από την ερευνητική κοινότητα τα τελευταία χρόνια. Έτσι, έχει προταθεί πλήθος από πρωτόκολλα διάδοσης πληροφορίας, πιθανές εφαρμογές, έχει υλοποιηθεί πλήθος λογισμικού, κτλ. Υπάρχει όμως περιορισμός στα διαθέσιμα εργαλεία για την ανάπτυξη εφαρμογών σε τέτοια δίκτυα, το οποίο σημαίνει από τη μια περιορισμό των διαθέσιμων δυνατοτήτων στους χρήστες και από την άλλη αυξημένη δυσκολία υλοποίησης κάποιας εφαρμογής. Σκοπός της εργασίας αυτής είναι ο σχεδιασμός και η ανάπτυξη ενός γενικού περιβάλλοντος, το οποίο θα προσφέρει στους χρήστες τη δυνατότητα να υλοποιούν σε μικρό χρονικό διάστημα μια εφαρμογή σε ασύρματα δίκτυα αισθητήρων. Το περιβάλλον αυτό, το οποίο ονομάζουμε jWebDust , εκτείνεται σε όλα τα επίπεδα που μπορεί να περιλαμβάνει μια τέτοια εφαρμογή, και επιτρέπει στο χρήστη να αναπτύξει μια εφαρμογή χωρίς ο χρήστης να χρειάζεται να υλοποιήσει ο ίδιος τα επίπεδα αυτά. Η συνεισφορά της παρούσας εργασίας συνοψίζεται σε δύο συνιστώσες: · Το πρωτόκολλο VTRP, το οποίο προσπαθεί να αντιμετωπίσει το πρόβλημα του εντοπισμού και διάδοσης πολλαπλών γεγονότων στα ασύρματα δίκτυα αισθητήρων. Το πρόβλημα αυτό συνίσταται στον εντοπισμό μέσα στο δίκτυο ενός πλήθους από γεγονότα και της διάδοσης των αντίστοιχων αναφορών σε ένα κέντρο ελέγχου, με έναν αποδοτικό τρόπο όσον αφορά την κατανάλωση ενέργειας και την ανοχή σε σφάλματα μετάδοσης. · Το περιβάλλον jWebDust, το οποίο αποσκοπεί στο να βοηθήσει το χρήστη να υλοποιήσει μια εφαρμογή σε ένα ασύρματο δίκτυο αισθητήρων εύκολα και γρήγορα. Βιβλιογραφία: 1. A. Antoniou, I. Chatzigiannakis, G. Mylonas, S. Nikoletseas, A. Boukerche: A new energy efficient and fault tolerant protocol for data propagation in smart dust networks using varying transmission range. In the proceedings of the 37th Annual ACM – IEEE Simulation Symposium (ANSS ’04), April 2004. 2. I. Chatzigiannakis, G. Mylonas, S. Nikoletseas: jWebDust: A Java-based Generic Application Environment for Wireless Sensor Networks. In the proceedings of DCOSS ’05 (International Conference on Distributed Computing in Sensor Systems), Marina Del Rey, June 30 – July 1, 2005 . / Wireless sensor networks are comprised of a vast number of ultra-small fully autonomous computing, communication and sensing devices, with very restricted energy supplies and computing capabilities, which co-operate to accomplish a large sensing task. Such networks can be very useful in practice, i.e. in the local detection of remote crucial events and the propagation of data reporting their realization to a control center. It is expected that, in the future, the wide range of applications of sensor networks will make them an integral part of our lives. The interest of the research community in these networks has grown steadily in the recent years and a plethora of data propagation protocols and possible applications has been proposed, along with a growing number of software applications and real network deployments. There is, though, a lack of available tools for developing applications in sensor networks, which means that there is a lack of available options for the final users and also an increased difficulty in implementing an application for such a network. The aim of this dissertation is the design and development of a generic environment, which will offer the possibility of implementing quick and easy an application for wireless sensor networks. This environment is called jWebDust, and its implementation is based on existing technologies, like the TinyOS operating system for sensor networks, and is targeted towards hardware platforms that are supported by TinyOS. The contribution of this dissertation can be summarized as follows: 1. The VTRP protocol [2], designed to face the (multiple event detection and propagation) problem in wireless sensor networks, which is defined as follows: how can each node in the network via cooperation with the rest of the nodes propagate the information regarding some event to the control center of the network in an efficient and fault-tolerant way. What differentiates VTRP to the other existing protocols is the change of the transmission range of each node, when this is necessitated by the conditions inside the network field. 2. The jWebDust environment [3], which aims at providing a simple interface for creating quick and easy an application for wireless sensor networks. jWebDust provides a simple interface to the final user, through which a variety of actions for administering a wireless sensor network can be performed, and also collection of data from the network nodes can be automated. This dissertation is comprised of the following parts: 1. Current research in wireless sensor networks (chapter 1 - 3): In the first part of this thesis we provide an introduction to the basic concepts in wireless sensor networks and a short overview of their history so far. A presentation of the current research regarding the most important hardware platforms and software applications presented so far concludes this part. 2. The VTRP protocol (chapter 4): a detailed description of the protocol is provided in this chapter, along with results from extensive simulation experiments conducted with the simDust network simulator [1]. 3. The jWebDust environment (chapters 5-6): The overall architecture of jWebDust is presented along with a detailed description of the functional specifications of the system. Bibliography: [1] S. Nikoletseas, I. Chatzigiannakis, H. Euthimiou, A. Kinalis, T. Antoniou and G. Mylonas, Energy efficient protocols for sensing multiple events in smart dust networks, 37th Annual ACM/IEEE Simulation Symposium (ANSS 2004), 2004, pp. 15-24. [2] T. Antoniou, A. Boukerche, I. Chatzigiannakis, G. Mylonas and S. Nikoletseas, A new energy efficient and fault-tolerant protocol for data propagation in smart dust networks using varying transmission range, 37th Annual ACM/IEEE Simulation Symposium (ANSS 2004), 2004, pp. 43-52. [3] I. Chatzigiannakis, G. Mylonas and S. Nikoletseas, jWebDust: A Java-based generic application environment for wireless sensor networks, International Conference on Distributed Computing in Sensor Systems (DCOSS

Wireless Sensor Networks (WSNs) have gained significant consideration these days, as opposed to wired sensor networks, by introducing multi-functional wireless nodes, which are smaller in size. The main advan-tage is that its wireless, so it costs less to install, maintain and reconfig-ure. These sensor nodes are used in various application areas. For ex-ample: residential, industrial, environmental and military application areas. However WSNs communication is prone to negative influences from the physical environment, such as physical obstacles and interfer-ence. Algorithms must be developed for handling these problems and also to investigate the channel properties. The purpose of this work is to design a testbed, which enables the communication of wireless sensor nodes, to capture the properties of the channel, which will, in the long run, enable better solutions to be designed which are, more appropriate to the errors in the channel. In this testbed, one channel, from the IEEE 802.15.4 channels spectrum, is dedicated as an emergency channel, which is used for handshaking and to handle channel/external interfer-ence or hardware failure between the communication of Transmitter (TX) and Receiver (RX) nodes. The remaining 15 channels are called data channels and are used for actual data transmission and control signals. Peer to Peer transmission of a transmitter-receiver pair is achieved with the introducing of beacons and acknowledgment (ACK) packets. The testbed also has the property of dual reception and data logging on a single PC by maeans of two RX nodes simultaneously from a single TX node. The dependency of the packet on the “Frame Length” byte(in the Frame header) during the reception is eliminated so that if the “Frame Length” byte is compromised, it will replace the programmer defined value with the “Frame Length” byte which helps to investigate the actual packets byte sent from the TX. Also, the Received Signal Strength (RSS) is calculated at the maximum sample rate of the channel. Power consumption is not considered in this testbed. The work is conducted on both the IEEE 802.15.4 physical and the application layers. Linux based TinyOS-2.x is used as an operating system for low power sensor devices. New algorithms are designed for each step in the development of the testbed. MICAz motes are used as nodes and an MIB520 programming board is used for burning the codes and for the purpose of gateways.

This thesis describes the possibilities of wireless sensor networks in monitoring buildings and summarizes the most common use of wireless sensor networks in practice. There are also described communication protocols needed for communication between each node and properties of topology of created network. Importance is lay on implementation of fully dynamic network with automatic network topology establishment. The application is designed for the TinyOS operating system and hardware platforms MICAz and IRIS, and its task is to establish the topology and send the data obtained from sensors to base station. The implemented protocol is based on the Collection Tree Protocol protocol and using best effort delivery is able to establish a dynamic topology. Further there is described  the method of storage and subsequent graphical and textual representation of data collected.

The reader is first introduced with history and possible applications for wireless sensor networks. The thesis then describes the problems of wireless sensor networks and implementation tools for wireless sensor networks. The thesis also presents the system WSageNt and its client web interface. Practical part is based on the design of agent elements. Describes gradual implementation, testing and practical realization of these agent elements in the system WSageNt. The final part discusses the advantages and disadvantages of the project and identifies possible future expansion of the system.

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Structural Health Monitoring (SHM) of automobile tires has been an active area of research in the last few years. Within this area, the monitoring of strain on tires using wireless devices and networks is gaining prominence because these techniques do not require any wired connections. Various tire manufacturers are looking into SHM of automobile tires due to the Transportation Recall Enhancement, Accountability and Documentation (TREAD) act which demands installation of tire pressure monitoring devices within the tire. Besides measuring tire pressures, tire manufactures are also examining ways to measure strain and temperature as well to enhance overall safety of an automobile. A sensor system that can measure the overall strain of a tire is known as a centralized strain sensing system. However, a centralized strain sensing system cannot find the location and severity of the damage on the tire, which is a basic requirement. Various sensors such as acceleration and optical sensors have also been proposed to be used together to get more local damage information on the tire. In this thesis we have developed a strain sensing system that performs local strain measurements on the tire and transmits them to a console inside the vehicle wirelessly. Our sensing system utilizes a new sensing material called Metal RubberTM which is shown to be conductive like metal, and flexible as rubber. Also, we have also developed a reliable and an energy efficient geographic routing protocol for transporting strain data wirelessly from a tire surface to the driver of the automobile. / Master of Science

Το OpenRSM (Open Remote System Management) είναι ένα εργαλείο ανοιχτού κώδικα για την απομακρυσμένη διαχείριση συστημάτων και δικτυακών συσκευών. Πρόκειται για ένα ολοκληρωμένο σύστημα που συνδυάζει και σε ορισμένες περιπτώσεις επεκτείνει έναν αριθμό εργαλείων ανοιχτού κώδικα παρέχοντας ένα κοινό περιβάλλον εργασίας με σκοπό την αποτελεσματική εκτέλεση λειτουργιών όπως: Ανακάλυψη περιουσιακών στοιχείων (Inventory), Εγκατάσταση και απεγκατάσταση λογισμικού (Deployment), Απομακρυσμένος έλεγχος σταθμών εργασίας (Remote Control), Εκτέλεση εντολών κελύφους (Command Execution). Το σύστημα μπορεί να χρησιμοποιηθεί και να υλοποιήσει οποιαδήποτε διαδικασία διαχείρισης συστημάτων και δικτύου. Έχει διερευνηθεί η χρήση του στα έξης: Διαχείριση ασύρματων access points, Ολοκλήρωση με συστήματα Grid και διαμοιρασμού υπολογιστικών πόρων. Το OpenRSM αποτελείται από μια κεντρική κονσόλα ελέγχου και διαχείρισης (Manager), έναν εξυπηρετητή διαχείρισης (Server) ο οποίος υλοποιεί την λογική εξυπηρετητή που ολοκληρώνει, προγραμματίζει, αποθηκεύει και εκτελεί τις διαχειριστικές λειτουργίες και τους πράκτορες (agents) οι οποίοι εγκαθίσταται στους διαχειριζόμενους σταθμούς και τους καθιστούν διαχειρίσιμους. Κατά την αρχική ανάπτυξη του OpenRSM επιλέχθηκε ως τεχνολογία υλοποίησης η γλώσσα προγραμματισμού Borland Delphi. Το αποτέλεσμα της συγκεκριμένης σχεδιαστικής επιλογής ήταν τα λειτουργικά τμήματα (Agent, Manager, Server) του OpenRSM να μπορούν να εγκατασταθούν μόνο σε υπολογιστές που διαθέτουν λειτουργικό σύστημα Microsoft Windows. Ο συγκεκριμένος περιορισμός σε συνδυασμό με την αυξανόμενη τα τελευταία χρόνια χρήση λειτουργικών συστημάτων που βασίζονται στον πυρήνα Linux από όλο και μεγαλύτερες ομάδες χρηστών οδήγησε στην ανάγκη επανασχεδιασμού του OpenRSM και στην εκ νέου υλοποίηση του. Βασικός σκοπός της παρούσας εργασίας αποτελεί ο επανασχεδιασμός του OpenRSM ώστε να παρέχει επιπλέον λειτουργίες και κυρίως η εκ νέου υλοποίηση του χρησιμοποιώντας ως τεχνολογία το Qt framework. Τελικός στόχος είναι η δημιουργία ενός ολοκληρωμένου συστήματος για την αποτελεσματική διαχείριση απομακρυσμένων συστημάτων που θα μπορεί να εγκατασταθεί σε όλα τα βασικά λειτουργικά συστήματα. Για τον σκοπό αυτό θα μελετηθεί η υπάρχουσα αρχιτεκτονική και θα προταθούν μια σειρά από βελτιώσεις/επεκτάσεις οι οποίες θα προσφέρουν στο σύστημα ένα σημαντικό αριθμό από νέες λειτουργίες. Οι πιο σημαντικές από αυτές είναι η ολοκλήρωση του λειτουργικού συστήματος TinyOS με το OpenRSM για την παρακολούθηση των ασύρματων δικτύων αισθητήρων (WSN) που βασίζονται σε αυτό, η δυνατότητα εγκατάστασης ενημερώσεων των εφαρμογών που έχουν εγκατασταθεί στους διαχειριζόμενους σταθμούς και η ολοκλήρωση του λογισμικού BOINC με το OpenRSM. Επιπλέον, εξετάζουμε ζητήματα που αφορούν την ενίσχυση των μηχανισμών ασφαλείας στην επικοινωνία των λειτουργικών τμημάτων του OpenRSM, καθώς και την ανάπτυξη λειτουργιών για το χρονοπρογραμματισμό των διαφόρων εργασιών και την ενεργειακή απόδοση των υπό-διαχείριση μηχανημάτων. / OpenRSM is a tool for remote management of workstations. It extends and integrates high-value open source projects in order to provide an integrated management platform. The goal has been to build a remote systems and network management platform capable to facilitate daily tasks. The system is designed to be fully functional yet simple, unlike most commercial management systems. OpenRSM is designed to offer: Inventory and assets management: information retrieval about installed assets, Software delivery: management of installed software. Supports user-interactive and silent installations/uninstallation among other, Remote procedure call: sending executable commands to stations, Remote Control, Wireless access points management, Integration with EGEE Grid technologies. The main components of OpenRSM are the server, the agent and the user console. The console accepts input from users and conveys it to the server in the form of task objects. The server is responsible for the coordination of the subsystems and task dispatch. The agent is a passive component on managed stations that accepts commands from the server and executes them. Borland Delphi programming language was initially used for the development of the OpenRSM system. The result of this design choice was the operating components (Agent, Manager, Server) of OpenRSM to be installed only on computers which run the operating system Microsoft Windows. This particular restriction in combination with the increase in the use of Linux-based operating systems led to the re-design of OpenRSM. The main purpose of this work is the development of OpenRSM using the Qt framework and the elaboration in functionality. The main goal has been to develop of a system capable to manage remote stations in a platform-independent manner. For this purpose, a study of the existing architecture is essential in order to propose a series of improvements which will provide the system with a significant number of new features. The most important of these features is the monitoring and management of wireless sensor networks, the ability to install updates for applications which are installed on the managed stations and the integration of open-source software platform BOINC with OpenRSM. As a result of this integration, OpenRSM would provide the operation of deploying BOINC software client and managing BOINC system into managed workstations. Moreover, we consider issues which are related to strengthening the security mechanisms in the communication between OpenRSM components and the development of new operations for scheduling jobs and for energy-efficiency of managed stations.

This thesis focuses on design of wireless network nodes using modular construction parts with respect to IEEEŽ 802.15.4 standard. Presented platform joins the benefits of the XBeeŽ wireless module and the AVR ATmega128 microcontroller development system. Sensor network prototype is designed to meet the desired first attempt functionality of embedded platform for collection and delivery of small volumes of control and sensor data between the network and the gateway. The control software was developed for TinyOS operating system. Designed platform is used as the framework for future development and possible functionality extensions in related applications.

Hardware-software co-design techniques are very suitable to develop the next generation of sensornet applications, which have high computational demands. By making use of a low power FPGA, the peak computational performance of a sensor node can be improved without significant degradation of the standby power dissipation. In this contribution, we present a methodology and tool to enable hardware/software co-design for sensor node application development. We present the integration of nesC, a sensornet programming language, with GEZEL, an easy-to-use hardware description language. We describe the hardware/software interface at different levels of abstraction: at the level of the design language, at the level of the co-simulator, and in the hardware implementation. We use a layered, uniform approach that is particularly suited to deal with the heterogeneous interfaces typically found on small embedded processors. We illustrate the strengths of our approach by means of a prototype application: the integration of a hardware-accelerated crypto-application in a nesC application. / Master of Science