In this thesis, the optical communication systems for millimeter-scale sensing and communication devises known as "Smart Dust" are described and analyzed. A smart dust element is a self-contained sensing and communication system that can be combined into roughly a cubic-millimeter mote to perform integrated, massively distributed sensor networks. The suitable passive optical and fiber-optic communication systems will be selected for the further performance design and analysis based on the requirements for implementing these systems. Based on the communication link designs of the free-space passive optical and fiber-optic communication systems, the simulations for link performance will be performed. / Master of Science

The main objective of this thesis is to develop a communication system that can minimize the micro-machine size and power consumption and maximize the link range and the number of micro-machines that can communicate simultaneously with the base station. Several possible communication systems are compared, including RF communications and active and passive free space optical communications. A directed, half duplex LOS link using a Ferroelectric liquid crystal (FLC) or multiple quantum well (MQW) modulating retroreflector-base passive uplink is then examined in more detail. Two potential geometries are described. In a broad-beam system, light from a source is broadcast to all micro-machines within the field of view (FOV). However, simulations show that the performance is unacceptable for most applications. In a narrow-beam system, light is holographically steered to active micro-machines within the same FOV. Therefore, the link budget has been improved. For a BER not exceeding 10-9, the 850 nm LC narrowbeam system can support maximum range of 146 m at a data rate of 10kbits/s, and the 1525 nm MQW narrowbeam system can support a maximum range of 34 m at a data rate of 10Mbits/s, when the transmitted power in the diffracted beam of the positive first order is 0.5 mW. Experiments have been carried out to verify the model. These were initially carried out with MQW Modulating RetroReflector (MRR). Results were then be used to modify the characteristics of these components in the model. Available components and discrete electronics have been used to set up a simple retro-reflecting link. Experiments have been performed at a limited data rate of 1 kbits/s over a limited range of 1m due to creating a uniform interrogation beam spot, and the active area of the receiver of 1 mm diameter. An algorithm to find the MQW MRR within the FOV is designed and tested.

The smart dust concept is a fairly recent phenomenon to engineering. It assumes monitoring of a real natural environment in which motes or smart dust machines swarm in collective and coordinate information among themselves and/or to a backend control platform. In analog mixed signal field work on such devices is gaining momentum such that it is conceived to be one of the emerging fields in technology, and work was only possible once the technology for fabrication touched the nanoscale regions. Smart dust network involves remote devices connected in a hive sensing burst type datum signals from the environment and relaying information amongst themselves in an energy efficient manner to coordinate an appropriate response to a detected stimulus. The project presumed a RF based communication strategy for coordination amongst the devices through a wireless medium. That is less susceptible to stringent requirements of LOS and a base band processing system that comprised of an environment sensor, an AFE module, an ADC, a DSP and a DAC. Essentially a 10 bit, 2 Mega Hertz MHz pipelined ADC implemented in a STM 65nm technology. The ADC benefits the smart dust device in allowing it to process data in an energy efficient way and also focusing on reduced complexity as itsdesign feature. While it differs in the other ADC of the system by operating at a higher frequency and assuming a different design philosophy assuming a coherent system sensitive to a clock. The thesis work assumes that various features ofenergy harvesting, regulation and power management present in the smart dustmote would enable the system to contain such a diverse ADC. The ADCs output digital datum would be compatible to the rest of the design modules consisting mainly of DSP sections. The ADC novelty is based on the fact that it removes the necessity of employing a high power consuming OpAmp whose design parameters become more complex as technology scales to the nanoscale era and further down. A systematic, bottom up, test driven approach to design is utilized and various behaviours of the system are captured in Cadence design environment with verilogto layout models and MATLAB and Simulink models.

This thesis concerns the development of optimisation algorithms to determine the relative co-location, (localisation), of a number of freely-flying 'Smart Dust mote' sensor platform elements using a non-deterministic data-set derived from the duplex wireless transmissions between elements. Smart dust motes are miniaturised, microprocessor based, electronic sensor platforms, frequently used for a wide range of remote environmental monitoring applications; including specific climate synoptic observation research and more general meteorology. For the application proposed in this thesis a cluster of the notional smart dust motes are configured to imitate discrete 'Radio Drop Sonde' elements of the wireless enabled monitoring system in use by meteorological research organisations worldwide. This cluster is modelled in software in order to establish the relative positions during the 'flight' ; the normal mode of deployment for the Drop Sonde is by ejection from an aeroplane into an upper-air zone of interest, such as a storm cloud. Therefore the underlying research question is, how to track a number of these independent, duplex wireless linked, free-flying monitoring devices in 3-dimensions and time (to give the monitored data complete spatio-temporal validity). This represents a significant practical challenge, the solution applied in this thesis was to generate 3-dimensional geometries using the only 'real-time' data available; the Radio Signal Strength Indicator (RSSI) data is generated through the 'normal' duplex wireless communications between motes. Individual RSSI values can be considered as a 'representation of the distance magnitude' between wireless devices; when collated into a spatio-temporal data-set it 'encodes' the relative, co-locational, 3-dimensional geometry of all devices in the cluster. The reconstruction, (or decoding), of the 3-dimensional geometries encoded in the spatio-temporal data-set is a complex problem that is addressed through the application of various algorithms. These include, Random Search, and optimisation algorithms, such as the Stochastic Hill-climber, and various forms of Evolutionary Algorithm. It was found that the performance of the geometric reconstruction could be improved through identification of salient aspects of the modelled environment, the result was heuristic operators. In general these led to a decrease in the time taken to reach a convergent solution or a reduction in the number of candidate search space solutions that must be considered. The software model written for this thesis has been implemented to generalise the fundamental characteristics of an optimisation algorithm and to incorporate them into a generic software framework; this then provides the common code to all model algorithms used.

Recently, smart dust or wireless sensor networks are gaining more attention.These autonomous, ultra-low power sensor-based electronic devices sense and process burst-type environmental variations and pass the data from one node (mote) to another in an ad-hoc network. Subsystems for smart dust are typically the analog interface (AI), analog-to-digital converter (ADC), digital signal processor (DSP), digital-to-analog converter (DAC), power management, and transceiver for communication. This thesis project describes an event-driven (ED) digital signal processing system (ADC, DSP and DAC) operating in continuous-time (CT) with smart dust as the target application. The benefits of the CT system compared to its conventional counterpart are lower in-band quantization noise and no requirement of a clock generator and anti-aliasing filter, which makes it suitable for processing burst-type data signals. A clockless EDADC system based on a CT delta modulation (DM) technique is presented. The ADC output is digital data, continuous in time, known as “data token”. The ADC employs an unbuffered, area efficient, segmented resistor-string (R-string) feedback DAC. A study of different segmented R-string DAC architectures is presented. A comparison in component reduction with prior art shows nearly 87.5% reduction of resistors and switches in the DAC and the D flip-flops in the bidirectional shift registers for an 8-bit ADC, utilizing the proposed segmented DAC architecture. The obtained SNDR for the 3-bit, 4-bit and 8-bit ADC system is 22.696 dB, 30.435 dB and 55.73 dB, respectively, with the band of interest as 220.5 kHz. The CTDSP operates asynchronously and process the data token obtained from the EDADC. A clockless transversal direct-form finite impulse response (FIR) low-pass filter (LPF) is designed. Systematic top-down test-driven methodology is employed through out the project. Initially, MATLAB models are used to compare the CT systems with the sampled systems. The complete CTDSP system is implemented in Cadence design environment. The thesis has resulted in two conference contributions. One for the 20th European Conference on Circuit Theory and Design, ECCTD’11 and the other for the 19th IFIP/IEEE International Conference on Very Large Scale Integration, VLSI-SoC’11. We obtained the second-best student paper award at the ECCTD.

The aim of this project was to produce an integrate-able free space optical transceiver for Specks. Specks are tiny computing units that together can form a powerful network called a SpeckNet. The SpeckNet platform is developed by the SpeckNet consortium, which consists of five Scottish Universities and combines computer science, electrical engineering and digital signal processing groups. The principal goal of creating an optical transceiver was achieved by integrating in-house fabricated VCSELs (with lasing thresholds below 400 uA) and custom designed detectors on the SpeckNet platform. The transceiver has a very low power consumption (approximately 100 uW), which removes the need for synchronous communication through the SpeckNet thus making the network more efficient. I describe both static and dynamic beam control techniques. For static control, I used micro-lenses. I fabricated the lenses by greyscale electron beam lithography and integrated them directly on VCSEL arrays. I achieved a steering angle of 10 degrees with this design. I also looked at integrated gratings etched straight into a VCSEL and observed beam steering with an efficiency of 60% For dynamic control, I implemented a liquid crystal (LC) design. I built a LC cell with 30 individually controlled pixels, but I only achieved a steering angle of 1 degree. Furthermore, I investigated two different techniques for achieving beam steering by interference, using coupled VCSELs (a phased array approach). Firstly, using photonic crystals etched into the surface of the VCSEL, I built coupled laser cavities. Secondly, I designed and built bow-tie type VCSELs that were optically coupled but electrically isolated. These designs work by differential current injection causing an interference effect in the VCSELs far field. This technique is the first stepping stone towards realising a phased optical array. Finally, I considered signal detection. Using the same VCSEL material, I built a resonant-cavity detector. This detector had a better background rejection ratio than commercially available silicon devices.

La réalisation d'objets intelligents de la taille du millimètre capables d'être sensibles à leur environnement, de réaliser des calculs pour traiter les données et de communiquer de façon autonome constitue une opportunité unique pour repenser l'interaction entre l'homme et son milieu environnant. Les systèmes émergeants de « Smart Dust» sont réalisés en associant massivement en réseaux distribués des centaines d'objets miniatures intelligents intégrant un système d'alimentation autonome, un ou plusieurs capteurs (lumière, température, vibration, acoustique, pression, champ magnétique, ...), des circuits analogiques et numériques pour réaliser des traitements de données et un système pour recevoir et transmettre des données. Pour faciliter la conception des systèmes radiofréquence RF ou millimétriques, l'intégration des dispositifs de système sur une même puce reste la solution souhaitée. <br /> Dans ce contexte, la première partie de ce manuscrit propose un état de l'art des différents composants d'un émetteur récepteur RF opérant à des fréquences millimétriques et intégré sur différentes technologies, ainsi l'étude de la faisabilité de la technologie CMOS SOI en réalisant un bilan de liaison à 60 GHz. Une étude sur les actifs et passifs de la technologie CMOS SOI montre les avantages du SOI et aussi les phénomènes spécifiques qu'il faut prendre en compte dans la phase de conception. La deuxième partie est consacrée à l'étude des structures d'interconnexion de la technologie SOI, notamment les lignes et les rubans coplanaires. Ainsi nous présentons les méthodes utilisées pour déterminer la permittivité effective et l'impédance caractéristique de ces lignes et un modèle analytique de la permittivité effective de l'antenne. <br /> La troisième partie traite le cas d'une antenne canonique de type dipôle intégré sur SOI et fonctionnant dans la bande millimétrique. Cette étude est basée sur les différents paramètres de la technologie SOI comme la permittivité, la résistivité et l'épaisseur de silicium. Ensuite, une étude de problématique de rayonnement des antennes intégrées en technologie SOI est présentée. Finalement un modèle des îlots métalliques « dummies » de la technologie SOI, basé sur le modèle dynamique de Tretyakov, est proposé. <br /> La dernière partie est consacrée à la conception, la réalisation, le test et la mesure de antennes intégrées sur SOI et fonctionnant dans la bande de 60 GHz. Quatre types d'antennes sont présentés notamment une antenne dipôle interdigitée, une antenne IFA, une antenne double fente et finalement une antenne spirale. Les paramètres électriques des antennes dipôles, IFA, et fente sont mesurés et sont conformes aux paramètres simulés. En plus, Nous avons présenté un dispositif de test pour mesurer le digramme de gain de ses antennes. La procédure de caractérisation a permis la validation expérimentale de ce dispositif et la récupération des diagrammes de gain des antennes au niveau de substrat SOI. Dans une optique de démonstrateur intégré, une conception conjointe d'un amplificateur faible bruit intégrée sur SOI avec une antenne intégrée, les deux fonctionnant à 60 GHz, permettant de s'affranchir de la contrainte 50 Ohms est conduite.

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