STEPS - an approach for human mobility modeling

In this paper we introduce Spatio-TEmporal Parametric Stepping (STEPS) - a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS makes abstraction of spatio-temporal preferences in human mobility by using a power law to rule the nodes movement. Nodes in STEPS have preferential attachment to favorite locations where they spend most of their time. Via simulations, we show that STEPS is able, not only to express the peer to peer properties such as inter-ontact/contact time and to reflect accurately realistic routing performance, but also to express the structural properties of the underlying interaction graph such as small-world phenomenon. Moreover, STEPS is easy to implement, exible to configure and also theoretically tractable

Hybrid performance modelling of opportunistic networks

We demonstrate the modelling of opportunistic networks using the process algebra stochastic HYPE. Network traffic is modelled as continuous flows, contact between nodes in the network is modelled stochastically, and instantaneous decisions are modelled as discrete events. Our model describes a network of stationary video sensors with a mobile ferry which collects data from the sensors and delivers it to the base station. We consider different mobility models and different buffer sizes for the ferries. This case study illustrates the flexibility and expressive power of stochastic HYPE. We also discuss the software that enables us to describe stochastic HYPE models and simulate them.Comment: In Proceedings QAPL 2012, arXiv:1207.055

Contributions to modeling, structural analysis, and routing performance in dynamic networks

Cette thèse apporte des contributions à la modélisation, compréhension ainsi qu’à la communication efficace d’information dans les réseaux dynamiques peuplant la périphérie de l’Internet. Par réseaux dynamiques, nous signifions les réseaux pouvant être modélisés par des graphes dynamiques dans lesquels noeuds et liens évoluent temporellement. Dans la première partie de la thèse, nous proposons un nouveau modèle de mobilité - STEPS - qui permet de capturer un large spectre de comportement de mobilité humains. STEPS mets en oeuvre deux principes fondamentaux de la mobilité humaine : l’attachement préférentiel à une zone de prédilection et l’attraction vers une zone de prédilection. Nous proposons une modélisation markovienne de ce modèle de mobilité. Nous montrons que ce simple modèle paramétrique est capable de capturer les caractéristiques statistiques saillantes de la mobilité humaine comme la distribution des temps d’inter-contacts et de contacts. Dans la deuxième partie, en utilisant STEPS, nous analysons les propriétés comportementales et structurelles fondamentales des réseaux opportunistes. Nous redéfinissons dans le contexte des réseaux dynamiques la notion de structure petit monde et montrons comment une telle structure peut émerger. En particulier, nous montrons que les noeuds fortement dynamiques peuvent jouer le rôle de ponts entre les composants déconnectés, aident à réduire significativement la longueur du chemin caractéristique du réseau et contribuent à l’émergence du phénomène petit-monde dans les réseaux dynamiques. Nous proposons une façon de modéliser ce phénomène sous STEPS. À partir d’un réseau dynamique régulier dans lequel les noeuds limitent leur mobilité à leurs zones préférentielles respectives. Nous recablons ce réseau en injectant progressivement des noeuds nomades se déplaçant entre plusieurs zones. Nous montrons que le pourcentage de tels nœuds nomades est de 10%, le réseau possède une structure petit monde avec un fort taux de clusterisation et un faible longueur du chemin caractéristique. La troisième contribution de cette thèse porte sur l’étude de l’impact du désordre et de l’irrégularité des contacts sur la capacité de communication d’un réseau dynamique. Nous analysons le degré de désordre de réseaux opportunistes réels et montrons que si exploité correctement, celui-ci peut améliorer significativement les performances du routage. Nous introduisons ensuite un modèle permettant de capturer le niveau de désordre d’un réseau dynamique. Nous proposons deux algorithmes simples et efficaces qui exploitent la structure temporelle d’un réseau dynamique pour délivrer les messages avec un bon compromis entre l’usage des ressources et les performances. Les résultats de simulations et analytiques montrent que ce type d’algorithme est plus performant que les approches classiques. Nous mettons également en évidence aussi la structure de réseau pour laquelle ce type d’algorithme atteint ses performances optimum. Basé sur ce résultat théorique nous proposons un nouveau protocole de routage efficace pour les réseaux opportunistes centré sur le contenu. Dans ce protocole, les noeuds maintiennent, via leurs contacts opportunistes, une fonction d’utilité qui résume leur proximité spatio-temporelle par rapport aux autres noeuds. En conséquence, router dans un tel contexte se résume à suivre le gradient de plus grande pente conduisant vers le noeud destination. Cette propriété induit un algorithme de routage simple et efficace qui peut être utilisé aussi bien dans un contexte d’adressage IP que de réseau centré sur les contenus. Les résultats de simulation montrent que ce protocole superforme les protocoles de routage classiques déjà définis pour les réseaux opportunistes. La dernière contribution de cette thèse consiste à mettre en évidence une application potentielle des réseaux dynamiques dans le contexte du « mobile cloud computing ». En utilisant les techniques d’optimisation particulaires, nous montrons que la mobilité peut augmenter considérablement la capacité de calcul des réseaux dynamiques. De plus, nous montrons que la structure dynamique du réseau a un fort impact sur sa capacité de calcul. ABSTRACT : This thesis contributes to the modeling, understanding and efficient communication in dynamic networks populating the periphery of the Internet. By dynamic networks, we refer to networks that can be modeled by dynamic graphs in which nodes and links change temporally. In the first part of the thesis, we propose a new mobility model - STEPS - which captures a wide spectrum of human mobility behavior. STEPS implements two fundamental principles of human mobility: preferential attachment and attractor. We show that this simple parametric model is able to capture the salient statistical properties of human mobility such as the distribution of inter-contact/contact time. In the second part, using STEPS, we analyze the fundamental behavioral and structural properties of opportunistic networks. We redefine in the context of dynamic networks the concept of small world structure and show how such a structure can emerge. In particular, we show that highly dynamic nodes can play the role of bridges between disconnected components, helping to significantly reduce the length of network path and contribute to the emergence of small-world phenomenon in dynamic networks. We propose a way to model this phenomenon in STEPS. From a regular dynamic network in which nodes limit their mobility to their respective preferential areas. We rewire this network by gradually injecting highly nomadic nodes moving between different areas. We show that when the ratio of such nomadic nodes is around 10%, the network has small world structure with a high degree of clustering and a low characteristic path length. The third contribution of this thesis is the study of the impact of disorder and contact irregularity on the communication capacity of a dynamic network. We analyze the degree of disorder of real opportunistic networks and show that if used correctly, it can significantly improve routing performances. We then introduce a model to capture the degree of disorder in a dynamic network. We propose two simple and efficient algorithms that exploit the temporal structure of a dynamic network to deliver messages with a good tradeoff between resource usage and performance. The simulation and analytical results show that this type of algorithm is more efficient than conventional approaches. We also highlight also the network structure for which this type of algorithm achieves its optimum performance. Based on this theoretical result, we propose a new efficient routing protocol for content centric opportunistic networks. In this protocol, nodes maintain, through their opportunistic contacts, an utility function that summarizes their spatio-temporal proximity to other nodes. As a result, routing in this context consists in following the steepest slopes of the gradient field leading to the destination node. This property leads to a simple and effective algorithm routing that can be used both in the context of IP networks and content centric networks. The simulation results show that this protocol outperforms traditional routing protocols already defined for opportunistic networks. The last contribution of this thesis is to highlight the potential application of dynamic networks in the context of "mobile cloud computing." Using the particle optimization techniques, we show that mobility can significantly increase the processing capacity of dynamic networks. In addition, we show that the dynamic structure of the network has a strong impact on its processing capacity

Virtual Mobility Domains - A Mobility Architecture for the Future Internet

The advances in hardware and wireless technologies have made mobile communication devices affordable by a vast user community. With the advent of rich multimedia and social networking content, an influx of myriads of applications, and Internet supported services, there is an increasing user demand for the Internet connectivity anywhere and anytime. Mobility management is thus a crucial requirement for the Internet today. This work targets novel mobility management techniques, designed to work with the Floating Cloud Tiered (FCT) internetworking model, proposed for a future Internet. We derive the FCT internetworking model from the tiered structure existing among Internet Service Provider (ISP) networks, to define their business and peering relationships. In our novel mobility management scheme, we define Virtual Mobility Domains (VMDs) of various scopes, that can support both intra and inter-domain roaming using a single address for a mobile node. The scheme is network based and hence imposes no operational load on the mobile node. This scheme is the first of its kind, by leveraging the tiered structure and its hierarchical properties, the collaborative network-based mobility management mechanism, and the inheritance information in the tiered addresses to route packets. The contributions of this PhD thesis can be summarized as follows: · We contribute to the literature with a comprehensive analysis of the future Internet architectures and mobility protocols over the period of 2002-2012, in light of their identity and handoff management schemes. We present a qualitative evaluation of current and future schemes on a unified platform. · We design and implement a novel user-centric future Internet mobility architecture called Virtual Mobility Domain. VMD proposes a seamless, network-based, unique collaborative mobility management within/across ASes and ISPs in the FCT Internetworking model. The analytical and simulation-based handoff performance analysis of the VMD architecture in comparison with the IPv6-based mobility protocols presents the considerable performance improvements achieved by the VMD architecture. · We present a novel and user-centric handoff cost framework to analyze handoff performance of different mobility schemes. The framework helps to examine the impacts of registration costs, signaling overhead, and data loss for Internet connected mobile users employing a unified cost metric. We analyze the effect of each parameter in the handoff cost framework on the handoff cost components. We also compare the handoff performance of IPv6-based mobility protocols to the VMD. · We present a handoff cost optimization problem and analysis of its characteristics. We consider a mobility user as the primary focus of our study. We then identify the suitable mathematical methods that can be leveraged to solve the problem. We model the handoff cost problem in an optimization tool. We also conduct a mobility study - best of our knowledge, first of its kind - on providing a guide for finding the number of handoffs in a typical VMD for any given user\u27s mobility model. Plugging the output of mobility study, we then conduct a numerical analysis to find out optimum VMD for a given user mobility model and check if the theoretical inferences are in agreement with the output of the optimization tool

Computing Nash Equilibrium in Wireless Ad Hoc Networks: A Simulation-Based Approach

This paper studies the problem of computing Nash equilibrium in wireless networks modeled by Weighted Timed Automata. Such formalism comes together with a logic that can be used to describe complex features such as timed energy constraints. Our contribution is a method for solving this problem using Statistical Model Checking. The method has been implemented in UPPAAL model checker and has been applied to the analysis of Aloha CSMA/CD and IEEE 802.15.4 CSMA/CA protocols.Comment: In Proceedings IWIGP 2012, arXiv:1202.422

Cognition-Based Networks: A New Perspective on Network Optimization Using Learning and Distributed Intelligence

IEEE Access Volume 3, 2015, Article number 7217798, Pages 1512-1530 Open Access Cognition-based networks: A new perspective on network optimization using learning and distributed intelligence (Article) Zorzi, M.a , Zanella, A.a, Testolin, A.b, De Filippo De Grazia, M.b, Zorzi, M.bc a Department of Information Engineering, University of Padua, Padua, Italy b Department of General Psychology, University of Padua, Padua, Italy c IRCCS San Camillo Foundation, Venice-Lido, Italy View additional affiliations View references (107) Abstract In response to the new challenges in the design and operation of communication networks, and taking inspiration from how living beings deal with complexity and scalability, in this paper we introduce an innovative system concept called COgnition-BAsed NETworkS (COBANETS). The proposed approach develops around the systematic application of advanced machine learning techniques and, in particular, unsupervised deep learning and probabilistic generative models for system-wide learning, modeling, optimization, and data representation. Moreover, in COBANETS, we propose to combine this learning architecture with the emerging network virtualization paradigms, which make it possible to actuate automatic optimization and reconfiguration strategies at the system level, thus fully unleashing the potential of the learning approach. Compared with the past and current research efforts in this area, the technical approach outlined in this paper is deeply interdisciplinary and more comprehensive, calling for the synergic combination of expertise of computer scientists, communications and networking engineers, and cognitive scientists, with the ultimate aim of breaking new ground through a profound rethinking of how the modern understanding of cognition can be used in the management and optimization of telecommunication network

Expressive policy based authorization model for resource-constrained device sensors.

Los capítulos II, III y IV están sujetos a confidencialidad por el autor 92 p.Upcoming smart scenarios enabled by the Internet of Things (IoT) envision smart objects that expose services that can adapt to user behavior or be managed with the goal of achieving higher productivity, often in multistakeholder applications. In such environments, smart things are cheap sensors (and actuators) and, therefore, constrained devices. However, they are also critical components because of the importance of the provided information. Given that, strong security in general and access control in particular is a must.However, tightness, feasibility and usability of existing access control models do not cope well with the principle of least privilege; they lack both expressiveness and the ability to update the policy to be enforced in the sensors. In fact, (1) traditional access control solutions are not feasible in all constrained devices due their big impact on the performance although they provide the highest effectiveness by means of tightness and flexibility. (2) Recent access control solutions designed for constrained devices can be implemented only in not so constrained ones and lack policy expressiveness in the local authorization enforcement. (3) Access control solutions currently feasible in the most severely constrained devices have been based on authentication and very coarse grained and static policies, scale badly, and lack a feasible policy based access control solution aware of local context of sensors.Therefore, there is a need for a suitable End-to-End (E2E) access control model to provide fine grained authorization services in service oriented open scenarios, where operation and management access is by nature dynamic and that integrate massively deployed constrained but manageable sensors. Precisely, the main contribution of this thesis is the specification of such a highly expressive E2E access control model suitable for all sensors including the most severely constrained ones. Concretely, the proposed E2E access control model consists of three main foundations. (1) A hybrid architecture, which combines advantages of both centralized and distributed architectures to enable multi-step authorization. Fine granularity of the enforcement is enabled by (2) an efficient policy language and codification, which are specifically defined to gain expressiveness in the authorization policies and to ensure viability in very-constrained devices. The policy language definition enables both to make granting decisions based on local context conditions, and to react accordingly to the requests by the execution of additional tasks defined as obligations.The policy evaluation and enforcement is performed not only during the security association establishment but also afterward, while such security association is in use. Moreover, this novel model provides also control over access behavior, since iterative re-evaluation of the policy is enabled during each individual resource access.Finally, (3) the establishment of an E2E security association between two mutually authenticated peers through a security protocol named Hidra. Such Hidra protocol, based on symmetric key cryptography, relies on the hybrid three-party architecture to enable multi-step authorization as well as the instant provisioning of a dynamic security policy in the sensors. Hidra also enables delegated accounting and audit trail. Proposed access control features cope with tightness, feasibility and both dimensions of usability such as scalability and manageability, which are the key unsolved challenges in the foreseen open and dynamic scenarios enabled by IoT. Related to efficiency, the high compression factor of the proposed policy codification and the optimized Hidra security protocol relying on a symmetric cryptographic schema enable the feasibility as it is demonstrated by the validation assessment. Specifically, the security evaluation and both the analytical and experimental performance evaluation demonstrate the feasibility and adequacy of the proposed protocol and access control model.Concretely, the security validation consists of the assessment that the Hidra security protocol meets the security goals of mutual strong authentication, fine-grained authorization, confidentiality and integrity of secret data and accounting. The security analysis of Hidra conveys on the one hand, how the design aspects of the message exchange contribute to the resilience against potential attacks. On the other hand, a formal security validation supported by a software tool named AVISPA ensures the absence of flaws and the correctness of the design of Hidra.The performance validation is based on an analytical performance evaluation and a test-bed implementation of the proposed access control model for the most severely constrained devices. The key performance factor is the length of the policy instance, since it impacts proportionally on the three critical parameters such as the delay, energy consumption, memory footprint and therefore, on the feasibility.Attending to the obtained performance measures, it can be concluded that the proposed policy language keeps such balance since it enables expressive policy instances but always under limited length values. Additionally, the proposed policy codification improves notably the performance of the protocol since it results in the best policy length compression factor compared with currently existing and adopted standards.Therefore, the assessed access control model is the first approach to bring to severely constrained devices a similar expressiveness level for enforcement and accounting as in current Internet. The positive performance evaluation concludes the feasibility and suitability of this access control model, which notably rises the security features on severely constrained devices for the incoming smart scenarios.Additionally, there is no comparable impact assessment of policy expressiveness of any other access control model. That is, the presented analysis models as well as results might be a reference for further analysis and benchmarkingGaur egun darabilzkigun hainbeste gailutan mikroprozesadoreak daude txertatuta, eragiten duten prozesuan neurketak egin eta logika baten ondorioz ekiteko. Horretarako, bai sentsoreak eta baita aktuadoreak erabiltzen dira (hemendik aurrera, komunitatean onartuta dagoenez, sentsoreak esango diegu nahiz eta erabilpen biak izan). Orain arteko erabilpen zabalenetako konekzio motak, banaka edota sare lokaletan konekatuta izan dira. Era honetan, sentsoreak elkarlanean elkarreri eraginez edota zerbitzari nagusi baten agindupean, erakunde baten prozesuak ahalbideratu eta hobetzeko erabili izan dira.Internet of Things (IoT) deritzonak, sentsoreak dituzten gailuak Internet sarearen bidez konektatu eta prozesu zabalagoak eta eraginkorragoak ahalbidetzen ditu. Smartcity, Smartgrid, Smartfactory eta bestelako smart adimendun ekosistemak, gaur egun dauden eta datozen komunikaziorako teknologien aukerak baliatuz, erabilpen berriak ahalbideratu eta eragina areagotzea dute helburu.Era honetan, ekosistema hauek zabalak dira, eremu ezberdinetako erakundeek hartzen dute parte, eta berariazko sentsoreak dituzten gailuen kopurua izugarri handia da. Sentsoreak beraz, berariazkoak, merkeak eta txikiak dira, eta orain arteko lehenengo erabilpen nagusia, magnitude fisikoren bat neurtzea eta neurketa hauek zerbitzari zentralizatu batera bidaltzea izan da. Hau da, inguruan gertatzen direnak neurtu, eta zerbitzari jakin bati neurrien datuak aldiro aldiro edota atari baten baldintzapean igorri. Zerbitzariak logika aplikatu eta sistema osoa adimendun moduan jardungo du. Jokabide honetan, aurretik ezagunak diren entitateen arteko komunikazioen segurtasuna bermatzearen kexka, nahiz eta Internetetik pasatu, hein onargarri batean ebatzita dago gaur egun.Baina adimendun ekosistema aurreratuak sentsoreengandik beste jokabide bat ere aurreikusten dute. Sentsoreek eurekin harremanak izateko moduko zerbitzuak ere eskaintzen dituzte. Erakunde baten prozesuetan, beste jatorri bateko erakundeekin elkarlanean, jokabide honen erabilpen nagusiak bi dira. Batetik, prozesuan parte hartzen duen erabiltzaileak (eta jabeak izan beharrik ez duenak) inguruarekin harremanak izan litzake, eta bere ekintzetan gailuak bere berezitasunetara egokitzearen beharrizana izan litzake. Bestetik, sentsoreen jarduera eta mantenimendua zaintzen duten teknikariek, beroriek egokitzeko zerbitzuen beharrizana izan dezakete.Holako harremanak, sentsoreen eta erabiltzaileen kokalekua zehaztugabea izanik, kasu askotan Internet bidez eta zuzenak (end-to-end) izatea aurreikusten da. Hau da, sentsore txiki asko daude handik hemendik sistemaren adimena ahalbidetuz, eta harreman zuzenetarako zerbitzu ñimiñoak eskainiz. Batetik, zerbitzu zuzena, errazagoa eta eraginkorragoa dena, bestetik erronkak ere baditu. Izan ere, sentsoreak hain txikiak izanik, ezin dituzte gaur egungo protokolo eta mekanismo estandarak gauzatu. Beraz, sare mailatik eta aplikazio mailarainoko berariazko protokoloak sortzen ari dira.Tamalez, protokolo hauek arinak izatea dute helburu eta segurtasuna ez dute behar den moduan aztertu eta gauzatzen. Eta egon badaude berariazko sarbide kontrolerako ereduak baina baliabideen urritasuna dela eta, ez dira ez zorrotzak ez kudeagarriak. Are gehiago, Gartnerren arabera, erabilpen aurreratuetan inbertsioa gaur egun mugatzen duen traba Nagusia segurtasunarekiko mesfidantza da.Eta hauxe da erronka eta tesi honek landu duen gaia: batetik sentsoreak hain txikiak izanik, eta baliabideak hain urriak (10kB RAM, 100 kB Flash eta bateriak, sentsore txikienetarikoetan), eta bestetik Internet sarea hain zabala eta arriskutsua izanik, segurtasuna areagotuko duen sarbide zuzenaren kontrolerako eredu zorrotz, arin eta kudeagarri berri bat zehaztu eta bere erabilgarritasuna aztertu

Expressive policy based authorization model for resource-constrained device sensors.

Los capítulos II, III y IV están sujetos a confidencialidad por el autor 92 p.Upcoming smart scenarios enabled by the Internet of Things (IoT) envision smart objects that expose services that can adapt to user behavior or be managed with the goal of achieving higher productivity, often in multistakeholder applications. In such environments, smart things are cheap sensors (and actuators) and, therefore, constrained devices. However, they are also critical components because of the importance of the provided information. Given that, strong security in general and access control in particular is a must.However, tightness, feasibility and usability of existing access control models do not cope well with the principle of least privilege; they lack both expressiveness and the ability to update the policy to be enforced in the sensors. In fact, (1) traditional access control solutions are not feasible in all constrained devices due their big impact on the performance although they provide the highest effectiveness by means of tightness and flexibility. (2) Recent access control solutions designed for constrained devices can be implemented only in not so constrained ones and lack policy expressiveness in the local authorization enforcement. (3) Access control solutions currently feasible in the most severely constrained devices have been based on authentication and very coarse grained and static policies, scale badly, and lack a feasible policy based access control solution aware of local context of sensors.Therefore, there is a need for a suitable End-to-End (E2E) access control model to provide fine grained authorization services in service oriented open scenarios, where operation and management access is by nature dynamic and that integrate massively deployed constrained but manageable sensors. Precisely, the main contribution of this thesis is the specification of such a highly expressive E2E access control model suitable for all sensors including the most severely constrained ones. Concretely, the proposed E2E access control model consists of three main foundations. (1) A hybrid architecture, which combines advantages of both centralized and distributed architectures to enable multi-step authorization. Fine granularity of the enforcement is enabled by (2) an efficient policy language and codification, which are specifically defined to gain expressiveness in the authorization policies and to ensure viability in very-constrained devices. The policy language definition enables both to make granting decisions based on local context conditions, and to react accordingly to the requests by the execution of additional tasks defined as obligations.The policy evaluation and enforcement is performed not only during the security association establishment but also afterward, while such security association is in use. Moreover, this novel model provides also control over access behavior, since iterative re-evaluation of the policy is enabled during each individual resource access.Finally, (3) the establishment of an E2E security association between two mutually authenticated peers through a security protocol named Hidra. Such Hidra protocol, based on symmetric key cryptography, relies on the hybrid three-party architecture to enable multi-step authorization as well as the instant provisioning of a dynamic security policy in the sensors. Hidra also enables delegated accounting and audit trail. Proposed access control features cope with tightness, feasibility and both dimensions of usability such as scalability and manageability, which are the key unsolved challenges in the foreseen open and dynamic scenarios enabled by IoT. Related to efficiency, the high compression factor of the proposed policy codification and the optimized Hidra security protocol relying on a symmetric cryptographic schema enable the feasibility as it is demonstrated by the validation assessment. Specifically, the security evaluation and both the analytical and experimental performance evaluation demonstrate the feasibility and adequacy of the proposed protocol and access control model.Concretely, the security validation consists of the assessment that the Hidra security protocol meets the security goals of mutual strong authentication, fine-grained authorization, confidentiality and integrity of secret data and accounting. The security analysis of Hidra conveys on the one hand, how the design aspects of the message exchange contribute to the resilience against potential attacks. On the other hand, a formal security validation supported by a software tool named AVISPA ensures the absence of flaws and the correctness of the design of Hidra.The performance validation is based on an analytical performance evaluation and a test-bed implementation of the proposed access control model for the most severely constrained devices. The key performance factor is the length of the policy instance, since it impacts proportionally on the three critical parameters such as the delay, energy consumption, memory footprint and therefore, on the feasibility.Attending to the obtained performance measures, it can be concluded that the proposed policy language keeps such balance since it enables expressive policy instances but always under limited length values. Additionally, the proposed policy codification improves notably the performance of the protocol since it results in the best policy length compression factor compared with currently existing and adopted standards.Therefore, the assessed access control model is the first approach to bring to severely constrained devices a similar expressiveness level for enforcement and accounting as in current Internet. The positive performance evaluation concludes the feasibility and suitability of this access control model, which notably rises the security features on severely constrained devices for the incoming smart scenarios.Additionally, there is no comparable impact assessment of policy expressiveness of any other access control model. That is, the presented analysis models as well as results might be a reference for further analysis and benchmarkingGaur egun darabilzkigun hainbeste gailutan mikroprozesadoreak daude txertatuta, eragiten duten prozesuan neurketak egin eta logika baten ondorioz ekiteko. Horretarako, bai sentsoreak eta baita aktuadoreak erabiltzen dira (hemendik aurrera, komunitatean onartuta dagoenez, sentsoreak esango diegu nahiz eta erabilpen biak izan). Orain arteko erabilpen zabalenetako konekzio motak, banaka edota sare lokaletan konekatuta izan dira. Era honetan, sentsoreak elkarlanean elkarreri eraginez edota zerbitzari nagusi baten agindupean, erakunde baten prozesuak ahalbideratu eta hobetzeko erabili izan dira.Internet of Things (IoT) deritzonak, sentsoreak dituzten gailuak Internet sarearen bidez konektatu eta prozesu zabalagoak eta eraginkorragoak ahalbidetzen ditu. Smartcity, Smartgrid, Smartfactory eta bestelako smart adimendun ekosistemak, gaur egun dauden eta datozen komunikaziorako teknologien aukerak baliatuz, erabilpen berriak ahalbideratu eta eragina areagotzea dute helburu.Era honetan, ekosistema hauek zabalak dira, eremu ezberdinetako erakundeek hartzen dute parte, eta berariazko sentsoreak dituzten gailuen kopurua izugarri handia da. Sentsoreak beraz, berariazkoak, merkeak eta txikiak dira, eta orain arteko lehenengo erabilpen nagusia, magnitude fisikoren bat neurtzea eta neurketa hauek zerbitzari zentralizatu batera bidaltzea izan da. Hau da, inguruan gertatzen direnak neurtu, eta zerbitzari jakin bati neurrien datuak aldiro aldiro edota atari baten baldintzapean igorri. Zerbitzariak logika aplikatu eta sistema osoa adimendun moduan jardungo du. Jokabide honetan, aurretik ezagunak diren entitateen arteko komunikazioen segurtasuna bermatzearen kexka, nahiz eta Internetetik pasatu, hein onargarri batean ebatzita dago gaur egun.Baina adimendun ekosistema aurreratuak sentsoreengandik beste jokabide bat ere aurreikusten dute. Sentsoreek eurekin harremanak izateko moduko zerbitzuak ere eskaintzen dituzte. Erakunde baten prozesuetan, beste jatorri bateko erakundeekin elkarlanean, jokabide honen erabilpen nagusiak bi dira. Batetik, prozesuan parte hartzen duen erabiltzaileak (eta jabeak izan beharrik ez duenak) inguruarekin harremanak izan litzake, eta bere ekintzetan gailuak bere berezitasunetara egokitzearen beharrizana izan litzake. Bestetik, sentsoreen jarduera eta mantenimendua zaintzen duten teknikariek, beroriek egokitzeko zerbitzuen beharrizana izan dezakete.Holako harremanak, sentsoreen eta erabiltzaileen kokalekua zehaztugabea izanik, kasu askotan Internet bidez eta zuzenak (end-to-end) izatea aurreikusten da. Hau da, sentsore txiki asko daude handik hemendik sistemaren adimena ahalbidetuz, eta harreman zuzenetarako zerbitzu ñimiñoak eskainiz. Batetik, zerbitzu zuzena, errazagoa eta eraginkorragoa dena, bestetik erronkak ere baditu. Izan ere, sentsoreak hain txikiak izanik, ezin dituzte gaur egungo protokolo eta mekanismo estandarak gauzatu. Beraz, sare mailatik eta aplikazio mailarainoko berariazko protokoloak sortzen ari dira.Tamalez, protokolo hauek arinak izatea dute helburu eta segurtasuna ez dute behar den moduan aztertu eta gauzatzen. Eta egon badaude berariazko sarbide kontrolerako ereduak baina baliabideen urritasuna dela eta, ez dira ez zorrotzak ez kudeagarriak. Are gehiago, Gartnerren arabera, erabilpen aurreratuetan inbertsioa gaur egun mugatzen duen traba Nagusia segurtasunarekiko mesfidantza da.Eta hauxe da erronka eta tesi honek landu duen gaia: batetik sentsoreak hain txikiak izanik, eta baliabideak hain urriak (10kB RAM, 100 kB Flash eta bateriak, sentsore txikienetarikoetan), eta bestetik Internet sarea hain zabala eta arriskutsua izanik, segurtasuna areagotuko duen sarbide zuzenaren kontrolerako eredu zorrotz, arin eta kudeagarri berri bat zehaztu eta bere erabilgarritasuna aztertu

Modelling Probabilistic Wireless Networks

We propose a process calculus to model high level wireless systems, where the topology of a network is described by a digraph. The calculus enjoys features which are proper of wireless networks, namely broadcast communication and probabilistic behaviour. We first focus on the problem of composing wireless networks, then we present a compositional theory based on a probabilistic generalisation of the well known may-testing and must-testing pre- orders. Also, we define an extensional semantics for our calculus, which will be used to define both simulation and deadlock simulation preorders for wireless networks. We prove that our simulation preorder is sound with respect to the may-testing preorder; similarly, the deadlock simulation pre- order is sound with respect to the must-testing preorder, for a large class of networks. We also provide a counterexample showing that completeness of the simulation preorder, with respect to the may testing one, does not hold. We conclude the paper with an application of our theory to probabilistic routing protocols

Impact of Random Deployment on Operation and Data Quality of Sensor Networks

Several applications have been proposed for wireless sensor networks, including habitat monitoring, structural health monitoring, pipeline monitoring, and precision agriculture. Among the desirable features of wireless sensor networks, one is the ease of deployment. Since the nodes are capable of self-organization, they can be placed easily in areas that are otherwise inaccessible to or impractical for other types of sensing systems. In fact, some have proposed the deployment of wireless sensor networks by dropping nodes from a plane, delivering them in an artillery shell, or launching them via a catapult from onboard a ship. There are also reports of actual aerial deployments, for example the one carried out using an unmanned aerial vehicle (UAV) at a Marine Corps combat centre in California -- the nodes were able to establish a time-synchronized, multi-hop communication network for tracking vehicles that passed along a dirt road. While this has a practical relevance for some civil applications (such as rescue operations), a more realistic deployment involves the careful planning and placement of sensors. Even then, nodes may not be placed optimally to ensure that the network is fully connected and high-quality data pertaining to the phenomena being monitored can be extracted from the network. This work aims to address the problem of random deployment through two complementary approaches: The first approach aims to address the problem of random deployment from a communication perspective. It begins by establishing a comprehensive mathematical model to quantify the energy cost of various concerns of a fully operational wireless sensor network. Based on the analytic model, an energy-efficient topology control protocol is developed. The protocol sets eligibility metric to establish and maintain a multi-hop communication path and to ensure that all nodes exhaust their energy in a uniform manner. The second approach focuses on addressing the problem of imperfect sensing from a signal processing perspective. It investigates the impact of deployment errors (calibration, placement, and orientation errors) on the quality of the sensed data and attempts to identify robust and error-agnostic features. If random placement is unavoidable and dense deployment cannot be supported, robust and error-agnostic features enable one to recognize interesting events from erroneous or imperfect data