In public warning message systems, information dissemination across the network is a critical aspect that has to be addressed. Dissemination of warning messages should be such that it reaches as many nodes in the network in a short time. In communication networks those based on device to device interactions, dissemination of the information has lately picked up lot of interest and the need for self organization of the network has been brought up. Self organization leads to local behaviors and interactions that have global effects and helps in addressing scaling issues. The use of self organized features allows autonomous behavior with low memory usage. Some examples of self organization phenomenon that are observed in nature are Lateral Inhibition and Flocking. In order to provide self organized features to communication networks, insights from such naturally occurring phenomenon is used. Achieving small world properties is an attractive way to enhance information dissemination across the network. In small world model rewiring of links in the network is performed by altering the length and the direction of the existing links. In an autonomous wireless environment such organization can be achieved using self organized phenomenon like Lateral inhibition and Flocking and beamforming (a concept in communication). Towards this, we first use Lateral Inhibition, analogy to Flocking behavior and beamforming to show how dissemination of information can be enhanced. Lateral Inhibition is used to create virtual regions in the network. Then using the analogy of Flocking rules, beam properties of the nodes in the regions are set. We then prove that small world properties are achieved using average path length metric. However, the proposed algorithm is applicable to static networks and Flocking and Lateral Inhibition concepts, if used in a mobile scenario, will be highly complex in terms of computation and memory. In a mobile scenario such as human mobility aided networks, the network structure changes frequently. In such conditions dissemination of information is highly impacted as new connections are made and old ones are broken. We thus use stability concept in mobile networks with beamforming to show how information dissemination process can be enhanced. In the algorithm, we first predict the stability of a node in the mobile network using locally available information and then uses it to identify beamforming nodes. In the algorithm, the low stability nodes are allowed to beamform towards the nodes with high stability. The difference between high and low stability nodes is based on threshold value. The algorithm is developed such that it does not require any global knowledge about the network and works using only local information. The results are validated using how quickly more number of nodes receive the information and different state of the art algorithms. We also show the effect of various parameters such as number of sources, number of packets, mobility parameters and antenna parameters etc. on the information dissemination process in the network. In realistic scenarios however, the dynamicity in the network is not only related to mobility. Dynamic conditions also arise due to change in density of nodes at a given time. To address effect of such scenario on the dissemination of information related to public safety in a metapopulation, we use the concepts of epidemic model, beamforming and the countrywide mobility pattern extracted from the $D4D$ dataset. Here, we also propose the addition of three latent states to the existing epidemic model ($SIR$ model). We study the transient states towards the evolution of the number of devices having the information and the difference in the number of devices having the information when compared with different cases to evaluate the results. Through the results we show that enhancements in the dissemination process can be achieved in the addressed scenario

Abstract The thesis concentrates on evaluating and improving performances of various multiple-input multiple-output (MIMO) relaying scenarios that are particularly relevant to future wireless systems. A greater emphasis is placed on important practical situations, considering relay deployments, availability of channel state information (CSI), limitations of spectrum, and information secrecy. Initially, the performance of a non-coherent amplify-and-forward (AF) MIMO relaying is analyzed when the relay is deployed with the relay-to-destination channel having a line-of-sight (LoS) path. The main attention is given to analyzing the performance of orthogonal space-time block coded based non-coherent AF MIMO system. Exact expressions of statistical parameters and performance metrics are derived considering the instantaneous signal-to-noise ratio (SNR) received at the destination. These performance metrics reveal that a strong LoS component in relay-destination channel always limits the performance promised by MIMO scattering environment when both nodes have multiple antennas. The thesis also considers scenarios in MIMO two-way relaying (TWR) with physical layer network coding (PNC) mapping at the relay. PNC mapping becomes complex with multiple streams being combined at the relay node. Joint precoder-decoder schemes are considered to ease this, and various studies are carried out depending on the CSI. The zero-forcing criterion is used at the nodes when perfect CSI is available. For the imperfect CSI scenario, a robust joint precoder-decoder design is considered. The precoder and decoder matrices are obtained by solving optimization problems, which are formulated to maximize sum-rate and minimize weighted mean square error (WMSE) under transmit power constraints on the nodes. Next, a precoder-decoder scheme for MIMO underlay device-to-device (D2D) communication system is investigated by considering two D2D modes; PNC based D2D and direct D2D. The joint design is based on minimizing mean square error (MSE) which is useful to mitigate interference, and to improve the performance of both D2D and cellular communications. Distributed and centralized algorithms are proposed considering bi-directional communication in both D2D and cellular communications. System performance is discussed with two transmit mode selection schemes as dynamic and static selection schemes. The results show that the PNC based D2D mode extends the coverage area of D2D communication. Finally, secure beamforming schemes for the PNC based MIMO TWR systems are investigated when multiple eavesdroppers are attempting to intercept the user information. The CSI of the user-to-eavesdropper channels is imperfect at the users. The channel estimation errors are assumed with both ellipsoidal bound and Gaussian Markov uncertainty models. Robust optimization problems are formulated considering both scenarios to design beamforming vectors at the users and relay. Numerical results suggest that the proposed algorithms converge fast and provide higher security. / Tiivistelmä Tässä väitöskirjassa keskitytään arvioimaan ja parantamaan suorituskykyä useissa moniantennitoistinjärjestelmissä, jotka ovat ajankohtaisia tulevaisuuden langattomissa verkoissa. Erityisesti työssä analysoidaan tärkeitä käytännön tilanteita, sisältäen toistimien sijoittamisen, kanavatiedon saatavuuden, rajoitetun taajuuskaistan ja tiedon salauksen. Aluksi epäkoherentin, vahvistavan ja jatkolähettävän moniantennitoistimen suorituskykyä analysoidaan tilanteessa, jossa toistin on sijoitettu siten, että kohteeseen on suora yhteys. Suorituskyvyn arvioinnin pääkohteena on ortogonaalinen tila-aika-tason lohkokoodattu epäkoherentti vahvistava ja jatkolähettävä moniantennitoistin. Työssä johdetaan tarkat lausekkeet tilastollisille parametreille ja suorituskykymittareille ottaen huomioon hetkellinen signaalikohinasuhde vastaanottimessa. Nämä suorituskykymittarit ilmaisevat, että toistimen ja kohteen välillä oleva vahva suoran yhteyden komponentti rajoittaa sitä suorituskykyä, jota moniantennijärjestelmän hajontaympäristö ennustaa. Työssä tutkitaan myös kahdensuuntaisia moniantennitoistimia, jotka käyttävät fyysisen kerroksen verkkokoodausta. Koodauksesta tulee monimutkaista, kun monia datavirtoja yhdistetään toistimessa. Tämän helpottamiseksi käytetään yhdistettyä esikoodaus-dekoodausmenetelmää, jota tutkitaan erilaisten kanavatietojen tapauksissa. Täydellisen kanavatiedon tapauksessa käytetään nollaanpakotuskriteeriä. Epätäydellisen kanavatiedon tapauksessa käytetään robustia yhdistettyä esikoodaus-dekoodausmenetelmää. Esikoodaus- ja dekoodausmatriisit saadaan ratkaisemalla optimointiongelmat. Nämä ongelmat on muodostettu maksimoimaan summadatanopeus, ja minimoimaan painotettu keskineliövirhe, kun optimointirajoitteina ovat solmujen lähetystehot. Seuraavaksi esikoodaus-dekoodausmenetelmää tutkitaan moniantennijärjestelmässä, jossa käytetään kahdentyyppistä laitteesta-laitteeseen (D2D) kommunikaatiomenetelmää: fyysisen kerroksen verkkokoodaukseen pohjautuvaa D2D- ja suoraa D2D-kommunikaatiota. Yhteissuunnittelu perustuu keskineliövirheen minimointiin, joka on hyödyllistä, kun halutaan vähentää häiriötä ja parantaa molempien verkkojen suorituskykyä. Työssä ehdotetaan hajautettuja ja keskitettyjä algoritmeja tilanteessa, jossa käytetään kaksisuuntaista kommunikaatiota molemmissa verkoissa. Järjestelmän suorituskykyä arvioidaan, kun käytetään kahta eri lähetystilan valintaa, dynaamista ja staattista. Tulokset osoittavat, että fyysisen kerroksen verkkokoodaukseen pohjautuva D2D kasvattaa D2D-kommunikaatiojärjestelmän kantamaa. Lopuksi, turvallisia keilanmuodostustekniikoita arvioidaan fyysisen kerroksen verkkokoodaukseen pohjautuvassa kahdensuuntaisessa moniantennitoistinjärjestelmässä, kun useat salakuuntelijat yritävät siepata käyttäjätiedon. Käyttäjillä on epäideaalinen kanavatieto heidän ja salakuuntelijoiden välisten linkkien kanavista. Kanavatiedon estimointivirheitä arvioidaan ellipsoidisella ja Gauss-Markov-epävarmuusmallilla. Robustit optimointiongelmat, joissa suunnitellaan keilanmuodostusvektorit käyttäjän ja toistimen välille, muodostetaan molemmille malleille. Numeeriset tulokset osoittavat, että ehdotetut algoritmit konvergoituvat nopeasti ja tarjoavat korkeamman turvallisuuden.

Dans les systèmes d'alertes publiques, l’étude de la diffusion des informations dans le réseau est essentielle. Les systèmes de diffusion des messages d'alertes doivent atteindre beaucoup de nœuds en peu de temps. Dans les réseaux de communication basés sur les interactions “device to device”, on s'est récemment beaucoup intéressé à la diffusion des informations et le besoin d'auto-organisation a été mis en évidence. L'auto-organisation conduit à des comportements locaux et des interactions qui ont un effet sur le réseau global et présentent un avantage de scalabilité. Ces réseaux auto-organisés peuvent être autonomes et utiliser peu d'espace mémoire. On peut développer des caractères auto-organisés dans les réseaux de communication en utilisant des idées venant de phénomènes naturels. Il semble intéressant de chercher à obtenir les propriétés des “small world” pour améliorer la diffusion des informations dans le réseau. Dans les modèles de “small world” on réalise un recâblage des liens dans le réseau en changeant la taille et la direction des liens existants. Dans un environnement sans-fils autonome une organisation de ce type peut être créée en utilisant le flocking, l'inhibition latérale et le “beamforming”. Dans ce but, l'auteur utilise d'abord l'analogie avec l'inhibition latérale, le flocking et le “beamforming” pour montrer comment la diffusion des informations peut être améliorée. L'analogue de l'inhibition latérale est utilisé pour créer des régions virtuelles dans le réseau. Puis en utilisant l'analogie avec les règles du flocking, on caractérise les propriétés des faisceaux permettant aux nœuds de communiquer dans les régions. Nous prouvons que les propriétés des “small world” sont vérifiées en utilisant la mesure des moyennes des longueurs des chemins. Cependant l'algorithme proposé est valable pour les réseaux statiques alors que dans les cas introduisant de la mobilité, les concepts d'inhibition latérale et de flocking nécessiteraient beaucoup plus de temps. Dans le cas d'un réseau mobile la structure du réseau change fréquemment. Certaines connexions intermittentes impactent fortement la diffusion des informations. L'auteur utilise le concept de stabilité avec le “beamforming” pour montrer comment on peut améliorer la diffusion des informations. Dans son algorithme il prévoit d'abord la stabilité du nœud en utilisant des informations locales et il utilise ce résultat pour identifier les nœuds qui réaliseront du beamforming. Dans l'algorithme, les nœuds de stabilité faible sont autorisés à faire du beamforming vers les nœuds de forte stabilité. La frontière entre forte et faible stabilité est fixée par un seuil. Cet algorithme ne nécessite pas une connaissance globale du réseau, mais utilise des données locales. Les résultats sont validés en étudiant le temps au bout duquel plus de nœuds reçoivent l'information et en comparant avec d'autres algorithmes de la littérature. Cependant, dans les réseaux réels, les changements de structure ne sont pas dus qu'à la mobilité, mais également à des changements de la densité des nœuds à un moment donné. Pour tenir compte de l'influence de tels événements sur la diffusion des informations concernant la sécurité publique, l'auteur utilise les concepts de modèle de métapopulation, épidémiologiques, “beamforming” et mobilité géographique obtenu à partir de données D4D. L'auteur propose la création de trois états latents qu'il ajoute au modèle épidémiologique connu: SIR. L'auteur étudie les états transitoires en analysant l'évolution du nombre de postes ayant reçu les informations et compare les résultats concernant ce nombre dans les différents cas. L'auteur démontre ainsi que le scenario qu'il propose permet d'améliorer le processus de diffusion des informations. Il montre aussi les effets de différents paramètres comme le nombre de sources, le nombre de paquets, les paramètres de mobilité et ceux qui caractérisent les antennes sur la diffusion des informations / In public warning message systems, information dissemination across the network is a critical aspect that has to be addressed. Dissemination of warning messages should be such that it reaches as many nodes in the network in a short time. In communication networks those based on device to device interactions, dissemination of the information has lately picked up lot of interest and the need for self organization of the network has been brought up. Self organization leads to local behaviors and interactions that have global effects and helps in addressing scaling issues. The use of self organized features allows autonomous behavior with low memory usage. Some examples of self organization phenomenon that are observed in nature are Lateral Inhibition and Flocking. In order to provide self organized features to communication networks, insights from such naturally occurring phenomenon is used. Achieving small world properties is an attractive way to enhance information dissemination across the network. In small world model rewiring of links in the network is performed by altering the length and the direction of the existing links. In an autonomous wireless environment such organization can be achieved using self organized phenomenon like Lateral inhibition and Flocking and beamforming (a concept in communication). Towards this, we first use Lateral Inhibition, analogy to Flocking behavior and beamforming to show how dissemination of information can be enhanced. Lateral Inhibition is used to create virtual regions in the network. Then using the analogy of Flocking rules, beam properties of the nodes in the regions are set. We then prove that small world properties are achieved using average path length metric. However, the proposed algorithm is applicable to static networks and Flocking and Lateral Inhibition concepts, if used in a mobile scenario, will be highly complex in terms of computation and memory. In a mobile scenario such as human mobility aided networks, the network structure changes frequently. In such conditions dissemination of information is highly impacted as new connections are made and old ones are broken. We thus use stability concept in mobile networks with beamforming to show how information dissemination process can be enhanced. In the algorithm, we first predict the stability of a node in the mobile network using locally available information and then uses it to identify beamforming nodes. In the algorithm, the low stability nodes are allowed to beamform towards the nodes with high stability. The difference between high and low stability nodes is based on threshold value. The algorithm is developed such that it does not require any global knowledge about the network and works using only local information. The results are validated using how quickly more number of nodes receive the information and different state of the art algorithms. We also show the effect of various parameters such as number of sources, number of packets, mobility parameters and antenna parameters etc. on the information dissemination process in the network. In realistic scenarios however, the dynamicity in the network is not only related to mobility. Dynamic conditions also arise due to change in density of nodes at a given time. To address effect of such scenario on the dissemination of information related to public safety in a metapopulation, we use the concepts of epidemic model, beamforming and the countrywide mobility pattern extracted from the $D4D$ dataset. Here, we also propose the addition of three latent states to the existing epidemic model ($SIR$ model). We study the transient states towards the evolution of the number of devices having the information and the difference in the number of devices having the information when compared with different cases to evaluate the results. Through the results we show that enhancements in the dissemination process can be achieved in the addressed scenario

Auf dem Gebiet der Gerätesteuerung existieren zahlreiche Insellösungen, die den Anspruch nach generischer Eignung nicht erfüllen. In besonderer Weise defizitär ist der Mangel an ganzheitlichen, offenen Frameworks, bei denen die Autokonfiguration, die Gerätezuordenbarkeit vor Ort, die Geräteüberwachbarkeit, die Inter-Gerätekommunikation und die Automatisierbarkeit von Abläufen Berücksichtigung finden. Vor diesem Hintergrund öffnet die Arbeit mit einer Bestandsaufnahme von Technologien, die Einzelanforderungen der generischen Gerätesteuerung erfüllen. Sie bilden im weiteren Verlauf das potentielle Architekturfundament. Der Betrachtungsrahmen wird hierbei soweit ausgedehnt, dass relevante Verfahrensschritte vom Geräteanschluss bis zur automatisierten Generierung von User Interfaces abgedeckt sind. Unter Rückgriff auf ausgewählte Technologien wird ein zweigliedriger Ansatz vorgestellt, der ein sehr breites Spektrum potentieller Steuergeräte unterstützt und gleichzeitig technologieoffen im Hinblick auf die Autogenerierung von User Interfaces ist. Höchstmögliche Funktionalität wird durch die Beschreibungssprache Device XML (DevXML) erreicht, deren Entwicklung einen Schwerpunkt der Arbeit darstellte. In Anlehnung an die etablierte Petrinetztheorie werden Abhängigkeiten zwischen Zuständen und Funktionen formal beschrieben. Das Sprachvokabular von DevXML ermöglicht hierauf aufbauend Regeldefinitionen mit dem Ziel der Ablaufautomatisierung. Das entworfene Framework wurde anhand von insgesamt elf praktischen Beispielen wie z.B. einem Schalter, einem Heizungsmodul, einem Multimeter bis hin zu virtuellen Geräten erfolgreich verifiziert.

We study Social Groups consisting of self-interested inter-connected nodes looking for common content. We can observe Social Groups in various socio-technological networks, such as Cellular Network assisted Device-to-Device communications, Cloud assisted Peer-to-Peer Networks, hybrid Peer-to-Peer Content Distribution Networks and Direct Connect Networks. Each node wants to acquire a universe of segments at least cost. Nodes can either access an expensive link to the content distributor for downloading data segments, or use the well-connected low cost inter-node network for exchanging segments among themselves. Activation of an inter-node link requires cooperation among the participating nodes and reduces the cost of downloading for the nodes. However, due to uploading costs, Non-Reciprocating Nodes are reluctant to upload segments, in spite of their interest in downloading segments from others. We define the Give-and-Take (GT) criterion, which prohibits non-reciprocating behaviour in Social Groups for all nodes at all instants. In the “Full Exchange” case studied, two nodes can exchange copies of their entire segment sets, if each node gains at least one new segment from the other. Incorporating the GT criterion in the Social Group, we study the problem of downloading the universe at least cost, from the perspective of a new node having no data segments. We analyze this NP-hard problem, and propose algorithms for choosing the initial segments to be downloaded from the content distributor and the sequence of nodes for exchange. We compare the performance of these algorithms with a few existing P2P downloading strategies in terms of cost and running time. In the second problem, we attempt to reduce the load on the content distributor by choosing a schedule of inter-node link activations such that the number of nodes with the universe is maximized. Link activation decisions are taken by a central entity, the facilitator, for achieving the social optimum. We present the asymptotically optimal Randomized algorithm. We also present other algorithms, such as the Greedy Links algorithm and the Polygon algorithm, which are optimal under special scenarios of interest. We compare the performances of all proposed algorithms with the optimal value of the objective. We observe that computationally intensive algorithms exhibit better performance. Further, we consider the problem of decentralized scheduling of links. The decisions of link activations are made by the participating nodes in a distributed manner. While conforming to the GT criterion for inter-node exchanges, each node's objective is to maximize its utility. Each node tries to find a pairing partner by preferentially exploring nodes for link formation. Unpaired nodes choose to download a segment using the expensive link with Segment Aggressiveness Probability (SAP). We present linear complexity decentralized algorithms for nodes to choose their best strategy. We present a decentralized randomized algorithm that works in the absence of the facilitator and performs close to optimal for large number of nodes. We define the Price of Choice to benchmark performance of Social Groups (consisting of non-aggressive nodes) with the optimal. We evaluate the performance of various algorithms and characterize the behavioural regime that will yield best results for node and Social Group as well.

Auf dem Gebiet der Gerätesteuerung existieren zahlreiche Insellösungen, die den Anspruch nach generischer Eignung nicht erfüllen. In besonderer Weise defizitär ist der Mangel an ganzheitlichen, offenen Frameworks, bei denen die Autokonfiguration, die Gerätezuordenbarkeit vor Ort, die Geräteüberwachbarkeit, die Inter-Gerätekommunikation und die Automatisierbarkeit von Abläufen Berücksichtigung finden. Vor diesem Hintergrund öffnet die Arbeit mit einer Bestandsaufnahme von Technologien, die Einzelanforderungen der generischen Gerätesteuerung erfüllen. Sie bilden im weiteren Verlauf das potentielle Architekturfundament. Der Betrachtungsrahmen wird hierbei soweit ausgedehnt, dass relevante Verfahrensschritte vom Geräteanschluss bis zur automatisierten Generierung von User Interfaces abgedeckt sind. Unter Rückgriff auf ausgewählte Technologien wird ein zweigliedriger Ansatz vorgestellt, der ein sehr breites Spektrum potentieller Steuergeräte unterstützt und gleichzeitig technologieoffen im Hinblick auf die Autogenerierung von User Interfaces ist. Höchstmögliche Funktionalität wird durch die Beschreibungssprache Device XML (DevXML) erreicht, deren Entwicklung einen Schwerpunkt der Arbeit darstellte. In Anlehnung an die etablierte Petrinetztheorie werden Abhängigkeiten zwischen Zuständen und Funktionen formal beschrieben. Das Sprachvokabular von DevXML ermöglicht hierauf aufbauend Regeldefinitionen mit dem Ziel der Ablaufautomatisierung. Das entworfene Framework wurde anhand von insgesamt elf praktischen Beispielen wie z.B. einem Schalter, einem Heizungsmodul, einem Multimeter bis hin zu virtuellen Geräten erfolgreich verifiziert.