The past few years have witnessed a significant evolution in mobile computing and communications, in which new trends and applications have the traditional role of computer networks into that of distributed service providers. In this thesis we explore an alternative way to form wireless ad-hoc networks whose topologies can be customized as required by the users’ software applications. In particular, we investigate the applicability of mobile codes to networks created by devices equipped with Bluetooth technology. Computer simulations results suggest that our proposed approach can achieve this task effectively, while matching the level of efficiency seen in other salient proposals in this area. This thesis also addresses the issue of service discovery in mobile ad-hoc networks. We propose the use of a directory whose network location varies in an attempt to reduce traffic overhead driven by users’ hosts looking for service information. We refer to this scheme as the Service Directory Placement Algorithm, or SDPA. We formulate the directory relocation problem as a Markov Decision Process that is solved by using Q-learning. Performance evaluations through computer simulations reveal bandwidth overhead reductions that range between 40% and 48% when compared with a basic broadcast flooding approach for networks comprising hosts moving at pedestrian speeds. We then extend our proposed approach and introduce a multi-directory service discovery system called the Service Directory Placement Protocol, or SDPP. Our findings reveal bandwidth overhead reductions typically ranging from 15% to 75% in networks comprising slow-moving hosts with restricted memory availability. In the fourth and final part of this work, we present the design foundations and architecture of a middleware system that called WISEMAN – WIreless Sensors Employing Mobile Agents. We employ WISEMAN for dispatching and processing mobile programs in Wireless Sensor Networks (WSNs). Our proposed system enables the dynamic creation of semantic relationships between network nodes that cooperate to provide an aggregate service. We present discussions on the advantages of our proposed approach, and in particular, how WISEMAN facilitates the realization of service-oriented tasks in WSNs.

The past few years have witnessed a significant evolution in mobile computing and communications, in which new trends and applications have the traditional role of computer networks into that of distributed service providers. In this thesis we explore an alternative way to form wireless ad-hoc networks whose topologies can be customized as required by the users’ software applications. In particular, we investigate the applicability of mobile codes to networks created by devices equipped with Bluetooth technology. Computer simulations results suggest that our proposed approach can achieve this task effectively, while matching the level of efficiency seen in other salient proposals in this area. This thesis also addresses the issue of service discovery in mobile ad-hoc networks. We propose the use of a directory whose network location varies in an attempt to reduce traffic overhead driven by users’ hosts looking for service information. We refer to this scheme as the Service Directory Placement Algorithm, or SDPA. We formulate the directory relocation problem as a Markov Decision Process that is solved by using Q-learning. Performance evaluations through computer simulations reveal bandwidth overhead reductions that range between 40% and 48% when compared with a basic broadcast flooding approach for networks comprising hosts moving at pedestrian speeds. We then extend our proposed approach and introduce a multi-directory service discovery system called the Service Directory Placement Protocol, or SDPP. Our findings reveal bandwidth overhead reductions typically ranging from 15% to 75% in networks comprising slow-moving hosts with restricted memory availability. In the fourth and final part of this work, we present the design foundations and architecture of a middleware system that called WISEMAN – WIreless Sensors Employing Mobile Agents. We employ WISEMAN for dispatching and processing mobile programs in Wireless Sensor Networks (WSNs). Our proposed system enables the dynamic creation of semantic relationships between network nodes that cooperate to provide an aggregate service. We present discussions on the advantages of our proposed approach, and in particular, how WISEMAN facilitates the realization of service-oriented tasks in WSNs.

The past few years have witnessed a significant evolution in mobile computing and communications, in which new trends and applications have the traditional role of computer networks into that of distributed service providers. In this thesis we explore an alternative way to form wireless ad-hoc networks whose topologies can be customized as required by the users’ software applications. In particular, we investigate the applicability of mobile codes to networks created by devices equipped with Bluetooth technology. Computer simulations results suggest that our proposed approach can achieve this task effectively, while matching the level of efficiency seen in other salient proposals in this area. This thesis also addresses the issue of service discovery in mobile ad-hoc networks. We propose the use of a directory whose network location varies in an attempt to reduce traffic overhead driven by users’ hosts looking for service information. We refer to this scheme as the Service Directory Placement Algorithm, or SDPA. We formulate the directory relocation problem as a Markov Decision Process that is solved by using Q-learning. Performance evaluations through computer simulations reveal bandwidth overhead reductions that range between 40% and 48% when compared with a basic broadcast flooding approach for networks comprising hosts moving at pedestrian speeds. We then extend our proposed approach and introduce a multi-directory service discovery system called the Service Directory Placement Protocol, or SDPP. Our findings reveal bandwidth overhead reductions typically ranging from 15% to 75% in networks comprising slow-moving hosts with restricted memory availability. In the fourth and final part of this work, we present the design foundations and architecture of a middleware system that called WISEMAN – WIreless Sensors Employing Mobile Agents. We employ WISEMAN for dispatching and processing mobile programs in Wireless Sensor Networks (WSNs). Our proposed system enables the dynamic creation of semantic relationships between network nodes that cooperate to provide an aggregate service. We present discussions on the advantages of our proposed approach, and in particular, how WISEMAN facilitates the realization of service-oriented tasks in WSNs. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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Ad-hoc networks suffer from dynamicity due to mobility of the nodes or node addition/removal to/from the system. This means, the formed topology may not be connected anymore or better topologies can be found as time passes if the position of the nodes changes or some nodes in the network is broken. Therefore, there is a need for an adaptive solution to make the network’s performance stable against these changes. A centralized manner induces a single point of failure, when the control unit’s service is unavailable, networks can not be formed and communication among the nodes is broken. Hence, a system that distributes the decision-making ability to nodes would be better to increase the robustness of the network. A detailed literature survey about the distributed network formation showed that two critical gaps that need to be filled. Firstly, provided solutions assumed that nodes are using the omnidirectional antennas, hence, they can make transmission and reception in all directions which inherently increases the total interference in the system. Therefore, we come up with the idea of using directional antennas to reduce the interference which requires antennas to point out each other for successful communication. This creates an optimization problem in terms of selecting directions of a certain amount of antennas deployed on a node to maximize the capacity while ensuring connectivity. Secondly, proposed distributed network formation solutions in literature depend on sequential decision-making algorithms that each node waits its turn to make a decision. In that case, deciding or distributing the rank of the nodes is another challenge that needs to be solved by the distributed algorithm. Therefore, in this work, we focused to design a distributed network formation algorithm for a system with directional antennas where all decisions are made simultaneously by nodes in the system. As a result, it is shown that the proposed reinforcement learning-based algorithm is successful and promising to give nodes the ability to adapt to new conditions cooperatively. / Ad-hoc-nätverk lider av dynamik på grund av nodernas mobilitet eller nodtillägg/borttagning till/från systemet. Detta betyder att den bildade topologin kanske inte är ansluten längre eller bättre topologier kan hittas allt eftersom nodernas position ändras eller om några noder i nätverket bryts. Därför finns det ett behov av en adaptiv lösning för att göra nätverkets prestanda stabil mot dessa förändringar. Ett centraliserat sätt inducerar en enda felpunkt, när kontrollenhetens tjänst inte är tillgänglig, nätverk kan inte bildas och kommunikationen mellan noderna bryts. Därför skulle ett system som fördelar beslutsförmågan till noder vara bättre för att öka nätverkets robusthet. En detaljerad litteraturundersökning om den distribuerade nätverksbildningen visade att två kritiska luckor måste fyllas. För det första antog förutsatta lösningar att noder använder rundstrålande antenner, och därför kan de göra sändning och mottagning i alla riktningar, vilket i sig ökar den totala störningen i systemet. Därför kommer vi på idén att använda riktade antenner för att minska störningarna som kräver att antenner pekar ut varandra för framgångsrik kommunikation. Detta skapar ett optimeringsproblem när det gäller att välja riktningar för en viss mängd antenner som är utplacerade på en nod för att maximera kapaciteten samtidigt som anslutningsmöjligheterna säkerställs. För det andra är föreslagna lösningar för distribuerad nätverksbildning i litteraturen beroende av sekventiella beslutsfattande algoritmer som varje nod väntar på sin tur för att fatta ett beslut. I så fall är att bestämma eller fördela nodernas rangordning en annan utmaning som måste lösas av den distribuerade algoritmen. Därför fokuserade vi i detta arbete på att designa en distribuerad nätverksbildningsalgoritm för ett system med riktade antenner där alla beslut fattas samtidigt av noder i systemet. Som ett resultat har det visat sig att den föreslagna förstärkningsinlärningsbaserade algoritmen är framgångsrik och lovande för att ge noder förmågan att anpassa sig till nya förhållanden i samarbete.