Numerous control and decision problems in networked systems can be posed as optimization problems. Examples include the framework of network utility maximization for resource allocation in communication networks, multi-agent coordination in robotics, and collaborative estimation in wireless sensor networks (WSNs). In contrast to classical distributed optimization, which focuses on improving computational efficiency and scalability, these new applications require simple mechanisms that can operate under limited communication. In this thesis, we develop several novel mechanisms for distributed optimization under communication constraints, and apply these to several challenging engineering problems. In particular, we devise three tailored optimization algorithms relying only on nearest neighbor, also known as peer-to-peer, communication. Two of the algorithms are designed to minimize a non-smooth convex additive objective function, in which each term corresponds to a node in a network. The first method is an extension of the randomized incremental subgradient method where the update order is given by a random walk on the underlying communication graph, resulting in a randomized peer-to-peer algorithm with guaranteed convergence properties. The second method combines local subgradient iterations with consensus steps to average local update directions. The resulting optimization method can be executed in a peer-to-peer fashion and analyzed using epsilon-subgradient methods. The third algorithm is a center-free algorithm, which solves a non-smooth resource allocation problem with a separable additive convex objective function subject to a constant sum constraint. Then we consider cross-layer optimization of communication networks, and demonstrate how optimization techniques allow us to engineer protocols that mimic the operation of distributed optimization algorithms to obtain an optimal resource allocation. We describe a novel use of decomposition methods for cross-layer optimization, and present a flowchart that can be used to categorize and visualize a large part of the current literature on this topic. In addition, we devise protocols that optimize the resource allocation in frequency-division multiple access (FDMA) networks and spatial reuse time-division multiple access (TDMA) networks, respectively. Next we investigate some variants of the consensus problem for multi-robot coordination, for which it is usually standard to assume that agents should meet at the barycenter of the initial states. We propose a negotiation strategy to find an optimal meeting point in the sense that the agents' trajectories to the meeting point minimize a quadratic cost criterion. Furthermore, we also demonstrate how an augmented state vector can be used to boost the convergence rate of the standard linear distributed averaging iterations, and we present necessary and sufficient convergence conditions for a general version of these iterations. Finally, we devise a generic optimization software component for WSNs. To this end, we implement some of the most promising optimization algorithms developed by ourselves and others in our WSN testbed, and present experimental results, which show that the proposed algorithms work surprisingly well. / QC 20100813

The use of communication networks in digital control systems introduces stability and reliability concerns. Standard reliability and safety assessment methods need further modification to accommodate the issue in the reliability assessment of networked control systems. In this thesis, it is demonstrated that the Dynamic Flowgraph Methodology (DFM) can be extended to model networked control systems. The modelling of the communication network influence on the performance of the control system is presented. The areas that can affect the reliability of the control system are identified using the methodology. The thesis also presents the application of the DFM to a nuclear-based thermochemical water splitting process for hydrogen production, the Copper-Chlorine (Cu-Cl) cycle. The architecture of a networked control system and configuration of instrumentation and control systems for the hydrogen production plant are proposed in the thesis. / UOIT

Networked control systems (NCSs) are a kind of distributed control systems in which the data between control components are exchanged via communication networks. Because of the attractive advantages of NCSs such as reduced system wiring, low weight, and ease of system diagnosis and maintenance, the research on NCSs has received much attention in recent years. The first part (Chapter 2 - Chapter 4) of the thesis is devoted to designing new controllers for NCSs by incorporating the network-induced delays. The thesis also conducts research on filtering of multirate systems and identification of Hammerstein systems in the second part (Chapter 5 - Chapter 6).<br /><br /> Network-induced delays exist in both sensor-to-controller (S-C) and controller-to-actuator (C-A) links. A novel two-mode-dependent control scheme is proposed, in which the to-be-designed controller depends on both S-C and C-A delays. The resulting closed-loop system is a special jump linear system. Then, the conditions for stochastic stability are obtained in terms of a set of linear matrix inequalities (LMIs) with nonconvex constraints, which can be efficiently solved by a sequential LMI optimization algorithm. Further, the control synthesis problem for the NCSs is considered. The definitions of <em>H₂</em> and <em>H_∞</em> norms for the special system are first proposed. Also, the plant uncertainties are considered in the design. Finally, the robust mixed <em>H₂/H_&infin;</em> control problem is solved under the framework of LMIs. <br /><br /> To compensate for both S-C and C-A delays modeled by Markov chains, the generalized predictive control method is modified to choose certain predicted future control signal as the current control effort on the actuator node, whenever the control signal is delayed. Further, stability criteria in terms of LMIs are provided to check the system stability. The proposed method is also tested on an experimental hydraulic position control system. <br /><br /> Multirate systems exist in many practical applications where different sampling rates co-exist in the same system. The <em>l₂-l_&infin;</em> filtering problem for multirate systems is considered in the thesis. By using the lifting technique, the system is first transformed to a linear time-invariant one, and then the filter design is formulated as an optimization problem which can be solved by using LMI techniques. <br /><br /> Hammerstein model consists of a static nonlinear block followed in series by a linear dynamic system, which can find many applications in different areas. New switching sequences to handle the two-segment nonlinearities are proposed in this thesis. This leads to less parameters to be estimated and thus reduces the computational cost. Further, a stochastic gradient algorithm based on the idea of replacing the unmeasurable terms with their estimates is developed to identify the Hammerstein model with two-segment nonlinearities. <br /><br /> Finally, several open problems are listed as the future research directions.

Communications scholarship faces a convergent crisis. Research on networks includes the role of information networks in supporting social movements, networked civil society, the information society, and new forms of communication. But while communications literature utilizes a variety of approaches to describe the impact of networked communications, a dearth of technical expertise permeates scholarship. Despite the discourse on networks potentially bridging previously distinct disciplines, the lack of a fundamental understanding of communications networks and relationships between technical and socio-political networks remains a consistent gap. This thesis will investigate the extent that opposition to the Anti-Counterfeiting Trade Agreement (ACTA) in Europe constitute a networked public sphere. Through studying the role of civl society and the networked public in the European ACTA debate, the horizontal and vertical dimensions of socio-political and communications technology networks are not only illuminated, but the importance of analyzing the mechanisms through which vertical hierarchies enclose the public sphere become abundantly clear. This research provides the foundation for an interdisciplinary approach to understanding the relationship between information technology and socio-political networks and offers lessons for information policy makers, communications scholars, and networked civil society within the context of European democracy.

This report focuses on the quality aspects of media delivery over the Internet. Weinvestigate the constructs of Knowledge Plane, Monitor Plane and Action Planeas controlling functions for the Internet. Our goal is to implement functionality formonitoring services in a home network, allowing the router to reason and take actionsto obtain an optimal traffic situation based on user preferences. The actions takento alter ongoing traffic are implemented in a modular router framework called Click.We will use this router to affect the media stream TCP connections into behavingin accordance with the networks optimal state. New features are implemented tocomplement the functionality found in Click, giving us the tools needed to obtainthe wanted results.Our focus is on adaptive video streaming in general and Silverlight SmoothStreaming in particular. Using custom Silverlight client code, we implemented asolution which allows the applications to report usage statistics to the home gateway.This information will be used by the home gateway to obtain an overview of traffic inthe network. Presenting this information to the user, we retrieve the user preferencesfor the given video streams. The router then dynamically reconfigures itself, andstarts altering TCP packets to obtain an optimal flow of traffic in the home network.Our system has been implemented on a Linux PC where it runs in its currentform. All the different areas of the solution, ranging from the clients, router, Knowl-edge Plane and traffic manipulation elements are put together. They form a workingsystem for QoE/QoS optimization which we have tested and demonstrated. In ad-dition to testing the concept on our own streaming services, the reporting featurefor Silverlight clients has also been implemented in a private build of TV2 Sumo.This is the Internet service of the largest commercial television station in Norway.Further testing with the TV2 Sumo client has given promising results. The systemis working as it is, although we would like to see more complex action reasoning toimprove convergence time for achieving the correct bit rate.

As cloud computing is becoming more mature and pervasive, almost all types of services are being deployed in clouds. This has also widened the spectrum of cloud users which encompasses from domestic users to large companies. One of the main concerns of large companies outsourcing their IT functions to clouds is the availability of their functions. On the other hand, availability requirements for domestic users are not very strict. This requires the cloud service providers to guarantee different dependability levels for different users and services. This thesis is based upon this requirement of dependability differentiation of cloud services depending upon the nature of services and target users.In this thesis, different types of services are identified and grouped together both according to their deployment nature and their target users. Also a range of techniques for guaranteeing dependability in the cloud environment are identified and classified. In order to quantify dependability provided by different techniques, a cloud system is modeled. Two different levels of dependability differentiation are considered, namely; differentiation depending upon the state of standby replica and differentiation depending upon the spatial separation of active and standby replicas. These two levels are separately modeled by using Markov state diagrams and reliability block diagrams respectively. Due to the limitations imposed by Markov models, the former differentiation level is also studied by using a simulation.Finally, numerical analysis is conducted and different techniques are compared. Also the best technique for each user and service class is identified depending upon the results obtained. The most crucial components for guaranteeing dependability in cloud environment are also identified. This will direct the future prospects of study and also provide an idea to cloud service providers about the cloud components that are worth investing in, for enhancing service availability.

Increasing traffic volumes in the Internet put strict requirements to the architectureof optical core networks. The exploding number of Internet users, andmassive increase in Internet content consumption forces carriers to constantlyupgrade and transform their core networks in order to cope with the trafficgrowth. The choice of both physical components and transport protocols inthe core network is crucial in order to provide satisfactorily performance.Data traffic in the core network consists of a wide variety of protocols.OTN is a digital wrapper technology, responsible for encapsulating existingframes of data, regardless of native protocol, and adding additional overheadfor addressing, OAM and error control. The wrapped signal is thentransported directly over wavelengths in the optical transport network. Thecommon OTN wrapper overhead makes it possible to monitor and controlthe signals, regardless of the protocol type being transported.OTN is standardized by the ITU through a series of recommendations,the two most important being ITU-T G.709 - &quot;Interfaces for the OpticalTransport Network&quot;, and ITU-T G.872 - &quot;Architecture of the Optical TransportNetwork&quot;. OTN uses a flexible TDM hierarchy in order to provide highwavelength utilization. The TDM hierarchy makes it possible to performswitching at various sub-wavelength bit rates in network nodes.An introduction to OTN and an overview of recent progress in OTNstandardization is given in the thesis. An OTN switch which utilizes theflexible multiplexing hierarchy of OTN is proposed, and its characteristics istested in a network scenario, comparing it to the packet switched alternative.Simulation results reveal that OTN switching doesn&#146;t provide any performancebenefits compared to packet switching in the core network. OTNswitches do however provide bypass of intermediate IP routers, reducing therequirements for router processing power in each network node. This reducesoverall cost, and improves network scalability.An automatically reconfigurable OTN switch which rearranges link subcapacitiesbased on differences in output buffer queue lengths is also proposedand simulated in the thesis. Simulation results show that the reconfigurableOTN switch has better performance than both pure packet switching andregular OTN switching in the network scenario.

Telephony has become an integral part in the day to day communication and new telephony services are quickly being deployed in the industry. There is a need for users to be provided with new services on the fly; these services can be composed from existing services to provide an added-value service. The vision is to allow ordinary people, who are the end users, to easily compose a set of available services and run them on their devices while they are on the move without requiring specialized IT or telecom skills.An end user service composition approach is followed that reduces the composition complexity and difficulty from the end user perspective. The approach enables the end users to personalize the compositions with a powerful presentation and supporting the end users to dynamically customize the service composition.A scenario based approach is followed whereby different practical composition scenarios are explored to shed light on several aspects of how the end users can personalize the composition process using the tool that has been presented by creating compositions that create added value services for the scenarios looked into.

With AMS comes great possibilities for increased energy efficiency, but to achieve its full potential, the end users must be provided with the necessary means of monitoring and controlling their consumption. This thesis describes the process of developing a web application prototype meant to serve such a purpose. It explains the various architectural and technological decisions that support the prototype, and it elaborates on how data from the users&#146; smart meters can be synthesized with price information to help users see the economic effect of their current consumption pattern. A working prototype has been developed and security- and performance tests have been carried out to mitigate bottlenecks and prevent security breaches. Observations during the pilot project have shown promising trends and it is hoped that this thesis will inspire further innovation in the field of smart energy solutions.

Nowadays, one of the aims of telepresence systems is to provide a sensation of nearness to people who are interacting with this type of systems. Many factors have a relevant repercussion in providing this feeling and some aspects are more important than others, depending on the scope of use. This thesis presents several studies made in order to analyse the degree of importance each factor has.One of these factors treated is the delay which limits the interactivity. For this reason, in this thesis, a method is proposed to measure the delay through a telepresence system. Another factor treated has been the frame rate in order to figure out which is its influence.In addition, an stereoscopic 3D setup was performed to analyse the degree of perceived depth which was introduced into the system.Finally, several pilot tests focused on musical rehearsals were made to evaluate the influence of the delay. The recording was made at 60fps in a high-definition quality.Subjective opinions about the interactivity and perception of this sort of systems were gathered.It was concluded that this sort of system was viable for interactive applications like conducting a choir, but an effort must be done when decreasing the amount of delay added by end devices. In fact, the conductor tolerated a delay (round-trip) about 118ms in rhythmic music, being still possible to conduct with difficulties. In contrast, the delay tolerance increased up to 160ms when conducting a more melodic piece of music. However, the use of 3D when there is more than one viewer does not produce much benefits. Instead of that, it is proposed to analyse multi-view systems as a future research.