Data driven wireless network design : a multi-level modeling approach

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Context-aware collaborative storage and programming for mobile users

Since people generate and access most digital content from mobile devices, novel innovative mobile apps and services are possible. Most people are interested in sharing this content with communities defined by friendship, similar interests, or geography in exchange for valuable services from these innovative apps. At the same time, they want to own and control their content. Collaborative mobile computing is an ideal choice for this situation. However, due to the distributed nature of this computing environment and the limited resources on mobile devices, maintaining content availability and storage fairness as well as providing efficient programming frameworks are challenging. This dissertation explores several techniques to improve these shortcomings of collaborative mobile computing platforms. First, it proposes a medley of three techniques into one system, MobiStore, that offers content availability in mobile peer-to-peer networks: topology maintenance with robust connectivity, structural reorientation based on the current state of the network, and gossip-based hierarchical updates. Experimental results showed that MobiStore outperforms a state-of-the-art comparison system in terms of content availability and resource usage fairness. Next, the dissertation explores the usage of social relationship properties (i.e., network centrality) to improve the fairness of resource allocation for collaborative computing in peer-to-peer online social networks. The challenge is how to provide fairness in content replication for P2P-OSN, given that the peers in these networks exchange information only with one-hop neighbors. The proposed solution provides fairness by selecting the peers to replicate content based on their potential to introduce the storage skewness, which is determined from their structural properties in the network. The proposed solution, Philia, achieves higher content availability and storage fairness than several comparison systems. The dissertation concludes with a high-level distributed programming model, which efficiently uses computing resources on a cloud-assisted, collaborative mobile computing platform. This platform pairs mobile devices with virtual machines (VMs) in the cloud for increased execution performance and availability. On such a platform, two important challenges arise: first, pairing the two computing entities into a seamless computation, communication, and storage unit; and second, using the computing resources in a cost-effective way. This dissertation proposes Moitree, a distributed programming model and middleware that translates high-level programming constructs into events and provides the illusion of a single computing entity over the mobile-VM pairs. From programmers’ viewpoint, the Moitree API models user collaborations into dynamic groups formed over location, time, or social hierarchies. Experimental results from a prototype implementation show that Moitree is scalable, suitable for real-time apps, and can improve the performance of collaborating apps regarding latency and energy consumption

Multi-objective Network Opportunistic Access for Group Mobility in Mobile Internet

The integration of existing and emerging heterogeneous wireless networks in mobile Internet is a combination of diverse but complementary wireless access technologies. Satisfying a set of imperative constrains and optimization objectives, access network selection (ANS) for mobile node (MN) is an inherent procedure in mobility management that needs to be solved in a reasonable manner for the whole system to operate in an optimal fashion. However, ANS remains a significant challenge. Because many MNs with distinctive call characteristics are likely to have correlated mobility and may need to perform mobility management at the same time, this paper, with the goal of investigating group mobility solutions, proposes a network opportunistic access for group mobility (NOA-GM) scheme. By analyzing the directional patterns of moving MNs and introducing the idea of opportunistic access, this scheme first identifies underloaded access networks as candidates. Then, the candidates are evaluated using normalized models of objective and subjective metrics. On this basis, the ANS problem for group mobility can be conducted as a multiobjective combination optimization and then transferred to a signal-objective model by considering the optimization of the performance of the whole system as a global goal while still achieving each MN\u27s performance request. Using an improved genetic algorithm with newly designed evolutionary operators to solve the signal-objective model, an optimal result option for ANS for group mobility is achieved. Simulations conducted on the NS-2 platform show that NOA-GM outperforms the compared schemes in several critical performance metrics

The Relationship Between Self Perceived Versus Peer Perceived Popularity and Alcohol Consumption in University Students

Previous research suggests that alcohol use and abuse is a growing problem for emerging adults (Lyons & Willott, 2008). Emerging adults typically attend social events with their natural drinking groups (Lange et al., 2006). Examining popularity level within the natural drinking group is critical for predicting heavy episodic drinking patterns. The objective of this study is to examine the association between group members’ peer-nominated popularity and heavy alcohol consumption and whether this association is heightened among individuals aware of their popular position. The present study provided 81 university students (Mage = 19.40 years; 69% female) recruited within their natural drinking groups (N = 21) with a longitudinal online survey. At two different time points 2 months apart, participants ranked their group members’ popularity, including their own. There were two main hypotheses. Firstly, peer-nominated popularity at Time 1 will predict increased heavy episodic drinking at Time 2 (while controlling for drinking at Time 1). Second, self-reported popularity will moderate the aforementioned relationship. Hierarchical Linear Modeling (HLM) was used for data analysis, which found that self-perceived popularity at Time 1 was a predictor of alcohol consumption at Time 2. However, there were no significant results for peer-perceived popularity. Implications and future directions are discussed along with possible prevention measures for university guidance departments

Privacy aware key establishment for publish/subscribe infrastructures in Ubiquitous environments

Ubiquitous Computing, UbiComp, is a vision of embedding computing to every aspect of our day to day life. In ubiquitous computing, interaction among communicating entities exists in highly dynamic, large scale and failure prone environments. Publish/Subscribe interaction paradigm, Pub/Sub, can be used to decouple interacting entities in ubiquitous environments by delivering events based on users interests. In this scenario, securing events dissemination and protecting users' privacy are essential requirements for ubiquitous applications. In this thesis, we propose an encryption key establishment scheme for encrypting disseminated events in ubiquitous Pub/Sub infrastructures. The proposed key establishment scheme considers the dynamism, scalability and failure tolerance issues of ubiquitous environments. More importantly, the generated encryption keys reflect multi level access control polices, which is important to enforce users' privacy polices

SPECTRUM-BASED AND COLLABORATIVE NETWORK TOPOLOGY ANALYSIS AND VISUALIZATION

Networks are of significant importance in many application domains, such as World Wide Web and social networks, which often embed rich topological information. Since network topology captures the organization of network nodes and links, studying net- work topology is very important to network analysis. In this dissertation, we study networks by analyzing their topology structure to explore community structure, the relationship among network members and links as well as their importance to the belonged communities. We provide new network visualization methods by studying network topology through two aspects: spectrum-based and collaborative visualiza- tion techniques. For the spectrum-based network visualization, we use eigenvalues and eigenvectors to express network topological features instead of using network datasets directly. We provide a visual analytics approach to analyze unsigned networks based on re- cent achievements on spectrum-based analysis techniques which utilize the features of node distribution and coordinates in the high dimensional spectral space. To assist the interactive exploration of network topologies, we have designed network visual- ization and interactive analysis methods allowing users to explore the global topology structure. Further, to address the question of real-life applications involving of both positive and negative relationships, we present a spectral analysis framework to study both signed and unsigned networks. Our framework concentrates on two problems of net- work analysis - what are the important spectral patterns and how to use them to study signed networks. Based on the framework, we present visual analysis methods, which guide the selection of k-dimensional spectral space and interactive exploration of network topology. With the increasing complexity and volume of dynamic networks, it is important to adopt strategies of joint decision-making through developing collaborative visualiza- tion approaches. Thus, we design and develop a collaborative detection mechanism with matrix visualization for complex intrusion detection applications. We establish a set of collaboration guidelines for team coordination with distributed visualization tools. We apply them to generate a prototype system with interactions that facilitates collaborative visual analysis. In order to evaluate the collaborative detection mechanism, a formal user study is presented. The user study monitored participants to collaborate under co-located and distributed collaboration environments to tackle the problems of intrusion detection. We have observed participants’ behaviors and collected their performances from the aspects of coordination and communication. Based on the results, we conclude several coordination strategies and summarize the values of communication for collaborative visualization. Our visualization methods have been demonstrated to be efficient topology explo- ration with both synthetic and real-life datasets in spectrum-based and collaborative exploration. We believe that our methods can provide useful information for future design and development of network topology visualization system

Decentralizing decision making in modern military organizations

Thesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2003.Includes bibliographical references (leaves 108-111).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.For organizations, the value of information is to improve decision making. In the military in particular, information's role in warfare has always been to affect decisions at all levels -- from strategic to tactical - to put one's forces in a position of advantage. In the information age, the cost of communicating such information has been so phenomenally reduced that it now becomes possible for individuals and entire organizations to tap vast amounts of information. This thesis seeks to address the question of how the modern military can best be designed to harness the power of the information revolution to enhance its ability to make faster, better decisions and thus to become more effective in war as well as in times of peace. To do so, the thesis first considers lessons from military history on the essence of decision making, analyzes the implications of the declining cost of communications and examines new organizational trends in both the corporate world and the military. With this foundation, new organizational designs for the military are proposed and scenarios for their use are described. These new organizational designs are optimized for the information age and incorporate increasingly decentralized making structures. Noting that such formal organizational restructuring by itself is inadequate, the thesis then looks at the shifts in leadership orientation and organizational culture necessary to create the environment that encourages empowerment of individuals as well as the competencies for the individual that are becoming increasingly important in an increasingly decentralized world. Finally, a framework that synthesizes the different ingredients necessary for designing the military organization in the 21st century is proposed.by Boon Kim Tan.S.M.M.O.T