Delaunay triangulation (DT) is a useful geometric structure for net-working applications. We define a distributed DT and present a necessary and sufficient condition for a distributed DT to be correct. This condition is used as a guide for protocol design. We investigate the design of join, leave, failure, and maintenance protocols for a set of nodes in d-dimension (d > 1) to construct and maintain a distributed DT in a dynamic environment. The join, leave, and failure protocols in the suite are proved to be correct for a single join, leave, and failure, respectively. For a system under churn, it is impossible to maintain a correct distributed DT continually. We define an accuracy metric such that accuracy is 100% if and only if the distributed DT is correct. The suite also includes a maintenance protocol designed to recover from incorrect system states and to improve accuracy. In designing the protocols, we make use of two novel observations to substantially improve protocol efficiency. First, in the neighbor discovery process of a node, many replies to the node's queries contain redundant information. Second, the use of a new failure protocol that employs a proactive approach to recovery is better than the reactive approaches used in prior work. Experimental results show that our new suite of protocols maintains high accuracy for systems under churn and each system converges to 100% accuracy after churning stopped. They are much more efficient than protocols in prior work. To illustrate the usefulness of distributed DT for networking applications, we also present several application protocols including greedy routing, finding a closest existing node, clustering, broadcast, and geocast. Bose and Morin proved in 2004 that greedy routing always succeeds to find the destination node on a DT. We prove that greedy routing always finds a closest existing node to a given point, and our broadcast and geocast protocols always deliver a message to every target node. Our broadcast and geocast protocols are also efficient in the sense that very few target nodes receive duplicate messages, and non-target nodes receive no message. Performance characteristics of greedy routing, broadcast, and geocast are investigated using simulation experiments. We also investigate the impact of inaccurate coordinates on the performance of greedy routing, broadcast, and geocast. / text

Information privacy is a paradoxical issue. Especially after Facebook, information privacy has become more important than before. College student Facebook users share a great deal of information on Facebook, and Facebook collects users’personal information. Users’ personal information on Facebook is linked to their identity; therefore negative consequences (privacy problems) have become possible on Facebook. This study focused on college students’ privacy concerns and awareness of privacy issues and settings. Moreover, heavy and light users’ privacy concerns were compared in this study. According to the survey results, privacy is still important to Facebook users and different privacy concerns exist among heavy and light users. Results also show that privacy on Facebook is not a simple thing. It is related to identity construction, users’ experience, and awareness of privacy implications. / text

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / Growing pressures on today's testing resources are driving the need for a change in the way telemetry is currently being done. As systems advance and become more complex, testing these systems becomes more difficult due to budget, schedule and test resource constraints. These pressures create the need to support more concurrent testing with ever increasing numbers of participants and bandwidth requirements, all while available resources are diminishing. In order to continue to provide support to the war fighter through timely and efficient testing of new systems, the test infrastructure needs to be updated to become more agile and efficient. We will examine the application of innovative new technologies and concepts to increase the capabilities of the testing infrastructure in the presence of shrinking resources. By leveraging advances in wireless technologies, telemetry networks and other technologies, we will present alternatives to the current telemetry paradigm.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / As data transport systems become exponentially larger and more complex, the need to simplify the level of user involvement in establishing the intercommunication pathways becomes increasingly vital to streamlined, effective mission management. The proliferation of open-architecture, modular approaches to data transport and multiplexing systems shows the need for a unified, high-level control scheme that helps to flatten the users' learning curve for increasingly sophisticated, expanding systems. Implementing a control package with the functionality described in this paper will improve the user experience by eliminating the need for low level hardware management, minimizing system network footprint and unifying this functionality for a diverse hardware package.

M. Tech. Electrical Engineering / In recent years, there has been an increasing interest in real-time and delay sensitive applications. This is partly due to the increase in the use of video and audio streaming services. Most of these services depend on the User Datagram Protocol which is known as a fast and best effort protocol. However, there is no guarantee that packets sent via User Datagram Protocol will be received in their entirety. This is due to the absence of any packet error recovery mechanism in User Datagram Protocol. The purpose of this dissertation is therefore to investigate and evaluate the performance of raptor codes in packet based wireless networks.

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

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Social bookmarking has gained popularity since the advent of Web 2.0. Keywords known as tags are created to annotate web content, and the resulting tag space composed of the tags, the resources, and the users arises as a new platform for web content discovery. Useful and interesting web resources can be located through searching and browsing based on tags, as well as following the user-user connections formed in the social bookmarking community. However, the effectiveness of tag-based search is limited due to the lack of explicitly represented semantics in the tag space. In addition, social connections between users are underused for web content discovery because of the inadequate social functions. In this research, we propose a comprehensive framework to reorganize the flat tag space into a hierarchical faceted model. We also studied the structure and properties of various networks emerging from the tag space for the purpose of more efficient web content discovery.The major research approach used in this research is social network analysis (SNA), together with methodologies employed in design science research. The contribution of our research includes: (i) a faceted model to categorize social bookmarking tags; (ii) a relationship ontology to represent the semantics of relationships between tags; (iii) heuristics to reorganize the flat tag space into a hierarchical faceted model using analysis of tag-tag co-occurrence networks; (iv) an implemented prototype system as proof-of-concept to validate the feasibility of the reorganization approach; (v) a set of evaluations of the social functions of the current networking features of social bookmarking and a series of recommendations as to how to improve the social functions to facilitate web content discovery.

We study the application of network coding in periodic safety broadcasting in Vehicular Ad hoc Networks. We design a sub-layer in the application layer of the WAVE architecture. Our design uses rebroadcasting of network coded safety messages, which considerably improves the overall reliability. It also tackles the synchronized collision problem stated in the IEEE 1609.4 standard as well as congestion problem and vehicle-to-vehicle channel loss. We study how massage repetition can be used to optimize the reliability in combination with a simple congestion control algorithm. We analytically evaluate the application of network coding using a sequence of discrete phase-type distributions. Based on this model, a tight safety message loss probability upper bound is derived. Completion delay is defined as the delay that a node receives the messages of its neighbour nodes. We provide asymptotic delay analysis and prove a general and a restricted tighter asymptotic upper bound for the completion delay of random linear network coding. For some safety applications, average vehicle to vehicle reception delay is of interest. An instantly decodable network coding based on heuristics of index coding problem is proposed. Each node at each transmission opportunity tries to XOR some of its received original messages. The decision is made in a greedy manner and based on the side information provided by the feedback matrix. A distributed feedback mechanism is also introduced to piggyback the side information in the safety messages. We also construct a Tanner graph based on the feedback information and use the Belief Propagation algorithm as an efficient heuristic similar to LDPC decoding. Layered BP is shown to be an effective algorithm for our application. Lastly, we present a simple experimental framework to evaluate the performance of repetition based MAC protocols. We conduct an experiment to compare the POC-based MAC protocol with a random repetition-based MAC.