Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / Chin-Hui Lee, Committee Member ; Hayriye Ayhan, Committee Member ; Jennifer E. Michaels, Committee Member ; James H. McClellan, Committee Chair ; Lance M. Kaplan, Committee Member.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Alec Yasinsac, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains ix, 34 pages. Includes bibliographical references.

Thesis (M.S.)--University of Florida, 2002. / Title from title page of source document. Document formatted into pages; contains 112 p.; also contains graphics. Includes vita. Includes bibliographical references.

Thesis (M.Phil.) - University of Queensland, 2006. / Includes bibliography.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Gustavo de Veciana. Vita. Includes bibliographical references. Also available from UMI.

Thesis ( M.E.E.)--University of Delaware, 2005. / Principal faculty advisor: Stephan Bohacek, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Thesis (M.E.)--University of Canterbury, 2006. / Typescript (photocopy). "November 2006." Includes bibliographical references (leaves 121-124). Also available via the World Wide Web.

Loosely Synchronized (LS) codes can be used as spreading codes in quasi­ synchronous code-division multiple-access (QS-CDMA) systems. In such CDMA systems, close control of synchronization is achieved at the chip level, interme­ diate between that in synchronous CDMA and that in asynchronous CDMA. The LS code can then capitalize on zero correlation in a limited synchronization window to reduce code correlations and so reduce interference. LS codes are {O, +1, -1} codes constructed using Hadamard matrices and Golay pairs. A variation of LS codes inserts short strings of zeros between the components of the Golay pairs to increase the number of codewords, with only limited dete­ rioration in the correlations. These strings of zeros are known as internal padding. One of the advantages normally claimed for CDMA systems is resistance to eavesdropping and jamming. It might appear at first sight that the structure of LS codes is rather predictable in comparison with codes constructed using linear feedback shift registers, such as m-sequences or Gold codes. One way to overcome any such difficulty would be to evolve the code very quickly, in such a way that by the time a generation of the code is determined (or determined to a moderate correlation value) it is too late to exploit it. This thesis explores the way that LS codes can be evolved in order to achieve resistance to eavesdropping and jamming. The thesis starts with a detailed account of the necessary background and of the construction of Loosely Synchronized codes. The early part of the thesis then concentrates on showing that many generations of LS code can be constructed in such a way that the correlation between distinct generations is small. This prevents one observed generation of the code from being used for jamming or prediction in another generation. Specifically: •The construction of Golay pairs is investigated and a search is carried out over all possible Golay pairs and their mates to find a set of pairs that leads to the satisfaction of a suitable correlation criterion; •Bent functions, almost bent functions and other second order Boolean functions are used to create sets of Hadamard matrices that are guaranteed to satisfy the same correlation criterion; •A sequential search method to generate a set of arrangements of the internal padding that satisfies the same correlation criterion is described. Later in the thesis this approach is replaced by a recency list approach. This ensures that the correlation criterion is satisfied against recently used generations of the code, in place of all generations of the code; •The way in which these evolutions of the components combine together is also explored. Attention turns in the second part of the thesis to the mechanisms for evolution and the way that these might be predicted by a third party observer. Transform methods that the third party might use are described. Detailed simulations quantify the ability of the third party to identify the code during the transmission of a single bit. It is shown that theoretical resistance to early code prediction is not possible, although it might be possible to demonstrate security arising from the relative speed of the necessary computations for the user and the observer. This would require a detailed hardware study, and this is listed as future work. In fact it is shown here that LS codes are actually better than linear feedback shift register codes, as a result of the Berlekamp-Massey algorithm. Attention is also focussed on the scenario in which details of the algorithms of one user are obtained by the third party. Only the Hadamard matrix provides protection against this scenario, as all other components of the construction are shared between all users. From this second viewpoint the true weakness of LS codes becomes apparent. Although the Hadamard matrix constructions are satisfactory if the order of the Hadamard matrix is not too small, it seems that the sequence of Hadamard matrix rows of each user must be computed centrally and distributed to users as private keys if this scenario is not to remain a major concern. The volume of private key distribution necessary may seem unattractive to operators. Ultimately it seems that evolution of the Golay pairs may have little real role except to increase the workload of the observer. The recency list based evolution of internal padding can take the main role in ensuring low correlation between close generations of the code. The evolution of the Hadamard matrix should be designed to concentrate on the second viewpoint, where the third party has obtained details of the algorithms of one user.

The management of long term chronic conditions is a complex and challenging task. The process relies on individuals engaging in regular recording of factors that affect their health. Yet currently, the mobile tools that people carry with them are not being fully utilised to assist in this process. This Thesis reports on research that has been completed to understand the role that mobile technologies can have in supporting people with chronic conditions. An individual engaging in personal monitoring is concerned with the data they collect, not the process used to capture the data. The results of the research conducted contribute to an advancement of knowledge around how mobile technologies can assist in personal reflection on health information to provide greater understanding of chronic disease management This understanding of the role of reflection in chronic condition management can then be used as a platform to improve the mobile interventions in future implementations. These findings are arrived at by conducting an initial investigation into the usage of existing health monitoring devices and an evaluation of these devices is detailed. The results of this early work suggests there exists a gap between real practice and the role that mobile technologies can play in assisting with the process. A deeper understanding of the management practices of people with diabetes is then achieved through a set of interviews with individuals with diabetes. The findings then define a model of chronic disease management, named the 'Diabetes Management Cycle.' Following the definition of the cycle, a mobile application was implemented and deployed during a four week evaluation with individuals with type 1 diabetes. This system was designed to support existing management practices and implemented simple methods of information capture. A second application was then developed to enable increased monitoring and subsequent reflection amongst individuals with cardiovascular conditions. The application was deployed in a six week in-situ evaluation and it was discovered a personalised 'tagging' mechanism allowed for the discovery of patterns affecting health. Based on the findings of the studies, the Thesis concludes by presenting definitions of ready- to-hand in the short- and long-term contexts of mobile health management. These ready-to-hand guidelines provide a platform for future research projects to build upon.

With the rapid growth of mobile, ubiquitous and wearable computing, location-based services become an indispensable part of mobile internet. These services rely on the geographical position of the mobile devices and provide location-dependent contents or services to users, such as location-based in- stant messaging, POI browsing, map navigation, and location-based virtual reality games. Most existing systems implement these location-based services by always storing and transmitting raw, plaintext GPS coordinates. However, location information is arguably a private asset of individual user, and the disclosure of such information could lead to severe privacy disclosure of other even more sensitive information, such as religion, sexuality, medical condition, or political affiliation. To address this issue, researchers have proposed a series of techniques to protect user location privacy against location-based service providers. How- ever, it is challenging to apply these theoretical and sophisticated techniques ii to practical location systems because of the computational or network over- head imposed on the mobile devices as well as the complexity of the secure protocols and algorithms for application developers. In this thesis, I will study two real-life privacy-preserving location systems and show how they can be adopted by developers with little security background. The rst is outdoor proximity detection that determines whether two users (or a user and an ob- ject) are within a given distance threshold. This is a fundamental service in many geo-social or map services. For example, \People nearby" in Wechat and QQ interconnect users because of their locality and/or mutual interests in some topics, such as food and movies. The second is indoor location mon- itoring and tracking. Wearable devices such as smart watch and bracelets continually broadcast Bluetooth Low Energy signals, which can be easily cap- tured by monitoring devices such as WiFi routers and Bluetooth scanners. As more and more wearable devices emerge, unauthorized monitoring and track- ing by adversary becomes great privacy threats not only in the cyberworld, but also in the physical world. To protect location privacy, I develop a real- life location monitoring system that is based on Bluetooth Low Energy (BLE) privacy feature that changes the device physical address periodically. To en- able users to better control their privacy level while still providing monitoring and tracking service to authorized parties (e.g., for child and elderly care), I extend BLE privacy by enriching its privacy semantics with a comprehensive set of metrics, such as simple opt-in/out, k-anonymity, and granularity-based anonymity. Both systems have been posted online and evaluated in terms of accuracy and user study.