Recent developments in information and communication technologies and their incor- poration into the medical domain have opened doors for the enhancement of health care services and thereby increasing the work ow at a reasonable rate. However, to implement such services, current medical system needs to be exible enough to support integration with other systems. This integration should be achieved in a secure manner and the resultant service should be made available to all health professionals and patients. This thesis proposes a new infrastructure for secure medical image sharing between legacy PACS and DI-r. The solution employs OpenID standard for user authentication, OAuth service to grant authorization and IHE XDS-I pro les to store and retrieve medical im- ages and associated meta data. In the proposed infrastructure cooperative agents are employed to provide a user action, patient consent and system policy based access con- trol mechanism to securely share medical images. This allows safe integration of PACS and DI-r systems within a standard EHR system. In addition to this, a behavior-pattern based security policy enhancement feature is added to the system to assist the system security administrator. The resulting secure and interoperable medical imaging systems are easy to expand and maintain. Behavior of the entire system is analysed using general- purpose model driven development tool IBM Rational Rhapsody. The code generation and animation capability of the tool makes it powerful for running e ective simulations. We mainly explore the use of state charts and their interactions with MySQL database to learn the behavior of the system.

Conventional Minimum-Variance (MV) channel estimation is affected by two sources of error, namely the finite number of samples used to estimate the covariance matrix and the asymptotic bias due to interference and additive noise. On the other hand, widely linear (WL) filtering has been shown to improve the estimation of improper complex signals. Researchers have recently demonstrated that the application of WL processing principles can significantly improve the performance of subspace-based channel estimation algorithms. However, in contrast to MV estimation algorithms, subspace-based algorithms assume knowledge of the total number of users in the system, and must be coupled with sophisticated user enumeration algorithm at the expense of increased complexity. In this work, in an effort to combine the practical advantages of MV channel estimation algorithms with the performance of WL filters we propose a widely linear version of the MV channel estimator in the context of multicarrier(MC) CDMA systems employing real modulation. We use numerical simulations to demonstrate that the widely linear minimum-variance algorithm yields more accurate channel estimates compared to the conventional MV algorithm. By considering two simplified transmission/reception models, we also show analytically that the widely linear estimator on average reduces both types of error.

We consider the distributed access enforcement problem for Role-Based Access Control (RBAC) systems. Such enforcement has become important with RBAC's increasing adoption, and the proliferation of data that needs to be protected. We provide a platform for assessing candidates for access enforcement in a distributed architecture for enforcement. The platform provides the ability to encode data structures and algorithms for enforcement, and to measure time-, space- and administrative efficiency. To validate our platform, we use it to compare the state of the art in enforcement, CPOL [6], with two other approaches, the directed graph and the access matrix [9, 10]. We consider encodings of RBAC sessions in each, and propose and justify a benchmark for the assessment. We conclude with the somewhat surprising observation that CPOL is not necessarily the most efficient approach for access enforcement in distributed RBAC deployments.

This thesis addresses the problem of usability in the context of administration of access control systems. We seek to relate the notion of declarative semantics, a recurring theme in research in access control, with usability. We adopt the concrete context of POSIX ACLs and the traditional interface for it that comprises two utilities getfacl and setfacl. POSIX ACLs are the de facto standard to which POSIX conformant systems such as Linux and OpenBSD adhere. The natural semantics of getfacl and setfacl is operational. By operational we mean that the semantics of these are speci ed procedurally. We have designed and implemented an alternate interface that we call askfacl whose natural semantics is declarative. Declarative semantics means "what you see is what it is." We also discuss our design of askfacl and articulate the following thesis that underlies our work: If the natural semantics of the interface for ACLs is declarative, then a user is able to more quickly, accurately and confidently, inspect and edit ACLs than if the semantics is operational. To validate our thesis we conducted a between participant human-subject usability study with 42 participants. The results of our study measurably demonstrate the goodness of declarative semantics in access control.

This thesis proposes a novel system to determine the best representation of a video in the sense that, a user watching the video reaches the highest level of satisfaction possible, given the resource capabilities of the viewing device. Utility theory is used to obtain a utility function representing the user satisfaction as a function of video coding parameters, and the viewing device capabilities. The utility function is formulated as the weighted sum of three individual components. These components are chosen such that, the satisfaction on any one of the components is independent of the satisfaction on every other component. The advantage of such decomposition is the ability to express individual components as simple mathematical relations, modeling user satisfaction. Afterwards, the unknown parameters of these models are determined by results of subjective tests, performed by a multitude of users. Finally, simulated annealing is utilized to find the global optimum of this utility function representing the user satisfaction. Simulation results based on subjective viewing tests on a resource limited mobile device indicate a consistent user satisfaction by the determined optimal encoding parameters of the video.

Cloud computing has seen a surge over the past decade as corporations and institutions have sought to leverage the economies-of-scale achievable through this new computing paradigm. However, the rapid adoptions of cloud computing technologies that implement the existing cloud computing paradigm threaten to undermine the long-term utility of the cloud model of computing. In this thesis we address how to accommodate the variety of access requirements and diverse hardware platforms of cloud computing users by developing extensions to the existing cloud computing paradigm that afford consumer-driven access requirements and integration of new physical hardware platforms.

Modern communications has become far more than point-to-point calling and wireless communications is part of every-day life. Driven by ever growing demand for high data rate communication, multiple-access techniques are of interest for allowing multiple users to share limited resources, such as frequency, time and space. Commercially introduced in 1995, Code-Division Multiple-Access (CDMA) quickly became one of the world's fastest-growing wireless technologies. However, CDMA is subject to some limiting factors, such as multiple-access interference (MAI), which dramatically affects the capacity of the wireless system and degrades performance. Fortunately, these effects can be alleviated by applying advanced signal processing techniques such as multiuser detection (MUD), which potentially provides a large increase in system capacity, enhances spectral efficiency, and relaxes requirements for power control. / Further improvements of MUD can be obtained through joint multiuser detection/decoding. However this is a very complex approach. Inspired by Turbo codes and iterative decoding, Turbo-MUD and iterative multiuser decoding have been proposed. The main objective of this research is to analyse the existing iterative techniques applied to Turbo multiuser decoding for coded CDMA systems and propose new decoder structures to improve the system performance. / In this thesis, we observe that many of the iterative multiuser decoding algorithms in the literature are focused on exchanging information obtained within the most current iteration. However, if correlations over iterations are low, then in principle the bit error rate (BER) performance can be improved by combining signal estimates over iterations. Inspired by this idea, iterative maximal ratio combining (MRC) is proposed in this thesis for application to iterative decoding structures. With this approach all previous estimates are recursively weighted and combined to refine the current signal estimates. The derivation of the corresponding weighting factors is based on the statistics of the decoder outputs over iterations, which leads to maximizing the resultant signal-to-noise ratio (SNR) for each current signal estimate. It is shown that the recursive MRC scheme can be widely applied to many existing iterative structures and provide significantly improved system performance with acceptable computational complexity. In addition, the analytic and numerical results illustrate that the resulting performance gain from the application of MRC is inversely proportional to the correlation of the decoder estimates across iterations. The more correlated the signal estimates over consecutive iterations are, the slower system convergence will be, if MRC is employed over all iterations. MRC over only a few initial iterations where correlation across those iterations is low provides faster convergence. A truncated MRC is suggested, which provides better performance while maintaining low computational complexity. Simulation results based on monte carlo averaging demonstrate that the system performance for the proposed techniques is better than many existing algorithms in the literature. / Thesis (MA(Telecommunications))--University of South Australia, 2005.

Thesis (Ph.D.)--University of South Australia, 1996.

The predicted growth in mobile phone traffic and the move towards enhanced mobility will lead to a need for a wireless infrastructure that provides increasing bandwidth per user. It is envisaged that our world will become increasingly interconnected, with mobile communications enabling us to perform an increasing range of tasks. / Future wireless networks will require an optical network to provide antenna Base Stations with sufficient bandwidth to provide individual users with a larger bandwidth. The combined optical and wireless network is referred to as a “fibre-radio” or “radio-over-fibre” or “fibre-wireless”; network. It is expected that such high-capacity networks will use Wavelength Division Multiplexing (WDM) to increase the total bandwidth transmitted over the optical access network. Such a high-capacity network would not be achievable using a single wavelength or using a copper or coax network. Optical crosstalk is present in WDM optical networks and degrades the received signal quality, increasing the bit-error-rate. Two types of crosstalk occur, depending on whether the crosstalk channel is a different wavelength to the signal or at the same wavelength (out-of-band and in-band crosstalk, respectively). An important consideration for fibre-radio networks is whether or not the optical network transports data at baseband, using standard intensity modulation, or at an RF frequency, using subcarrier modulation. The nature of the optical modulation scheme has implications for the design of the Central Office and the Base Stations, and potentially for optical crosstalk. (For complete abstract open document)

Studies of nonresident fathers have largely neglected the influence of their personality on their contact and involvement with children. The present two-stage study, using quantitative and qualitative data collection methods, undertook to investigate the extent to which selected personality characteristics influenced nonresident fathers� continued engagement with children. The study initially collected demographic and personal data from two hundred and sixty nonresident fathers throughout Australia. This first stage of data collection focussed on fathers� experience of the separation and their subsequent frequency and level of contact and their level of involvement with children. It included several multi-item variables, which measured nonresident fathers� relationships with former partners and children, their adjustment to their new parental role, their role satisfaction and role strain. It also included measures of fatherhood salience, nonresident fathers� parental authority within the separated family, their satisfaction with that authority, their attitude to child support and their perception of resident mothers� attitude to contact. It also administered abridged Sensitivity and Impulsivity scales devised by Eysenck (1969). At the second stage of the study, one hundred and thirty-five of these fathers participated in an interview. One hundred and twenty of them completed a personality questionnaire, which measured scores on the four folk scales of Responsibility, Socialization, Self-control and Good Impression, taken from the California Psychological Inventory. The study found Socialization was the only selected personality characteristic to be significantly associated with nonresident fathers� engagement with children. All four folk scales were positively correlated with nonresident fathers� role adjustment, which was significantly associated with nonresident fathers� contact and was part of the model best predicting their involvement with children. Results showed that nonresident fathers� scores on the Sensitivity measure were negatively associated with role adjustment. Most nonresident fathers in the study had frequent contact with children but limited involvement with them. They reported having little scope to share in parental decision making or to be involved in children�s schooling. The study found fatherhood salience, role adjustment, parental authority and attitude to child support to be positively associated with engagement. It showed interparental hostility, interparental conflict and nonresident fathers� role strain to be negatively correlated with engagement. The study also found that dissatisfaction with parental authority within the separated family, role strain and a negative attitude to child support were associated with ongoing interparental hostility. Qualitative data confirmed nonresident fathers� common experience of being marginalised within the family. They also revealed that many participants went to great lengths to maintain some parental relevancy for their children, despite social and legal systems tending to impede them from meeting parental responsibilities and caring for their children.