Department of Computer and Electrical Engineering and Computer Science

This thesis is concerned with the performance analysis of mobile cellular systems under various distributions of portable users. The performance measure used is the average outage probability. Performance analysis is performed for macrocellular as well as microcellular systems, for different distributions of mobile users such as uniform, ring, and bell distribution. The outage probability is evaluated for systems with hexagonal, triangular, and square grid layouts. The effect of macroscopic diversity on system performance is also considered. Finally, computer simulations are used to verify the evaluated results.

A user interface that has objects familiar to the user will be easier to use. In this thesis, a user interface that is customizable to any color bitmap is proposed. The most significant problem with this approach is the problem of finding objects in a color bitmap. A solution to the problem is proposed and evaluated using an analysis tool, developed for this thesis, called Workbench. Current image detection methods are evaluated and compared to the solution proposed using Workbench. The proposed solution is then evaluated for the YIQ and HSI color mappings. The results of this investigation and recommendations for future work is proposed.

The project that was created for this thesis is a Case Based Reasoning application to be used in high level software design for Siemens' Telecommunications software. Currently, design engineers search for existing subtasks in the software that are similar to subtasks in their new designs by reading documentation and consulting with other engineers. The prototype for Software Design Using Case Based Reasoning (SDUCBR) stores these subtasks in a case library and enables the design engineer to locate relevant subtasks via three different indexing techniques. This thesis addresses knowledge representation and indexing mechanisms appropriate for this application. SDUCBR is domain-dependent. Cases are stored in a relational hierarchy to facilitate analyzing the existing implementation from various perspectives. The indexing mechanisms were designed to provide the software design engineer with the flexibility of describing a problem differently based on the objective, level of granularity, and special characteristics of the subtask.

A unified performance analysis of token-passing local area networks is reported in this thesis. The primary performance criterion is the mean transfer delay of a message, which is defined as the time from the instant a message becomes available for transmission at a station until the end of its successful reception at the destination. Other performance criteria are power and effective transmission ratio. Analytical expressions for the criteria are derived for exhaustive, gated, and limited service disciplines. Simulation models are also used to support the investigations. The effects of service time distribution (constant, exponential, and hyperexponential) are examined. It is found that under any traffic intensity, service discipline or packet length distribution, token bus gives higher delay and has lower power and lower effective transmission ratio than token ring. Also, the token bus is found to be less sensitive to message length distribution, performing about the same for constant, exponential, and hyperexponential distribution.

This dissertation deals with novel vision-based motion cues called the Visual Threat Cues (VTCs), suitable for autonomous navigation tasks such as collision avoidance and maintenance of clearance. The VTCs are time-based and provide some measure for a relative change in range as well as clearance between a 3D surface and a moving observer. They are independent of the 3D environment around the observer and need almost no a-priori knowledge about it. For each VTC presented in this dissertation, there is a corresponding visual field associated with it. Each visual field constitutes a family of imaginary 3D surfaces attached to the moving observer. All the points that lie on a particular imaginary 3D surface, produce the same value of the VTC. These visual fields can be used to demarcate the space around the moving observer into safe and danger zones of varying degree. Several approaches to extract the VTCs from a sequence of monocular images have been suggested. A practical method to extract the VTCs from a sequence of images of 3D textured surfaces, obtained by a visually fixation, fixed-focus moving camera is also presented. This approach is based on the extraction of a global image dissimilarity measure called the Image Quality Measure (IQM), which is extracted directly from the raw data of the gray level images. Based on the relative variations of the measured IQM, the VTCs are extracted. This practical approach to extract the VTCs needs no 3D reconstruction, depth information, optical flow or feature tracking. This algorithm to extract the VTCs was tested on several indoor as well as outdoor real image sequences. Two vision-based closed-loop control schemes for autonomous navigation tasks were implemented in a-priori unknown textured environments using one of the VTCs as relevant sensory feedback information. They are based on a set of IF-THEN fuzzy rules and need almost no a-priori information about the vehicle dynamics, speed, direction of motion, etc. They were implemented in real-time using a camera mounted on a six degree-of-freedom flight simulator.

With the continuing advances in computing and wireless technologies, mobile ad hoc networks (MANETs) are expected to become an indispensable part of the computing environment in the near future. Wireless devices are constantly growing in computing speed, memory, communication capabilities and features, while shrinking in weight and size. With this growth and the proliferation of these devices in every aspect of society, the need for such devices to communicate in a seamless manner is becoming increasingly essential. Multiple routing protocols have been developed for MANETs [51]. As MANETs gain popularity, their need to support real time and multimedia applications is growing as well. Such applications have stringent quality of service (QoS) requirements such as bandwidth, delay, and delay fitter. Design and development of routing algorithms with QoS support is experiencing increased research interest. Several approaches which propose various routing algorithms with QoS support for MANETs have been presented in research. This dissertation addresses the issues and challenges of QoS routing in MANETS and presents three new protocols which provide QoS support for this environment. First, a brief classification of existing QoS routing algorithms is provided. Then, the three new protocols for QoS routing support in MANETs are presented. These protocols focus on resource reservation for QoS provisioning in TDMA-based MANETs. The first protocol improves QoS support by eliminating racing conditions during multiple reservations of QoS paths. The second protocol is a new protocol for resource reservation for QoS support in TDMA-based MANETs using directional antennas. The last protocol provides dynamic range resource reservation for QoS support in MANETs and represents an extension of the previous protocols.

Publish/subscribe is a powerful paradigm for distributed applications based on decoupled clients of information. In pub/sub applications, there exist a large amount of publishers and subscribes ranging from hundreds to millions. Publish/subscribe systems need to disseminate numerous events through a network of brokers. Due to limited resources of brokers, there may be lots of events that cannot be handled in time which in turn causes overload problem. Here arises the need of admission control mechanism to provide guaranteed services in publish/subscribe systems. Our approach gives the solution to this overload problem in the network of brokers by limiting the incoming subscriptions by certain criteria. The criteria are the factors like resources which include bandwidth, CPU, memory (in broker network), resource requirements by the subscription.

Promoting healthcare and wellbeing requires the dedication of a multi-tiered health service delivery system, which is comprised of specialists, medical doctors and nurses. A holistic view to a patient care perspective involves emotional, mental and physical healthcare needs, in which caring is understood as the essence of nursing. Properly and efficiently capturing and managing nursing knowledge is essential to advocating health promotion and illness prevention. This thesis proposes a document-indexing framework for automating classification of nursing knowledge based on nursing theory and practice model. The documents defining the numerous categories in nursing care model are structured with the help of expert nurse practitioners and professionals. These documents are indexed and used as a benchmark for the process of automatic mapping of each expression in the assessment form of a patient to the corresponding category in the nursing theory model. As an illustration of the proposed methodology, a prototype application is developed using the Latent Semantic Indexing (LSI) technique. The prototype application is tested in a nursing practice environment to validate the accuracy of the proposed algorithm. The simulation results are also compared with an application using Lucene indexing technique that internally uses modified vector space model for indexing. The result comparison showed that the LSI strategy gives 87.5% accurate results compared to the Lucene indexing technique that gives 80% accuracy. Both indexing methods maintain 100% consistency in the results.