Mobile handset manufacturers have begun to include wireless LAN (WLAN) interfaces in their cellular handsets. This allows users to access WLAN networks when they are available and to revert to conventional cellular communications otherwise. In this way the handset can dynamically use the "best" available network, by switching connections between the two network interfaces. This switching is referred to as a vertical handoff (VHO). When handling real-time connections, handsets must be capable of performing a seamless vertical handoff. This occurs when the interface switching does not disrupt the quality of service requirements of the active connections. Vertical handoffs are generally time consuming, and this delay creates a difficult problem since WLAN coverage can be lost very abruptly. In this thesis, we propose and investigate several methods of mitigating this problem. A solution based on using a Vertical Handoff Support Node (VHSN) is proposed. When the WLAN link is lost, the VHSN is able to quickly redirect packets through the local cellular base-station during the time that handoff is taking place. This approach can eliminate VHO link loss. It is shown that the act of WLAN-to-cellular handoff can result in a severe bandwidth deficit problem on the WLAN. A novel bandwidth reservation and securing mechanism is proposed which overcomes this problem and performs significantly better than schemes based on modified versions of the static guard channel scheme used in cellular networks. The work is characterized by simulation and analytic models which investigate the key performance aspects of this type of system. / Thesis / Doctor of Philosophy (PhD)

Edge computing is a distributed computing paradigm where computing resources are located physically closer to the data source compared to the traditional cloud computing paradigm. Edge computing enables computation offloading from resource-constrained devices to more powerful servers in the edge and cloud. To offer edge and cloud support to real-time industrial applications, the communication to the servers and the server-side computation needs to be predictable. However, the predictability of offloading cannot be guaranteed in an environment where multiple devices are competing for the same edge and cloud resources due to potential server-side scheduling conflicts. To the best or our knowledge, no offloading scheme has been proposed that provides a highly predictable real-time task scheduling in the face of multiple devices offloading to a set of heterogeneous edge/cloud servers. Hence, this thesis approaches the problem of predictable offloading in real-time environments by proposing a centralized server time reservation system to schedule the offloading of real-time tasks to edge and cloud servers. Our reservation system allows end-devices to request external execution time in advance for real-time tasks that will be generated in the future, therefore when such a task is created, it already has a designated offloading server that guarantees its timely execution. Furthermore, this centralized reservation system is capable of optimizing the reservation scheduling strategy with the goal of minimizing energy consumption of edge servers while meeting the stringent deadline constraints of real-time applications. / Edge computing är ett distribuerat datorparadigm där datorresurser är fysiskt placerade närmare datakällan jämfört med det traditionella molnberäkningsparadigmet. Edge computing möjliggör beräkningsavlastning från resursbegränsade enheter till mer kraftfulla servrar i kanten och molnet. För att erbjuda kant- och molnstöd till industriella tillämpningar i realtid måste kommunikationen till servrarna och beräkningen på serversidan vara förutsägbar. Förutsägbarheten av avlastning kan dock inte garanteras i en miljö där flera enheter konkurrerar om samma kant- och molnresurser på grund av potentiella schemaläggningskonflikter på serversidan. Så vitt vi vet har inget avlastningsschema föreslagits som ger en mycket förutsägbar uppgiftsschemaläggning i realtid inför flera enheter som laddas av till en uppsättning heterogena edge-/molnservrar. Därför närmar sig denna avhandling problemet med förutsägbar avlastning i realtidsmiljöer genom att föreslå ett centraliserat servertidsreservationssystem för att schemalägga avlastningen av realtidsuppgifter till edge- och molnservrar. Vårt reservationssystem tillåter slutenheter att begära extern exekveringstid i förväg för realtidsuppgifter som kommer att genereras i framtiden, därför när en sådan uppgift skapas har den redan en utsedd avlastningsserver som garanterar att den utförs i tid. Dessutom kan detta centraliserade bokningssystem optimera bokningsschemaläggningsstrategin med målet att minimera energiförbrukningen för edge-servrar samtidigt som de stränga deadline-begränsningarna för realtidsapplikationer uppfylls.

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<p> Telemedicine traffic transmission over wireless cellular networks has gained in importance during the last few years. Most of the current research in the field has focused on software and hardware implementations for telemedicine transmission, without discussing the case of simultaneous transmission of both urgent telemedicine traffic and regular multimedia traffic over the network.</p> <p> Due to the fact that telemedicine traffic carries critical information regarding the patients' condition, it is vitally important that this traffic has highest transmission priority in comparison to all other types of traffic in the cellular network. However, the need for expedited and correct transmission of telemedicine traffic calls for a guaranteed bandwidth to telemedicine users. This creates a tradeoff between the satisfaction of the very strict Quality of Service (QoS) requirements of telemedicine traffic and the loss of the guaranteed bandwidth in the numerous cases when it is left unused, due to the infrequent nature of telemedicine traffic. This waste of the bandwidth may lead to a lack of sufficient bandwidth for regular traffic, hence degrading its QoS.</p> <p> To resolve this complex problem, in this thesis, we propose a) an adaptive bandwidth reservation scheme based on road map information and on users' mobility, and b) a fair scheduling scheme for video traffic transmission over wireless cellular networks. The proposed combination of the two schemes, which is evaluated over a hexagonal cellular structure, is shown to achieve high channel bandwidth utilization while offering full priority to telemedicine traffic.</p> / Thesis / Master of Applied Science (MASc)

This research explores the feasibility of providing innovative and effective solutions for traffic congestion. The design of reservation systems is being considered as an alternative and/or complementary travel demand management (TDM) strategy. A reservation indicates that a user will follow a booking procedure defined by the reservation system before traveling so as to obtain the right to access a facility or resource. In this research, the reservation system is introduced for a cordon-based downtown road network, hereafter called the Downtown Space Reservation System (DSRS). The research is executed in three steps. In the first step, the DSRS is developed using classic optimization techniques in conjunction with an artificial intelligence technology. The development of this system is the foundation of the entire research, and the second and third steps build upon it. In the second step, traffic simulation models are executed so as to assess the impact of the DSRS on a hypothetical transportation road network. A simulation model provides various transportation measures and helps the decision maker analyze the system from a transportation perspective. In this step, multiple simulation runs (demand scenarios) are conducted and performance insights are generated. However, additional performance measurement and system design issues need to be addressed beyond the simulation paradigm. First, it is not the absolute representation of performance that matters, but the concept of relative performance that is important. Moreover, a simulation does not directly demonstrate how key performance measures interact with each other, which is critical when trying to understand a system structure. To address these issues, in the third step, a comprehensive performance measurement framework has been applied. An analytical technique for measuring the relative efficiency of organizational units, or in this case, demand scenarios called network Data Envelopment Analysis (DEA), is used. The network model combines the perspectives of the transportation service provider, the user and the community, who are the major stakeholders in the transportation system. This framework enables the decision maker to gain an in-depth appreciation of the system design and performance measurement issues. / Ph. D.

The state of Virginia has been a leader in the design and implementation of welfare reform measures. State welfare reforms were enacted in 1996 and federal reforms followed shortly after in 1996. Initial decreases in program caseloads and the movement of former recipients from unemployment to employment have led initial reform measures to be widely heralded as successes. Significant concerns remain, however, about the ability of non-metropolitan labor markets to absorb female household heads currently on welfare. This thesis addresses potential differences in the impact of welfare reform measures in non-metropolitan and metropolitan labor markets by estimating wage and reservation wage equations for female household heads in Northern and Southwest Virginia. The results suggest young children and lack of access to automobiles create significantly greater barriers to employment in non-metropolitan than metropolitan labor markets. Estimated potential earnings in Southwest Virginia were lower than in Northern Virginia and suggest that female household heads will have trouble escaping poverty through employment. In fact, initial reported earnings for both areas have fallen below estimates of living wages needed to escape poverty. The results also suggest traditional labor market characteristics do not explain all of the differences in earnings, particularly the differences in the observed wages of persons exiting welfare as compared to the general population. If this is the case, policies that only address child care and transportation costs may have little impact as to the ability of welfare recipients to get and keep jobs that enable them to become economically self-sufficient. / Master of Science

Grid computing provides the necessary infrastructure to pool together diverse and distributed resources interconnected by networks to provide a unified virtual computing resource view to the user. One of the important responsibilities of the grid software is resource management and techniques to allow the user to make optimal use of the resources for executing applications. In addition to the goals of minimizing job completion time and achieving good throughput there are other minimum requirements such as minimum memory and cpu requirements, choice of operating system, fine grained file access permissions etc. Currently such requirements are being fulfilled by resource brokers, which act as mediating agents between users and resource owners. In this thesis we approach the resource brokering architectural issue in a different manner. Instead of a monolithic broker, which performs all the superscheduling functions we propose a Modular Framework based Architecture for Task Initiation and Scheduling (MFATIC) based on the three main stages in the superscheduling process. There are three major goals of this research. The first aim is to develop a decoupled architectural model that not only provides a clear distinction in the responsibilities of each of the components but also provides the user the flexibility to replace one component with another functionally equivalent component. Secondly each of these components should be configurable and extensible to be able to accommodate user requirements. Finally, the design should enable the user to plug in modules within components of different deployments of the resource broker and thus promoting software reuse. / Master of Science

Indigenous languages worldwide are rapidly disappearing, forced out of use by the spread of dominant Western culture and its languages. On the Warm Springs reservation of Oregon, the Culture and Heritage department, the tribal agency in charge of language preservation, is offering instruction in all three languages of the reservation: Wasco, Sahaptin and Northern Paiute. Most of the class offerings target the children of the tribes. In an effort to stimulate their interest, Culture and Heritage has considered creating language learning computer games. During a ten-week internship with Culture and Heritage in the spring of 1999, I did preliminary research for a Wasco computer game. Using participant observation and informal interviews with children, elders and Warm Springs Elementary School teachers, I developed a possible structure and scenario for a game centered on traditional subsistence activities. I also identified obstacles to the realization of language computer games, such as lack of technological resources in Warm Springs, and elders' resistance to computers. Results and recommendations were issued in a public meeting in Warm Springs and presented in a report. This thesis is a case study exploring in greater depth issues that arose during my internship, like the politics of anthropological fieldwork on reservations, and issues related to the Wasco computer game project, such as the pragmatics of language preservation and the role of computers in reversing language shift. On the latter, it was found that the introduction of computers tends to disrupt traditional hierarchies and patterns for the transmission of knowledge. In view of the cultural, financial and logistic costs, the benefits of Computer Assisted Language Learning for the preservation of severely endangered languages are uncertain at best. / Graduation date: 2002