The rapid growth in the functionality of Wi-Fi networking in recent years has benefited academic environments. Consistent with their role as centers of innovation academic institutions have an interest in facilitating as much mobile, computer networking functionality as possible to parties of varying levels of affiliation, while also assuring confidentiality and integrity of communications. Providing secure yet functional Wi-Fi access to guests and affiliates in an academic environment presents significant challenges. Academic institutions have taken a wide variety of approaches to this problem. This study presents and analyzes data gathered from semi-structured telephone interviews with employees focused on computer networking and security in academic environments regarding their institutions’ approaches toward striking a balance between security and functionality. The results are summarized, conclusions are presented, and solutions to common problems are reviewed. Finally, remaining significant research questions are presented and explored.

Internet has gained much popularity among the public since the mid 1990's and is now an integrated part of our society. A large range of high-speedbroadband providers and the development of new and more efficient Internet applications increase the possibilities to watch movies and live TV, use IP-telephony and share files over the Internet. Such applications demand high data transmission rates, which in turn consume network bandwidth. Since several users must share the common bandwidth capacity on the Internet, there will be locations in the network where the demand is higher than the capacity. This causes network congestion, which has negative impact on both the data transmission rate and transmission quality. This thesis is about methods for measuring the available bandwidth of a network path between two computers. The available bandwidth can be interpreted as the maximum transfer rate possible without causing congestion. By deploying the methods studied in this thesis the available bandwidth can be measured without previous knowledge of the network topology. When an estimate of the available bandwidth is obtained, the transfer rate when sending messages between computers can be set to the measured value in order to avoid congestion. In the thesis an active end-to-end available bandwidth measurement method called "Bandwidth Available in Real Time" (BART for short) is evaluated. BART measures the available bandwidth by injecting probe packets into the network at a given rate and then analysing how this rate has changed on the receiving side. A Kalman filter is used to update the current estimate of the available bandwidth using the new measurement sample. The focus of the thesis is on how methods, such as BART, function in wireless 802.11 networks, which are very popular in work as well as in home environments. Wireless networks have a different construction compared to many other types of networks and this can affect the accuracy of the measurement methods discussed in this thesis. The effects must be analyzed and understood in order to obtain accurate available bandwidth estimates. Since wireless links are often parts of the network path between a sender and a receiver on the Internet, it is important to study how these links affect the estimates of the available bandwidth.

In recent years, integrated circuit technology has spawned the development of many low cost and high performance microprocessors and microcontrollers. With these devices, there is an increasing interest in the implementation of distributed control networks, utilizing microprocessors in the control nodes. In this work, a low-cost liquid crystal display (LCD) unit utilizing a Hitachi HD44780 controller was designed to provide a visual display node for COLAN (Control Oriented Local Area Network). An Intel 8051 microprocessor was used to provide control services for the display and also to provide a communication interface to the network. The users in the COLAN network can remotely display and easily control the panel of LCDs by sending commands to the display control nodes through the local area network. This capability is especially useful to provide instructions to operators, provide synchronization for human interaction, and for use in locating faults in the system. The software necessary for implementing display and control functions has been developed, including file transfer and text transfer between supervisory nodes and display nodes. This software fits within the task structure associated with the COLAN communication protocols. The display node has been designed, fabricated, and tested in a system involving multiple COLAN nodes and a personal computer host. The emphasis of this work is in the implementation of the display control node and HD44780 controller including hardware and software developments. The hardware work includes designing and interfacing, and the software work includes high level and low level language programming. / Graduation date: 1993

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

Multi-channel wireless networks represent a direction that future state-of-the-art fourth generation (4G) wireless communication standards evolve towards. The IEEE 802.16 family of standards, or referred to as WiMAX, has emerged as one of the most important 4G networks to provide high speed data communication in metropolitan areas. There will be huge challenges in designing the networking protocols to allow WiMAX to provide high quality of services. How to effectively control the errors in the wireless channels and how to efficiently manage the scarce spectrum and power resources in different communication scenarios are crucial for network performance. This thesis aims to solve these challenges to improve the performance of multi-channel wireless networks, using WiMAX as a representative, through a number of techniques. First, we take advantage of the favorable properties of network coding, and design the adaptive MAC-layer and symbol-level network coding protocols. They tightly integrate with WiMAX physical and MAC layers, effectively perform error control, and efficiently utilize scarce wireless spectrum. Second, we investigate multicast services and the femto-cell architecture in WiMAX, and offer a cooperative multicast scheduling protocol as well as a cognitive WiMAX architecture with femto cells. They implement dynamic resource allocation in the networks through techniques of cooperative communication and dynamic optimization. Evaluated with rigorous analysis and extensive simulations, our proposed protocols are able to achieve substantial performance improvement over traditional protocols in the literature.

Multi-channel wireless networks represent a direction that future state-of-the-art fourth generation (4G) wireless communication standards evolve towards. The IEEE 802.16 family of standards, or referred to as WiMAX, has emerged as one of the most important 4G networks to provide high speed data communication in metropolitan areas. There will be huge challenges in designing the networking protocols to allow WiMAX to provide high quality of services. How to effectively control the errors in the wireless channels and how to efficiently manage the scarce spectrum and power resources in different communication scenarios are crucial for network performance. This thesis aims to solve these challenges to improve the performance of multi-channel wireless networks, using WiMAX as a representative, through a number of techniques. First, we take advantage of the favorable properties of network coding, and design the adaptive MAC-layer and symbol-level network coding protocols. They tightly integrate with WiMAX physical and MAC layers, effectively perform error control, and efficiently utilize scarce wireless spectrum. Second, we investigate multicast services and the femto-cell architecture in WiMAX, and offer a cooperative multicast scheduling protocol as well as a cognitive WiMAX architecture with femto cells. They implement dynamic resource allocation in the networks through techniques of cooperative communication and dynamic optimization. Evaluated with rigorous analysis and extensive simulations, our proposed protocols are able to achieve substantial performance improvement over traditional protocols in the literature.

The original promise behind the Internet Protocol was to deliver data from a sender to the receiver using a best-effort approach. This means that the protocol makes no guarantees except that it will try to deliver the data to the destination. If some problem occurs the packet may be discarded by the network without any notice. No guarantees are made regarding the time it takes to deliver the data, the rate at which data will be delivered or if data is delivered in the same order it was sent. The best-effort approach is arguably the reason behind the success of the Internet Protocol and is what makes IP scalable to networks the size of the Internet. However, this approach is also a problem for network operators who want to offer better quality of service to some of their customers. This master thesis will discuss some of the theories behind the implementation of quality of service schemes in an IP network and also provide an example of how to implement it in an existing network.

This thesis focuses on two grand challenges facing data analytical system designers and operators nowadays. First, how to fuse information from multiple autonomous, yet correlated sources and to provide consistent views of underlying phenomena? Second, how to respect externally imposed constraints (privacy concerns in particular) without compromising the efficacy of analysis? To address the first challenge, we apply a general correlation network model to capture the relationships among data sources, and propose Network-Aware Analysis (NAA), a library of novel inference models, to capture (i) how the correlation of the underlying sources is reflected as the spatial and/or temporal relevance of the collected data, and (ii) how to track causality in the data caused by the dependency of the data sources. We have also developed a set of space-time efficient algorithms to address (i) how to correlate relevant data and (ii) how to forecast future data. To address the second challenge, we further extend the concept of correlation network to encode the semantic (possibly virtual) dependencies and constraints among entities in question (e.g., medical records). We show through a set of concrete cases that correlation networks convey significant utility for intended applications, and meanwhile are often used as the steppingstone by adversaries to perform inference attacks. Using correlation networks as the pivot for analyzing privacy-utility trade-offs, we propose Privacy-Aware Analysis (PAA), a general design paradigm of constructing analytical solutions with theoretical backing for both privacy and utility.

<p>The original promise behind the Internet Protocol was to deliver data from a sender to the receiver using a best-effort approach. This means that the protocol makes no guarantees except that it will try to deliver the data to the destination. If some problem occurs the packet may be discarded by the network without any notice. No guarantees are made regarding the time it takes to deliver the data, the rate at which data will be delivered or if data is delivered in the same order it was sent. The best-effort approach is arguably the reason behind the success of the Internet Protocol and is what makes IP scalable to networks the size of the Internet. However, this approach is also a problem for network operators who want to offer better quality of service to some of their customers. This master thesis will discuss some of the theories behind the implementation of quality of service schemes in an IP network and also provide an example of how to implement it in an existing network.</p>

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 129-135). Available also in a digital version from Dissertation Abstracts.