published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

Approved for public release, distribution is unlimited / With the rapidly growing demand for portable devices such as laptops, handheld computers and Personal Digital Assistants (PDAs) with wireless networking capabilities, the need for reliable wireless data network communication has also increased. Just like in mobile voice communication, users demand uninterrupted, secure wireless data communication as they move from place to place. Mobile IP satisfies some of these demands - it enables mobile devices with fixed IP addresses to be permanently reachable even as their point of attachment to the network changes. This allows for routing of data packets to and from the mobile device irrespective of its location on the network. While uninterrupted data flow can be achieved with Mobile IP, it introduces additional security vulnerabilities, including data privacy, data integrity and authentication. The goal of this thesis is to investigate such vulnerabilities and explore implementations to overcome them. / Civilian, National Science Foundation

by Hung King Fai Kevin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 82-85 (2nd gp.)). / Abstracts in English and Chinese. / ACKNOWLEDGEMENT --- p.ii / ABSTRACT --- p.iii / 摘要 --- p.v / TABLE OF CONTENTS --- p.vi / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- OBJECTIVES --- p.1 / Chapter 1.2 --- NEED FOR PATIENT-MONITORING SYSTEM --- p.1 / Chapter 1.2.1 --- Aging Population --- p.1 / Chapter 1.2.2 --- Increasing Population with Heart Diseases --- p.2 / Chapter 1.3 --- ECG BASICS --- p.3 / Chapter 1.4 --- EXISITING ECG-MONITORING TECHNOLOGIES --- p.4 / Chapter 1.5 --- CHALLENGES IN PATIENT-MONITORING --- p.5 / Chapter 1.6 --- DEVELOPMENT OF AN ECG-MONITORING SYSTEM --- p.6 / Chapter 1.6.1 --- Overall Structure --- p.6 / Chapter 1.6.2 --- Considerations --- p.7 / Chapter CHAPTER 2 --- EMI FILTERS IN ECG ACQUISITION CIRCUIT --- p.8 / Chapter 2.1 --- OVERVIEW OF NOISE SOURCES IN ECG ACQUISITION --- p.8 / Chapter 2.1.1 --- Other Biopotentials --- p.8 / Chapter 2.1.2 --- Motion Artifact --- p.8 / Chapter 2.1.3 --- Power-line Interference --- p.10 / Chapter 2.1.4 --- High-Frequency Electromagnetic Interference --- p.15 / Chapter 2.2 --- EMI FILTERS --- p.16 / Chapter 2.2.1 --- Introduction to EMI Filters --- p.16 / Chapter 2.2.2 --- Types of EMI Filter --- p.17 / Chapter 2.2.3 --- EMI Filters in ECG Monitoring --- p.21 / Chapter 2.3 --- MODELING OF INTERFERENCE IN ECG-MONITORING SYSTEM --- p.22 / Chapter 2.3.1 --- Model and Parameters --- p.22 / Chapter 2.3.2 --- Method --- p.24 / Chapter 2.3.2 --- Results --- p.27 / Chapter 2.3.3 --- Discussion --- p.30 / Chapter 2.4 --- BUILDING AN ECG ACQUISITION CIRCUIT WITH EMI FILTERS --- p.30 / Chapter 2.4.1 --- Purpose --- p.30 / Chapter 2.4.2 --- Experimental Setup and Method --- p.30 / Chapter 2.4.3 --- Results --- p.32 / Chapter 2.4.4 --- Discussion --- p.46 / Chapter CHAPTER 3 --- ADAPTIVE FILTER --- p.48 / Chapter 3.1 --- OBJECTIVE --- p.48 / Chapter 3.2 --- INTRODUCTION TO ADAPTIVE FILTER --- p.48 / Chapter 3.3 --- METHOD --- p.50 / Chapter 3.4 --- RESULTS --- p.52 / Chapter 3.5 --- DISCUSSION --- p.57 / Chapter CHAPTER 4 --- WAP-BASED TELEMEDICINE APPLICATIONS --- p.59 / Chapter 4.1 --- INTRODUCTION TO TELEMEDICINE --- p.59 / Chapter 4.2 --- INTRODUCTION TO WAP --- p.59 / Chapter 4.3 --- WAP APPLICATIONS --- p.60 / Chapter 4.4 --- SYSTEM IMPLEMENTATION --- p.63 / Chapter 4.4.1 --- Overall Structure --- p.63 / Chapter 4.4.2 --- Relational Database --- p.63 / Chapter 4.4.3 --- Program Flow --- p.64 / Chapter 4.4.4 --- ECG Browsing and Feature Extraction --- p.70 / Chapter 4.5 --- EMULATION --- p.72 / Chapter 4.6 --- EXPERIENCE WITH WAP PHONE --- p.74 / Chapter 4.7 --- DISCUSSION AND CONCLUSION --- p.75 / Chapter CHAPTER 5: --- CONCLUSION AND FUTURE WORK --- p.77 / Chapter 5.1 --- CONCLUSION --- p.77 / Chapter 5.2 --- FUTURE WORK --- p.77 / Chapter 5.3 --- MARKET ANALYSIS --- p.79 / BIBLIOGRAPHY --- p.80

Ad hoc networks are commonly known to implement IEEE 802.11 standard as their medium access control (MAC) protocol. It is well known that token passing MAC schemes outperform carrier-sense-multiple-access (CSMA) schemes, therefore, token passing MAC protocols have gained popularity in recent years. In recent years, the research extends the concept of token passing ' scheme to wireless settings since they have the potential of achieving higher channel utilization than CSMA type schemes. In this thesis, a hybrid Token-CDMA MAC protocol that is based on a token passing scheme with the incorporation of code division multiple access (CDMA) is introduced. Using a dynamic code distribution algorithm and a modified leaky-bucket policing system, the hybrid protocol is able to provide both Quality of Service (QoS) and high network resource utilization, while ensuring the stability of a network. This thesis begins with the introduction of a new MAC protocol based on a token-passing strategy. The input traffic model used in the simulation is a two-state Markov Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multi-layered Gilbert-Elliot model. The performance of the proposed MAC scheme is examined by simulation, and compared to the performance of other MAC protocols published in the literature. Simulation results demonstrate that the proposed hybrid MAC scheme is effective in decreasing packet delay and significantly shortens the length of the queue. The thesis continues with the discussion of the analytical model for the hybrid Token CDMA protocol. The proposed MAC scheme is analytically modelled as a multiserver multiqueue (MSMQ) system with a gated service discipline. The analytical model is categorized into three sections viz. the vacation model, the input model and the buffer model. The throughput and delay performance are then computed and shown to closely match the simulation results. Lastly, cross-layer optimization between the physical (PHY) and MAC layers for the hybrid token-CDMA scheme is discussed. The proposed joint PHY -MAC approach is based on the interaction between the two layers in order to enable the stations to dynamically adjust the transmission parameters resulting in reduced mutual interference and optimum system performance. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.

Wireless Sensor Networks (WSN), a new class of devices, has the potential to revolutionize the capturing, processing, and communication of critical data at low cost. Sensor networks consist of small, low-power, and low-cost devices with limited computational and wireless communication capabilities. These sensor nodes can only transmit a finite number of messages before they run out of energy. Thus, reducing the energy consumption per node for end-to-end data transmission is an important design consideration for WSNs. The Medium Access Control (MAC) protocols aim at providing collision-free access to the wireless medium. MAC protocols also provide the most direct control over the utilization of the transceiver, which consumes most of the energy of the sensor nodes. The major part of this thesis is based on a proposed MAC protocol called Distributed Receiver-oriented MAC (DRMACSN) protocol for code division multiple access (CDMA) based WSNs. The proposed MAC protocol employs the channel load blocking scheme to reduce energy consumption in the network. The performance of the proposed MAC protocol is verified through simulations for average packet throughput, average delay and energy consumption. The performance of the proposed MAC protocol is also compared to the IEEE 802.15.4 MAC and the MAC without the channel load sensing scheme via simulations. An analytical model is derived to analyse the average packet throughput and average energy consumption performance for the DRMACSN MAC protocol. The packet success probability, the message success and blocking probabilities are derived for the DRMACSN MAC protocol. The discrete-time multiple vacation queuing models are used to model the delay behaviour of the DRMACSN MAC protocol. The Probability Generating Functions (PGF) of the arrivals of new messages in sleep, back-off and transmit states are derived. The PGF of arrivals of retransmitted packets of a new message are also derived. The queue length and delay expressions for both the Bernoulli and Poisson message arrival models are derived. Comparison between the analytical and simulation results shows that the analytical model is accurate. The proposed MAC protocol is aimed at having an improved average packet throughput, a reduced packet delay, reduced energy consumption performance for WSN. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 243-251) Also available in print.

Thesis (M. Sc.)(Electronic Engineering)--University of Pretoria, 2004. / Summaries in English and Afrikaans. Includes bibliographical references (125-128).

Thesis (M.S. in Information Technology Management and M.S. in Computer Science)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Alexander Bordetsky, Gilbert M. Lundy. Includes bibliographical references (p. 69-75). Also available online.

Modern day computer networks have become very complex and attackers have benefited due to this complexity and have found vulnerabilities and loopholes in the network architecture. In order to identify the attacks from an attacker all aspects of network architecture needs to be carefully examined such as packet headers, network scans, versions of applications, network scans, network anomalies etc. and after the examination attributes playing a significant impact on the security posture of the organization needs to be highlighted so that resources and efforts are directed towards those attributes. In this work we extensively look at network traffic at dormitory network of a large campus and try to identify the attributes that play a significant role in the infection of a machine. Our scheme is to collect as much attributes from the network traffic applying the heuristic of network infection and then devise a scheme called decision centric rank ordering of security metric that gives the priority to the security metrics so that network administrators can channel their efforts in the right direction. Another aspect of this research is to identify the probability of an attack on a communication infrastructure. A communication infrastructure becomes prone to attack if certain elements exist in it, such as vulnerabilities in the comprising elements of the system, existence of an attacker and motivation for him to attack. Focus of this study is on vulnerability assessment and security metrics such as user behavior, operating systems, user applications, and software updates. To achieve a quantified value of risk, a set of machines is carefully observed for the security metrics. Statistical analysis is applied on the data collected from compromised machines and the quantified value of risk is achieved.

The evolution of the intemet protocol (IP) to offer quality of service (QoS) makes it a suitable core network protocol for next generation networks (NGN). The QoS features incorporated to IP will enable future lP-based wireless networks to meet QoS requirements of various multimedia traffic. The Differentiated Service (Diffserv) Architecture is a promising QoS technology due to its scalability which arises from traffic flow aggregates. For this reason, in this dissertation a network infrastructure based on DiffServ is assumed. This architecture provides assured service (AS) and premium service (PrS) classes in addition to best-effort service (BE). The medium access control (MAC) protocol is one of the important design issues in wireless networks. In a wireless network carrying multimedia traffic, the MAC protocol is required to provide simultaneous support for a wide variety of traffic types, support traffic with delay and jitter bounds, and assign bandwidth in an efficient and fair manner among traffic classes. Several MAC protocols capable of supporting multimedia services have been proposed in the literature, the majority of which were designed for wireless A1M (Asynchronous Transfer Mode). The focus of this dissertation is on time division multiple access and code division multiple access (TDMAlCDMA) based MAC protocols that support QoS in lP-based wireless networks. This dissertation begins by giving a survey of wireless MAC protocols. The survey considers MAC protocols for centralised wireless networks and classifies them according to their multiple access technology and as well as their method of resource sharing. A novel TDMAlCDMA based MAC protocol incorporating techniques from existing protocols is then proposed. To provide the above-mentioned services, the bandwidth is partitioned amongst AS and PrS classes. The BE class utilizes the remaining bandwidth from the two classes because it does not have QoS requirements. The protocol employs a demand assignment (DA) scheme to support traffic from PrS and AS classes. BE traffic is supported by a random reservation access scheme with dual multiple access interference (MAl) admission thresholds. The performance of the protocol, i.e. the AS or PrS call blocking probability, and BE throughput are evaluated through Markov analytical models and Monte-Carlo simulations. Furthermore, the protocol is modified and incorporated into IEEE 802.16 broadband wireless access (BWA) network. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.