Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (p. 159-167). Also available in electronic format on the Internet.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 106-113). Also available in electronic version.

abstract: It is commonly known that High Performance Computing (HPC) systems are most frequently used by multiple users for batch job, parallel computations. Less well known, however, are the numerous HPC systems servicing data so sensitive that administrators enforce either a) sequential job processing - only one job at a time on the entire system, or b) physical separation - devoting an entire HPC system to a single project until recommissioned. The driving forces behind this type of security are numerous but share the common origin of data so sensitive that measures above and beyond industry standard are used to ensure information security. This paper presents a network security solution that provides information security above and beyond industry standard, yet still enabling multi-user computations on the system. This paper's main contribution is a mechanism designed to enforce high level time division multiplexing of network access (Time Division Multiple Access, or TDMA) according to security groups. By dividing network access into time windows, interactions between applications over the network can be prevented in an easily verifiable way. / Dissertation/Thesis / M.S. Computer Science 2013

Ho Chi-Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 63-[64]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The 2.5G Systems --- p.3 / Chapter 1.2.1 --- HSCSD --- p.3 / Chapter 1.2.2 --- GPRS --- p.3 / Chapter 1.2.3 --- EDGE --- p.4 / Chapter 1.2.4 --- IS-136 --- p.4 / Chapter 1.3 --- The Evolution from 2G/2.5G to 3G --- p.4 / Chapter 1.3.1 --- GSM Data Evolution --- p.4 / Chapter 1.3.2 --- TDMA Data Evolution --- p.5 / Chapter 1.3.3 --- CDMA Data Evolution --- p.6 / Chapter 1.4 --- UTRA --- p.7 / Chapter 1.4.1 --- UTRA FDD --- p.8 / Chapter 1.4.2 --- UTRA TDD --- p.18 / Chapter 1.4.3 --- Transport Channels --- p.25 / Chapter 2 --- Spreading Factor Optimization for FDD Downlink --- p.27 / Chapter 2.1 --- The Optimal Channel Splitting Problem --- p.28 / Chapter 2.2 --- Spreading Factor Optimization for FDD Downlink Dedicated Chan- nel --- p.30 / Chapter 3 --- Random Access Channel Stability Control --- p.33 / Chapter 3.1 --- Random Access Slotted Aloha --- p.33 / Chapter 3.1.1 --- System model --- p.33 / Chapter 3.1.2 --- Probability of Code-Collision --- p.34 / Chapter 3.1.3 --- Throughput Analysis of Random Access in TD/CDMA System --- p.37 / Chapter 3.1.4 --- Retransmission --- p.42 / Chapter 3.1.5 --- System Delay --- p.42 / Chapter 3.2 --- Random Access Channel Stability Control --- p.43 / Chapter 3.2.1 --- System Model --- p.43 / Chapter 3.2.2 --- Random Access Procedure --- p.44 / Chapter 3.3 --- Random Access Channel Stability Control Alogrithm --- p.47 / Chapter 3.3.1 --- Simulation --- p.49 / Chapter 3.4 --- Multi-class Model --- p.55 / Chapter 4 --- Conclusions and Topics for Future Study --- p.60 / Chapter 4.1 --- Thesis Conclusions --- p.60 / Chapter 4.2 --- Future Work --- p.61 / Chapter 4.2.1 --- Downlink and Uplink resource allocation in TDD --- p.61 / Chapter 4.2.2 --- Resource Unit Packing in TDD --- p.62 / Chapter 4.2.3 --- Other Topics --- p.62 / Bibliography --- p.63

This dissertation studies fundamental limits of modern digital communication systems in presence/absence of delay and secrecy constraints. In the first part of this dissertation, we consider a typical time-division wireless communication system wherein the channel strengths of the wireless users vary with time with a power constraint at the base station and which is not subject to any delay constraint. The objective is to allocate resources to the wireless users in an equitable manner so as to achieve a specific throughput. This problem has been looked at in different ways by previous researchers. We address this problem by developing a systematic way of designing scheduling schemes that can achieve any point on the boundary of the rate region. This allows us to map a desired throughput to a specific scheduling scheme which can then be used to service the wireless users. We then propose a simple scheme by which users can cooperate and then show that a cooperative scheduling scheme enlarges the achievable rate region. A simple iterative algorithm is proposed to find the resource allocation parameters and the scheduling scheme for the cooperative system. In the second part of the dissertation, a downlink time-division wireless sys- tem that is subject to a delay constraint is studied, and the rate region and optimal scheduling schemes are derived. The result of this study concludes that the achievable throughput of users decrease as the delay constraint is increased. Next, we consider a problem motivated by cognitive radio applications which has been proposed as a means to implement efficient reuse of the licensed spectrum. Previous research on this topic has focussed largely on obtaining fundamental limits on achievable throughput from a physical layer perspective. In this dissertation, we study the impact of im- posing Quality of Service constraints (QoS) on the achievable throughput of users. The result of this study gives insights on how the cognitive radio system needs to be operated in the low and high QoS constraint regime. Finally, the third part of this dissertation is motivated by the need for commu- nicating information not only reliably, but also in a secure manner. To this end, we study a source coding problem, wherein multiple sources needs to be communicated to a receiver with the stipulation that there is no direct channel from the transmitter to the receiver. However, there are many \agents" that can help carry the information from the transmitter to the receiver. Depending on the reliability that the transmit- ter has on each of the agents, information is securely encoded by the transmitter and given to the agents, which will be subsequently given to the receiver. We study the overhead that the transmitter has to incur for transmitting the information to the receiver with the desired level of secrecy. The rate region for this problem is found and simple achievable schemes are proposed. The main result is that, separate secure coding of sources is optimal for achieving the sum-rate point for the general case of the problem and the rate region for simple case of this problem.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / As the integrated Network Enhanced Telemetry (iNET) program prepares for developmental flights tests, refinements are being made to the Radio Access Network Standard that ensures interoperability of networked radio components. One key aspect of this interoperability is the definition of Telemetry Network System (TmNS) RF Data Link Layer functionality for conducting efficient communications between radios in a TDMA (Time Division Multiple Access) channel sharing scheme. This paper examines the overall structure of the TmNS RF Data Link Layer and provides an overview of its operation. Specific topics include Medium Access Control (MAC) scheduling and framing in the context of a burst-oriented TDMA structure, link layer encryption, the priority-enabled Automatic Repeat reQuest (ARQ) protocol, high-level network packet and link control message encapsulation, payload segmentation and reassembly, and radio Link Layer Control Messaging.

For opportunistic spectrum access and spectrum sharing in cognitive radio networks, one key problem is how to develop wireless access schemes for secondary users so that harmful interference to primary users can be avoided and quality-of-service (QoS) of secondary users can be guaranteed. In this research, dynamic wireless access protocols for secondary users are designed and optimized for both infrastructure-based and ad-hoc wireless networks. Under the infrastructure-based model, the secondary users are connected through a controller (i.e., an access point). In particular, the problem of wireless access for eHealth applications is considered. In a single service cell, an innovative wireless access scheme, called electromagnetic interference (EMI)-aware prioritized wireless access, is proposed to address the issues of EMI to the medical devices and QoS differentiation for different eHealth applications. Afterwards, the resource management problem for multiple service cells, specifically, in multiple spatial reuse time-division multiple access (STDMA) networks is addressed. The problem is formulated as a dual objective optimization problem that maximizes the spectrum utilization of secondary users and minimizes their power consumption subject to the EMI constraints for active and passive medical devices and minimum throughput guarantee for secondary users. Joint scheduling and power control algorithms based on greedy approaches are proposed to solve the problem with much less computational complexity. In an ad-hoc wireless network, the robust transmission scheduling and power control problem for collision-free spectrum sharing between secondary and primary users in STDMA wireless networks is investigated. Traditionally, the problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem, a robust power control problem is formulated. A column generation based algorithm is proposed to solve the problem by considering only the potential subset of variables when solving the problem. To increase the scalability, a novel distributed two-stage algorithm based on the distributed column generation method is then proposed to obtain the near-optimal solution of the robust transmission schedules for vertical spectrum sharing in an ad-hoc wireless network.

Wireless sensor networks are battery operated computing and sensing devices that collaborate to achieve a common goal for a specific application. They are formed by a cluster of sensor nodes where each sensor node is composed of a single chip with embedded memory (microprocessor), a transceiver for transmission and reception (resulting in the most energy consumption), a sensor device for event detection and a power source to keep the node alive. Due to the environmental nature of their application, it is not feasible to change or charge the power source once a sensor node is deployed. The main design objective in WSNs (Wireless Sensor Networks) is to define effective and efficient strategies to conserve energy for the nodes in the network. With regard to the transceiver, the highest consumer of energy in a sensor node, the factors contributing to energy consumption in wireless sensor networks include idle listening, where nodes keep listening on the channel with no data to receive; ovehearing, where nodes hears or intercept data that is meant for a different node; and collision, which occurs at the sink node when it receives data from different nodes at the same time. These factors all arise during transmission or reception of data in the Transceiver module in wireless sensor networks. A MAC (Medium Access Control) protocol is one of the techniques that enables successful operation while minimizing the energy consumption in the network. Its task is to avoid collision, reduce overhearing and to reduce idle listening by properly managing the state of each node in the network. The aim, when designing a MAC protocol for WSNs is to achieve a balance amongst minimum energy consumption, minimum latency, maximum fault-tolerance and providing QoS (Quality of Service). To carefully achieve this balance, this dissertation has proposed, designed, simulated and analyzed a new cooperative MAC scheme with an overhearing avoidance technique with the aim of minimizing energy consumption by attempting to minimize the overhearing in the WSN. The new MAC protocol for WSNs supports the cooperative diversity and overhearing communications in order to reduce the effects of energy consumption thus increase the network lifetime, providing improved communication reliability and further mitigating the effects of multipath fading in WSNs. The MAC scheme in this work focuses on cooperation with overhearing avoidance and reducing transmissions in case of link failures in order to minimize energy consumption. The cooperative MAC scheme presented herein uses the standard IEEE 802.15.4 scheme as its base physical model. It introduces cooperation, overhearing avoidance, receiver based relay node selection and a Markov-based channel state estimation. The performance analysis of the developed Energy Efficient Distributed Receiver based MAC (E2DRCMAC) protocol for WSNs shows an improvement from the standard IEEE 802.15.4 MAC layer with regard to the energy consumption, throughput, reliability of message delivery, bit error rates, system capacity, packet delay, packet error rates, and packet delivery ratios. / M.Sc.Eng. University of KwaZulu-Natal, Durban 2013.

For opportunistic spectrum access and spectrum sharing in cognitive radio networks, one key problem is how to develop wireless access schemes for secondary users so that harmful interference to primary users can be avoided and quality-of-service (QoS) of secondary users can be guaranteed. In this research, dynamic wireless access protocols for secondary users are designed and optimized for both infrastructure-based and ad-hoc wireless networks. Under the infrastructure-based model, the secondary users are connected through a controller (i.e., an access point). In particular, the problem of wireless access for eHealth applications is considered. In a single service cell, an innovative wireless access scheme, called electromagnetic interference (EMI)-aware prioritized wireless access, is proposed to address the issues of EMI to the medical devices and QoS differentiation for different eHealth applications. Afterwards, the resource management problem for multiple service cells, specifically, in multiple spatial reuse time-division multiple access (STDMA) networks is addressed. The problem is formulated as a dual objective optimization problem that maximizes the spectrum utilization of secondary users and minimizes their power consumption subject to the EMI constraints for active and passive medical devices and minimum throughput guarantee for secondary users. Joint scheduling and power control algorithms based on greedy approaches are proposed to solve the problem with much less computational complexity. In an ad-hoc wireless network, the robust transmission scheduling and power control problem for collision-free spectrum sharing between secondary and primary users in STDMA wireless networks is investigated. Traditionally, the problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem, a robust power control problem is formulated. A column generation based algorithm is proposed to solve the problem by considering only the potential subset of variables when solving the problem. To increase the scalability, a novel distributed two-stage algorithm based on the distributed column generation method is then proposed to obtain the near-optimal solution of the robust transmission schedules for vertical spectrum sharing in an ad-hoc wireless network.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 124-127). Also available in electronic format on the Internet.