Chen, Darui. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 62-67). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.vii / List of Tables --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Related Works --- p.2 / Chapter 1.3 --- Contributions --- p.6 / Chapter 1.4 --- Organization --- p.8 / Chapter Chapter 2 --- Preliminaries --- p.9 / Chapter 2.1 --- MAC Protocol in IEEE 802.11 WLANs --- p.9 / Chapter 2.1.1 --- IEEE 802.11 DCF --- p.9 / Chapter 2.1.2 --- Performance Anomaly of DCF --- p.11 / Chapter 2.2 --- Multi-Rate WLANs with Rate Adaptation --- p.12 / Chapter 2.2.1 --- PHY-Layer Rate Adaptation Model --- p.12 / Chapter 2.2.2 --- Two Typical WLANs with Rate Adaptation --- p.13 / Chapter Chapter 3 --- Performance Analysis and Evaluation of Multi-Rate IEEE802.11 WLANs --- p.15 / Chapter 3.1 --- Theoretical Analysis of Multi-Rate IEEE 802.11 WLANs --- p.15 / Chapter 3.1.1 --- Markov Chain Model for Backoff Process --- p.15 / Chapter 3.1.2 --- Saturation Throughput --- p.18 / Chapter 3.1.3 --- Theoretical Throughput Limit and Dynamic Backoff --- p.20 / Chapter 3.2 --- Performance Evaluation of Multi- Rate WLANs --- p.22 / Chapter 3.2.1 --- Model Validation --- p.22 / Chapter 3.2.2 --- Theoretical Throughput Limit --- p.24 / Chapter Chapter 4 --- Rate-aware DCF Protocol --- p.30 / Chapter 4.1 --- Proposed R-DCF Protocol --- p.30 / Chapter 4.2 --- Theoretical Analysis of R-DCF --- p.34 / Chapter 4.2.1 --- Markov Chain Model for Backoff Process --- p.34 / Chapter 4.2.2 --- Saturation Throughput --- p.36 / Chapter 4.2.3 --- Simplified Models --- p.39 / Chapter 4.3 --- Performance Evaluation --- p.41 / Chapter 4.3.1 --- Model Validation --- p.41 / Chapter 4.3.2 --- R-DCF with Homogeneous Users --- p.42 / Chapter 4.3.3 --- R-DCF in Fixed-Rate WLANs --- p.49 / Chapter Chapter 5 --- Performance Enhancement of the R-DCF Protocol --- p.52 / Chapter 5.1 --- Maximizing Throughput of R-DCF --- p.52 / Chapter 5.2 --- Offline Adaptive Backoff Methods --- p.55 / Chapter Chapter 6 --- Conclusions --- p.60 / Bibliography --- p.62

Cheung, Kwok Sum. / Thesis submitted in: October 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 71-74). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Infrastructure of Wireless Mesh Networks --- p.1 / Chapter 1.2 --- Characteristics and Advantages of WMNs --- p.4 / Chapter 1.3 --- Challenges --- p.7 / Chapter 2 --- Background Study --- p.10 / Chapter 2.1 --- Maximum Concurrent Flow Problem --- p.10 / Chapter 2.2 --- Channel Assignment --- p.12 / Chapter 2.3 --- Congestion Control --- p.13 / Chapter 3 --- Problem Formulation --- p.16 / Chapter 3.1 --- Physical Model --- p.16 / Chapter 3.2 --- MCFP of Multiple Channels --- p.19 / Chapter 3.2.1 --- MCFP Channel Assignment Pattern --- p.19 / Chapter 3.2.2 --- Min-max Spectral Radius Optimization --- p.22 / Chapter 3.2.3 --- Min-max Channel Assignment Problem --- p.24 / Chapter 4 --- Min-max Pattern in Chain Network --- p.26 / Chapter 4.1 --- Chain Network --- p.26 / Chapter 4.2 --- Min-max Channel Assignment Pattern --- p.28 / Chapter 5 --- Bottleneck Assignment Heuristic Algorithm --- p.35 / Chapter 5.1 --- Algorithm Description --- p.35 / Chapter 5.1.1 --- Introduction --- p.35 / Chapter 5.1.2 --- First Part of the BAHA --- p.38 / Chapter 5.1.3 --- Second Part of the BAHA --- p.43 / Chapter 5.2 --- Optimality --- p.47 / Chapter 5.3 --- Simulation of the BAHA --- p.53 / Chapter 5.3.1 --- Performance evaluation --- p.55 / Chapter 6 --- Sequential Assignment Heuristic Algorithm --- p.59 / Chapter 6.1 --- Algorithm Description --- p.59 / Chapter 6.1.1 --- Introduction --- p.59 / Chapter 6.1.2 --- Lower bound of spectral radius --- p.60 / Chapter 6.1.3 --- Procedures of SAHA --- p.62 / Chapter 6.2 --- Simulation Result --- p.64 / Chapter 6.3 --- Performance evaluation --- p.64 / Chapter 7 --- Conclusion --- p.69 / Bibliography --- p.71

The Wireless Applications Service Providers Association (WASPA) is a self-regulatory body for the wireless application industry in South Africa – and employs its Code of Conduct as the primary instrument in regulating the industry. The purpose of this qualitative study is to evaluate how effective the Code has been in regulating the behaviour of the wireless applications service providers in the country. The findings from the research study suggest that the WASPA Code has more weaknesses than strengths. A significant finding is that WASPA is viewed as a legitimate regulator of the WASP industry – and its Code enjoys wide support from the industry. However, there are some questions around the organisation and the Code‟s credibility in a number of important areas. Some of the more important negative findings include, amongst others, the following: WASPA might have been captured by the established players in the industry; the WASPA Code seems to have insufficient focus on business-to-business aggregators; and the WASPA regulatory regime must cover the network operators‟ VAS services in order to ensure more meaningful industry

Tese de mestrado integrado. Engenharia Mecânica (Opção de Automação). Faculdade de Engenharia. Universidade do Porto. 2010

Estágio realizado na KTH e orientado pelo Eng.º Karl H. Johansson / Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores-Major Automação. Faculdade de Engenharia. Universidade do Porto. 2008

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Telecomunicações). Faculdade de Engenharia. Universidade do Porto. 2009

Using multi-agent systems to execute a variety of missions such as environmental monitoring and target tracking has been made possible by the advances in control techniques and computational capabilities. Communication abilities between agents allow them to coact and execute several coordinated missions, among which there is optimal coverage. The optimal coverage problem has several applications in engineering theory and practice, as for example in environmental monitoring, which belongs to the broad class of resource allocation problems, in which a finite number of mobile agents have to be deployed in a given spatial region with the assignment of a sub-region to each agents with respect to a suitable coverage metric. The coverage metric encodes the sensing performance of individual agent with respect to points inside the domain of interest, and a distribution of risk density. Usually the risk density function measures the relative importance assigned to inner regions. The optimal coverage problem in which the risk density is time-invariant has been widely studied in previous research. The solution to this class of problems is centroidal Voronoi tessellation, in which each agent is located on the centroid of the related Voronoi cell. However, there are many scenarios that require to be modelled by time-varying risk density rather than time-invariant one, as for example in area coverage problems where the environment evolves independently of the evolution for the robotic agents deployed to cover the area. In this work, the changing environment is modeled by a time-varying density function which is governed by a convection-diffusion equation. Mixed boundary conditions are considered to model a scenario in which a diffusive substance (e.g., oil from a leaking event or radioactive material from a nuclear accident) enters the area with convective component from the boundary. A non-autonomous feed- back law is employed whose generated trajectories maximize the coverage metric. The asymptotic stability of the multi-agent system is proven by using Barbalat’s lemma, and then theoretical predictions are illustrated by several simulations that represent idealized scenarios.

Continuing advances in wireless communications and MEMS (Micro-Electro Mechan- ical Systems) technologies have fostered the construction of a wide variety of sensor and ad hoc networks. These networks have broad applications spanning wide ar- eas, such as environmental monitoring, infrastructure maintenance, traffic manage- ment, energy management, disaster mitigation, personal medical monitoring, smart building, as well as military and defence. While these applications require high per- formance from the network, they suffer from resource constraints (such as limited battery power, processing capability, buffer space, etc.) that do not appear in tra- ditional wired networks. The inherent infrastructure-less characteristic of the sensor and ad hoc networks creates significant challenges. This dissertation addresses these challenges with two protocol designs. The main contributions of this dissertation are the design and evaluation of CS- MAC (stands for CDMA Sensor MAC), a novel multi-channel media access control (MAC) protocol for direct sequence code division multiple access (DS-CDMA) wire- less sensor networks. Our protocol design uses combination of DS-CDMA and fre- quency division to reduce the channel interference and consequently improves system capacity and network throughput. We provide theoretical characterisation of the mean multiple access interference (MAI) at a given node in relation to the number of frequency channels. We show that by using only a small number of frequency chan- nels, the mean MAI can be reduced significantly. Through discrete event simulation (using UC Berkerly NS-2 simulator), we provide comparison of our proposed system to a pure DS-CDMA system as well as a contention based system. Simulation results reveal that our proposed system can achieve significant improvement in system efi ciency (measured in packet/second/channel) of a contention based system. When the same number of packets are transmitted in the network, our system consumes much less communication energy compared to the contention based system. A distributed channel allocation protocol is also proposed for the network forma- tion phase. We prove that our algorithm converges with correct channel assignments. Simulation results reveal that a much smaller number of channels is required than theoretical value when nodes are uniformly randomly deployed. The second contribution of this dissertation involves the design and evaluation of two location-aware select optimal neighbour (SON) algorithms for CSMA/CA based MAC protocol for wireless ad hoc networks. Both algorithms concentrate on the improvement of energy eficiency of the whole network through the optimisation of the number of neighbours of each node. Our algorithms not only consider radio electronic energy consumption (e.g., coding, decoding) and radio transmission energy consumption (e.g., power amplifier), but also the electronic energy consumption at those irrelevant receivers (those who are not addressed by the transmission) that are located within the transmission range. Through simulations, we show that our algorithms can achieve signi??cant energy savings compared to the standard IEEE 802.11.

"Dissertation submitted, September 2003." / Includes bibliographical references (leaves 159-172) / xvi, 172 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Electrical and Electronic Engineering, 2004

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.