As wireless networks continue streaking through more aspects of our lives, it is seriously constrained by limited network resources, in terms of time, frequency and power. In order to enhance performance for wireless networks, it is of great importance to allocate resources smartly based on the current network scenarios. The focus of this dissertation is to investigate radio resource management algorithms to optimize performance for different types of wireless networks. Firstly, we investigate a joint optimization problem on relay node placement and route assignment for wireless sensor networks. A heuristic binary integer programming algorithm is proposed to maximize the total number of information packets received at the base station during the network lifetime. We then present an optimization algorithm based on binary integer programming for relay node assignment with the current node locations. Subsequently, a heuristic algorithm is applied to move the relay nodes to the locations iteratively to better serve their associated edge nodes. Secondly, as traditional goal of maximizing the total throughput can result in unbalanced use of network resources, we study a joint problem of power control and channel assignment within a wireless mesh network such that the minimal capacity of all links is maximized. This is essentially a fairness problem. We develop an upper bound for the objective by relaxing the integer variables and linearization. Subsequently, we put forward a heuristic approach to approximate the optimal solution, which tries to increase the minimal capacity of all links via setting tighter constraint and solving a binary integer programming problem. Simulation results show that solutions obtained by this algorithm are very close to the upper bounds obtained via relaxation, thus suggesting that the solution produced by the algorithm is near-optimal. Thirdly, we study the topology control of disaster area wireless networks to facilitate mobile nodes communications by deploying a minimum number of relay nodes dynamically. We first put forward a novel mobility model for mobile nodes that describes the movement of first responders within a large disaster area. Secondly, we formulate the square disk cover problem and propose three algorithms to solve it, including the two-vertex square covering algorithm, the circle covering algorithm and the binary integer programming algorithm. Fourthly, we explore the joint problem of power control and channel assignment to maximize cognitive radio network throughput. It is assumed that an overlaid cognitive radio network (CRN) co-exists with a primary network. We model the opportunistic spectrum access for cognitive radio network and formulate the cross-layer optimization problem under the interference constraints imposed by the existing primary network. A distributed greedy algorithm is proposed to seek for larger network throughput. Cross-layer optimization for CRN is often implemented in centralized manner to avoid co-channel interference. The distributed algorithm coordinates the channel assignment with local channel usage information. Thus the computation complexity is greatly reduced. Finally, we study the network throughput optimization problem for a multi-hop wireless network by considering interference alignment at physical layer. We first transform the problem of dividing a set of links into multiple maximal concurrent link sets to the problem of finding the maximal cliques of a graph. Then each concurrent link set is further divided into one or several interference channel networks, on which interference alignment is implemented to guarantee simultaneous transmission. The network throughput optimization problem is then formulated as a non-convex nonlinear programming problem, which is NP-hard generally. Thus we resort to developing a branch-and-bound framework, which guarantees an achievable performance bound.

This document presents the Centralized Energy Management System (CEMS), a dynamic fault-tolerant reclustering protocol for wireless sensor networks. CEMS reconfigures a homogeneous network both periodically and in response to critical events (e.g. cluster head death). A global TDMA schedule prevents costly retransmissions due to collision, and a genetic algorithm running on the base station computes cluster assignments in concert with a head selection algorithm. CEMS' performance is compared to the LEACH-C protocol in both normal and failure-prone conditions, with an emphasis on each protocol's ability to recover from unexpected loss of cluster heads.

The development in wireless technology, mobile smart devices and Internet of Things has gave birth to a booming era or the wireless indoor geolocation. This technology have been increasingly used within our daily life and help people to build up the tracking system which could be used by fulfillment centers and grocery stores. To achieve higher localization accuracy with wireless geolocation, we need a higher density of deployment which involves high deployment and maintenance cost. To balance the accuracy and the cost, people have begun using wireless localization employing inertial navigation system (INS) which provide speed and direction of movement. When we combine Radio Frequency (RF) localization with INS, we have a hybrid INS/RF localization system which can achieve high localization accuracy with low cost. In this thesis, we use accelerometers and magnetometers in an Android smart phone to build a hybrid INS/RF system and use two different technologies for RF localization: Radio Frequency Identification Device (RFID) and Wi-Fi. Using this system, we conducted measurements of the hybrid localization system and evaluate its performance. The specific contributions of the thesis are: (1)Empirical performance evaluation of the INS/RFID localization system. It relates the localization error to the number and position of RFID tags. (2)Model the effect of metallic objects on accuracy of magnetometer. The model shows the relation between direction error and distance to metallic component. (3)Model shadow fading in close proximity of RF transmitter. It builds a distance dependent shadow fading model. (4)Model based performance evaluation of hybrid localization. The test bench uses our models to simulate the hybrid localization data.

"This thesis develops a system for synchronizing two wireless transmitters so that they are able to implement a distributed beamformer in several different channel models. This thesis considers a specific implementation of the system and proposes a metric to quantify its performance. The system's performance is investigated in single-path and multi-path time-invariant channel scenarios, as well as in single-path time-varying channel scenarios. Where prior systems have difficulty in implementing a distributed beamformer in multi-path channels and/or mobile scenarios, the results of this thesis show that the Round-Trip Time-Division distributed beamforming system is able to perform as a beamformer in all three of the channel models considered. "

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Chan Pak To Patrick. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 82-86). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.viii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- The Problems --- p.3 / Chapter 1.3 --- My Contribution --- p.4 / Chapter 1.4 --- Thesis Organization --- p.5 / Chapter 2 --- Wireless LAN Security Model --- p.6 / Chapter 2.1 --- Preliminary Definitions on WLAN --- p.6 / Chapter 2.2 --- Security Model --- p.7 / Chapter 2.2.1 --- Security Attributes --- p.7 / Chapter 2.2.2 --- Security Threats in WLAN --- p.8 / Chapter 2.2.3 --- Attacks on Authentication Scheme --- p.10 / Chapter 2.2.4 --- Attacks on Keys --- p.10 / Chapter 2.3 --- Desired Properties of WLAN Authentication --- p.11 / Chapter 2.3.1 --- Security Requirements of WLAN Authentication --- p.11 / Chapter 2.3.2 --- Security Requirements of Session Keys --- p.12 / Chapter 2.3.3 --- Other Desired Properties of WLAN Authentication --- p.12 / Chapter 3 --- Cryptography --- p.14 / Chapter 3.1 --- Overview on Cryptography --- p.14 / Chapter 3.2 --- Symmetric-key Encryption --- p.15 / Chapter 3.2.1 --- Data Encryption Standard (DES) --- p.15 / Chapter 3.2.2 --- Advanced Encryption Standard (AES) --- p.15 / Chapter 3.2.3 --- RC4 --- p.16 / Chapter 3.3 --- Public-key Cryptography --- p.16 / Chapter 3.3.1 --- RSA Problem and Related Encryption Schemes --- p.17 / Chapter 3.3.2 --- Discrete Logarithm Problem and Related Encryption Schemes --- p.18 / Chapter 3.3.3 --- Elliptic Curve Cryptosystems --- p.19 / Chapter 3.3.4 --- Digital Signature --- p.19 / Chapter 3.4 --- Public Key Infrastructure --- p.20 / Chapter 3.5 --- Hash Functions and Message Authentication Code --- p.21 / Chapter 3.5.1 --- SHA-256 --- p.22 / Chapter 3.5.2 --- Message Authentication Code --- p.22 / Chapter 3.6 --- Entity Authentication --- p.23 / Chapter 3.6.1 --- ISO/IEC 9798-4 Three-pass Mutual --- p.23 / Chapter 3.6.2 --- ISO/IEC 9798-4 One-pass Unilateral --- p.24 / Chapter 3.7 --- Key Establishment --- p.24 / Chapter 3.7.1 --- Diffie-Hellman Key Exchange --- p.24 / Chapter 3.7.2 --- Station-to-Station Protocol --- p.25 / Chapter 3.8 --- Identity-Based Cryptography --- p.25 / Chapter 3.8.1 --- The Boneh-Franklin Encryption Scheme --- p.26 / Chapter 3.8.2 --- Au and Wei's Identification Scheme and Signature Scheme --- p.27 / Chapter 4 --- Basics of WLAN Security and WEP --- p.29 / Chapter 4.1 --- Basics of WLAN Security --- p.29 / Chapter 4.1.1 --- "Overview on ""Old"" WLAN Security" --- p.29 / Chapter 4.1.2 --- Some Basic Security Measures --- p.29 / Chapter 4.1.3 --- Virtual Private Network (VPN) --- p.30 / Chapter 4.2 --- WEP --- p.31 / Chapter 4.2.1 --- Overview on Wired Equivalent Privacy (WEP) --- p.31 / Chapter 4.2.2 --- Security Analysis on WEP --- p.33 / Chapter 5 --- IEEE 802.11i --- p.38 / Chapter 5.1 --- Overview on IEEE 802.11i and RSN --- p.38 / Chapter 5.2 --- IEEE 802.1X Access Control in IEEE 802.11i --- p.39 / Chapter 5.2.1 --- Participants --- p.39 / Chapter 5.2.2 --- Port-based Access Control --- p.40 / Chapter 5.2.3 --- EAP and EAPOL --- p.40 / Chapter 5.2.4 --- RADIUS --- p.41 / Chapter 5.2.5 --- Authentication Message Exchange --- p.41 / Chapter 5.2.6 --- Security Analysis --- p.41 / Chapter 5.3 --- RSN Key Management --- p.43 / Chapter 5.3.1 --- RSN Pairwise Key Hierarchy --- p.43 / Chapter 5.3.2 --- RSN Group Key Hierarchy --- p.43 / Chapter 5.3.3 --- Four-way Handshake and Group Key Handshake --- p.44 / Chapter 5.4 --- RSN Encryption and Data Integrity --- p.45 / Chapter 5.4.1 --- TKIP --- p.45 / Chapter 5.4.2 --- CCMP --- p.46 / Chapter 5.5 --- Upper Layer Authentication Protocols --- p.47 / Chapter 5.5.1 --- Overview on the Upper Layer Authentication --- p.47 / Chapter 5.5.2 --- EAP-TLS --- p.48 / Chapter 5.5.3 --- Other Popular ULA Protocols --- p.50 / Chapter 6 --- Proposed IEEE 802.11i Authentication Scheme --- p.52 / Chapter 6.1 --- Proposed Protocol --- p.52 / Chapter 6.1.1 --- Overview --- p.52 / Chapter 6.1.2 --- The AUTHENTICATE Protocol --- p.56 / Chapter 6.1.3 --- The RECONNECT Protocol --- p.59 / Chapter 6.1.4 --- Packet Format --- p.61 / Chapter 6.1.5 --- Ciphersuites Negotiation --- p.64 / Chapter 6.1.6 --- Delegation --- p.64 / Chapter 6.1.7 --- Identity Privacy --- p.68 / Chapter 6.2 --- Security Considerations --- p.68 / Chapter 6.2.1 --- Security of the AUTHENTICATE protocol --- p.68 / Chapter 6.2.2 --- Security of the RECONNECT protocol --- p.69 / Chapter 6.2.3 --- Security of Key Derivation --- p.70 / Chapter 6.2.4 --- EAP Security Claims and EAP Methods Requirements --- p.72 / Chapter 6.3 --- Efficiency Analysis --- p.76 / Chapter 6.3.1 --- Overview --- p.76 / Chapter 6.3.2 --- Bandwidth Performance --- p.76 / Chapter 6.3.3 --- Computation Speed --- p.76 / Chapter 7 --- Conclusion --- p.79 / Chapter 7.1 --- Summary --- p.79 / Chapter 7.2 --- Future Work --- p.80 / Bibliography --- p.82

Ng Cho Yiu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 70-74). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Preface --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Multiple Access --- p.1 / Chapter 1.1.1 --- Time Division Multiple Access --- p.2 / Chapter 1.1.2 --- Frequency Division Multiple Access --- p.3 / Chapter 1.1.3 --- Code Division Multiple Access --- p.3 / Chapter 1.1.4 --- Hybrid Multiple Access Scheme --- p.4 / Chapter 1.2 --- Goal Programming --- p.5 / Chapter 2 --- Previous Works in Channel Assignment --- p.10 / Chapter 2.1 --- Voice Service Network --- p.10 / Chapter 2.2 --- Data Network --- p.11 / Chapter 2.2.1 --- Throughput Optimization --- p.13 / Chapter 2.2.2 --- Channel Assignment Schemes with QoS Consideration --- p.14 / Chapter 3 --- General Channel Assignment Scheme --- p.16 / Chapter 3.1 --- Baseline Model --- p.17 / Chapter 3.2 --- Goal Ranking --- p.22 / Chapter 3.3 --- Model Transformation --- p.22 / Chapter 3.4 --- Proposed Algorithms --- p.23 / Chapter 3.4.1 --- Channel Swapping Algorithm --- p.24 / Chapter 3.4.2 --- Best-First-Assign Algorithm --- p.26 / Chapter 4 --- Special Case Algorithms --- p.28 / Chapter 4.1 --- Single Order of Selection Diversity --- p.28 / Chapter 4.1.1 --- System Model --- p.29 / Chapter 4.1.2 --- Proposed Algorithm --- p.30 / Chapter 4.1.3 --- Extension of Algorithm --- p.31 / Chapter 4.2 --- Single Channel Assignment --- p.32 / Chapter 4.2.1 --- System Model --- p.33 / Chapter 4.2.2 --- Proposed Algorithms --- p.34 / Chapter 5 --- Performance Evaluation --- p.37 / Chapter 5.1 --- General Channel Assignment and Single Channel Assignment --- p.37 / Chapter 5.1.1 --- System Model --- p.38 / Chapter 5.1.2 --- Lower Bound of Weighted Sum of Unsatisfactory Function --- p.40 / Chapter 5.1.3 --- Performance Evaluation I --- p.41 / Chapter 5.1.4 --- Discussion --- p.44 / Chapter 5.1.5 --- Performance Evaluation II --- p.44 / Chapter 5.2 --- Single Order of Selection Diversity Algorithm --- p.47 / Chapter 5.2.1 --- System Model --- p.47 / Chapter 5.2.2 --- Performance Evaluation I --- p.49 / Chapter 5.2.3 --- Performance Evaluation II --- p.53 / Chapter 6 --- Conclusion and Future Works --- p.58 / Chapter 6.1 --- Conclusion --- p.58 / Chapter 6.2 --- Future Works --- p.60 / Chapter 6.2.1 --- Multi-cell Channel Assignment --- p.60 / Chapter 6.2.2 --- Theoretical Studies --- p.62 / Chapter 6.2.3 --- Adaptive Algorithms --- p.62 / Chapter 6.2.4 --- Assignment of Non-orthogonal Channels --- p.63 / Chapter A --- Proof of Proposition 3.1 --- p.64 / Chapter B --- Proof of Proposition 4.1 --- p.66 / Chapter C --- Assignment Problem --- p.68 / Bibliography --- p.74

Mutual Coupling (MC) is the exchange of energy between multiple antennas when placed on the same PCB, it being one of the critical parameters and a significant issue to be considered when designing MIMO antennas. It appears significantly where multiple antennas are placed very close to each other, with a high coupling affecting the performance of the array, in terms radiation patterns, the reflection coefficient, and influencing the input impedance. Moreover; it degrades the designed efficiency and gain since part of the power that could have been radiated becomes absorbed by other adjacent antennas' elements. The coupling mechanism between multiple antenna elements is identified as being mainly through three different paths or channels: surface wave propagation, space (direct) radiation and reactive near-field coupling. In this thesis, various coupling reduction approaches that are commonly employed in the literature are categorised based on these mechanisms. Furthermore, a new comparative study involving four different array types (PIFA, patch, monopole, and slot), is explained in detail. This thesis primarily focuses on three interconnected research topics for mutual coupling reduction based on new isolation approaches for different wireless applications (i.e. Narrowband, Ultra-wide-band and Multi-band). First, a new Fractal based Electromagnetic Band Gap (FEBG) decoupling structure between PIFAs is proposed and investigated for a narrowband application. Excellent isolation of more than 27 dB (Z-X plane) and 40 dB (Z-Y plane) is obtained without much degradation of the radiation characteristics. It is found that the fractal structures can provide a band-stop effect, because of their self-similarity features for a particular frequency band. Second, new UWB-MIMO antennas are presented with high isolation characteristics. Wideband isolation (≥ 31 dB) is achieved through the entire UWB band (3.1-10.6 GHz) by etching a novel compact planar decoupling structure inserted between these multiple UWB antennas. Finally, new planar MIMO antennas are presented for multi-band (quad bands) applications. A significant isolation improvement over the reference (≥ 17 dB) is achieved in each band by etching a hybrid solution. All the designs reported in this thesis have been fabricated and measured, with the simulated and measured results agreeing well in most cases.

by Tam Wing-Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 55-57). / Abstracts in English and Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / 哲學碩士論文摘要 --- p.iii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Research Background --- p.2 / Chapter 1.2 --- Contribution of the Thesis --- p.5 / Chapter 1.3 --- Organization of the Thesis --- p.6 / Chapter Chapter 2 --- Content Repurposing System Architecture --- p.7 / Chapter 2.1 --- Introduction to ICAP-based Content Repurposing System --- p.7 / Chapter 2.2 --- Generic Service-enabling Platform --- p.8 / Chapter 2.3 --- Rule Engine --- p.10 / Chapter 2.4 --- ICAP-enabled Application Server --- p.10 / Chapter 2.5 --- Store-and-forward Transcoding and Streamed Transcoding --- p.11 / Chapter Chapter 3 --- Transcoding Techniques --- p.18 / Chapter 3.1 --- Text Transcoding --- p.19 / Chapter 2.2 --- Image Transcoding --- p.20 / Chapter 3.3 --- Audio Transcoding --- p.23 / Chapter 3.4 --- Video Transcoding --- p.25 / Chapter Chapter 4 --- Adaptation Policy --- p.28 / Chapter 4.1 --- Delay Analysis of Content Repurposing System --- p.30 / Chapter 4.2 --- Store-and-forward Transcoding for Image Files --- p.31 / Chapter 4.2.1 --- Distribution of Input Web Images --- p.34 / Chapter 4.2.2 --- Transcoding Web images to WBMP --- p.34 / Chapter 4.2.3 --- Adaptation policy of Transformation to WBMP --- p.36 / Chapter 4.2.4 --- Adaptation policy of JPEG images --- p.36 / Chapter 4.3 --- Streamed Transcoding for Audio/Video Files --- p.39 / Chapter 4.3.1 --- Audio Transcoding --- p.41 / Chapter 4.3.2 --- Video Transcoding --- p.42 / Chapter 4.4 --- Case Study --- p.43 / Chapter 4.4.1 --- Weak Device with Insufficient Bandwidth --- p.43 / Chapter 4.4.2 --- Weak Device with Sufficient Bandwidth --- p.43 / Chapter 4.4.3 --- Strong Device with Insufficient Bandwidth --- p.44 / Chapter Chapter 5 --- Conclusion --- p.54 / Bibliography --- p.55