The frequency spectrum allocated to cellular mobile telephone systems is very limited. Efficient channel assignment schemes can significantly increase the utilization of the available frequency channels. Virtually Fixed Channel Assignment (VFCA) is a dynamic channel assignment method. The idea behind it is simple: each cell is allocated a set of nominal channels. A call request generated in a cell is assigned a nominal channel if one is available. Otherwise, a channel from an adjacent cell is borrowed to serve this call as long as frequency interference constraints are satisfied. VFCA is a promising method because (i) it is efficient in channel assignment, and (ii) it is relatively easy to implement compared to other dynamic channel assignment methods. VFCA has been analyzed based primarily on simulation studies in the past twenty years. In this thesis, we focus our study on development of new channel borrowing strategies and analytical models for VFCA. The contribution of this work is summarized as follows. (1) Development of an queuing model for performance analysis of VFCA. This model may also be used to conduct sensitivity analysis on some system parameters when VFCA is used. (2) Proposed a new channel reservation scheme for handoffs. (In a cellular system, when a call using a channel crosses a cell boundary, it needs to be handed off to a new channel in the new cell. This is called a handoff.) An optimization model for this channel reservation scheme is developed. (3) Applied the fluid-flow approach to modeling an integrated mobile cellular system that uses VFCA to estimate the distribution of data queue length in a cell of the system. These results are useful in the design, performance analysis and optimization of VFCA schemes.

No description available.

Ultrawideband (UWB) wireless systems employ signals with bandwidths in excess of 500 MHz or with relative bandwidth more than 20%. The radiated signals have low power spectral density. A decade ago, UWB wireless systems were deemed to be the technology that will deliver 'Gigabit-wireless' for short range communications. However, the performance of current systems is significantly below the initial expectations. This thesis explores the UWB wireless channel and shows how its properties limit the performance of current UWB systems. Furthermore, it is shown that if the knowledge of the channel is fully exploited a significant performance improvement of UWB systems can be achieved. The thesis begins with exploration of the channel properties. Unlike previous work, that has investigated either the 'classical narrowband' channel with bandwidth <100 MHz or the UWB channel with bandwidth >1 GHz, this work studies the transition between the narrowband channels with bandwidth of 1 MHz to the extremely wide band channels with bandwidths of up to 10 GHz. The thesis concludes that for signals with bandwidth <1 GHz UWB antennas and antenna arrays can be described by the classical means of gain and array factor, i.e. they treat such signals as 'narrowband'. In contrast, wireless propagation for signals with bandwidth > 100 MHz has properties 'like UWB channels' with bandwidths in the GHz range. Additionally, the thesis suggests a correction to the IEEE802.15.4a model for channel impulse response because as will be shown in the thesis many multi paths in the model are manifes- tations of the antenna impulse response. Hence multiple multipaths in the IEEE802.15.4a model actually represent a single multipath component. This reduces the number of multipath components in the model by approximately factor of five. The understanding of the transition between narrowband and ultrawideband channel is used to improve the spectral efficiency of impulse radio systems which traditionally use signals with bandwidth> 1 GHz. It is shown that the optimum signal bandwidth for impulse radio systems is in the range 150-450 MHz. Such systems balance the robustness against frequency selective fading with the reduction of duty cycle. Hence, the data-rate of impulse radio systems can be significantly improved. The frequency selective fading is shown to be the main limiting factor for the performance of the commercial UWB WiMedia systems with OFDM. It is shown that adaptive loading of OFDM sub carriers , which is compatible with the frequency selectivity of the channel, is more suitable for UWB OFDM systems than the use of strong Forward-Error-Correction measures. The introduction of the adaptive OFDM is not a significant change to the design of the scheme because the commercial WiMedia standard already foresees pilot OFDM symbols for channel estimation. The adaptive OFDM for UWB has already been considered by some authors. Unlike previous works, this thesis explores the performance of such a system in a large number of measured wireless channels. Finally, the thesis studies the MIMO techniques for UWB systems. Suitable schemes for fixed and adaptive OFDM are discussed. A realistic simulation using measured wireless channel shows that a 4x 1 system with a low complexity beam-steering and adaptive OFDM can deliver a data-rate of 400 Mbps over a range of 9 m. This performance is for a system with bandwidth 528 MHz (like in the WiMedia standard). A further increase can be achieved with the increase of the system's bandwidth.

M.Sc.(Eng.), Faculty of Engineering and the Built Environment, 2011 / The main objective of seamless mobility is to enable mobile users to stay connected while roaming across heterogeneous networks. As cellular networks evolve from the third generation Universal Mobile Telecommunication System (UMTS) to the Long Term Evolution (LTE), a new Evolved Packet Core (EPC) will support heterogeneous radio access networks on the same platform. UMTS provides voice services in the circuit switched domain; while LTE operates in the packet switched domain. Cellular network operators thus face the challenge of providing voice services during initial deployment of LTE due to difficulty in mobility between the two domains. Seamless voice handover between packet switched LTE and the circuit switched UMTS network is therefore an important tool in solving this problem. This report investigates the performance of inter-Radio Access Technology voice handover between LTE and UMTS. The schemes evaluated were Voice Call Continuity (VCC) for UMTS to LTE handover and Single Radio Voice Call Continuity (SRVCC) for LTE to UMTS handover. The performance evaluation was done using mathematical models and equations that were derived for the handover service interruption time. The resulting equations were simulated and the output was analysed and compared with the Third Generation Partnership Project (3GPP) specifications.

Chen Chung-Shue. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 100-102). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Evolution to 3G Mobile --- p.2 / Chapter 1.1.1 --- First Generation --- p.2 / Chapter 1.1.2 --- Second Generation --- p.3 / Chapter 1.1.3 --- Third Generation --- p.3 / Chapter 1.2 --- UTRA Framework --- p.5 / Chapter 1.2.1 --- FDD and TDD --- p.6 / Chapter 1.2.2 --- Channel Spreading --- p.6 / Chapter 1.2.3 --- OVSF Code Tree --- p.8 / Chapter 1.3 --- Cellular Concepts --- p.10 / Chapter 1.3.1 --- System Capacity --- p.10 / Chapter 1.3.2 --- Multiple Access --- p.11 / Chapter 1.3.3 --- Resource Management --- p.15 / Chapter 1.4 --- Organization of the Thesis --- p.16 / Chapter 2. --- Analysis on Multi-rate Operations --- p.18 / Chapter 2.1 --- Related Works in Multi-rate Operations --- p.18 / Chapter 2.1.1 --- Variable Spreading Factor --- p.19 / Chapter 2.1.2 --- Data Time-multiplexing --- p.20 / Chapter 2.1.3 --- Multi-carrier Transmission --- p.21 / Chapter 2.1.4 --- Hybrid TDMA/CDMA --- p.23 / Chapter 2.2 --- Problems in Multi-rate Operations --- p.24 / Chapter 2.2.1 --- Conventional CDMA --- p.24 / Chapter 2.2.2 --- Data Time-multiplexing --- p.25 / Chapter 2.2.3 --- MC-CDMA --- p.25 / Chapter 2.2.4 --- TD-CDMA --- p.27 / Chapter 2.3 --- Multi-user multi-rate Operations --- p.28 / Chapter 3. --- Bandwidth Allocation --- p.29 / Chapter 3.1 --- Most Regular Binary Sequence --- p.30 / Chapter 3.1.1 --- Properties of MRBS --- p.31 / Chapter 3.1.2 --- Construction of MRCS --- p.32 / Chapter 3.1.3 --- Zero-one Sequence under MRBS --- p.33 / Chapter 3.2 --- MRBS in TD-CDMA --- p.35 / Chapter 3.2.1 --- Time Slot Optimization --- p.36 / Chapter 3.2.2 --- Sequence Generator --- p.37 / Chapter 3.3 --- Most Regular Code Sequence --- p.38 / Chapter 3.3.1 --- Properties of MRCS --- p.38 / Chapter 3.2.2 --- Construction of MRCS --- p.41 / Chapter 3.3.3 --- Fraction-valued Sequence under MRCS --- p.42 / Chapter 3.3.4 --- LCC and UCC --- p.45 / Chapter 3.4 --- MRCS in WCDMA --- p.46 / Chapter 3.4.1 --- Spreading Factor Optimization --- p.46 / Chapter 3.4.2 --- Code Generator --- p.48 / Chapter 3.4.3 --- Uplink and Downlink --- p.50 / Chapter 4. --- Multi-access Control --- p.52 / Chapter 4.1 --- Conflict and Resolution --- p.53 / Chapter 4.1.1 --- Conflicts in MRBS and MRCS --- p.53 / Chapter 4.1.2 --- Resolution with Buffering --- p.55 / Chapter 4.2 --- MRBS Transmission Scheduling --- p.56 / Chapter 4.2.1 --- Slot Scheduling on MRBS --- p.56 / Chapter 4.2.2 --- Properties of Scheduling Algorithm --- p.59 / Chapter 4.2.3 --- Scheduled MRBS --- p.71 / Chapter 4.3 --- MRCS Transmission Scheduling --- p.73 / Chapter 4.3.1 --- Slot Scheduling on MRCS --- p.73 / Chapter 4.3.2 --- Properties of Scheduling Algorithm --- p.75 / Chapter 4.3.3 --- Scheduled MRBS --- p.76 / Chapter 4.4 --- Performance Evaluation --- p.78 / Chapter 4.4.1 --- Simulation on Algorithm --- p.78 / Chapter 4.4.2 --- Resource Utilization and Delay Bound --- p.79 / Chapter 4.4.3 --- Blocking Model and System Capacity --- p.80 / Chapter 4.4.4 --- Numerical Analysis --- p.86 / Chapter 5. --- Conclusions and Future works --- p.92 / Appendix A --- p.94 / Appendix B --- p.98 / Bibliography --- p.100

From wirelessly connected robots to car-to-car communications, and to smart cities, almost every aspect of our lives will benefit from future wireless communications. While promise an exciting future world, next-generation wireless communications impose requirements on the data rate, spectral efficiency, and latency (among others) that are higher than those for today's systems by several orders of magnitude. Full-duplex wireless, an emergent wireless communications paradigm, breaks the long-held assumption that it is impossible for a wireless device to transmit and receive simultaneously at the same frequency, and has the potential to immediately double network capacity at the physical (PHY) layer and offers many other benefits (such as reduced latency) at the higher layers. Recently, discrete-component-based demonstrations have established the feasibility of full-duplex wireless. However, the realization of integrated full duplex radios, compact radios that can fit into smartphones, is fraught with fundamental challenges. In addition, to unleash the full potential of full-duplex communication, a careful redesign of the PHY layer and the medium access control (MAC) layer using a cross-layer approach is required. The biggest challenge associated with full duplex wireless is the tremendous amount of transmitter self-interference right on top of the desired signal. In this dissertation, new self-interference-cancellation approaches at both system and circuit levels are presented, contributing towards the realization of full-duplex radios using integrated circuit technology. Specifically, these new approaches involve elimination of the noise and distortion of the cancellation circuitry, enhancing the integrated cancellation bandwidth, and performing joint radio frequency, analog, and digital cancellation to achieve cancellation with nearly one part-per-billion accuracy. In collaboration with researchers at higher layers of the stack, a cross-layer approach has been used in our full-duplex research and has allowed us to derive power allocation algorithms and to characterize rate-gain improvements for full-duplex wireless networks. To enable experimental characterization of full-duplex MAC layer algorithms, a cross-layered software-defined full-duplex radio testbed has been developed. In collaboration with researchers from the field of micro-electro-mechanical systems, we demonstrate a multi-band frequency-division duplexing system using a cavity-filter-based tunable duplexer and our integrated widely-tunable self-interference-cancelling receiver.

對於無線網絡運營商來說，聯合優化其經濟和技術方面的決策以獲得商業成功正在變得越來越重要。一個運營商的決策可能包括對技術的選取和部署時間的把握、資源投資的數量，以及針對他所提供的服務的定價。考慮到這些決策彼此之間有關聯，我們需要對這些決策進行聯合優化，特別當運營商面對有限的資源、不成熟的技術和市場競爭時，該優化會變得困難。本論文綜合考慮兩類網絡中的這些因素。注意到在所有絨線技術中蜂窩網絡擁有最廣泛的市場佔有率，我們先研究蜂窩網路中的經濟學。然後我們研究認知無線電中的經濟學，考慮到該技術代表了未來無線技術發展的一個主要趨勢。 / 在本論文的第一部分，我們研究一個蜂窩網絡運營商在經濟和技術方面的決策，涉及到網路升級、服務分類和社交應用。首先，我們提出了一套博弈論模型來研究互相競爭的運營商從目前3G 蜂窩技術升級為未來一代(4G) 技術的部署時間。我們的分析指出運營商通常會選擇不同的升級時間以避免激烈的競爭。升級早的運營商在市場佔有方面有優勢，而升級晚的運營商只需承擔少量的升級成本並將面對一個更成熟的4G市場。其次，我們研究一個運營商是否有經濟動機在他已有的蜂窩基站C(macrocell)的基礎上再鋪設家庭基站(femtocell)。家庭基站能解決4G 網絡中室內用戶信號接收差的問題，但是該服務會佔用運營商原本就有限的頻譜資源。最後，我們嘗試去理解一個運營商該如何為異構的智慧手機用戶提供經濟刺激來鼓勵他們協助社交應用(比如，信息收集和分布式計算)的建立。在信息不對稱的情況下，我們設計了有效的激勵機制來根據智慧手機用戶不同的隱私損失、使用能耗和計算效率來提供獎勵。 / 在本論文的第二部分，我們在認知其在線電網絡中研究投資的便利性、頻譜感知的不確定性和安全性將如何影響一個次級(沒有頻譜執照的)運營商的決策。首先，我們研究一個可以通過動態頻譜租賞和頻譜感知兩種靈活方式來獲得絨線頻譜的次級運營商。我們聯合研究該運營商的投資選擇和對底層用戶的定價策略來使其利益最優。與動態頻譜租貸相比，頻譜感知不穩定但是能節約投資成本。其次，我們考慮一個包含兩個運營商的競爭市場，並研究他們之間在投資和定價方面的競爭。我們指出該競爭會給底層用戶帶來顯著好處而給運營商們帶來的收益總損失不會超過25% 。最後，一個運營商可能想利用多用戶合作式頻譜感知技術來提高感知的精確性但是該技術容易遭受數據偽造攻擊(data falsification attacks) 。我們通過合適的攻擊檢測和懲罰設計了有效的機制以防範攻擊。 / It is becoming increasingly important for wireless network operators to jointly optimize economic and technological decisions for business success. An operator's decisions may involve the choices and timings of technology adoptions, the amount of resources to invest, and the prices to set for his services. These decisions are coupled with each other and need to be jointly optimized, and such optimization will be challenging when the operator faces limited resources, immature technology, and market competition. This thesis focuses on such issues in two types of networks. We first study the economics of cellular networks, which have the largest market occupancy among all wireless technologies. We then look at the economics of cognitive radios networks, which represent one of the main development trends for wireless technologies in the near future. / In the first part of this thesis, we study a cellular operator's economic and technological decisions related to network upgrade, service differentiation, and social applications. First, we develop a game theoretic model for studying competitive operators' upgrade timing decisions from the existing 3G cellular technology to the next generation (4G) technology. Our analysis shows that operators often select different upgrade times to avoid severe competition. The operator upgrading earlier has advantage in increasing market share, while the one upgrading later benefit from decreased upgrade cost and a more mature 4G market. Second, we study an operator's economic incentive of deploying femtocell service on top of his existing macrocell service. The femtocell can resolve the issue of poor signal receptions for indoor users in 4G networks, but need to occupy the operator's limited spectrum resources. Finally, we try to understand how an operator can provide economic incentives for the heterogeneous smartphone users to collaborate in social applications (e.g., data acquisition and distributed computing). Under asymmetric information, we design effcient incentive mechanisms that reward smartphone users according to their different sensitivities to privacy loss, energy and computing effciencies. / In the second part of this thesis, we study how investment flexibility, sensing uncertainty, and sensing security in cognitive radio networks affect a secondary (unlicensed) operator's decisions. First, we study a secondary operator, who can flexibly acquire wireless spectrum through both dynamic spectrum leasing and spectrum sensing. We jointly study an operator's investment choices and pricing strategy to the end users to maximize his profit. Compared to spectrum leasing, spectrum sensing is unreliable but has a small cost. Second, we consider a competitive market with two operators, and study their competition in both investment and pricing. We show that end users significantly benefit from such market competition, and the operators' total profit loss due to competition is lower bounded by 25% of the maximum. Finally, an operator may want to deploy collaborative spectrum sensing to improve sensing accuracy, but this approach is vulnerable to data falsification attacks. We design effective attack prevention mechanisms through proper attack detection and punishment. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Duan, Lingjie. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 310-336). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Acknowledgement --- p.vi / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Economics of Cellular Networks --- p.3 / Chapter 1.2 --- Economic Viability of Cognitive Radio Networks --- p.5 / Chapter 1.3 --- Outline and Contributions --- p.9 / Chapter I --- Economics of Cellular Networks --- p.13 / Chapter 2 --- Economics of 4G Cellular Network Upgrade --- p.14 / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.1.1 --- Related Work --- p.18 / Chapter 2.2 --- System Model --- p.19 / Chapter 2.2.1 --- Value of Cellular Networks --- p.19 / Chapter 2.2.2 --- User Churn during Upgrade from 3G to 4G Services --- p.23 / Chapter 2.2.3 --- Operators' Revenues and Upgrade Costs --- p.25 / Chapter 2.3 --- 4G Monopoly Market --- p.26 / Chapter 2.4 --- 4G Competition Market: Duopoly Model and Game Formulation --- p.32 / Chapter 2.4.1 --- Operators' Long-term Profits --- p.34 / Chapter 2.4.2 --- Duopoly Upgrade Game --- p.37 / Chapter 2.5 --- 4G Competition Market: No Inter-network switching --- p.39 / Chapter 2.6 --- 4G Competition Market: Practical Inter-network Switching Rate --- p.40 / Chapter 2.7 --- Summary --- p.50 / Chapter 2.8 --- Appendix --- p.50 / Chapter 2.8.1 --- Proof Sketch of Theorem 2 --- p.50 / Chapter 2.8.2 --- Proof Sketch of Theorem 3 --- p.52 / Chapter 3 --- Economics of Femtocell Service Provision --- p.55 / Chapter 3.1 --- Introduction --- p.55 / Chapter 3.1.1 --- Related Work --- p.60 / Chapter 3.2 --- Benchmark: Macrocell Service Only --- p.62 / Chapter 3.2.1 --- Users' Bandwidth Demands in Stage II --- p.63 / Chapter 3.2.2 --- Operator's Pricing in Stage I --- p.65 / Chapter 3.3 --- Provision of Femtocell Service --- p.67 / Chapter 3.3.1 --- Users' Service Choices and Bandwidth Demands in Stage II --- p.71 / Chapter 3.3.2 --- Operator's Spectrum Allocations and Pricing in Stage I --- p.73 / Chapter 3.4 --- Impact of Users' Reservation Payoffs --- p.75 / Chapter 3.5 --- Impact of Femtocell Frequency Reuse --- p.82 / Chapter 3.6 --- Impact of Femtocell Operational Cost --- p.84 / Chapter 3.7 --- Impact of Limited Femtocell Coverage --- p.89 / Chapter 3.8 --- Summary --- p.95 / Chapter 4 --- Smartphone Collaboration on Social Applications --- p.96 / Chapter 4.1 --- Introduction --- p.96 / Chapter 4.1.1 --- Related Work --- p.100 / Chapter 4.2 --- Collaboration on Data Acquisition Application --- p.102 / Chapter 4.2.1 --- System Model of Data Acquisition --- p.102 / Chapter 4.2.2 --- Collaboration under Complete Information --- p.105 / Chapter 4.2.3 --- Collaboration under Symmetrically Incomplete Information --- p.106 / Chapter 4.2.4 --- Collaboration under Asymmetrically Incomplete Information --- p.109 / Chapter 4.3 --- Collaboration on Distributed Computing Application --- p.117 / Chapter 4.3.1 --- System Model on Distributed Computation --- p.117 / Chapter 4.3.2 --- Contractual Interactions between Client and Users --- p.119 / Chapter 4.3.3 --- Contract Design under Complete Information --- p.120 / Chapter 4.3.4 --- Client's Contract Design under Asymmetrically Incomplete Information --- p.123 / Chapter 4.4 --- Summary --- p.133 / Chapter 4.5 --- Appendix --- p.134 / Chapter 4.5.1 --- Discussion of Model (4.2) in Different Information Scenarios --- p.134 / Chapter 4.5.2 --- Proof of Theorem 9 --- p.135 / Chapter 4.5.3 --- Proof of No Collaboration and Pure Strategy NE in Theorem 10 --- p.136 / Chapter 4.5.4 --- Proof of Existence And Uniqueness of Equilibrium Threshold in Theorem 12 --- p.137 / Chapter 4.5.5 --- Proof of Theorem 13 --- p.139 / Chapter 4.5.6 --- Proof of Theorem 14 --- p.141 / Chapter 4.5.7 --- The proof of Proposition 1 --- p.142 / Chapter 4.5.8 --- Approximated Algorithm to Solve Problem (4.23) --- p.146 / Chapter II --- Economics of Cognitive Radio Networks --- p.149 / Chapter 5 --- Monopoly Spectrum Market Using Cognitive Radios --- p.150 / Chapter 5.1 --- Introduction --- p.150 / Chapter 5.1.1 --- Related Work --- p.155 / Chapter 5.2 --- Network Model --- p.157 / Chapter 5.2.1 --- Background on Spectrum Sensing and Leasing --- p.157 / Chapter 5.2.2 --- Notations and Assumptions --- p.159 / Chapter 5.2.3 --- A Stackelberg Game --- p.163 / Chapter 5.3 --- Backward Induction of the Four-stage Game --- p.164 / Chapter 5.3.1 --- Spectrum Allocation in Stage IV --- p.165 / Chapter 5.3.2 --- Optimal Pricing Strategy in Stage III --- p.167 / Chapter 5.3.3 --- Optimal Leasing Strategy in Stage II --- p.171 / Chapter 5.3.4 --- Optimal Sensing Strategy in Stage I --- p.173 / Chapter 5.4 --- Equilibrium Summary and Numerical Results --- p.179 / Chapter 5.4.1 --- Robustness of the Observations --- p.185 / Chapter 5.5 --- The Impact of Spectrum Sensing Uncertainty --- p.187 / Chapter 5.6 --- Learning the Distribution of Sensing Realization Factor α --- p.191 / Chapter 5.6.1 --- Performance Evaluation of Machine Learning --- p.193 / Chapter 5.7 --- Summary --- p.195 / Chapter 5.8 --- Appendix --- p.196 / Chapter 5.8.1 --- Proof of Theorem 18 --- p.196 / Chapter 5.8.2 --- Proof of Theorem 19 --- p.197 / Chapter 5.8.3 --- Supplementary Proof of Theorem 21 --- p.198 / Chapter 6 --- Competitive Spectrum Market Using Cognitive Radios --- p.204 / Chapter 6.1 --- Introduction --- p.204 / Chapter 6.1.1 --- Related Work --- p.209 / Chapter 6.2 --- Network and Game Model --- p.211 / Chapter 6.2.1 --- Users' and Operators' Models --- p.213 / Chapter 6.3 --- Backward Induction of the Three-Stage Game --- p.215 / Chapter 6.3.1 --- Spectrum Allocation in Stage III --- p.217 / Chapter 6.3.2 --- Operators' Pricing Competition in Stage II --- p.221 / Chapter 6.3.3 --- Operators' Leasing Strategies in Stage I --- p.226 / Chapter 6.4 --- Equilibrium Summary --- p.231 / Chapter 6.4.1 --- How Network Dynamics Affect Equilibrium Decisions --- p.234 / Chapter 6.5 --- Equilibrium Analysis under General SNR Regime --- p.237 / Chapter 6.6 --- Impact of Operator Competition --- p.239 / Chapter 6.6.1 --- Maximum Profit in the Coordinated Case --- p.239 / Chapter 6.6.2 --- Impact of Competition on Operators' Profits --- p.242 / Chapter 6.6.3 --- Impact of Competition on Users' Payoffs --- p.244 / Chapter 6.7 --- Summary --- p.245 / Chapter 6.8 --- Appendix --- p.246 / Chapter 6.8.1 --- Proof of Theorem 24 --- p.246 / Chapter 6.8.2 --- Proof of Theorem 25 --- p.250 / Chapter 7 --- Security Protection in Collaborative Spectrum Sensing --- p.256 / Chapter 7.1 --- Introduction --- p.256 / Chapter 7.1.1 --- Related Work --- p.260 / Chapter 7.2 --- Preliminary --- p.261 / Chapter 7.2.1 --- CRN Model and Assumptions --- p.261 / Chapter 7.2.2 --- Spectrum Sensing and Opportunistic Access Model --- p.264 / Chapter 7.2.3 --- Collision Penalty --- p.265 / Chapter 7.2.4 --- Decision Fusion Rule --- p.266 / Chapter 7.3 --- Attackers' Behaviors Without Punishment --- p.268 / Chapter 7.3.1 --- All SUs sense the channel idle --- p.270 / Chapter 7.3.2 --- All honest SUs sense the channel idle, but some attacker(s) senses the channel busy --- p.270 / Chapter 7.3.3 --- Some honest SUs sense the channel busy --- p.272 / Chapter 7.4 --- Attack-Prevention Mechanism: A Direct Punishment --- p.273 / Chapter 7.5 --- Attack-Prevention Mechanism: An Indirect Punishment --- p.277 / Chapter 7.6 --- Summary --- p.286 / Chapter 7.7 --- Appendix --- p.286 / Chapter 7.7.1 --- Relaxation of Assumptions A1 and A3 --- p.286 / Chapter 7.7.2 --- Attack Prevention in Case:AT of Section 7.5 --- p.293 / Chapter 7.7.3 --- Proof of Lemma 6 --- p.297 / Chapter 8 --- Conclusion and Future Work --- p.299 / Chapter 8.1 --- Conclusion --- p.299 / Chapter 8.2 --- Extensions of 4G Network Upgrade in Chapter 2 --- p.302 / Chapter 8.3 --- Extensions of Femtocell Service Provision in Chapter 3 --- p.303 / Chapter 8.4 --- Extensions of Smartphone Collaboration on Social Applications in Chapter 4 --- p.304 / Chapter 8.5 --- Extensions of Monopoly Spectrum Market in Chapter 5 --- p.305 / Chapter 8.6 --- Extensions of Competitive Spectrum Market in Chapter 6 --- p.306 / Chapter 8.7 --- Extensions of Security Protection in Collaborative Spectrum Sensing in Chapter 7 --- p.308 / Bibliography --- p.310

協作多點 (CoMP)是一種最近興起的傳輸技術，其主要作用為應付新一代無線通訊系統中的小區間干擾問題。在過去十數年內，研究員研發了 CoMP中一些關鍵的新技術，當中包括 MIMO合作和干擾協調。本論文考慮一個聯合用戶排程和干擾協調的問題。在傳統的研究中，用戶排程和干擾協調通常作為獨立的問題進行研究。可是，從本質上這兩個問題是相互影響的，因此傳統的研究將導致系統性能退化。為此，本論文探討了一個聯合用戶排程和波束形成（JACoB）的問題，這當中採用了一種稱為協同波束形成（CoBF）的干擾協調技術。具體而言，本文把 JACoB問題表達成了一個可支持用戶數最大化的問題，而其中的 CoBF設計將盡可能地配合用戶的需求而改變。 / 本論文有兩個主要的貢獻。第一，本文把 JACoB問題轉換成一個 ℓ₀範數最小化問題。其後本文採用 ℓ₁範數近似法將 JACoB問題近似為一個凸優化問題。第二，本文提出一種新型的分佈 JACoB方法。本文提出的分佈方法是基於塊坐標下降法。該方法不同於傳統的基於次梯度方法的分佈方法，如原始/對偶分解。 / 仿真結果顯示，採用本文提出的 JACoB方法（無論是集中的或是分佈的）所能支持的用戶數量遠超過現有的固定波束形成方法。此外，本文提出的分佈 JACoB方法能達到與集中JACoB方法相近的性能，而且其收斂速度亦是相當快的。 / Coordinated MultiPoint (CoMP) cooperative transmission has recently emerged as a promising technique for mitigating intercell interference in next generation wireless communication systems. Several key techniques for CoMP have been endeavored over the past decades, for example, MIMO cooperation and interference coordination. The present work studies a joint user scheduling and interference coordination problem in the CoMP downlink systems. Conventionally, user scheduling and interference coordination are treated as separate problems. This may result in a degradation of the system performance as the two problems are actually intertwined with each other. As such, this thesis considers a joint admission control and beamforming (JA-CoB) problem which employs a popular interference coordination technique called coordinated beamforming (CoBF). In particular, the JA-CoB problem is stated as a user number maximization problem where the CoBF design can be adapted to the set of selected users. / There are two major contributions in this thesis. Firstly, the JA-CoB problem is cast as an ℓ₀ norm minimization problem and then tackled by the now popularized ℓ₁ approximation technique. Secondly, a novel decentralized JACoB method is developed. The proposed de-centralized method is based on the simple block coordinate descent method, which is different from the conventional approaches which em-ploy subgradient-based method such as dual/primal decomposition. / The simulation results indicate that: i) the proposed centralized method yields a performance close to the optimum JACoB design while the complexity is significantly reduced; ii) employing the proposed JA-CoB methods (either centralized or decentralized) gives a significant gain over a fixed beamformers design in terms of the number of supported users. Moreover, the decentralized JACoB method achieves a performance close to its centralized counterpart, whilst the convergence speed is considerably fast. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wai, Hoi To. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 77-80). / Abstracts also in Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of techniques for CoMP --- p.2 / Chapter 1.2 --- Overview of user scheduling algorithms --- p.4 / Chapter 1.3 --- Contributions --- p.6 / Chapter 2 --- The JACoB problem and the related works --- p.8 / Chapter 2.1 --- System model --- p.8 / Chapter 2.2 --- Joint admission control and beamforming (JACoB) --- p.10 / Chapter 2.2.1 --- Coordinated beamformers design --- p.11 / Chapter 2.2.2 --- Semide nite relaxation for the CoBF problem --- p.13 / Chapter 2.3 --- Related works --- p.14 / Chapter 2.3.1 --- Common trend in JACoB - deflation heuristic . --- p.18 / Chapter 2.4 --- Decentralized methods --- p.19 / Chapter 3 --- Centralized JACoB method --- p.21 / Chapter 3.1 --- Step 1 - a new formulation to JACoB --- p.21 / Chapter 3.2 --- Step 2 - ℓ₁ approximation to JACoB --- p.24 / Chapter 3.2.1 --- Properties of the ℓ₁ JACoB problem --- p.26 / Chapter 3.3 --- Proposed JACoB method --- p.28 / Chapter 3.3.1 --- Prescreening procedure --- p.28 / Chapter 4 --- Decentralized JACoB method --- p.31 / Chapter 4.1 --- Block coordinate descent method --- p.32 / Chapter 4.2 --- Smooth approximation to ℓ₁ JACoB --- p.34 / Chapter 4.2.1 --- Empirical iteration complexity of the BCD method --- p.38 / Chapter 4.3 --- Proposed decentralized JACoB method --- p.40 / Chapter 5 --- Simulation results --- p.43 / Chapter 5.1 --- Performance of centralized JACoB methods --- p.44 / Chapter 5.2 --- Performance of decentralized JACoB methods --- p.48 / Chapter 5.3 --- Summary --- p.52 / Chapter 6 --- Conclusions and future directions --- p.53 / Chapter 6.1 --- Future directions --- p.53 / Chapter 6.1.1 --- From a practical point of view --- p.54 / Chapter 6.1.2 --- From a theoretical point of view --- p.54 / Chapter A --- A primal decomposition method for (3.4) --- p.56 / Chapter B --- A projected gradient method for (4.3) --- p.60 / Chapter C --- Proofs --- p.67 / Chapter C.1 --- KKT conditions for (2.6) and (3.5) --- p.67 / Chapter C.2 --- Proof of Proposition 2.1 --- p.68 / Chapter C.3 --- Proof of Proposition 3.3 --- p.69 / Chapter C.4 --- Proof of Proposition 3.2 --- p.69 / Chapter C.5 --- Proof of Proposition 3.5 --- p.71 / Chapter C.6 --- Proof of Fact 4.1 --- p.75 / Bibliography --- p.77

The widespread use of TCP as a transport layer protocol for mobile ad-hoc networks and wireline networks has motivated the need to make its implementation highly power efficient specially with respect to ad hoc radio networks. Over the past years many researchers have developed energy efficient protocols for mobile ad-hoc networks. This thesis deals with the various modifications and fine-tunings in the TCP code which, when applied, help in conserving battery power at nodes by saving on the software overhead at the mobile nodes. The various modifications proposed have been tested with actual experiments done on two laptops with Lucent WaveLan wireless cards. The results obtained from the experiments indicate that with certain modifications made in the implementation of TCP code, significant savings in power can be achieved along with an increase in the overall efficiency of TCP over wireless links. Finally, a discussion of how other modifications can be researched and tested as the hardware for mobile systems change is proposed. / Graduation date: 2000

Thesis (M.E.)--University of Florida, 2001. / Title from title page of source document. Document formatted into pages; contains xi, 76 p.; also contains graphics. Includes vita. Includes bibliographical references.