Due to the inherent complexity of the power-controlled scheduling problem, finding optimal schedules and power allocations for large-size networks will still consume extraordinary large amounts of time despite the performance of our method. We therefore propose an approximation algorithm, called the Guaranteed and Greedy Scheduling (GGS), which can find near optimal solutions within a short runtime. GGS is a polynomial time algorithm with a provable upper bound for the approximation ratio relative to the optimal solution. / For the distributed scheduling algorithm design, we focus on the CSMA (Carrier-Sense Multiple-Access) network, which is the most widely used distributed wireless network in practice. We establish a rigorous conceptual framework, upon which effective solutions to interference-safe transmissions can be constructed under the physical interference model. Specifically, we propose to use the concept of "safe carrier sensing range", which guarantees interference-safe transmissions under the physical interference model. We further propose a novel carrier-sensing mechanism, called Incremental-Power Carrier-Sensing (IPCS), which implements the safe carrier-sensing range concept in a simple way. Extensive simulation results show that IPCS can boost spatial reuse and network throughput by more than 60% relative to the conventional carrier-sensing mechanism. / This thesis studies the wireless link scheduling problem under the physical interference model. Such problem is more realistic than the widely studied wireless scheduling problem under the protocol interference model. However, it is a challenging problem because the physical interference model considers the cumulative effect of the interference powers from all the other concurrent transmitters. This thesis covers the complexity analysis and algorithm design (both centralized and distributed) for such a challenging problem. / We first give a rigorous NP-completeness proof for the power-controlled scheduling with consecutive transmission constraint under the physical interference model. We then present a centralized scheduling algorithm based on a column generation method which finds the optimal schedules and transmit powers. We further consider an integer constraint that requires the number of time slots allocated to a link to be an integer. Building upon the column generation method, we propose a branch-and-price method which can find the optimal integer solution. By simplifying the pricing problem and designing a new branching rule, we significantly improve the efficiency of both the column generation and the branch-and-price methods. For example, the average runtime is reduced by 99.86% in 18-link networks compared with the traditional column generation method. / Fu, Liqun. / Advisers: Soung Chang Liew; Jianwei Huang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 133-144). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

After that, the cooperative transmission scheme is extended for the scenario of more than two source-destination pairs. One objective is to investigate the relationship between the diversity order and the number of source-destination pairs. This is done by considering the sum power minimization problem. A pricing game is derived to provide a distributed implementation. At Nash Equilibrium of the game, the total transmission power is minimized. Simulation results show the rapid convergence of the game and its adaptation to channel fluctuations. It also shows that the cooperative transmission scheme achieves full diversity order. / Apart from replacing a superposition code based cooperative transmission scheme by a TDM based scheme, the implementation can be simplified by introducing a partner selection scheme to the nodes. In that network, the cooperative transmission code still uses superposition code as the building block. Instead of relaying the messages from all other nodes, in this new scheme, the source nodes only relay the messages for their assigned partners. A natural question is: How can we assign the partners to the source nodes such that the total transmission power is minimized. The problem is solved in two phases. Firstly, we solve the sum power minimization problem for each pair of nodes. In some cases, this problem has closed-form solutions while for the other cases, a simple iterative algorithm can solve this problem. / Firstly, cooperative orthogonal-division channel is defined and two cooperative transmission schemes based on dirty-paper coding and superposition code are proposed and compared through simulations. Simulation Results show the significant improvement over the pure direct transmission schemes. Although one cooperative transmission scheme achieves a slightly larger rate region, the other scheme has a much simpler implementation so the remaining parts of the thesis focus on this scheme. The outage performance of this scheme is also compared with a simplified Han-Kobayashi scheme through simulations. Simulation results illustrate the significant improvement in the diversity gain of this scheme over the Han-Kobayashi scheme. / However, it is noted that the complexity of implementing superposition code, which is a building block of the cooperative transmission code, is very high when there are many users in the network. Hence, another time-division multiplex (TDM) based cooperative transmission scheme is proposed. Similar to the superposition code based scheme, there is a pricing game which can provide a distributed sum power minimization. Simulation results also show that the game has high convergence rate and it can adapt to changes of channel conditions efficiently. In addition, this cooperative transmission scheme also achieves full diversity order. / In this thesis, different codes and resource allocation algorithms for cooperative transmissions are proposed. Briefly speaking, in cooperative transmission, a number of wireless nodes form a coalition in which they exchange and cooperatively transmit messages. As a result, the order of diversity can be increased without installing additional antennas. / Next, a weighted sum rate maximization algorithm is proposed. There are two purposes of this algorithm. Firstly, this algorithm is adopted to find the Pareto-optimal points of the boundary of the achievable rate region through simulations. Secondly, this algorithm can be extended to solve the max-min fairness problem and the joint utility maximization algorithm by the proposed framework. / This thesis is ended with some future research directions. / With this information, we can assign the partners by Gabow's algorithm, which solves the maximum weighted matching problem that is mapped from the original partner selection problem. Nonetheless, it is noted that when the number of users is very large, it involves a large amount of the communication and computational cost to solve the sum power minimization problem for each pair of nodes as well as the partner selection problem. Therefore, the Grouping Algorithm is proposed to reduce the aforementioned implementation cost. Simulation results show that the optimal algorithm and the Grouping Algorithm can achieve full diversity order. Moreover, although the Grouping Algorithm is sub-optimal in general, it costs only 1dB of the sum power more than the optimal algorithm. / Ng, Cho Yiu. / Adviser: Tal M. Lok. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 152-162). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Finally, we present a novel algorithm for intruder detection in a sinkhole attack of wireless sensor network. The algorithm can identify the intruder and deal with multiple malicious nodes effectively. We have evaluated the performance of the proposed algorithm through both numerical analysis and simulations, which confirmed the effectiveness and accuracy of our algorithm. / In this thesis, we propose a general reliability-centric framework for event reporting in WSANs. We point out that the reliability in such a real-time system depends not only on the accuracy, but also the importance and freshness of the reported data. Our proposed design thus integrates three key modules, (1) an efficient and fault-tolerant event data aggregation algorithm, (2) a delay-aware data transmission protocol, and (3) an adaptive actuator allocation algorithm for unevenly distributed events. We further propose a latency-oriented fault tolerant data transport protocol (LOFT) and a power-controlled real-time data transport protocol (POWER-SPEED) for WSANs. LOFT balances the workload of sensors by checking their queue utilization and handles node/link failures by an adaptive replication algorithm. POWER-SPEED transmits packets in an energy-efficient manner while maintaining soft real-time packet transport. We evaluate our framework and the two proposed protocols through extensive simulations, and the results demonstrate that they achieve the desirable reliability for WSANs. / To minimize the data collection time, we propose a new routing design. We present the mathematical formulation of the route design problem, and show that it is computationally intractable. We then propose two practical algorithms to reduce the delay of the sensors. Our algorithms adaptively adjust the actuator visiting frequencies to the sensors according to their relative weights and data generation patterns. We further propose a probabilistic route design (PROUD) algorithm which adapts to network dynamics. We present the distributed implementation for PROUD and an extension which accommodates actuators with variable speeds. We also propose algorithms for load balancing among the actuators. Simulation results show that our algorithms can effectively reduce the overall data collection time. They adapt to the network dynamics and balances the energy consumption of the actuators. / Wireless sensor-actuator networks, or WSANs, greatly enhance the existing wireless sensor network architecture by introducing powerful and mobile actuators. These actuators are expected to work with the sensor nodes and perform much richer application-specific actions. For the applications which request for fast and accurate report of the environmental events, an efficient and reliable communication/coordination scheme is urged. Unfortunately, multi-hop communication in a WSAN is inherently unreliable due to frequent sensor failures and network partitions. Excessive delays, introduced by congestion or in-network data aggregation, further aggravate the problem. / Ngai, Cheuk Han. / "August 2007." / Adviser: Michael R. Lyu. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1113. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 191-207). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Finally, we study a typical heterogeneous network, Wireless Biomedical Sensor Network (WBSN), as it consists of various types of biosensors to monitor different physiological parameters. WBSN will help to enhance medical services with its unique advantages in long-term monitoring, easy network deployment, wireless connections, and ambulatory capabilities. (Abstract shortened by UMI.) / Secondly, for the purpose of providing geographical information for the topology management, we investigate the problem of power adaptive localization based on received signal strength (RSS), aiming at tackling the problem of inconsistent signal strength observation caused by tuning power levels. We propose a localization algorithm based on the particle filtering technique for sensor networks assisted by multiple transmission power levels. As a result, the novel contribution in this part is to intelligently incorporate changing transmission power levels into the particle filtering process as dynamic evidences and make an accurate localization. The proposed particle filtering technique based localization algorithm effectively circumvents the inconsistent observations under different power settings. It picks up the information of RSS from the beacons or the neighboring nodes to infer position information, without requiring additional instrumentation. We then evaluate the power adaptive localization algorithm via simulation studies and the results indicate that the proposed algorithm outperforms the algorithm of iterative least-square estimation, which does not utilize multiple power levels. In addition, we proposed a particle-filtering localization based on the acoustic asymmetric patterns of the acoustic sensors. As a result, the proposed particle filter based localization algorithms can facilitate the topology management in heterogeneous sensor networks. / We start by formulating the problem of topology optimization in the context of game theory and then analyze the equilibrium resulted from the decentralized interactions between the heterogeneous sensors. Majority of the existing topology control approaches require a centralized controller to obtain a global network graph and formulate the issue as a problem of transmission range assignment. The centralized algorithms are inapplicable for large-scale sensor networks due to the heavy communication overhead. In addition, these algorithms rarely consider the cross-layer consequences of the power adjustment, such as the quality of received signals at physical layer, the network connectivity, and the spatial reuse at network layer. Considering the aforementioned cross-layer interactive effects caused by power scheduling, we study the utility function that balances the physical layer link quality characterized by the frame success rate and the network layer robustness characterized by K-connectivity, while minimizing the power consumption. We prove the existence of the Nash equilibrium for complete-information game formulation. Because the heterogeneous sensors typically react to neighboring environment based on local information and the states of sensors are evolving over time, the power-scheduling problem in WHSN is further formulated into a more realistic incomplete-information dynamic game model. We then analyze the separating equilibrium, one of the perfect Bayesian equilibriums resulted from the dynamic game, with the sensors revealing their operational states from the actions. The sufficient and necessary conditions of the separating equilibrium existence are derived for the dynamic Bayesian game, which provide theoretical basis to the proposed power scheduling algorithms. / Wireless Heterogeneous Sensor Network (WHSN) is constructed from various sensor nodes with diverse capabilities in sensing units, transmission power levels, and energy resources, among a few others. The primary objective of the research reported in this thesis is to address the problem of power efficient topology optimization in WHSN, which is a much more complicated issue for network reliability, compared with homogeneous wireless sensor network (WSN). Two fundamental problems of topology management are addressed in this thesis: power scheduling based topology control and power adaptive localization. Distributed power scheduling offers an efficient way for the dynamic construction of network topology to meet its connectivity and reliability requirements. Power adaptive localization provides geographical information for topology management during the process of power adjustment. / Ren, Hongliang. / "February 2008." / Adviser: Qing-Hu Max Meng. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4944. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 140-157). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Fu Chengpeng. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 102-119). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

by Wan Shan. / "June, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Nam Chung Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 68-71). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview and Motivation --- p.1 / Chapter 1.2 --- Organization of the Thesis --- p.5 / Chapter Chapter 2 --- Background --- p.6 / Chapter 2.1 --- Basics of 802.11 Standard --- p.6 / Chapter 2.1.1 --- Distributed Coordination Function (DCF) / Point Coordination Function (PCF) --- p.7 / Chapter 2.1.2 --- RTS/CTS --- p.8 / Chapter 2.2 --- Types of Networks --- p.9 / Chapter 2.3 --- Automatic Repeat request (ARQ) in 802.11b --- p.11 / Chapter 2.3.1 --- Importance of Link-layer ARQ in Wireless Networks --- p.12 / Chapter 2.3.2 --- MAC Algorithm of 802.11b Standard --- p.13 / Chapter 2.3.3 --- Modified MAC algorithm in 802.11b commercial products --- p.14 / Chapter 2.4 --- Automatic Adjustment of Radio Data Rate in Commercial 802.11b Products --- p.15 / Chapter Chapter 3 --- Head-of-Line Blocking in Access Points --- p.17 / Chapter 3.1 --- Cause of HOL blocking in 802.11b --- p.17 / Chapter 3.1.1 --- Calculation of Worst-Case Service Time for Packet at Head of Queue --- p.19 / Chapter 3.2 --- Simulation Settings --- p.21 / Chapter 3.2.1 --- Propagation Models Available in NS2 --- p.21 / Chapter 3.2.2 --- Variables of Shadowing Model --- p.25 / Chapter 3.3 --- Simulation Results on UDP --- p.26 / Chapter 3.4 --- Experimental Results on UDP --- p.28 / Chapter 3.5 --- Simulation Results on TCP --- p.32 / Chapter 3.6 --- Experimental Results on TCP --- p.34 / Chapter 3.7 --- Possible Solutions of HOL Blocking Problem --- p.35 / Chapter 3.7.1 --- Weakening Link-layer ARQ in 802.11b --- p.36 / Chapter 3.7.2 --- Effectiveness of ARQ in 802.11b --- p.37 / Chapter 3.7.2.1 --- Set-up for Network Experiments --- p.38 / Chapter 3.7.2.2 --- Results and Analysis --- p.39 / Chapter 3.7.3 --- Virtual Queuing --- p.45 / Chapter Chapter 4 --- Study of Uplink Traffic --- p.50 / Chapter 4.1 --- Poor Pulling Down the Rich --- p.51 / Chapter 4.2 --- Signal Capturing Effect --- p.53 / Chapter 4.2.1 --- Mathematical Analysis of Signal Capturing Effect --- p.55 / Chapter Chapter 5 --- Packet Loss Patterns in 802.11b WLAN --- p.61 / Chapter 5.1 --- """Random Loss"" vs ""Bursty Loss""" --- p.61 / Chapter 5.2 --- Experimental Evaluation --- p.62 / Chapter Chapter 6 --- Conclusion --- p.65 / Bibliography --- p.68

Weiyan Ge. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 64-68). / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction of Power Control Problem --- p.2 / Chapter 1.1.1 --- Classification of Power Control Problem --- p.2 / Chapter 1.1.2 --- Previous Works --- p.7 / Chapter 1.2 --- Scope and Contribution of the Thesis --- p.11 / Chapter 1.3 --- Organization of the Thesis --- p.12 / Chapter 2 --- Background --- p.14 / Chapter 2.1 --- Stochastic Approximation --- p.14 / Chapter 2.2 --- Lognormal Distribution --- p.17 / Chapter 2.2.1 --- Definition and Properties --- p.17 / Chapter 2.2.2 --- Application on Radio Propagation --- p.18 / Chapter 3 --- System Model and Centralized Algorithm --- p.21 / Chapter 3.1 --- System Model --- p.21 / Chapter 3.2 --- Problem Statement and the Centralized Algorithm --- p.25 / Chapter 4 --- Proposed Stochastic Power Control Algorithm --- p.30 / Chapter 4.1 --- Proposed Power Control Algorithm --- p.30 / Chapter 4.2 --- Basic Properties of the Algorithm --- p.33 / Chapter 4.3 --- Convergence Property --- p.38 / Chapter 5 --- Numerical Results --- p.44 / Chapter 5.1 --- Simulation Model --- p.44 / Chapter 5.2 --- Numerical Results --- p.47 / Chapter 6 --- Conclusions And Future Works --- p.58 / Chapter 6.1 --- Conclusions --- p.58 / Chapter 6.2 --- Future Works --- p.60 / Chapter A --- Basic Properties of LOG-Distribution --- p.62 / Bibliography --- p.64

Zheng Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 63-66). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Review of space-time coding and blind channel estimation --- p.1 / Chapter 1.2 --- Introduction of space-time coding system --- p.4 / Chapter 1.3 --- Diversity gain of space-time coding --- p.6 / Chapter 1.4 --- Re-estimation --- p.7 / Chapter 1.5 --- Notations --- p.8 / Chapter 1.6 --- Outline of thesis --- p.8 / Chapter 2. --- Estimation for BPSK Signals --- p.10 / Chapter 2.1 --- Introduction to maximum likelihood estimation --- p.10 / Chapter 2.2 --- System model --- p.11 / Chapter 2.3 --- Deterministic ML algorithm --- p.14 / Chapter 2.4 --- Re-estimation --- p.16 / Chapter 2.5 --- Application to other constellations --- p.18 / Chapter 2.6 --- Simulation results --- p.18 / Chapter 2.7 --- Summary --- p.21 / Chapter 3. --- Estimation for Flat Fading Channels --- p.22 / Chapter 3.1 --- Introduction of constant modulus algorithm (CMA) --- p.22 / Chapter 3.2 --- System model for flat fading channels --- p.24 / Chapter 3.3 --- Blind estimation with CMA --- p.26 / Chapter 3.3.1 --- Problem statement --- p.26 / Chapter 3.3.2 --- Estimating channel with CMA --- p.28 / Chapter 3.3.3 --- Solving the ambiguity problem --- p.32 / Chapter 3.4 --- Re-estimation for flat fading channels --- p.39 / Chapter 3.5 --- Estimation algorithm --- p.39 / Chapter 3.6 --- Application to multi-antenna system --- p.41 / Chapter 3.7 --- Simulation results --- p.42 / Chapter 3.8 --- Summary --- p.46 / Chapter 4. --- Estimation lor Frequency Selective Fading Channels --- p.48 / Chapter 4.1 --- Introduction of space-time coded OFDM --- p.48 / Chapter 4.2 --- System model --- p.51 / Chapter 4.3 --- Estimation Algorithm --- p.54 / Chapter 4.4 --- Simulation results --- p.56 / Chapter 4.5 --- Summary --- p.59 / Chapter 5. --- Conclus ions and Future Work --- p.60 / Chapter 5.1 --- Conclusions --- p.60 / Chapter 5.2 --- Future work --- p.61 / Bibliography: --- p.63

This dissertation examines the intersecting changes of African decolonization and the post-World War II internationalization of public health by showing how Cameroonian and French health officials shaped global health programs on the ground in the 1950s and 60s. I approach this topic through the lens of two tightly interwoven developments in Cameroon: the history of colonial mobile health teams created by French military doctors and the advent of postwar global disease eradication campaigns. While colonial medicine and international health are typically treated as distinct historical subjects, I argue that global disease eradication programs in this period in Cameroon relied entirely on colonial mobile health teams and their reformulation after independence as a basis of infrastructure, personnel and knowledge. I specifically assert that Cameroonian and French health officials positioned mobile health teams as cornerstones of national health policy and regional health coordination in Central Africa and, in turn, as the basis for operations of attempted global disease eradication programs within Cameroon. As Cameroonian, French and international health officials negotiated the work of the mobile health teams through decolonization and the first decade of the independence, they were moreover charting new structures of authority and control over medicine and public health between the global and the local, and forging an international politics of public health rooted in the particular tensions of decolonization in the country. My project thus demonstrates how Africans charted new models for public health through decolonization, models that reflected both the deeply enduring impact of empire and a new post-colonial politics.