University of the Witwatersrand Faculty of Engineering and the Built Environment School of Information and Electrical Engineering / Mobile Broadband is now more of a necessity than a luxury, especially amongst the younger generation, irrespective of where they live. Mobile WiMax and LTE, the latest and fastest Mobile Broadband technologies, mark significant improvements over 3G networks because they use IP (Internet Protocol) end-to-end. To end-users, this means faster network speeds, better quality services, and increased coverage area. To the Network Operators, this means simplified network architectures, efficient use of resources, and improved security. In this report, the different issues and challenges related to deploying Mobile WiMax (802.16e or 802.16m) in rural South Africa, were identifed and explored. In this project, Atoll, SONAR, and Touch Point analysis tools were used to determine which Mobile Broadband technology is economically and technically suited for rural South Africa. It was found that LTE yields superior performance results than WiMax, which in turn yields superior performance results to all other existing 3G technologies. However it will take time for LTE to reach rural areas therefore WiMax can be considered as a solution to extend Broadband services to rural South Africa and thus assist in bridging the digital divide. Recommendations on how best to deploy Mobile WiMax are made based on observations made from the experimental work. / MT2017

A research report submitted to the Faculty of Humanities, University of the Witwatersrand in fulfilment of the requirements for the degree of Masters of Arts by Research (Development Studies), August, 2017 / In this master’s dissertation report, I explore how the National Union of Small-scale Farmers of Mozambique (UNAC) transnationalised its activism through its membership to La Via Campesina (LVC), covering the period between 2004 and 2014, to understand the nature of transnational activism of national peasant movement organisations. I identify the factors behind national peasant movement organisations embarking on transnational activism, the structure put in place to secure their transnational activism and the possible opportunities and threats transnational activism poses to their national mandate. I applied ethnography and more concretely Michael Burawoy’s approach to the extended case method to reconstruct (by extending) neo-Marxist approaches to the study of peasantry, peasant movements and social movements in general. Based on a qualitative approach to the data collected, the research conducted documentary analysis and in-depth interviews with relevant actors. Results suggest that peasants’ national movement organisations transnationalise part of their activism through joining an already transnational peasant’s movement organisation by adopting and campaigning for its political themes, building transnational peasant activists, and by practising transnational solidarity. Results also suggest that national peasant movement organisations transnationalise their activism precisely because they share a common interest of fighting capitalism with the movement organisation they affiliate with, they seek to expand their political messages and because they are looking for international solidarity. Added to this, results show that this type of transnational activism does not necessarily require specific administrative structures and does not pose major threats to the national mandate of national peasant movement organisations. More importantly, results suggest re-theorising the neo-Marxists’ approach to social movements by accommodating transnational agency of national peasant movement organisations. / XL2018

The world is getting connected in both small and bigger systems. Internet of Things (IoT) has flourished the past years and we no longer just connect our computers and phones but also our cars, wallets, keys and even the furniture and lighting in homes are talking. It is time to take things one step further, give your food and supplies a voice. This master thesis has the purpose to construct a smart inventory using the IoT. Its outcome is a prototype that consists of three main parts: 1) a number of sensor nodes to measure what products are left, 2) a hub to collect the inventory from the sensor nodes through acoustic communication and store it, and 3) an app on a mobile device to receive the inventory from a hub via Bluetooth and display it in a list for the user. The acoustic communication between the sensor node and the hub are thoroughly investigated taking into account the distance and angle as well as reliability. The Bluetooth communication between the hub and the mobile device with the app can be established automatically when the app is opened or when the user requests an update. The finished prototype has been tested and its performance evaluated. The results show that it functions with great satisfaction, being capable of measuring inventory, storing it and display it on the app. The sensor node and hub have highly reliable communicate within the distance of 1.9 m, a horizontal angle of 25 degrees and a vertical angle of 30 degrees. When the system is exposed to a lot of disturbance it has a reliability of 66% and the Bluetooth connection between the hub and the app can automatically connect about 70% of the times. This smart inventory system can be used in homes, storage rooms, offices, workshops and stores without Internet connection so that no one outside of Bluetooth coverage can get the information, or be expand with Internet connection so that the inventory can be updated anywhere and anytime around the world.

This thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel estimation process was 1.83 % and 6.1810 %, respectively for simulated and experimental data. Using experimental data, the RMSE before MIMO deconvolution process was 141.3 % and dropped down to 60.224 % and to 4.4545 %, respectively after LE and ICLE. At raw reception, the RMSE was 101.83 % and dropped down to 9.36 % and to 1.86 % using respectively LE and ICLE with simulated data. / by Gaultier Real. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

However, applying directional antennas to wireless networks can also cause new collisions, such as the new hidden terminal problem and the deafness problem. We study the challenges in the MAC layer design with directional antennas and present the state of the art of current MAC protocols with directional antennas. Then, we propose a novel collision avoidance scheme in terms of BT-DMAC (Busy-Tone based Directional Medium Access Control) to address the new collisions with directional antennas. Both the analytical and simulation results show that transmitting busy tones on a different channel can effectively reduce the hidden nodes and mitigate the deafness problem. Thus, integrating multiple channels with directional antennas can bring numerous benefits. Furthermore, we also explore some techniques in the MAC layer design with directional antennas. Some useful insights are also given. / The capacity of wireless networks are mainly affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies have found that, using multiple channels can separate concurrent transmissions and significantly improve network throughput. However, those studies only consider wireless nodes that are only equipped with omni-directional antennas, which cause high collisions. On the other hand, some researchers have found that directional antennas bring more benefits such as the reduced interference and the increased spatial reuse compared with omni-directional antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. In this thesis, we propose a novel network architecture, in terms of multi-channel networks using multiple directional antennas ( MC-MDA), which integrates the two technologies of multiple channels and directional antennas together and potentially brings more benefits. / We study the capacity of MC-MDA networks and explore the benefits of such networks. We have found that using directional antennas in multi-channel networks can greatly increase the network capacity. Furthermore, such networks require fewer channels than multi-channels with omni-directional antennas. More specifically, we study the channel assignment problem of such MC-MDA networks. Our results indicate that using directional antennas in wireless networks can significantly reduce the required number of channels. Directional antennas have a better spectrum reuse than omni-directional antennas. / Dai, Hongning. / Adviser: Kam-Wing Ng. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3596. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 173-183). / 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.

This thesis investigates two systems that exploit multi-user interference in wireless communication in which multiple users transmit simultaneously. The thesis consists of two parts that aim for two different wireless network setups: the first part focuses on the decoding of convolutional-coded physical-layer network coding (PNC) in a two-way relay network (TWRN); the second part presents a scalable multi-user multiple-input multiple-output (MU-MIMO) architecture supporting real-time MIMO decoding. Both systems take advantage of multi-user interference to boost the system performance. The investigations of the two systems involve both theoretical analysis and system prototyping on software radio. / The first part of this thesis investigates the decoding process of asynchronous convolutional-coded PNC systems. Specifically, we put forth a layered decoding framework for convolutional-coded PNC consisting of three layers: symbol realignment layer, codeword realignment layer, and joint channel-decoding network coding (Jt-CNC) decoding layer. Our framework can deal with phase asynchrony (phase offset) and symbol arrival-time asynchrony (symbol misalignment) between the signals simultaneously transmitted by multiple sources. A salient feature of this framework is that it can handle both fractional and integral symbol misalignments. For the decoding layer, instead of Jt-CNC, previously proposed PNC decoding algorithms (e.g., XOR-CD and reduced-state Viterbi algorithms) can also be used with our framework to deal with general symbol misalignments. Our Jt-CNC algorithm based on belief propagation (BP) is BER-optimal for synchronous PNC and near optimal for asynchronous PNC. Extending beyond convolutional codes, we further generalize the Jt-CNC decoding algorithm for all cyclic codes. Our simulations show that Jt-CNC outperforms the previously proposed XOR-CD algorithm and reduced-state Viterbi algorithm by 2 dB for synchronous PNC. For both phase-asynchronous and symbolasynchronous PNC, Jt-CNC performs better than the other two algorithms. Importantly, for real wireless network experimentation, we implemented our decoding algorithm in a PNC prototype built on the USRP software radio platform. Our experiment shows that the proposed Jt-CNC decoder works well in practice. / The second part of the thesis presents BigStation, a scalable architecture that enables real-time signal processing in large-scale MU-MIMO systems with tens or hundreds of antennas. Our strategy to scale the system is to extensively parallelize the MU-MIMO processing on many simple and low-cost commodity computing devices. Our design can incrementally support more antennas by proportionally adding more computing devices. To reduce the overall processing latency, which is a critical constraint for wireless communication, we parallelize the MU-MIMO decoding process with a distributed pipeline based on its computation and communication patterns. At each stage of the pipeline, we further use data partitioning and computation partitioning to speed up the signal processing. As a proof of concept, we have built a BigStation prototype based on commodity PC servers and SORA software radio platform. Our prototype employs 15 PC servers and can support realtime signal processing of 12 software radio antennas. Our results show that the BigStation is able to scale to tens to hundreds of antennas. With 12 antennas, our BigStation prototype can increase wireless throughput by 6.8 x with a low mean latency of 860μs. While this latency is not yet low enough for the 802.11 MAC, it already satisfies the real-time requirements of many existing wireless standards such as LTE and WCDMA. / 本論文探討了兩種可以利用多個無線用戶同時傳輸時所造成的多用戶干擾的無線通信系統。本文由旨在針對不同的無線網絡結構的兩部分構成：第一部分論述了雙向中繼網絡（TWRN）中卷積編碼的非同步物理層網絡編碼（PNC）的解碼; 第二部分介紹了一種支持實時解碼的可擴展的多用戶多輸入多輸出（MU-MIMO）架構。這兩種系統都利用了無線通信中的多用戶干擾以提高系統性能。在對這兩個系統的探討中，我們都進行了理論分析，並搭建了基於軟件無線電的原型系統。 / 論文的第一部分研究卷積編碼的非同步物理層網絡編碼系統的解碼過程。具體來說，我們提出了一種非同步物理層網絡編碼的分層解碼架構。該架構由三層組成：符號對齊層，碼字對齊層，以及聯合信道解碼網絡編碼（Jt-CNC）解碼層。我們的這種架構能夠處理由多個用戶同時發送信號時造成的相位不同步（相位偏移）和符號到達時間不同步（符號偏移）。這種架構的一個顯著特點是，它可以同時處理分數和整數的符號偏移。對於解碼層，除了Jt-CNC算法，先前提出的各種PNC解碼算法（例如，XOR-CD 和減少狀態的Viterbi算法）也可以應用於我們的解碼架構用來解決符號偏移問題。我們基於置信度傳播理論（BP）的Jt-CNC算法，對於同步PNC是比特差錯率（BER）最優的，對於非同步PNC是接近最優的。除了卷積碼以外，我們進一步將Jt-CNC解碼算法推廣到了所有循環碼。我們的仿真表明，對於同步PNC，Jt-CNC的性能超過先前提出的XOR-CD算法和減少狀態Viterbi算法2 dB。對於相位非同步和符號非同步PNC，Jt-CNC均優於前述兩種算法。重要的是，為了進行真實環境下的無線網絡實驗，我們在基於USRP軟件無線電平台的PNC原型系統上實現了我們的解碼算法。我們的實驗顯示，該Jt-CNC解碼器在真實環境下中表現優越。 / 論文的第二部分介紹了BigStation，一個可擴展的MU-MIMO系統架構。該架構支持帶有幾十甚至上百根天線的大規模MU-MIMO系統的實時信號處理。我們的系統擴展策略是將MU-MIMO信號處理並行化到大量簡單廉價的商用計算單元上。我們的這種設計可以通過成比例地增加計算單元以支持更多的天線。為了減少系統的整體處理延遲，我們根據MU-MIMO信號處理的計算和通信模式，利用分布式流水線把解碼過程並行化。在流水線的各級，我們進一步使用數據分割和計算分割來加速信號處理。作為概念驗證，我們基於商用個人電腦和SORA軟件無線電平台開發了BigStation原型系統。我們的原型使用了15 台個人電腦並且可以支持12 根軟件無線電天線的實時解碼。我們的實驗結果表明，BigStation系統能夠擴展到幾十甚至幾百根天線。當有12 根天線時，我們的BigStation原型系統將無線網絡吞吐量提高了6.8 倍，而平均延遲則低至860 μs。雖然這個延遲對於802.11 的MAC 還不足夠低，但它已滿足了許多現有的無線標准諸如LTE和WCDMA的實時性要求。 / Yang, Qing. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 101-108). / Abstracts also in Chinese. / Title from PDF title page (viewed on 21, December, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

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

by Chung Ling Chi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 74-76). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview --- p.1 / Chapter 1.2 --- Motivation and Proposed Solution --- p.2 / Chapter 1.3 --- Organization of the Thesis --- p.4 / Chapter Chapter 2 --- Background --- p.5 / Chapter 2.1 --- Basics of Transmission Control Protocol --- p.5 / Chapter 2.1.1 --- Slow Start and Congestion Avoidance --- p.5 / Chapter 2.1.2 --- Fast Retransmit and Fast Recovery --- p.7 / Chapter 2.2 --- SACK TCP Mechanism --- p.8 / Chapter 2.2.1 --- SACK-permitted Option during Three-way Handshake --- p.8 / Chapter 2.2.2 --- SACK blocks in SACK Option --- p.9 / Chapter 2.2.3 --- Interpreting the SACK Option using Scoreboard --- p.10 / Chapter 2.2.4 --- Retransmission Strategy --- p.11 / Chapter 2.3 --- TCP Veno Mechanism --- p.13 / Chapter 2.3.1 --- Refined Additive Increase --- p.13 / Chapter 2.3.2 --- Refined Multiplicative Decrease --- p.14 / Chapter Chapter 3 --- SACK TCPVeno --- p.16 / Chapter 3.1 --- Distinguishing between Types of Packet Loss --- p.17 / Chapter 3.2 --- Refined Multiplicative Decrease --- p.21 / Chapter 3.2.1 --- Algorithm --- p.21 / Chapter 3.2.2 --- Recovery in Consecutive packet Losses --- p.22 / Chapter 3.2.3 --- Recovering Multiple Packet Losses within a Single Window --- p.26 / Chapter 3.3 --- Refined Additive Increase --- p.37 / Chapter 3.3.1 --- Algorithm --- p.37 / Chapter 3.3.2 --- Advantages --- p.40 / Chapter 3.4 --- Other Issues --- p.43 / Chapter 3.4.1 --- Two Side Modifications --- p.43 / Chapter Chapter 4 --- Experiments --- p.44 / Chapter 4.1 --- The Network Scenario --- p.44 / Chapter 4.1.1 --- Dummynet --- p.45 / Chapter 4.2 --- Experiment Results --- p.47 / Chapter 4.2.1 --- Single Connection --- p.47 / Chapter 4.2.1.1 --- Congestion Window Evolution --- p.47 / Chapter 4.2.1.2 --- Sending Rate and Throughput Evolution --- p.49 / Chapter 4.2.1.2.1 --- Impact of Packet Loss Rate Due to Lossy Link --- p.49 / Chapter 4.2.1.2.2 --- Impact of Buffering --- p.52 / Chapter 4.2.1.2.3 --- Impact of Propagation Delay --- p.57 / Chapter 4.2.2 --- Multiple Connections --- p.62 / Chapter 4.2.2.1 --- Fairness --- p.62 / Chapter 4.2.2.2 --- Compatibility --- p.67 / Chapter Chapter 5 --- Conclusion --- p.72 / Bibliography --- p.74

Ho Wang Hei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 93-94). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation and Contributions --- p.1 / Chapter 1.1.1 --- Scalability of Network Capacity with Power Control --- p.1 / Chapter 1.1.2 --- Trade-off between network capacity and fairness with Power Control --- p.3 / Chapter 1.2 --- Related Work --- p.4 / Chapter 1.3 --- Organization of the Thesis --- p.6 / Chapter Chapter 2 --- Background --- p.8 / Chapter 2.1 --- Hidden- and Exposed-node Problems --- p.8 / Chapter 2.1.1 --- HN-free Design (HFD) --- p.9 / Chapter 2.1.2 --- Non-Scalable Capacity in 802.11 caused by EN --- p.11 / Chapter 2.2 --- Shortcomings of Minimum-Transmit-Power Approach --- p.13 / Chapter Chapter 3 --- Simultaneous Transmissions Constraints with Power Control --- p.15 / Chapter 3.1 --- Physical-Collision Constraints --- p.16 / Chapter 3.1.1 --- Protocol-Independent Physical-Collision Constraints --- p.17 / Chapter 3.1.2 --- Protocol-Specific Physical-Collision Constraints --- p.17 / Chapter 3.2 --- Protocol-Collision-Prevention Constraints --- p.18 / Chapter 3.2.1 --- Transmitter-Side Carrier-Sensing Constraints --- p.18 / Chapter 3.2.2 --- Receiver-Side Carrier-Sensing Constraints --- p.19 / Chapter Chapter 4 --- Graph Models for Capturing Transmission Constraints and Hidden-node Problems --- p.20 / Chapter 4.1 --- Link-Interference Graph from Physical-Collision Constraints --- p.21 / Chapter 4.2 --- Protocol-Collision-Prevention Graphs --- p.22 / Chapter 4.3 --- Ideal Protocol-Collision-Prevention Graphs --- p.22 / Chapter 4.4 --- Definition of HN and EN and their Investigation using Graph Model --- p.23 / Chapter 4.5 --- Attacking Cases --- p.26 / Chapter Chapter 5 --- Scalability of Network Capacity with Adaptive Power Control --- p.27 / Chapter 5.1 --- Selective Disregard of NAVs (SDN) --- p.27 / Chapter 5.2 --- Scalability of Network Capacity: Analytical Discussion --- p.29 / Chapter 5.3 --- Adaptive Power Control for SDN --- p.31 / Chapter 5.3.1 --- Per-iteration Power Adjustment --- p.32 / Chapter 5.3.2 --- Power Control Scheduling Strategy --- p.35 / Chapter 5.3.3 --- Power Exchange Algorithm --- p.39 / Chapter 5.3.4 --- Comparison of Scheduling Strategies --- p.41 / Chapter 5.4 --- Scalability of Network Capacity: Numerical Results --- p.43 / Chapter Chapter 6 --- Decoupled Adaptive Power Control (DAPC) --- p.45 / Chapter 6.1 --- Per-iteration Power Adjustment --- p.45 / Chapter 6.2 --- Power Exchange Algorithm --- p.47 / Chapter 6.3 --- Implementation of DAPC --- p.48 / Chapter 6.4 --- Deadlock Problem in DAPC --- p.50 / Chapter Chapter 7 --- Progressive-Uniformly-Scaled Power Control (PUSPC): Deadlock-free Design --- p.53 / Chapter 7.1 --- Algorithm of PUSPC --- p.53 / Chapter 7.2 --- Deadlock-free property of PUSPC --- p.60 / Chapter 7.3 --- Deadlock Resolution of DAPC using PUSPC --- p.62 / Chapter Chapter 8 --- Incremental Power Adaptation --- p.65 / Chapter 8.1 --- Incremental Power Adaptation (IPA) --- p.65 / Chapter 8.2 --- Maximum Allowable Power in EPA --- p.68 / Chapter 8.3 --- Numerical Results of IPA --- p.71 / Chapter Chapter 9 --- Numerical Results and the Trade-off between EN and HN --- p.78 / Chapter Chapter 10 --- Conclusion --- p.83 / Appendix I: Proof of the Correct Operation of PE Algorithm for APC for SDN --- p.86 / Appendix II: Proof of the Correct Operation of PE Algorithm for DAPC --- p.89 / Appendix III: Scalability of the Communication Cost of PE Algorithm --- p.91 / Bibliography --- p.93

隋著移動數據網絡的迅速發展，世界各地部署著不同制式的3G，HSPA和LTE網絡，這給移動互聯網應用帶來新的機遇和挑戰。不像他們的對手, 有線網絡，移動數據網絡有較長的延遲，較高的包率，以及急劇波動的頻寬。為了應付這些挑戰，移動無線基站往往配備較大的緩衝區（KBs以至數百多MBs），以吸收短期的頻寬波動，並促進鏈路層重傳。然而，由於大部分互聯網協議，並特別是TCP，全都假設路由器只擁有較小緩衝區，所以在移動網絡的大型緩衝區下，往往導致TCP展現出次優的性能。本論文解決兩個根本性的問題來克服這一項挑戰。首先，我們開發了一種新算法 (SoD）專門來估計網絡的鏈路緩衝區的大小和隊列長度。在今天的3G移動數據網絡，本文以大量網絡數據驅動的模擬結果證明 SoD 表現優於現有的算法，如 Max-min 和 Loss-pair。另外，我們採用 SoD算法來創造新的TCP擁塞控制模塊以解決移動網絡的大型緩衝區以及的頻寬波動問題。這個新的TCP變種，稱為 TCP- QA，在模擬情況以及移動數據網絡下均表現出大大優於現有的TCP變種，包括TCP CUBIC ，TCP Vegas，TCP Westwood，和FAST TCP。 / The rapidly emerging mobile data networks fueled by the world-wide deployment of 3G, HSPA, and LTE networks created new opportunities and challenges for developing mobile Internet applications. Unlike their wired counterpart, mobile data networks are known to exhibit longer delay, higher packet loss rate, and rapidly fluctuating bandwidth. To tackle these challenges mobile radio base stations are often equipped with large buffers (from hundreds of KBs to multi-MBs) to absorb short-term bandwidth fluctuations and to facilitate link-layer retransmissions. However as most Internet protocols in general, and TCP in particular, were designed with the assumption of small router buffer size, the large buffer in mobile networks can and do interact, often negatively, with the Internet protocols, leading to sub-optimal performance. This work tackles two fundamental problems in overcoming this challenge. First, we developed a novel Sum-of-Delays (SoD) algorithm specifically designed to estimate the link buffer size and queue length of bandwidth-varying networks. Extensive trace-driven simulation results showed that SoD outperforms existing algorithms such as max-min and loss-pair by orders of magnitude in today’s 3G mobile data networks. Second, we apply the SoD algorithm to TCP’s congestion control module to incorporate and compensate for the mobile network’s large buffer size. This new TCP variant, called TCP-Queue-length-Adaptive (TCP-QA), substantially outperforms existing TCP variants including TCP CUBIC, TCP Vegas, TCP Westwood, and FAST TCP. / Detailed summary in vernacular field only. / Chan, Chi Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.ii / 摘要 --- p.iii / Acknowledgements --- p.iv / Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background and Related Work --- p.5 / Chapter 2.1 --- Link Buffer Size Estimation --- p.6 / Chapter 2.2 --- Queue Length Estimation --- p.8 / Chapter 2.3 --- Performance over Fixed Networks --- p.10 / Chapter 2.4 --- Performance over Bandwidth-Varying Networks --- p.15 / Chapter Chapter 3 --- Sum-Of-Delay Method --- p.19 / Chapter Chapter 4 --- Performance Evaluation --- p.22 / Chapter 4.1 --- Link Buffer Size Estimation in Fixed Bandwidth Networks --- p.23 / Chapter 4.2 --- Link Buffer Size Estimation in Variable Bandwidth Networks --- p.25 / Chapter 4.3 --- Queue Length Estimation in Fixed Bandwidth Networks --- p.28 / Chapter 4.4 --- Queue Length Estimation in Variable Bandwidth Networks --- p.31 / Chapter 4.5 --- Convergence --- p.34 / Chapter 4.6 --- Limitations in Passive Estimation --- p.40 / Chapter Chapter 5 --- Impact of Competing Traffic --- p.42 / Chapter 5.1 --- Simulation Setup --- p.42 / Chapter 5.2 --- Link Buffer Size Estimation --- p.44 / Chapter 5.3 --- Queue Length Estimation --- p.50 / Chapter 5.4 --- Discussions --- p.54 / Chapter Chapter 6 --- TCP-Queue-Length-Adaptive (TCP-QA) --- p.56 / Chapter 6.1 --- Challenges in Mobile Networks --- p.57 / Chapter 6.2 --- Queue-Length-Adaptive Congestion Control --- p.59 / Chapter 6.3 --- Performance Comparisons --- p.65 / Chapter Chapter 7 --- Summary and Future Work --- p.76 / Bibliography --- p.78