The growing widespread use of data communication networks has led to increased reliance on the availability of network resources. The network itself is a critical resource which must be managed in a timely and effective manner. In order to manage the network effectively, the network manager must have powerful tools that present network information in a fast and logical way. The work presented here is the design and development of a network management tool for Sytek broadband networks. The Sytek Network Management Package (SNMP) incorporates a commercial database management system, Rbase System V, and menu oriented management functions for the University of Arizona Sytek broadband networks. The SNMP is written in C and executes on a PC connected to the Sytek network. The SNMP allows a network manager to manage both the Sytek LocalNet 20 and System 2000 networks.

With the unprecedented growth of the communication industry that the world is experiencing, the demand from rural inhabitants for high quality communications at an economically affordable cost is growing. However, rural areas are rather restricted from deploying communication services due to the rough natural environment, and the shortage of rudimentary communication facilities and technical personnel. Appropriate models for building rural wireless networks and a concomitant simulation environment are, therefore, expected to enable the construction of technologically-optimal and economically-efficient networks in specified rural areas.<br /> <br /> The research has set up two independent models, one for the economic need and the other for the technical need of building networks in rural areas. One model was the Impact of Telecommunications Model, which disclosed the importance of building a wireless network in specified rural areas by choosing an economic parameter to forecast the profitability of the network. The other was the Service Model, which collected primitive data from given rural areas and abstracted these data by flowing them through four technical layers to form the predicted technical wireless network. Both of the models had been applied to real-world cases to demonstrate how to use them.<br /> <br /> A simulation environment was finally designed and implemented to realize the above two models for the sake of instantiation. This environment could simulate the specified rural network by constructing a wireless network on the invented areas and evaluating its quality and economic efficiency. It was written in Scilab simulation language, which was an open source.

This thesis describes the implementation of the Flexible AC Transmission Systems (FACTS) devices to develop a market-based approach to the problem of transmission congestion management in a Balancing Market. The causes, remedies and pricing methods of transmission congestion are briefly reviewed. Balancing Market exists in markets in which most of the trading is done via decentralized bilateral contracts. In these markets only final adjustments necessary to ensure secure system operation is carried out at a centralized Balancing Market. Each market player can participate in the Balancing Market by submitting offers and bids to increase and decrease its initially submitted active generation output. In this research a method is proposed to reduce costs associated with congestion re-dispatch in a Balancing Market by optimal placement of FACTS devices, and in particular Thyristor Controlled Phase Shifter Transformers (TCPST). The proposed technique is applicable to both Mixed Integer Linear Programming (MILP) and Mixed Integer Non-Linear Programming (MINLP). In the MILP a power system network is represented by a simplified DC power flow under a MILP structure and the Market participants' offers and bids are also represented by linear models. Results show that applications of FACTS devices can significantly reduce costs of congestion re-dispatch. The application of the method based on the MINLP creates a nonlinear and non-convex AC OPF problem that might be trapped in local sub-optima solutions. The reliability of the solution that determines the optimal placement of FACTS devices is an important issue and is carried out by investigation of alternative solvers. The behavior of the MINLP solvers is presented and finally the best solvers for this particular optimization problem are introduced. The application of DC OPF is very common in industry. The accuracy of the DC OPF results is investigated and a comparison between the DC and AC OPF is presented.

An evaluation of the performance of a SONET management system was conducted to better understand its management capabilities due to network disruptions in the presence of a traffic load. This study analyzed the Cisco Transport Manager (CTM) which manages a testbed of four Cisco ONS15454 optical systems. The network was injected with HTTP and FTP traffic generated by the Spirent Smartbits system installed with TeraMetrics Gigabit Ethernet modules and load calibration configured by the Spirent Avalanche software. To simulate real-world situations, power disruptions were applied to the network while collecting CTM traffic using Ethereal. Using queuing analysis, the arrival rates and service times were computed for various CTM traffic components and a utilization for 2500 network elements (NE) extrapolated. Self-similarity analysis was performed and the logvariance was plotted to extract the Hurst values. Finally, the results and findings were compared with prior research for loading and no-loading cases. The results of this study are useful in determining the maximum number of network elements manageable in a disruptive environment. Final analysis on the effects of link utilization on the queue size showed that the CTM is able to manage more NEs when the network is disrupted. Unfortunately, managing more NEs increases the queue size even though the utilization was found to be 0.83 for 5450 NEs. Consequently, in order to maintain a moderate queue size, the maximum number of NEs manageable was found to be 2495. This value is close to CISCO's specification of a CTM server managing a maximum of 2500 NEs.

在通信網絡中，當我們要傳輸私密信息時，可能有一些非法用戶希望能獲取這些私密信息。在這裡，我們分別稱這個網絡模型模型和非法用戶為竊聽網絡和竊聽者。在本文中，我們希望在某些限制條件下，設計一種編碼來抵抗竊聽者。 / 為了保護私密信息，我們不會在網絡中直接傳遞它，而是傳遞一些加密過的信息，即密文。現在通行的一個方法是:用一些隨機生成的密碼給這些私密信息加密。即使竊聽者能獲取我傳遞的密文，也無法知道確切的私密信息。在本中文，我們考慮了兩種安全級別:完美安全和非完美安全。在完美安全中，密文和私密信息從統計上講是完全獨立的，也就是說竊聽者得到的是一些安全隨機的信息。在非完美安全中，竊聽者被允許獲得一部私密信息。這部分私密信息，是由竊聽者的信息模糊度來衡量的。如果信息模糊度的大小等於私密信息，那麼非完美安全等價於完美安全。 / 本文的重點在於如何以最小的代價保護私密的信息。我們用Ç =(V ， Σ) 來表示通信網絡。其中， ν是所有節點的集合，Σ 是所有信道的集合。一個竊聽者能夠監聽某些信道上的信息。在我們的模型中，每個竊聽者竊聽的信道的集合是固定的。所有這些被竊聽的信道構成了一個竊聽集。我們把所有竊聽集的集合記作A 。 / 在竊聽網絡中，如果考慮完美安全，現有的工作表明，當A是由所有大小為r 的 Σ的子集構成的時候，存在一個線性網絡編碼，在下面兩個標準下是最優的: / 1)私 密信息的長度最大化; / 2) 隨即密鑰的長度最小化。但是，當A 由任意的5 的子集構成的時候，關於性能界的結果很少。 / 在本文的第一部分中，我們著手研究這個方面的問題並得到了以下結論: / 1) 對於私密信息的長度，我們獲得了一個上界並提供了一個多項式算法去計算它。 / 2)對於隨機密鑰的長度，我們從分教覆蓋和分數包裝的為度進行分析，分別獲得了兩個下界。這兩個下界， 我們證明了他們之間存在一個對偶性。接下來，我們討論暸如何去計算這個下界，我們設計了一個暴力算法和一個關於 / 接下來，我們更關注於點對點系統中的非完美安全問題。我們推廣了一個經典的安全模型: II型竊聽信道。在經典的II型竊聽信道模型中，私密信息是通過若干端到端的信道發送的。在這個模型中，假設每個竊聽者只能竊聽A 中的一個竊聽集，其中A是由所有大小為r的信道集構成。在這裡，保護私密信息的策略也和竊聽網絡中一樣。更確切的，我們可以找到一個關於隨機密碼長度的下界，而且這個下界可以通過一個群編碼獲得。我們在推廣中假設A的構成是任意的，每個竊聽者被允許獲得一定的私密信息。在這個模型下，我們定義了關於私密信息，隨機密碼，每個竊聽者的信息模糊度的一個元組。關於這個元組，我們獲得了一個緊的區域。這個區域可以看成是竊聽網絡上關於割集的一個界。 / In a communication network on which a secure message is transmitted, there may exist illegal users who want to obtain information about the message. Here we refer to the network and those illegal users as the wiretap network and wiretappers, respectively. In secure network coding, we aim to find a network code which can protect the message against the wiretappers under certain constraints. / To protect the message we transmit a ciphertext which is a mixture of the message and a private random key, through the channels in the network. In this work, we consider two kinds of security levels: perfect security and imperfect security. In perfect security, the cipher-text is statistically independent of the message, i.e., the wiretapper can obtain only some randomly generated messages. While in imperfect security, the wiretapper can obtain partial information about the message which is measured by the wiretapper's equivocation. If the wiretapper's equivocation is equal to the message size, then the imperfect security reduces to perfect security. / The focus of our work is to protect the message at the minimum cost, which is measured by the size the key and the bandwidth of the network. Here we denote the network by Ç = (V; Σ), where V is the set of nodes and Σ is the set of point-to-point channels in the network. A wiretapper may access the information transmitted on a certain subset of Σ. In our model, it is assumed that the wiretapper can access any one but not more than one set of channels, called a wiretap set, out of a collection A of all possible wiretap sets. / In a wiretap network, if perfect security is required, existing works show that when A consists of all the r -subsets of Σ (i.e. subsets of size r), there exists a linear network code, which is optimal according to the following two criteria: / i) the size of the message is maximum; / ii) the size of random key is minimum. / But when A consists of arbitrary subsets of Σ, very little is known about the fundamental performance limit. / In the first part of our work, we investigate this problem and obtain some results on the above fundamental performance limits. In this work, we adopt the convention that the size of a random variable X is measured by its entropy H(X). / 1) For the size of the message, we derive an upper bound on H(M) and provide a polynomial algorithm to compute it. / 2) For the size of the key, we analyze it from the aspects of fractional covering and fractional packing, respectively, by which we obtain two bounds on H(K) and we prove the duality between them. n520 Then we discuss the algorithms to compute the lower bound, in- cluding a brute force algorithm and a polynomial algorithm in terms of / In the remaining part, we are largely concerned with imperfect security in a point-to-point communication system, where a classical security model referred to as the wire-tap channel II is generalized by introducing imperfect security. In wire-tap channel II, information is sent to the receiver through a set of point-to-point channels. It is assumed that the wiretapper can access any one but not more than one set in A which consists of all the subsets of the channel set with size r. The strategy to protect the private message is the same as that in the wiretap network. Specifically, a lower bound on the size of the key which can be attained by a group code was proved. In our extension, A is arbitrary and from each wiretap set in A, the wiretapper can obtain some partial information about the message. Under these settings, we define an achievable rate tuple in terms of the message, the key and the wiretapper's equivocation, and prove a tight rate region of the rate tuples. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Cheng, Fan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 103-108). / 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.ii / Acknowledgement --- p.ix / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Network Coding --- p.2 / Chapter 1.2 --- Secure Network Coding --- p.3 / Chapter 1.2.1 --- Perfect Secrecy System --- p.3 / Chapter 1.2.2 --- Imperfect Secrecy System --- p.8 / Chapter 1.3 --- Thesis Organization --- p.10 / Chapter 2 --- Basic Concepts and Tools --- p.13 / Chapter 2.1 --- Basic Concepts in Information Theory --- p.14 / Chapter 2.1.1 --- A Universal Approach for Bounds --- p.17 / Chapter 2.2 --- Information Inequalities for Joint Entropy --- p.18 / Chapter 2.2.1 --- Han's Inequalities --- p.18 / Chapter 2.2.2 --- Madiman-Tetali's Inequalities --- p.19 / Chapter 3 --- Performance Bounds on a Wiretap Network --- p.23 / Chapter 3.1 --- Problem Formulation --- p.24 / Chapter 3.1.1 --- Admissible Code --- p.25 / Chapter 3.1.2 --- Performance Measures of an Admissible Code . --- p.27 / Chapter 3.2 --- Related Works and Our Contribution --- p.27 / Chapter 3.3 --- Blocking Sets and Wiretap Sets --- p.29 / Chapter 3.4 --- An Upper Bound on the Message Size --- p.32 / Chapter 3.5 --- The Fractional Packing Bound --- p.34 / Chapter 3.6 --- An Alternative Bound --- p.37 / Chapter 3.7 --- A Duality Result --- p.38 / Chapter 3.8 --- Some Properties about the Lower Bound --- p.42 / Chapter 3.9 --- Algorithms for Computing the Lower Bound --- p.44 / Chapter 3.9.1 --- A Brute Force Algorithm --- p.44 / Chapter 3.9.2 --- A Polynomial Algorithm --- p.45 / Chapter 3.10 --- Tightness of the Lower Bound --- p.50 / Chapter 3.10.1 --- When the Best Lower bound is Zero --- p.52 / Chapter 3.10.2 --- Point-to-Point Communication System --- p.52 / Chapter 4 --- Imperfect Secrecy in Wire-tap Channel II --- p.63 / Chapter 4.1 --- Problem Formulation and Related Result --- p.64 / Chapter 4.1.1 --- Problem Formulation --- p.64 / Chapter 4.1.2 --- Related Result --- p.67 / Chapter 4.2 --- Rate Region of the Rate Tuple --- p.70 / Chapter 4.3 --- A Subregion of the Rate Region --- p.71 / Chapter 4.3.1 --- Converse --- p.72 / Chapter 4.3.2 --- Achievability --- p.76 / Chapter 4.4 --- General Rate Region --- p.85 / Chapter 4.4.1 --- Converse --- p.86 / Chapter 4.4.2 --- Achievability --- p.88 / Chapter 5 --- Conclusion --- p.91 / Chapter A --- Some Related Results --- p.97 / Chapter A.1 --- Definitions and Theorems in Linear Programming --- p.98 / Chapter A.2 --- An Equivalent Lower Bound --- p.101 / Bibliography --- p.103

本論文研究非同步物理層網絡編碼(PNC) 系統。本文由兩部分構成。在第一部分中，我們提出了一個物理層網絡編碼整體框架，來處理碼元和載波相位異步問題。基於上述框架，本文證明了非同步的物理層網絡編碼可以提高系統性能。本文的第一個重要貢獻在於，不同於以往的主要理解，我們發現在採取適當的解碼方案後，非同步問題並不會降低系統性能。在第二部分中，我們通過理論和實際系統展示了物理層網絡編碼的原型機。特別是，我們採用正交頻分複用(OFDM) 系統，來解決時域的碼元非同步問題。本文的第二個重要貢獻在於，該工作是自五年前物理層網絡編碼理論提出之後，第一個真正的應用系統。 / 第一部分:在本文的第一部分里， 我們研究物理層網絡編碼系統中存在的碼元和載波相位異步問題。在物理層網絡編碼系統中，一個關鍵的問題是，接收機如何處理不同發射機發送的信號之間存在的不同步問題。也就是說，不同的發射機發送的信號達到接收機的時候，存在碼元移位的相位相對偏差。另一個關鍵的問題是，如何將信道編碼投衛和物理層網絡編碼相結合，來實現可靠的信息傳輸。本文研究上迷兩個重要問題，並且有如下四個主要貢獻1)我們提出並且分析了一個基於置信度傳遞(BP) 的物理層網絡編碼整體框架。該框架可以高效地解決碼元和相位異步問題，並且適用於有信道編碼的系統。2) 對於未經信道編碼的物理層網絡編碼系統， 在BPSK 和QPSK 調製下，我們的BP 算法可以顯著地降低非同步帶來的系統性能損失。3) 對於未經信道編碼的物理層網絡編碼系統，在相對碼元偏移為半碼元長度時，我們的BP 算法可以有效地將相位異步帶來的系統性能損失從6dB 降低到不足1dB。4) 對於經過信道編碼的物理層網絡編碼系統，在應用BP 算法後，異步系統性能優於同步系統。最後，在經過信道編碼的物理層網絡編碼系統中， 我們發現由各種碼元和相位異步組合產生的性能損失不超過ldB。上述貢獻3) 說明，如果我們可以精確地控制信號接收時間，那麼人為產生半個碼元偏移會給未經信道編碼的物理層網絡編碼系統帶來好處。上述貢獻4）說明，在採用了信道編碼後，碼元和相位非同步， 將不再是物理層網絡編碼一個主要擔憂的問題。 / 第二部分:在本文的第二部分里，我們展示了第一個物理層網絡編碼原型機的實現過程，這個原型機可以應用於雙向中繼網絡(TWRC) 。截至目前，僅有簡化的物理層網絡編碼系統，稱作模擬網絡編碼(ANC) 投街，被成功實現。模擬網絡編碼的好處在於它的簡單和容易實現;而它的缺點則是，中繼節點在放大信號的同時也放大了噪聲，因而帶來系統性能損失。在物理層網絡編碼系統中，中繼節點只有實現異或(XOR) 運算或者是去噪聲(denoising) PNC 映射，才能能顯著地提高系統性能。但是，要實現上途的XOR PNC 系統我們需要面對很多挑戰。比如， 中繼節點必須能夠處理接收信號的碼元和相位的異步問題，並且可以在解碼前實現信道估計。本文研究頻域物理曾網絡編碼實現，命名為FPNC，來解決上述問題。FPNC 基於OFDM 調製方式實現。在FPNC 系統中， XOR 映射發生在每一個OFDM 碼元的各個子載波上，而不是在時域的採樣點上。我們在通用軟件無線電設備(USRP) 平臺上實現了上述FPNC 系統。需要強調的是，我們的FPNC 實現僅需稍微修改現有的802. lla/g OFDM系統物理層前導序列。在循環前綴(CP) 的幫助下，碼元異步和多經效應都可以被相應地去除。實驗結果顯示，對於經過信道編碼的和未經信道編碼的FPNC 系統，碼元同步系統和碼元異步系統性能沒有區別。 / This thesis investigates asynchronous physical-layer network coding (PNC) systems. It consists of two parts, each part contains a major contribution within the domain of PNC research. The first part presents a theoretical framework for dealing with phase and symbol asynchronies in PNC. We show how this framework can turn asynchronies to an advantage to boost system performance. The major contribution here is the insight that, contrary to the prior belief, asynchrony is not detrimental to the performance of PNC systems with the right methods to deal with it. The second part reports the first PNC implementation prototype. In particular, we demonstrate both in theory and practice that using OFDM in the PNC system can remove the symbol asynchrony in the time domain. The major contribution here is that this is the first experimental feasibility demonstration of the PNC concept since it was conceived theoretically five years ago. / Part I: In the first part of this thesis, we study the phase and symbol asynchrony problems in PNC. A key issue in physical-layer network coding (PNC) is how to deal with the asynchrony between signals transmitted by multiple transmitters. That is, symbols transmitted by different transmitters could arrive at the receiver with symbol misalignment as well as relative carrier-phase offset. A second important issue is how to integrate channel coding with PNC to achieve reliable communication. This thesis investigates these two issues and makes the following contributions: 1) We propose and investigate a general framework for decoding at the receiver based on belief propagation (BP). The framework can effectively deal with symbol and phase asynchronies while incorporating channel coding at the same time. 2) For non-channelcoded PNC, we show that for BPSK and QPSK modulations, our BP method can significantly reduce the asynchrony penalties compared with prior methods. 3) For non-channel-coded PNC, with half symbol offset between the transmitters, our BP method can drastically reduce the performance penalty due to phase asynchrony, from more than 6 dB to no more than 1 dB. 4) For channel-coded PNC, with our BP method, both symbol and phase asynchronies actually improve the system performance compared with the perfectly synchronous case. Furthermore, the performance spread due to different combinations of symbol and phase offsets between the transmitters in channel-coded PNC is only around 1 dB. The implication of 3) is that if we could control the symbol arrival times at the receiver, it would be advantageous to deliberately introduce a half symbol offset in non-channel-coded PNC. The implication of 4) is that when channel coding is used, symbol and phase asynchronies are not major performance concerns in PNC. / Part II: In the second part of this thesis, we present the first implementaii tion of a two-way relay network based on the principle of physical-layer network coding. To date, only a simplified version of physical-layer network coding (PNC) method, called analog network coding (ANC), has been successfully implemented. The advantage of ANC is that it is simple to implement; the disadvantage, on the other hand, is that the relay amplifies the noise along with the signal before forwarding the signal. PNC systems in which the relay performs XOR or other denoising PNC mappings of the received signal have the potential for significantly better performance. However, the implementation of such PNC systems poses many challenges. For example, the relay must be able to deal with symbol and carrier-phase asynchronies of the simultaneous signals received from the two end nodes, and the relay must perform channel estimation before detecting the signals. We investigate a PNC implementation in the frequency domain, referred to as FPNC, to tackle these challenges. FPNC is based on OFDM. In FPNC, XOR mapping is performed on the OFDM samples in each subcarrier rather than on the samples in the time domain. We implement FPNC on the universal soft radio peripheral (USRP) platform. Our implementation requires only moderate modifications of the packet preamble design of 802.11a/g OFDM PHY. With the help of the cyclic prefix (CP) in OFDM, symbol asynchrony and the multi-path fading effects can be dealt with in a similar fashion. Our experimental results show that symbol-synchronous and symbol-asynchronous FPNC have essentially the same BER performance, for both channel-coded and non-channelcoded FPNC. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Lu, Lu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 123-128). / 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.viii / Publications --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Asynchrony Problems in Physical-Layer Network Coding --- p.3 / Chapter 1.2 --- Implementation of Physical-Layer Network Coding --- p.4 / Chapter 1.3 --- Outline of the Thesis --- p.5 / Chapter 2 --- Asynchronous PNC --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Related Work --- p.10 / Chapter 2.2.1 --- Classification --- p.11 / Chapter 2.2.2 --- Non-channel-coded PNC --- p.11 / Chapter 2.2.3 --- Channel-coded PNC --- p.12 / Chapter 2.3 --- System Model --- p.14 / Chapter 2.4 --- Non-channel-coded PNC --- p.19 / Chapter 2.4.1 --- Synchronous Non-channel-coded PNC --- p.19 / Chapter 2.4.2 --- BP-UPNC: A Belief Propagation based Non-channelcoded PNC Scheme --- p.20 / Chapter 2.4.3 --- Numerical Results --- p.27 / Chapter 2.4.4 --- Diversity and Certainty Propagation --- p.29 / Chapter 2.5 --- Channel-coded PNC --- p.33 / Chapter 2.5.1 --- Channel-decoding and Network-Coding (CNC) Process --- p.34 / Chapter 2.5.2 --- Jt-CNC: A Joint Channel-decoding and Network-Coding Scheme --- p.36 / Chapter 2.5.3 --- XOR-CD: A Disjoint Channel-decoding and Network-Coding Scheme --- p.40 / Chapter 2.5.4 --- Numerical Results --- p.43 / Chapter 2.5.5 --- Shannon Limits for Gaussian Channel --- p.48 / Chapter 2.5.6 --- Diversity and Certainty Propagation in Jt-CNC --- p.50 / Chapter 2.6 --- Conclusions --- p.51 / Chapter 3 --- Implementation of Asynchronous PNC --- p.54 / Chapter 3.1 --- Introduction --- p.54 / Chapter 3.1.1 --- Challenges --- p.56 / Chapter 3.2 --- Effect of Delay Asynchrony in Frequency Domain --- p.60 / Chapter 3.2.1 --- Effective Discrete-time Channel Gains --- p.60 / Chapter 3.2.2 --- Delay-Spread-Within-CP Requirement --- p.63 / Chapter 3.3 --- FPNC Frame Format --- p.66 / Chapter 3.3.1 --- FPNC Short Training Symbol --- p.68 / Chapter 3.3.2 --- FPNC Long Training Symbol --- p.69 / Chapter 3.3.3 --- FPNC Pilot --- p.70 / Chapter 3.4 --- Addressing Key Implementation Challenges in FPNC --- p.71 / Chapter 3.4.1 --- FPNC Carrier Frequency Offset (CFO) Compensation --- p.71 / Chapter 3.4.2 --- FPNC Channel Estimation --- p.75 / Chapter 3.4.3 --- FPNC Mapping --- p.76 / Chapter 3.5 --- Experimental Results --- p.80 / Chapter 3.5.1 --- FPNC Implementation over Software Radio Platform --- p.80 / Chapter 3.5.2 --- Experimental Results --- p.81 / Chapter 3.6 --- Conclusions --- p.88 / Chapter 4 --- Conclusions and Future Work --- p.90 / Chapter 4.1 --- Conclusions --- p.90 / Chapter 4.2 --- Future Work --- p.92 / Chapter 4.2.1 --- Asynchronous PNC --- p.93 / Chapter 4.2.2 --- Implementation of PNC --- p.94 / Chapter A --- Message Update Steps of Jt-CNC --- p.97 / Chapter A.1 --- Step 1. Updates of messages below code nodes X: --- p.98 / Chapter A.2 --- Step 2. Updates of upward messages into check nodes C: --- p.98 / Chapter A.3 --- Step 3. Update of upward messages into the source nodes S: --- p.99 / Chapter A.4 --- Step 4. Update of downward messages into the check nodes C: --- p.100 / Chapter A.5 --- Step 5. Updates of downward messages into code nodes X: --- p.100 / Chapter B --- Channel-coded Collision Resolution --- p.101 / Chapter B.1 --- Introduction --- p.101 / Chapter B.2 --- System Model --- p.103 / Chapter B.3 --- C-CRESM --- p.105 / Chapter B.3.1 --- Review of RA code --- p.106 / Chapter B.3.2 --- Virtual Tanner Graph for RA coded CRESM --- p.107 / Chapter B.3.3 --- Definitions --- p.108 / Chapter B.3.4 --- Message Update Rules --- p.109 / Chapter B.4 --- Comparison of Different Methods --- p.115 / Chapter B.4.1 --- Independent Multiuser Detection and Channel Decoding (Independent MU-CD) --- p.116 / Chapter B.4.2 --- Turbo-SIC --- p.117 / Chapter B.4.3 --- Channel-coded CRESM (C-CRESM) --- p.118 / Chapter B.5 --- Simulation Results --- p.119 / Chapter B.6 --- Conclusion --- p.121 / Bibliography --- p.123

OFS provisions bandwidth in the granularity of one wavelength. With such a coarse granularity, most applications including video download, HDTV, 3D movie, and 3D TV etc. will have very short flow sizes, in the order of seconds or even sub-second, which brings challenges to the utilization efficiency of bandwidth capacity. In this thesis we study the performance of OFS for short flows. The constraint of network resources is investigated. The effect of destination and path blocking is studied. A distributed scheduling protocol called Multi-Destination Control Protocol (MDCP) is proposed to deal with such constraint. Both single wavelength and multi-wavelength configurations are studied and characterized. Simulation results demonstrate that MDCPcan improve the OFS network throughput significantly and can be as much as eighty to one hundred percent for a single-wavelength OFS network. Even for an OFS network with four wavelengths, the throughput improvement can still approach 40%. / The Internet traffic has been growing tremendously. China Telecom predicts that the compound annual growth rate of IP traffic for the next decade is at 56% - 80% and the backbone capacity will grow by another two orders of magnitudes. Furthermore, the power consumption incurred by the next generation of huge electronic IP packet switching routers in the backbone will exceed gigawatts. In view of the grave enviromnental concerns, there is a great need for a more efficient way of transporting and switching the bits. This thesis investigates a new all-optical networking technology called optical flow switching (OFS). OFS bypasses electronic routers, and provides end-to-end transparent connections, thus taking full advantage of the enormous transmission capacity of optical networks and enjoying the extremely low error rate of transparent data transmission. The most important point about OFS is that it reduces the electrical power consumption by off-loading the huge electronic routers, which could be a major constraint for future Internet growth. Unlike many other exotic all-optical switching technologies, OFS is immediately deployable using the current optical technologies, Therefore OFS is very attractive for the next generation optical networks. / Qian, Zhengfeng. / Adviser: Kwok-wai Cheung. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 113-118). / 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.

Chromatic dispersion (CD) is due to the fact that light with different frequencies travel at different speeds inside fiber. It causes pulse spreading and intersymbol interference (ISI) which would severely degrade the transmission performance. By feeding a signal into a fiber loop which consists of a high-birefringence (Hi-Bi) fiber, we experimentally show that the amount of experienced dispersion can be deduced from the RF power at a specific selected frequency which is determined by the length of the Hi-Bi fiber. Experimental results show that this technique can provide high monitoring resolution and dynamic range. / Polarization mode dispersion (PMD) splits an optical pulse into two orthogonally polarized pulses traveling along the fiber at different speeds, causing crosstalk and ISI. The third part of the thesis demonstrates two different PMD monitoring schemes. The first one is based on the analysis of frequency-resolved state-of-polarization (SOP) rotation, with signal spectrum broadened by self-phase modulation (SPM) effect. Experimental results show that the use of broadened signal spectrum induced by SPM not only relaxes the filter requirement and reduces the computational complexity, but also improves the estimation accuracy, and extends the monitoring range of the pulsewidth. The second one is based on the delay-tap asynchronous waveform sampling technique. By examining the statistical distribution of the measured scatter plot, unambiguous PMD measurement range up to 50% of signal bit-period is demonstrated. / The final part of the thesis focuses on the monitoring of alignment status between the pulse carver and data modulator in an optical system. We again employ the two-tap asynchronous sampling technique to perform such kind of monitoring in RZ-OOK transmission system. Experimental results show that both the misalignment direction and magnitude can be successfully determined. Besides, we propose and experimentally demonstrate the use of off-center optical filtering technique to capture the amount of spectrum broadening induced by the misalignment between the pulse-carver and the data modulator in RZ-DPSK transmission system. The same technique was also applied to monitor the synchronization between the old and the new data in synchronized phase re-modulation (SPRM) system. / The tremendous increase of data traffic in the worldwide Internet has driven the rapid development of optical networks to migrate from numerous point-to-point links towards meshed, transparent optical networks with dynamically routed light paths. This increases the need for appropriate network supervision methods. In view of this, optical performance monitoring (OPM) has emerged as an indispensable element for the quality assurance of an optical network. This thesis is devoted to the proposal of several new and accurate techniques to monitor different optical impairments so as to enhance proper network management. / When the optical signal is carried on fiber links with optical amplifiers, the accumulated amplified spontaneous emission (ASE) noise will result in erroneous detection of the received signals. The first part of the thesis presents a novel, simple, and robust in-band optical signal to noise ratio (OSNR) monitoring technique using phase modulator embedded fiber loop mirror (PM-FLM). This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The robustness against polarization mode dispersion, chromatic dispersion, bit-rate, and partially polarized noise is experimentally demonstrated. / Ku, Yuen Ching. / "August 2007." / Adviser: Chan Chun-Kit. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1208. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 109-120). / 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.

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Orientador: Antonio Padilha Feltrin / Banca: Marcos Julio Rider Flores / Banca: Delberis Araujo Lima / Resumo: O ambiente competitivo motivado pela liberalização da indústria de fornecimento de energia elétrica muitas vezes conduz à ocorrência de sobrecargas no sistema de transmissão, afetando a segurança e a economia durante a operação dos sistemas de potência. Um novo procedimento para aliviar sobrecargas, proposto na literatura, é o redespacho de reativos. Por outro lado, a conexão de geradores distribuídos nos sistemas de transmissão, equipados com sofisticados controles para o fornecimento de potência reativa, cria a possibilidade de contar com novas fontes de potência reativa nos sistemas elétricos de potência. Neste trabalho, avaliou-se a aplicação do redespacho de reativos como procedimento para o alívio de sobrecargas, considerando a utilização da capacidade de fornecimento de suporte de reativos por parte das unidades de geração distribuída conectadas nas redes de transmissão. Para verificar o potencial que a geração distribuída teria no alívio de sobrecargas foram utilizados modelos de sensibilidade e de programação linear, um algoritmo de fluxo de potência AC convencional com controles de tensão e conceitos de solução da teoria de jogos cooperativos. Simulações, desenvolvidas para estudar os aspectos técnicos e econômicos da utilização destas tecnologias na resolução de sobrecargas, foram efetuadas em cenários que consideraram a inserção de geração distribuída e ocorrências de sobrecargas no sistema teste de 118 barras do IEEE. Os resultados permitem verificar que os suportes reativos fornecidos por geradores distribuídos podem ser empregados tanto no alívio quanto na eliminação de sobrecargas, especialmente quando existe falta de equipamentos com capacidade para controlar o fornecimento de potência reativa nos sistemas de potência / Abstract: The competitive environment defined by the liberalization of the electricity industry sometimes causes overloads on the transmission system, affecting the safety and economy during the operation of power systems. A procedure proposed in the literature for solving this problem is the reactive redispatch. On the other hand the connection of distributed generators equipped with sophisticated controls for the supply of reactive power creates power in electric the possibility power systems.This of having new work sources evaluated the of reactive application of reactive redispatch as a procedure to overloads relief, considering the capacity of distributed generation units connected in transmission networks to provide reactive power suport. To verify the potential of distributed generation to overloads relief a sensitivity model, linear programming, a power flow algorithm and solution concepts of cooperative game theory were used. The simulations developed to study the technical and economic aspects of using these technologies, in overloads relief were carried out in scenarios that consider the connection of distributed generation and the occurrences of overloads in the IEEE 118 test bus system. Results showed that the reactive support provided by distributed generators can be employed both in relief and in the elimination of overload, especially when there is lack of equipment for the control of reactive power in power systems / Mestre