Transmit diversity usually employs multiple antennas at the transmitter. However, many wireless devices such as mobile cellphones, Personal Digital Assistants (PDAs), just to name a few, are limited by size, hardware complexity, power and other constraints to just one antenna. A new paradigm called cooperative communication which allows single antenna mobiles in a multi-user scenario to share their antennas has been proposed lately. This multi-user configuration generates a virtual Multiple-Input Multiple-Output system, leading to transmit diversity. The basic approach to cooperation is for two single-antenna users to use each other's antenna as a relay in which each of the users achieves diversity. Previous cooperative signaling methods encompass diverse forms of repetition of the data transmitted by the partner to the destination. A new scheme called coded cooperation [15] which integrates user cooperation with channel coding has also been proposed. This method maintains the same code rate, bandwidth and transmit power as a similar non-cooperative system, but performs much better than previous signaling methods [13], [14] under various inter-user channel qualities. This dissertation first discusses the coded cooperation framework that has been proposed lately [19], coded cooperation with Repeat Convolutional Punctured Codes (RCPC) codes and then investigates the application of turbo codes in coded cooperation. In this dissertation we propose two new cooperative diversity schemes which are the Repeat-Punctured Turbo Coded cooperation and coded cooperation using a Modified Repeat-Punctured Turbo Codes. Prior to that, Repeat-Punctured Turbo codes are introduced. We characterize the performance of the two new schemes by developing the analytical bounds for bit error rate, which is confirmed by computer simulations. Finally, the turbo coded cooperation using the Forced Symbol Method (FSM) is presented and validated through computer simulations under various inter-user Signal-to-Noise Ratios (SNRs). / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2008.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24389号 / 理博第4888号 / 新制||理||1699(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 玉川 安騎男, 教授 並河 良典, 教授 望月 新一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The objective of this thesis is to improve the performance of real-time communication overa wireless channel, by means of specifically tailored channel coding. The deadlinedependent coding (DDC) communication protocol presented here lets the timeliness and thereliability of the delivered information constitute quality of service (QoS) parametersrequested by the application. The values of these QoS parameters are transformed intoactions taken by the link layer protocol in terms of adaptive coding strategies.Incremental redundancy hybrid automatic repeat request (IR-HARQ) schemes usingrate compatible punctured codes are appealing since no repetition of previously transmittedbits is made. Typically, IR-HARQ schemes treat the packet lengths as fixed and maximizethe throughput by optimizing the puncturing pattern, i.e. the order in which the coded bitsare transmitted. In contrast, we define an IR strategy as the maximum number of allowedtransmissions and the number of code bits to include in each transmission. An approach isthen suggested to find the optimal IR strategy that maximizes the average code rate, i.e., theoptimal partitioning of n-kparity bits over at most M transmissions, assuming a givenpuncturing pattern. Concatenated coding used in IR-HARQ schemes provides a new arrayof possibilities for adaptability in terms of decoding complexity and communication timeversus reliability. Hence, critical reliability and timing constraints can be readily evaluatedas a function of available system resources. This in turn enables quantifiable QoS and thusnegotiable QoS. Multiple concatenated single parity check codes are chosen as examplecodes due to their very low decoding complexity. Specific puncturing patterns for thesecomponent codes are obtained using union bounds based on uniform interleavers. Thepuncturing pattern that has the best performance in terms of frame error rate (FER) at a lowsignal-to-noise ratio (SNR) is chosen. Further, using extrinsic information transfer (EXIT)analysis, rate compatible puncturing ratios for the constituent component code are found.The puncturing ratios are chosen to minimize the SNR required for convergence.The applications targeted in this thesis are not necessarily replacement of cables inexisting wired systems. Instead the motivation lies in the new services that wireless real-time communication enables. Hence, communication within and between cooperatingembedded systems is typically the focus. The resulting IR-HARQ-DDC protocol presentedhere is an efficient and fault tolerant link layer protocol foundation using adaptiveconcatenated coding intended specifically for wireless real-time communications. / Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie, 2198, Technical report. D, 29,

[pt] Códigos turbo são uma técnica de correção de erro eficiente que vem sendo proposta em diversos padrões de comunicações atuais. Esta técnica apresenta um desempenho que se aproxima dos limites teóricos estabelecidos na Teoria de Codificação. A razão para o excelente desempenho deste tipo de código baseia-se em dois fatores: uma estrutura de codificação composta por codificadores concatenados e uma estrutura de decodificação iterativa. Neste trabalho é realizada uma revisão da literatura onde a decodificação turbo é discutida segundo duas abordagens: uma que baseia-se na estrutura dos codificadores empregados e outra baseada na moderna teoria de grafos- fatores. O desempenho destes códigos é avaliado através de simulações. São considerados fatores como a estrutura dos codificadores, o tipo de modulação empregada, o algoritmo de decodificação utilizado, entre outros. / [en] Turbo codes are an efficient error correcting technique that has been proposed for many communications standards. This technique achieves a performance that is near the theoretical limits established by Information Theory. The reason for this excellent performance of turbo codes relies on two aspects: a coding structure that is composed by concatenated encoders and an iterative decoding procedure. In the literature, two approaches for turbo decoding are presented: one that is based on the encoder structure and another that is built around the factor graphs theory. Both approaches are discussed in this work. Performance evaluation for these codes are obtained through simulations. Some aspects such as encoder structure, modulation scheme and decoding algorithm are considered and evaluated. Also codes derived from turbo codes by puncturing and shortening have been studied in this work.

本文以「歷史制度主義」為途徑，去分析毛澤東時期「二線分工」的運作與變遷。並就「歷史制度主義」的三個主要觀點，包括「路徑依賴」、「關鍵點」以及「漸續平衡」為架構，去鋪陳本文的論證。 首先，在「路徑依賴」上，本文認為因「民主集中制」的矛盾，使得中共政治在運作上，衍生出另一套非正式制度以修補之。而「二線分工」就是這套非正式制度，其目的是為了防制「民主集中制」的三項缺失，包括權力集中、非正式政治的影響以及政治繼承的危機。是故，只要中共堅持「民主集中制」，則「二線分工」就會成為一項路徑依賴，以修補「民主集中制」的缺失。毛時期「二線分工」的起點是在一九五六年九月的八大，該會決議重組中央書記處，以作為和中央政治局分工的機構。因此，開啟了毛時期「二線分工」的運作。 其次，在「關鍵點」的改變上，以一九五九年四月，毛辭去國家主席，退居政務二線為重要的關鍵。促成該關鍵點的成因上，可以「內因」和「外因」分別說明之。「內因」是起於反右運動、大躍進運動以來，逐步繁瑣的內政事務，使得毛決心辭去國家主席，以減輕工作負擔。「外因」則起於中蘇關係的惡化，使得毛有意識的了解培養革命繼承人的重要性，遂將劉少奇扶植至政務一線，以培養其接班能力。 最後，在「漸續平衡」上，在歷經一九五九年四月的「關鍵點」後，中共的「二線分工」運作由原來的「優勢政治」型演變為「權力平衡」型。在「關鍵點」之前，毛集黨務、政務一線於一身，可以直接參與黨務與政務決策的制定，因此呈現出以毛為主的「優勢政治」運作。但在「關鍵點」之後，毛雖仍居黨務一線，但因退居政務二線，所以大幅減少對於重要會議的直接參與，部分決策權轉移至劉少奇、鄧小平手中，故乃呈現出一、二線互為抗衡的「權力平衡」型。 本文在最後的結論，將討論毛時期立下的「二線分工」運作，對於後毛時期的延續性。此外，將提出中共政治的「二線分工」模式，以做為本論文的研究發現與研究成果。 / In the political regime of CCP, democratic centralism is the formal system of an organized form. “Two-front arrangement” is informal system, which is used to renovate three defects of democratic centralism, including the effects of informal system, power centralization, and the crisis of political successor. This article is used three concepts of ”historical institutionalism”, which are path dependence, critical juncture, and punctured equilibrium, to explain the transition of “two-front arrangement” in CCP. First, in the path dependence, “two-front arrangement” is a method used by CCP to repair the deficiency of democratic centralism. Second, the path of “two-front arrangement” was gone through two critical junctures of transition, one is the CCP twelve party congress in 1982, and two is the CCP sixteenth party congress in 2002. At last, the results of these critical junctures produced new punctured equilibrium . The work of “two-front arrangement” changed to patron-client type after the CCP twelve party congress and evolved to functional type after the CCP sixteenth party congress. The change of “two-front arrangement” is gradually evolving to some kinds of institutionalization. From the random type in Mao’s era, the patron-client type in Deng’s era, to the functional type in Jiang’s era, we can find that the “two-front arrangement” has remarkable function to repair three defects of democratic centralism as time went by. So we can take it as the formation of institutionalization. We analyze the “two-front arrangement” during Mao Zedong’s era. “First-front” leaders are those who participated in the policy-making process directly while leaders on the “second-front” are referred to those who only indirectly involved in the process. The article argues that the best way to identify leaders in their affiliation in the “two-fronts” division of work is to have a detailed breakdown on personnel in the highest decision-making bodies, the Politburo and the Central Secretariat. We divide Chinese leadership during Mao’s era into four categories according to official document and reputation and status of the leaders. The article further delineates the operation of the “two-front arrangement” according to the division of work between the party and the state, charisma of the leaders and formal institutions. At the end, we try to assess the impact of the “two-fronts” model on Chinese politics.

To support video communication over mobile environments has been one of the objectives of many engineers of telecommunication networks and it has become a basic requirement of a third generation of mobile communication systems. This dissertation explores the possibility of optimizing the utilization of shared scarce radio channels for live video transmission over a GSM (Global System for Mobile telecommunications) network and realizing error resilient video communication in unfavorable channel conditions, especially in mobile radio channels. The main contribution describes the adoption of a SEC (Second Error Correction) approach using ECC (Error Correction Coding) based on a Punctured Convolutional Coding scheme, to cope with residual errors at the application layer and enhance the error resilience of a compressed video bitstream. The approach is developed further for improved performance in different circumstances, with some additional enhancements involving Intra Frame Relay and Interleaving, and the combination of the approach with Packetization. Simulation results of applying the various techniques to test video sequences Akiyo and Salesman are presented and analyzed for performance comparisons with conventional video coding standard. The proposed approach shows consistent improvements under these conditions. For instance, to cope with random residual errors, the simulation results show that when the residual BER (Bit Error Rate) reaches 10-4, the video output reconstructed from a video bitstream protected using the standard resynchronization approach is of unacceptable quality, while the proposed scheme can deliver a video output which is absolutely error free in a more efficient way. When the residual BER reaches 10-3, the standard approach fails to deliver a recognizable video output, while the SEC scheme can still correct all the residual errors with modest bit rate increase. In bursty residual error conditions, the proposed scheme also outperforms the resynchronization approach. Future works to extend the scope and applicability of the research are suggested in the last chapter of the thesis.