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    Title: 合作式通訊系統於時間選擇性衰減通道下之接收機設計
    Other Titles: Receiver Designs for Cooperative Communication Systems in Time-Selective Fading Channels
    Authors: 易志孝
    Contributors: 淡江大學電機工程學系
    Keywords: 差動式調變;合作式通訊;放大與傳送式中繼;解碼與傳送式中繼;效能分析;多符元差動式檢測;循環式解碼;中繼站選擇;實體層網路編碼;Differential modulation;cooperative communications;amplify-and-forward relaying;decoded-and-forward relaying;performance analysis;multiple-symbol differential detection;iterative decoding;relay selection;physical layer network coding
    Date: 2012-08
    Issue Date: 2015-05-19 15:58:00 (UTC+8)
    Abstract: 合作式通訊可以達到空間分集增益,卻無傳統多天線通訊系統受到實體大小而無法達到獨立接收 的限制。合作式通訊的主要概念是藉由在空間中分離的中繼站來使得目的地端產生獨立的接收訊號。 針對中繼站的信號處理,已有許多協定被提出來。在此專題研究計劃案中,我們將專注於「放大與傳 送」及「解碼與傳送」兩種中繼站系統,因為它們擁有低複雜度與優異性能的緣故。 當同調調變被傳輸端所採用時,一個分集通訊系統的接收機必須取得通道狀態資訊來執行最大比 例結合,此種分集結合方式可造成最小錯誤率。然而,在快速變化無線環境中,欲藉由導航信號或訓 練序列來獲得準確的通道狀態資訊並不容易。此困難在合作式通訊中將更為顯著,其原因是若欲在合 作式通訊系統目的地端上執行最大比例分集結合,其接收機除需估計各分集鏈路的通道狀態資訊外, 還需要估計各分集鏈路的等效雜訊功率,如此一來,導航信號的數量或功率必須增加,以達到一定的 估計精確度。 為了降低同調調變中通道狀態資訊估計的複雜度及減少在導航信號上的功率與頻寬損失,在此專 題計畫中,我們將考慮於具有時間選擇性的衰減通道中,使用差動式調變於合作式通訊系統上。之前 已出版有關差動式調變應用於合作式通訊系統的文獻中,均假設通道增益在相鄰兩符元週期內保持不 變,此假設雖然可以簡化推導最佳分集結合的權重值,然而其並不能反應出快速衰減通道中,時間選 擇性對整體系統效能的影響。我們將針對於時間選擇性衰減通道中的差動式合作通訊系統,根據最大 後驗機率檢測準則來推導出最佳與次佳的分集組合權重表示式,並進一步分析其效能。除此之外,本 專題計畫中也將研究下列議題: 1. 基於上述推導的結果,決定操作於時間選擇性衰減通道的差動式合作通訊系統中最佳的功率分配。 為了改善頻譜效能並兼顧系統錯誤率,我們也將考慮針對差動式振幅相位調變推導其於合作通訊 系統在時間選擇性衰減通道下的最佳組合權重值。 2. 眾所週知差動式調變效能較傳統同調調變且具完美通道狀態資訊時的效能為差,為了縮小此一效 能損失,我們將推導可使用於合作式通訊系統的多重符元差動式檢測演算法並分析其效能。 3. 上述的推導將針對放大與傳送式中繼協定及解碼與傳送式中繼協定來進行,當推導出的最佳分 集組合權重表示式過於複雜,並不適合用來執行或分析時,我們將簡化其表示式並評估此低複雜 度、次佳的分集組合權重值之效能。 4. 將差動式調變與錯誤更正碼結合形成一個串列連結碼,並使用循環式解碼來進行解調與解碼。此 研究的重點將放在推導適用於操作在時間選擇性衰減通道下合作通訊系統之位元解碼度量,當此 度量值過於複雜時應做適當的簡化。 5. 在時間選擇性衰減通道下,考慮具有多中繼站的雙向合作式通訊系統,結合設計中繼站選擇演算 法與實體層網路編碼來同時達到確保信號接收品質與提升頻譜使用效率的雙重目的。
    Cooperative communications can achieve spatial diversity gains without the physical size limitation existing in conventional multiple-antenna communications systems. The key idea of cooperative communications is to create independent diversity receptions at the destination via spatially separated relays. Many different protocols have been proposed to perform signal processing at the relay node. In this project proposal, we focus on amplify-and-forward (AF) and decode-and-forward (DF) relaying systems for their lower complexity and superior performance. When coherent modulation is employed at the transmitter, the receiver of a diversity communication system must acquire channel state information (CSI) to perform maximal ratio combining (MRC) which is optimal in the sense of minimum error probability. However, accurate CSI estimates via pilots or training sequences are hard to obtain in a rapidly changing mobile environment. This difficult becomes more significant in cooperative communication systems because the MRC receiver for the AF relaying system also requires the knowledge of the individual link equivalent noise variance to perform diversity combining. To ease the CSI estimation process and reduce the power and bandwidth overhead occurred in coherent modulation schemes, we consider the cooperative communication system employing differential modulation in time-selective fading channels. Unlike the previous work on this topic which always assumed the channel gains are the same over two adjacent symbol periods, we model the channel time-selectivity exactly in our formulation. To be more specific, we will focus on researches of the following issues in this project: 1. Derive the optimal and suboptimal diversity combining rules and analyze their performance for AF relaying systems with differential modulation in time-selective fading channels. Determine the optimum power allocation between the source node and the relay node. Extend the above analysis and design to the scenarios of multi-node, multi-hop, and high-order differential amplitude/phase modulation. 2. Improve the performance of differential modulation based on the multiple-symbol differential detection (MDD) algorithm. 3. Study the optimal and suboptimal diversity combining rules for decode-and-forward (DF) relaying systems with differential modulation in time-selective fading channels. 4. Develop the iterative decoding algorithm for the coded relaying system with differential modulation in time-selective fading channels. 5. Propose a relay selection algorithm combined with physical layer network coding for multiple AF relay nodes employing differential modulation in time-selective fading channels.
    Appears in Collections:[電機工程學系暨研究所] 研究報告

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