臺灣博碩士論文加值系統

本論文深入探討應用於正交分頻多工系統的低複雜度預編碼技術，這些技術可以改善因子通道遭受破壞而遺失資訊所產生的系統錯誤性能衰退。在論文中我們回顧許多現存使用於正交分頻多工的預編碼技術，利用電腦模擬與數值分析方法來評估這些架構的性能。同時在跨越不同星座圖，使用先前我們提出的星座索引預編碼技術，將資料符元映射成新的碼字，再將這組碼字結合空時方塊碼使用正交分頻多工系統傳送，試圖獲取更多的編碼與分集增益。
利用推導出的碼評估指標建立尋碼架構，可以有效率的搜尋出高性能的預編碼，透過電腦蒙地卡羅模擬與錯誤率之聯集上界的數值分析，證實正交分頻多工系統使用結合星座索引預編碼技術與空時碼的技術，在犧牲適度的硬體實現複雜度下，可以獲得有效的系統性能改善。

In this thesis, we investigate a simple and low complexity precoding technique which is applied to an OFDM system, in order to improve the performance degradation caused by the null subchannels. We also review some existing precoding techniques for an OFDM system. Computer simulations and numerical analysis have been conducted to evaluate the performance of these schemes. The considered constellation index precoding technique is to transform each information symbol into a codeword and cross different constellations. Subsequently, these codewords will be transmitted along with the space-time block code by an OFDM system to achieve further diversity/coding gains.
By using the code merit figure derived from the CIP technique, we establish a code search criterion to find the good codes efficiently. We present the Monte Carlo simulation and the analysis of the union bound of codeword error probability. From the results of analytical and simulation, the CIP-STBC-OFDM can be shown to improve the performance of conventional OFDM systems while sacrificing appropriate complexity of hardware implementation.

目錄
第一章 緒論 1
1.1 前言 1
1.2 研究背景與動機 4
1.3 論文架構與研究方向 10
第二章 相關技術介紹與文獻探討 11
2.1 正交分頻多工系統介紹 11
2.2 預編碼技術 15
2.3 預編碼正交分頻多工系統 20
2.4 空時碼介紹 25
第三章 研究方法與系統模型 36
3.1 星座索引預編碼 36
3.2 星座索引預編碼建碼架構 44
3.3 星座索引預編碼與空時碼之串接系統 46
第四章 數值分析與性能比較 50
4.1 錯誤率分析 50
4.2 模擬結果 52
第五章 結論 61
參考文獻 62
附錄一 重要數學符號說明 64
附錄二 專業術語中、英文縮寫對照 65


圖目錄
【圖2.1】 多載波系統FDM與OFDM在頻譜上之關係 12
【圖2.3】 擴展轉換於文獻 [21] 提出時的傳送模型 17
【圖2.4】 擴展轉換在文獻 [17] 的傳送模型 18
【圖2.5】 CDM-OFDM方塊圖 21
【圖2.6】 LCP串接未編碼OFDM系統之傳送端模型 22
【圖2.7】 LCP-OFDM傳送端模型 23
【圖2.8】 兩支傳送、一支接收天線之空時碼架構 26
【圖2.9】 兩支傳送、兩支接收天線之空時碼架構 29
【圖2.10】 兩支傳送、一支接收天線的STBC結合OFDM系統 35
【圖3.1】 CIP-OFDM傳送端方塊示意圖 37
【圖3.2】 CIP-OFDM接收端方塊示意圖 37
【圖3.3】 資料符元在碼群psi(1,4;2,16)中透過G=[4,7]進行映射 41
【圖3.4】 CIP-STBC-OFDM傳送端方塊示意圖 47
【圖3.5】 CIP-STBC-OFDM接收端方塊示意圖 49
【圖4.1】 碼長為2、頻寬效益=1的情況下，CIP-STBC-OFDM與STBC-OFDM之系統錯誤性能比較 55
【圖4.2】 在碼長為2、接收天線數為1、頻寬效益=1的情況下，CIP-STBC-OFDM與STBC-OFDM之系統錯誤性能比較 56
【圖4.3】 在碼長為2、接收天線數為2、頻寬效益=1的情況下，CIP-STBC-OFDM與STBC-OFDM之系統錯誤性能比較 57
【圖4.4】 在碼長為4、接收天線數為1、頻寬效益=1的情況下，CIP-STBC-OFDM與STBC-OFDM之系統錯誤性能比較 58
【圖4.5】 在碼長為2、頻寬效益=1的情況下，CIP-STBC-OFDM與不同預編碼方式之系統錯誤性能比較 59
【圖4.6】 在碼長為4、頻寬效益=1的情況下，CIP-STBC-OFDM與不同預編碼方式之系統錯誤性能比較 60


表目錄
【表2.1】 LCP-OFDM之編碼矩陣 24
【表2.2】 在兩支傳送、一支接收天線的空時碼架構下之傳送編碼方塊 27
【表2.3】 在兩支傳送、兩支接收天線的空時碼架構下接收訊號與天線及時間的關係 30
【表2.4】 在兩支傳送、兩支接收天線的空時碼架構下天線間之通道定義 30
【表2.5】 在四支傳送、一支接收天線的空時碼架構下天線間之通道定義 32
【表3.1】 CIP-OFDM在頻寬效益 設計之高效能碼參數 43

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