臺灣博碩士論文加值系統

在數位通訊系統中，GMSK是一種廣泛使用且充分利用系統頻寬資源與訊號功率的調變方式。但因為其非線性的特質導致設計與分析上的困難，所以在本篇論文中，我們提出利用近似GMSK訊號之線性模型及de-rotation與分數間距取樣，推導出利用一根天線可產生四個次通道的DF-SIMO系統架構（de-rotation and fractionally-spaced single input and multiple output system）。在此新的系統架構上，我們使用最小平方參數估計法（least squares estimation）設計三種通道鑑定器-只用訓練碼的通道鑑定器、已知脈波波形及利用訓練碼的通道鑑定器與半盲蔽（semi-blind）式的通道鑑定器，並且作一比較。針對此DF-SIMO系統架構結合通道鑑定器，我們發展出最佳化訊號結合（optimum combining）之線性MMSE（minimum mean squared error）接收機及非線性的DFE（decision feedback equalizer）接收機、EDFE（eraseures decision feedback equalizer）接收機與MLSE（maximum likelihood sequence estimator）接收機。我們並假設各種GSM通道和非時變通道模型，以電腦模擬比較接收機其性能。我們也發現DF-SIMO架構優於傳統T-Spaced的D-SI2O架構，並且基於DF-SIMO系統模型下，EDFE接收機在架構上不僅複雜度較MLSE接收機低，而且在GSM系統時變通道中的效能與MLSE接收機相差不遠，甚至在TU（typical urban）時變通道中的BER表現，比MLSE還要好。

As is well known, GMSK is a spectral and power efficient modulation scheme that is adopted by the GSM system. However, the non-linearity of GMSK often brings about difficulties in design and analysis.
In view of this, we first base on the linear approximation GMSK (Gaussian-filtered Minimum Shift Keying) signals model proposed by Laurent [1], and utilize it to derive a linearly approximated GMSK signals model for replacing the traditional GMSK model. More specificcally, a linearized SI4O (single input and four outputs) model and associated receivers for single-channel GMSK reception are proposed. The model is called DF-SIMO model since it is resulted from the usage of De-rotation and T/2 Fractionally-spaced sampling of the received signal. Next, We study the resulting multi-channel estimation problem by applying three least squares estimators, namely, (1) batch LS estimator based on training sequence only, (2) structured LS estimator using the known pulse-shaping function, and (3) a semi-blind channel estimator.
Finally, With our proposed DF-SIMO model and channel estimators, four optimum multichannel receivers according to MMSE and ML criteria are developed, including linear MMSE (Minimum Mean Squared Error) receiver, non-linear DFE (Decision Feedback Equalizer) receiver, non-linear EDFE (Erasures Decision Feedback Equalizer) receiver, and non-linear MLSE (Maximum Likelihood Sequence Estimation) receiver.
Using extensive and realistic computer simulations, the signal-channel model, channel estimators, and T-spaced or T/2-spaced receivers are thoroughly investigated, by hypothesizing various GSM and non-time-variant channel models. It is demonstrated that the DF-SIMO scheme is superior to the traditional T-spaced D-SI20 scheme. And we concluded that among all the receiver structures, the EDFE receiver is recommended since its complexity is not only much less than the MLSE, but also its performance can be very close the MLSE under various time-variant channels. Moreover, in some important case such as typical urban (TU) channels, it is found that the bit error rate (BER) performance of the EDFE receiver is even better than that of the MLSE.

目錄
中文摘要…………………………………………………………………………………………………I
英文摘要…………………………………………………………………………………………………II
誌謝………………………………………………………………………………………………………IV
目錄………………………………………………………………………………………………………V
圖目錄……………………………………………………………………………………………………VIII
表目錄……………………………………………………………………………………………………IX
第一章 簡介 …………………………………………………………………………………………1
1.1 研究動機 ……………………………………………………………………………………1
1.2 論文組織 ……………………………………………………………………………………3
第二章 訊號的模型 …………………………………………………………………………………4
2.1 GMSK訊號及其線性模型 …………………………………………………………………4
2.1.1 非線性GMSK訊號 …………………………………………………………………………4
2.1.2 PAM訊號重疊方法近似GMSK訊號 ………………………………………………………6
2.2 反旋轉方法與分數間距取樣 ………………………………………………………………11
2.2.1 反旋轉方法 …………………………………………………………………………………11
2.2.2 分數間距取樣通道模型[11] ………………………………………………………………12
2.3 D-SI2O（DE-ROTATION-SI2O）通道模型 ………………………………………………14
第三章 DF-SIMO模型下通道鑑定及其接收機設計 ………………………………………………18
3.1 DF-SIMO通道模型 …………………………………………………………………………18
3.2 通道鑑定 ……………………………………………………………………………………26
3.2.1 利用訓練碼的通道鑑定 ……………………………………………………………………26
3.2.2 用訓練碼與已知脈波波形的通道鑑定 ……………………………………………………28
3.2.3 利用訓練碼與互參考性質（mutual reference）的半盲蔽式通道鑑定 …………………32
3.3 線性平行等化器組接收機 …………………………………………………………………36
3.3.1 MMSE平行等化器組 ………………………………………………………………………37
3.3.2 MMSE決策延遲參數之選擇 ………………………………………………………………41
3.4 非線性平行等化器組接收機 ………………………………………………………………43
3.4.1 傳統DFE平行等化器組 ……………………………………………………………………43
3.4.2 決策回授限制型EDFE平行等化器組[9] …………………………………………………53
3.4.3 MLSE平行等化器組 ………………………………………………………………………55
第四章 模擬與實驗結果 ……………………………………………………………………………59
4.1 訊號的產生 …………………………………………………………………………………61
4.1.1 非線性GSMK訊號 …………………………………………………………………………61
4.1.2 線性化GMSK訊號 …………………………………………………………………………63
4.1.3 驗證次通道的存在性 ………………………………………………………………………64
4.2 通道估測 ……………………………………………………………………………………67
4.2.1 只有雜訊與授控符碼間效應（controlled ISI）的通道估測………………………………67
4.2.2 實數通道估測 ………………………………………………………………………………69
4.2.3 複數通道估測 ………………………………………………………………………………71
4.2.4 三種通道鑑定器的比較 ……………………………………………………………………73
4.2.5 通道長度大小與通道鑑定 …………………………………………………………………75
4.3 MMSE、DFE、EDFE與MLSE的平行等化組的實驗結果…………………………………77
4.3.1 MMSE、DFE與EDFE平行等化器組的等化結果比較 ……………………………………77
4.3.2 只有雜訊與授控符碼間效應的通道下MMSE、DFE、EDFE與MLSE的平行等化結果…79
4.3.3 實數通道下MMSE、DFE、EDFE與MLSE的平行等化結果………………………………83
4.3.4 複數通道下MMSE、DFE、EDFE與MLSE的平行等化結果………………………………86
4.3.5 非線性GMSK訊號去除第二項PAM成份之等化器結果比較 ……………………………89
4.4 GSM系統時變通道下MMSE、EDFE、MLSE的等化結果 ………………………………92
第五章 結論 …………………………………………………………………………………………103
參考文獻 ………………………………………………………………………………………………105
附錄 ……………………………………………………………………………………………………108
A. PAM訊號重疊法 ……………………………………………………………………………108

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