在一般的正交分頻多工的演算法中，有個相當重要的演算法就是通道估測，因為在無線的環境下傳輸，傳輸的訊號會通常會受到通道的影響，改變其振幅與相位，並且無線通道通常也具有多重路徑效應，造成符際干擾，但如果能預先知道通道長度，就可以減低運算複雜度，增加運作的效能。本篇論文特別研究了如何利用已知的雜訊功率與提出的價值函數來達到通道長度估測，另外也提出了當在載波頻率偏移的情況下做通道長度估測的方法。
而雜訊功率是正交分頻多工系統中一項重要的參數，利用這項數值，可以做到最小平均平方誤差的通道估測，像是渦輪碼、功\率分配也須用到這項參數來動作。而我們的方法是利用虛擬子載波，再讓快速富立葉矩陣做奇異值分解，利用其矩陣的特殊性質達到雜訊變異數估測。而且所提出的方法不像傳統的方法需要用到循環字首，我們可以不用到循環字首而達到更好的效能。

In many algorithms for Orthogonal Frequency Division Multiplexing (OFDM) systems, the channel estimation is one of the most essential factors. In wireless environment, channel is change very fast, and the channel has multipath effect, the channel length is obtained by channel estimation. In this paper, we estimation the channel length and the SNR by virtual carriers (VC) and Singular value decomposition, when channel estimator known the information for channel length, then calculate complicated can be reduced. Besides, we proposed the estimated method at carriers frequency offset effect.
Noise variance (or noise power) can improve performance of channel estimator, e.g. MMSE channel estimator, turbo code or power allocation. In this paper, we were estimate noise variance by using the blind method of property of orthogonality of matrix, which is differed from the traditional method of Pilots.

第一章 導論 1
1.0 引言 1
1.1 研究動機 2
1.2 論文架構 2
1.3 標記法 3
第二章 正交分頻多工系統 4
2.0 引言 4
2.1 正交分頻多工系統的架構 4
2.3 常見的正交分頻多工通道估測法 7
2.4 正交分頻多工之全盲式雜訊變異數估測 11
第三章 奇異值分解法介紹 13
3.0 引言 13
3.1 奇異值分解的特性 13
第四章 訊號雜訊比估測器 16
4.0 引言 16
4.1 全盲式雜訊變異數估測 16
4.2 全盲式訊號功率估測 19
4.3 全盲式訊號雜訊比估測 21
4.4 考慮有CFO情況下之全盲式訊號雜訊比估測 22
第五章 全盲式通道長度估測器 24
5.0 引言 24
5.1全盲式通道長度估測 24
5.2同步誤差下之全盲式通道長度估測 29
5.3不同通道模型下通道長度估測器效能分析 33
第六章 模擬結果 39
6.1 所提出的非資料補助型訊號與雜訊比效能 40
6.2 所提出的全盲式通道長度估測效能 45
第七章 結論 48
中英對照表 49
全名縮寫對照表 52
參考文獻 54

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