未來第四代行動通訊系統必需提供高傳輸速率、高的系統容量，故多調分碼多重接取系統就被提出，此系統結合了分碼多重接取和正交分頻多工的優點，可以提高傳輸速率、系統的效能，本論文將其修正成改良式多調分碼多重接取系統，以便使用多通道領航符號去輔助系統通道估測的準確性。
本論文主要在探討使用不同領航符號之通道估測的效能，其中通道估測使用了LS估測法、一階線性內插法、spline內插法、FFT/IFFT演算法及所提出spline內插法串聯FFT/IFFT演算法去評估改良式多調分碼多重接取系統的好壞，由模擬的結果可知，本系統中，使用spline內插法串聯FFT/IFFT演算法的位元錯誤率(BER)會比LS估測法、一階線性內插法等等還要來的低。最後提出結論和未來研究的方向。

The fourth generation cellular mobile communication system in the future needs to provide high data rate transmissions. Multi-Tone CDMA (MT-CDMA) system combines the advantages of CDMA and OFDM, and it is one of the promising choices for the fourth cellular mobile communication system. In order to raise the performance, we amend MT-CDMA named Modified MT-CDMA. We use different pilot arrangement in different channel to enhance the channel estimation of system.
The receiver architecture includes a baseband signal detection and a channel estimation. We use a pilot symbol to estimation the channel. In this thesis, we make a study of pilot arrangement on different channel estimation performance of system. We use Least Square estimation(LS)、linear interpolation、spline interpolation、FFT/IFFT interpolation and spline interpolation combine FFT/IFFT algorithm to estimate the system performance.

第一章 導論..................................................................................................................1
1.1研究動機………..............................................................................................1
1.2論文架構..........................................................................................................2
第二章OFDM 簡介......................................................................................................3
2.1OFDM架構演進...............................................................................................4
2.2.1傳統OFDM架構………………………………………………………5
2.2. DFT OFDM架構………………………………………………………..6
2.2 OFDM系統架構..............................................................................................7
2.3 OFDM的特性..................................................................................................9
2.3.1 防護區間………………………………………………………………9
2.3.2 OFDM正交性……………………………………………………...…11
2.3.3 OFDM優缺點………………………………………………………...12
2.4 OFDM系統參數設定..................................................................................13
第三章 通道估測技術................................................................................................15
3.1領航訊號通道估測器基本原理....................................................................17
3.1.1共用領航通道(Common Pilot Channel，CPICH)...............................17
3.1.2上傳通道估測器(Uplink Channel Estimator).......................................19
3.1.3下傳通道估測器(Downlink Channel Estimator)..................................24 3.2估測理論........................................................................................................28
3.2.1無偏差估測器.....................................................................................28
3.2.2最小變異數方法(Minimum Variance Criterion).................................29
3.3通道估測技術..................................................................................................30
3.3.1 WCDMA系統通道估測......................................................................31
3.3.1.1 簡單平均法(Simple Average).......................................................31
3.3.1.2 線性內插法(Linear Interpolation)…………………………........33
3.3.1.3 適應性濾波器中的Wiener Filter法...........................................34
3.3.1.4 Weighted Multi-Slot Averaging (WMSA)..................................35
3.3.2 IEEE 802.11a OFDM系統通道估測………………………………..36
3.3.2.1 頻率領域之通道估測…………………………………………..38
3.3.2.2 時間領域之通道估測…………………………………………..39
第四章 改良式多調分碼多重接取系統之通道估測...............................................44
4.1改良式多調分碼多重接取系統架構.........................................................44
4.2指標符號排列規則.....................................................................................47
4.3利用領航訊號之通道估測方法.................................................................49
4.3.1 最小平方法(Least Square，LS) .................................................50
4.3.2 ㄧ階線性內插法...............................................................................53 4.3.3 Spline內插法.....................................................................................54
4.3.4 ㄧ階離散型傅立葉轉換............................................................55
4.3.5串連spline內插法和一階離散型傅立葉轉換.................................57
第五章 模擬結果........................................................................................................59
5.1 多重路徑衰減通道模型………………………………………………….59
5.2 模擬結果.....................................................................................................60
第六章 結論................................................................................................................86
參考文獻......................................................................................................................87

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