具有冗餘資料量(redundancy)之正交分頻多工(OFDM)系統已被使用於許多高速傳輸的無線通訊系統之中。由於信號在通過具有高度分散性之通道會造成很嚴重的區塊間干擾(IBI)，為了處理這個問題，在傳輸端引入冗餘資料量將提供我們解決的方法。然而，這個冗餘資料量長度的選擇將會影響系統的效能及頻寬效益，且它也與通道脈衝響應的長度有著高度的相關性。在本篇論文中，我們將以偽隨機後置編碼(PRP)正交分頻多工系統之架構為基礎而提出一個新的區塊式正交分頻多工收發機架構。由於在偽隨機後置編碼正交分頻多工系統中，利用接收信號的一階統計特性我們將可利用偽隨機後置編碼來做半盲蔽式之通道估測。因此，在冗餘資料量足夠的條件下，偽隨機編碼正交分頻多工系統結合貝氏決定迴授等化器(Bayesian decision-feedback equalizer)將可用來同時消除區塊間干擾及符碼間干擾(ISI)。然而，在冗餘資料量不足的條件之下，即，冗餘資料量的長度比通道階數少時，我們將對通道估測的方法先做一個修正。為了更進一步的降低接收機的複雜度，我們將使用最大縮短信號雜訊比之時域等化器(MSSNR-TEQ)結合貝氏迴授等化器分別來消除區塊間干擾及符碼間干擾。換言之，在得到了通道的資訊之後，便可以使用最大信號雜訊比之時域等化器來消除區塊間干擾，以及使用貝氏決定迴授等化器來消除符碼間干擾以改善系統之效能。在電腦模擬的部分，我們將使用位元錯誤率來做系統效能的分析，並且與使用傳統的最小均方誤差之迴授等化器之系統做比較 (MMSE-DFE)。

Orthogonal frequency division multiplexing (OFDM) modulator with redundancy has been adopted in many wireless communication systems for higher data rate transmissions. The introduced redundancy at the transmitter allows us to overcome serious inter-block interference (IBI) problems due to highly dispersive channel. However, the selection of redundancy length will affect the system performance and spectral efficiency, and is highly dependent on the length of channel impulse response. In this thesis, based on the pseudorandom postfix (PRP) OFDM scheme we propose a novel block-based OFDM transceiver framework. Since in the PRP-OFDM system the PRP can be employed for semi-blind channel estimation with order-one statistics of the received signal. Hence, for sufficient redundancy case the PRP-OFDM system with the Bayesian decision feedback equalizer (DFE) is adopted for suppressing the IBI and ISI simultaneously. However, for the insufficient redundancy case (the length of redundancy is less than the order of channel), we first propose a modified scheme for channel estimation. To further reduce the complexity of receiver, the maximum shortening signal-to-noise-ratio time domain equalizer (MSSNR TEQ) with the Bayesian DFE is developed for suppressing the IBI and ISI, separately. That is, after knowing the channel state information (CSI) and removing the effect of IBI with MSSNR TEQ, the Bayesian DFE is applied for eliminating the ISI. Via computer simulation, we verify that performance improvement, in terms of bit error rate (BER), compared with the conventional block-based minimum mean square error (MMSE)-DFE can be achieved.

Abstract...i
Contents...ii
List of Figures and Tables...iv
Chapter 1 Introduction...1
Chapter 2 Block-based OFDM Transmission Systems...5
2.1 Introduction...5
2.2 Block Transmission Model...6
2.3 Decision Feedback Equalizer...12
2.3.1 MMSE-DFE...13
2.3.2 MMSE-IBI-DFE...16
Chapter 3 Bayesian Decision Feedback Equalization with Semi-Blind Channel Estimation...20
3.1 Introduction...20
3.2 Pseudo Random Postfix OFDM...21
3.2.1 Notations and PRP-OFDM modulator...21
3.2.2 Semi-blind channel estimation of the PRP-OFDM system...24
3.3 The MSSNR TEQ...28
3.3.1 Description of MSSNE TEQ...24
3.3.2 PRP-OFDM combining with the MSSNR TEQ for semi-blind channel estimation under the condition of insufficient redundancy...29
3.4 Bayesian Decision Feedback Equalizer...30
Chapter 4 Computer Simulation...36
4.1 Introduction...36
4.2 Channel Estimation for PRP-OFDM System...36
4.2.1 Sufficient Case (P - M >= L + 1)...37
4.2.2 Insufficient Case (P - M < L)...37
4.3 Channel Estimation with Shortening Approach...40
4.4 Bit Error Rate Performance of Receivers with Different Equalizer...41
4.4.1 Sufficient Case (P - M >= L)...41
4.4.2 Insufficient Case (P - M < L)...44
Chapter 5 Conclusions...48
References...49
Appendix A...51
Appendix B...53

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