本論文中，我們提出一個矩陣架構以產生完美序列(Perfect sequence)。此矩陣中的列序列(Row sequence)和列序列經富利葉轉換(Discrete Fourier transform)後產生的序列皆為完美序列。行序列(Column sequence)在任意的循環位移下彼此為正交。而且將行序列乘上等振幅的複數係數後相加組合產生的序列，亦為一組完美序列。
此外，我們亦提出一種在OFDM系統中利用疊加序列的進行通道估測的演算法。由於完美序列具備有在時域和頻域都等振幅的特性，因此我們選擇完美序列作為疊加的序列。雖然因為未知的資料對通道估測造成了額外的干擾，我們所提出的通道估測器效能並沒有比傳統利用領航訊號的通道估測效能好，但是卻節省了傳輸領航訊號的頻寬，明顯增加有效資料傳輸速率。此外藉著完美序列在時域上為等振幅的特性，也可以同時改善傳送訊號的PAPR(Peak-to-average power ratio)。

A complex array for constructing perfect sequences is presented in this paper. The row sequences and their discrete Fourier transform form two sets of perfect sequences. The column sequences are orthogonal to each other for any cyclic shift. In addition, any combination of the column sequences with complex weighting coefficients of equal amplitude is also a perfect sequence.
In addition, a superimposed training scheme is also proposed for channel estimation in OFDM systems. The perfect sequence is adopted since it has a constant magnitude in both the time domain and the frequency domain. Although the derived channel estimator has a slightly worse performance since the unknown data contributes extra noise, the effective data throughput is substantially increased. In addition, the proposed scheme is shown to have a much better peak-to-average power ratio (PAPR) because the added perfect sequence has a constant magnitude in the time domain.

Chapter 1 Introduction ……………………………………………………1
1.1 Channel Estimation in OFDM Systems……………………………5

Chapter 2 Construction of The Proposed Array And Properties of The Constructed Sequences …………………………………………………10
2.1 Construction of The Proposed Array ……………………………10
2.2 Properties of The Proposed Sequences …………………………11
2.3 Applications of The Proposed Perfect Sequences…………………22

Chapter 3 Proposed Channel Estimation Scheme with Superimposed Training Sequences ………………………………………………………26
3.1 The Proposed System Model………………………………………26
3.2 The Proposed LS Channel Estimator …...………………………28
3.3 The Proposed Low-Complexity MMSE Channel Estimator ……32
3.4 The Simplified MMSE Channel Estimator ………………………36

Chapter 4 Simulation Results And Discussions…………………………38
4.1 The Power Allocation Factor………………………………….…...38
4.2 MSE of The Proposed MMSE Channel Estimator………………40
4.3 BER And Effective Data Throughput of The Proposed System….42
4.4 The PAPR of The Proposed System……………………………….45

Chapter 5 Conclusions And Future Researches………………………47
5.1 Conclusions……………………………………………….……….47
5.2 Future Researches ………………………………………………48

Appendix …………………………………………………………………50

References ………………………………………………………………51

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