在這篇論文中，我們提出了在正交分頻多工(orthogonal frequency-division multiplexing)的系統中，結合子載波預留(tone reservation)與子載波注入(tone injection)來降低功率峰均比(peak-to-average power ratio，簡稱PAPR)。在第一個步驟中，我們透過計算特定的公制去計算每一個保留的子載波降低峰值的能力，而這些公制的定義是計算保留的子載波對降低峰值的貢獻。這樣在每個保留的子載波中可以選擇一個適當的星座點做傳送使得PAPR能夠降低到某個程度。在第二個步驟中，我們應用星座點擴充的技術來繼續降低PAPR。我們計算所有可以擴充的頻域資料點的新的公制，而這些公制是用來評估它們對所對應的時域的高峰值取樣點的貢獻度，然後選擇擁有對於頻域上輸入資料點貢獻度最多者進行子載波注入。重複第二個步驟，直到PAPR值達到所需求的PAPR門檻或是達到所限定的最大執行次數。所提出的方法不需要傳送額外訊息(side information)給接收端，所以在接收端也不需要額外的負載來做訊息偵測。比較第二代數位地面電視傳輸(Digital Video Broadcasting-Second Generation Terrestrial，簡稱DVB-T2)標準中的結合子載波注入以及主動式星座圖擴充(active constellation extension)的方法，提出的方法可以達到較好的PAPR效能以及較低的傳送能量。

In this thesis, we propose a peak-to-average power ratio (PAPR) reduction scheme based on tone reservation and tone injection for orthogonal frequency-division multiplexing systems. In the first step of the proposed scheme, we evaluate the peak-reduction capability of each of the reserved tones (or subcarriers) by computing the corresponding metrics. Based on the resulting metrics, we determine the transmitted values of each reserved tone. In the second step, we apply a constellation extension technique, tone injection, to the data subcarriers for further PAPR reduction, where each extendable constellation point is with only one possible extended constellation point. We compute new metrics of all extendable frequency-domain data samples for measuring their contributions to the corresponding time-domain peak samples, and then select the data sample with the largest metric for tone injection. The second step is repeated unless the PAPR value is lower than a predetermined threshold or the maximum number of injected tones has been reached. The proposed scheme does not need to transmit any side information to the receiver. As compared with the combined tone reservation and active constellation extension scheme adopted in the DVB-T2 standard, the proposed one can achieve better PAPR reduction performance with lower transmitted power.

Abstract i
Contents iii
List of Figures v
List of Tables vii
Chapter 1 Introduction
1.1 Basics of OFDM 1
1.2 PAPR Problem 2
1.3 Thesis Outline 3
Chapter 2 PAPR Reduction Techniques
2.1 Side Information-Aided 5
2.1.1 Selected Mapping 6
2.1.2 Partial Transmit Sequences 7
2.2 Non-Side Information-Aided 7
2.2.1 Clipping and Filtering 8
2.2.2 Coding 8
2.2.3 Tone Reservation 8
2.2.4 Constellation Extension 9
2.2.4.1 Tone Injection 10
2.2.4.2 Active Constellation Extension 11
2.2.4.3 Metric-Based Symbol Predistortion Techniques 12
2.3 PAPR Reduction Techniques in the speciation of DVB-T2 16
2.3.1 Active Constellation Extension 16
2.3.2 Tone Reservation 18
Chapter 3 PAPR Reduction by Using Tone Reservation and Tone Injection
3.1 Motivation 24
3.2 The Proposed Scheme for PAPR Reduction 25
3.3 Summary 30
Chapter 4 Simulation Results and Comparison of Computational Complexity
4.1 PAPR Reduction Performance 35
4.2 Comparison of Computational Complexity 37
4.3 Summary 40
Chapter 5 Conclusions 46
Bibliography 47

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