臺灣博碩士論文加值系統

因大多數的5G候選波形仍立基於OFDM的多載波傳輸架構，所以由正交分頻多工（Orthogonal Frequency Division Multiplexing; OFDM）訊號所引發高峰均功率比（Peak-to-Average Power Ratio; PAPR）的問題，即便隨著第五代移動通信系統(5G)技術的演進，將越發嚴重。由於高PAPR訊號通過通訊射頻模組中的高功率放大器（High Power Amplifier; HPA）時，易使HPA工作於其特性曲線之飽和區造成非線性失真，造成接收訊號引入大量雜訊。現今的非線性補償方法如數位預失真法(Digital Predistortion)、功率回退法等等通常都需要額外的元件來輔助才能改善HPA的非線性特性，然其效果有限且需承受額外大功率消耗的缺點。為此，在本篇論文當中提出了改良版的帕波氏（Papoulis-Gerchberg）疊代演算法，演算法可內嵌於系統接收端的基頻晶片內，將接收的可能失真訊號進行訊號還原，並結合Decision-Aided Reconstruction (DAR)演算法改善系統效能。透過IEEE 802.11ad為雛形的模擬證實，以此方法可有效將接收端之OFDM失真訊號進行非線性補償，故發送端將不再承受額外的大功率消耗；也同時也發現在功率回退為6dB時的條件下，PGA在疊代5次以內，就能發揮最大的還原效能。

Though the development of 5G (Fifth-generation wireless systems) technology, the high PAPR (Peak-to-Average Power Ratio) problem that caused by the OFDM (Orthogonal Frequency Division Multiplexing) signal may remain in it, as possible candidate waveforms of 5G are still based on OFDM’s multi-carrier transition structure.
The high PAPR signal passing through the HPA (High Power Amplifier) in the RF (Radio Frequency) module, this may induces the HPA work at the saturation region of its characteristic line and cause the nonlinear distortion with more noise into the signal for the receiver side.
The current solution of high PAPR (e.g. Digital Predistortion, Input Power Back-off, etc.) usually require additional components and endure the high power consumption to assist in improving the nonlinear property of HPA.
This paper proposed an improved Papoulis-Gerchberg iterative algorithm (PGA) and combining the Decision-Aided Reconstruction(DAR) to enhance the system’s performance, this algorithm can be embedded in the baseband radio processor at the receiver, and restore the received distortion signal. By performing the experiment in IEEE 802.11ad standard, we confirmed this algorithm can effectively compensate the received OFDM distortion signal at the receiver, and the transmitter won’t cause any additional power consumption. And found that when the iteration is within 5 times, the PGA perform highest restoration effect for the input back-off with 6dB.

誌謝 ii
摘要 iii
ABSTRACT iv
圖目錄 vii
表目錄 ix
第壹章 緒論 1
1.1 研究背景與動機 1
1.2 研究目標 2
1.3 本文架構 3
第貳章 文獻探討與背景知識 4
2.1 4G調變技術：OFDM 4
2.2 5G通訊系統 6
2.2.1 5G之特性要求 7
2.2.2 5G背景技術簡介 8
2.3 PAPR介紹 11
2.3.1 5G之高PAPR現象 11
2.3.2 高PAPR於HPA產生之問題介紹 13
2.4 現階段解決高PAPR之方法介紹 14
2.4.1 使用機率與失真降低OFDM訊號PAPR之技術 14
2.4.2 將高功率放大器線性化之技術 15
2.4.3 使用SC-FDM技術降低PAPR 18
2.5 帕波氏疊代演算法 18
2.6 總結 21
第参章 改良系統演算法 22
3.1 改良帕波氏疊代演算法 22
3.1.1利用失真訊號作為PGA之遺失訊號初值設定以減少疊代次數 22
3.1.2 Decision-Aided Reconstruction(DAR)演算法 24
3.2 最適當更新點(update threshold point)尋找方法 27
3.3 更新點位置之取捨與訊號平均功率點之關係 29
3.4 總結 31
第肆章 系統模擬 33
4.1 系統模組 33
4.1.1 IEEE 802.11ad之OFDM系統模擬 33
4.2 誤差向量幅度 37
4.3 模擬實驗與結果分析 38
4.4 總結 47
第陸章 結論 48
參考文獻 49

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