OTFS 系統中降低功率峰均比的研究

Abstract

正交時頻空間(Orthogonal Time Frequency Space, OTFS)系統對於高速移動無線通信至關重要，能在挑戰性的環境中提供穩健的性能。然而，OTFS系統的一個顯著問題是高峰均功率比(Peak-to-Average Power Ratio, PAPR)，這可能導致功率放大器中的非線性失真，並降低整體系統性能。傳統峰均功率比的降低方法，如μ-law 壓縮，雖然有效，但往往會導致位元錯誤率(Bit Error Rate, BER)增加，因此在降低峰均功率比和保持信號品質之間需要做權衡。 本研究探討了窗口技術在OTFS系統中解決高峰均功率比問題的應用。我們探索了三種類型的窗口：多普勒偏移窗口、時間延遲窗口和複合窗口。使用了包括網格搜索和參數推導在內的各種參數選擇方法來評估這些窗口技術的有效性。實驗結果表明，窗口技術顯著降低了峰均功率比，同時保持了可控的位元錯誤率增加。 儘管結果令人鼓舞，我們的研究卻有參數計算複雜度等限制。未來的研究應集中於通過先進的算法來優化窗口參數。此外，將窗口技術與其他峰均功率比減少策略結合，可能會帶來更好的性能改進。 總之，本文提供了一種在OTFS系統中降低峰均功率比的新方法，驗證了窗口技術的有效性，並突出了它們在不顯著增加位元錯誤率的情況下提高高速移動無線通信性能的潛力。

Orthogonal Time Frequency Space (OTFS) systems are essential for high-mobility wireless communications, providing robust performance in challenging environments. However, a significant issue in OTFS systems is the high Peak-to-Average Power Ratio (PAPR), which can cause non-linear distortions in power amplifiers and degrade overall system performance. Traditional PAPR reduction methods, such as μ-law companding, while effective, often result in increased Bit Error Rate (BER), presenting a trade-off between reducing PAPR and maintaining signal quality. This research investigates the application of windowing techniques to address the PAPR problem in OTFS systems. We explored three types of windows: Doppler shift window, time delay window, and complex window. Various parameter selection methods, including grid search and parameters derivation, were employed to evaluate the effectiveness of these windowing techniques. Our experimental results demonstrate that windowing methods significantly reduce PAPR while maintaining a manageable increase in BER. Despite the promising results, our study acknowledges limitations such as the computational complexity of parameter optimization. Future research should focus on optimizing window parameters through advanced algorithms. Additionally, combining windowing methods with other PAPR reduction strategies could yield even better performance improvements. In conclusion, this thesis provides a novel approach to PAPR reduction in OTFS systems, validating the effectiveness of windowing techniques and highlighting their potential for enhancing high-mobility wireless communications without significantly increasing BER.