載波頻率偏移估測技術應用於不同的正交分頻多工通訊系統

Carrier Frequency Offset Estimation Techniques for Various OFDM Communication Systems

林紋正(Wen-Jeng Lin)

指導教授 ： 林容杉 ； 洪志偉 ； 郭耀文

國立暨南國際大學/科技學院/電機工程學系/博士(2015年)

https://doi.org/10.6837/NCNU.2015.00317

摘要

時間同步和頻率同步是正交分頻多工（OFDM）通信系統重要且必要的一環。為了避免信號的失真，同步通常是接收器首要完成的主要任務。而頻率偏移補償是用於保持子載波中的正交性，對於系統性能表現有顯著的影響。
有三種類型的OFDM通信系統在本文中進行討論和研究。第一個是典型的循環前綴的OFDM（CP-OFDM）系統。其次，在IEEE802.11p的車載資通訊技術，其結構是基於OFDM的系統進行研究，其車載資通訊技術已經在美國和歐洲進行車輛間的通訊應用。最後，對時域同步OFDM（TDS-OFDM）系統進行研究，它也是一種基於OFDM的傳輸技術，所以它仍然有頻率同步的基本問題。
於本文中所提出的載波頻率校正偏移（CFO）估測演算法，是使用具有特定編碼的訓練序列，此頻率同步演算法採用兩個相同的訓練序列之間的相關性。首先，將一組隨機參數用於粗略的頻率補償。然後，一個改進的CFO估測演算法被提出，此演算法需要比較功能去篩選出正確的載波頻率偏移。最後，在本論文中所提出的CFO估測演算法的確具有相比於這三個通信系統的另一常規方案，進一步提高了均方誤差（MSE）的性能。

關鍵字

正交分頻多工系統 ； 頻率同步 ； 序列配置

並列摘要

Synchronization for both time and frequency is important and necessary in orthogonal frequency division multiplexing (OFDM) systems. In order to avoid signal distortion, synchronization is the major task to be completed generally in the receiver end. To preserve the property of orthogonality among subcarriers, the compensation of frequency offset is significant for system performance.
Three types of OFDM communication systems are discussed and investigated. The first one is the typical cyclic-prefix OFDM (CP-OFDM). Secondly, the IEEE 802.11p standard whose configuration is an OFDM-based system is studied and it has been employed in the U.S. and Europe for inter-vehicle communications. Finally, the time-domain synchronous OFDM (TDS-OFDM) system is investigated and it is one of OFDM-based transmission techniques, so it still has to cope with the issue of frequency synchronization.
The proposed estimation algorithm with a particular preamble pattern is developed for the correction of carrier frequency offset (CFO). This synchronization algorithm employs the correlation between two identical halves of a training sequence. First of all, the coarse compensation is used for a rough synchronization. Then, an improved CFO estimation method is proposed with the comparison of two correlation functions. Some simulation results are given to illustrate the advantages of the proposed synchronization schemes. As a result, the proposed estimation method indeed has the potentials to further enhance the mean square error (MSE) performance compared to the other conventional schemes in those three communication systems.

並列關鍵字

OFDM systems ； frequency synchronization ； preamble pattern

參考文獻

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