超高速移動環境下正交分頻多工系統載波頻率偏移估測之研究

A Study on Carrier Frequency Offset Estimation for OFDM in Very High Mobility Environment

簡銘成(Ming-Cheng Chien)

指導教授 ： 張進福

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02680

摘要

本論文主要在探討OFDM在超高移動速度環境下頻率偏移估計的效能分析，首先我們回顧文獻上兩個常被討論的頻率偏移估計的方法(在此我們簡稱ad hoc估計子與BLUE估計子)，並探討這兩個估計子在超高移動速度環境下估計的準確度。

本論文的第一個部分即使用選擇參數H的方法，使得估計子在計算延遲相關的時候能在同調時間內計算，以降低時變通道破壞原訓練符元的相關性，進而提升估計子在高速移動下的準確性。在第二個部分中加入權重的概念，提高估計較準的估計子的權重以減低高移動速度下時變通道的干擾。第三個部分利用高鐵路徑已知且平原區訊號的主路徑波訊號較強的特性，將都普勒偏移在接收端先補償回來，以提升頻率偏移估計的準確性。

關鍵字

超高速移動環境 ； 正交分頻多工 ； 載波頻率偏移 ； 都普勒效應 ； 雙選擇性通道 ； 頻率同步 ； 最佳線性無偏估計

並列摘要

This thesis considers the problem of carrier frequency offset estimation for OFDM system in very high mobility environment. First of all, two mostly cited methods for carrier frequency offset estimation, which are ad hoc estimator and BLUE estimator, are reviewed and. Then we used the two estimation method in very high mobility environment and discuss the estimation accuracy.
In the first part of this thesis, we propose a method that the delay correlation was calculated in coherence time for improving the estimation accuracy in very high mobility.
In order to achieve better estimation accuracy, we propose a frequency offset estimator based on weighting method. The mean square error (MSE) performance is better than the method without weighting.
In the last part of this thesis, we applied the character of Taiwan high speed rail that the route is known in advance in order to compensate the Doppler frequency before the carrier frequency offset estimator. The proposed methods achieve substantial mean square error (MSE) performance improvement.

並列關鍵字

OFDM ； Carrier frequency offset ； Doppler effect ； BLUE ； Frequency synchronization ； Doubly selective channel ； Very high mobility environment

參考文獻

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