於正交分頻多工系統中雙選擇性通道之到達角，都卜勒頻率偏移以及通道估測

Estimation of Angle-of-Arrival, Doppler Frequency Offset and Channel for Doubly Selective Channel in OFDM Systems

宋志浩(Chih-Hao Sung)

指導教授 ： 馮世邁

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202203145

摘要

正交分頻多工系統在無線通訊系統中是一個常見的技術。對於頻率選擇性通道，正交分頻多工系統可以藉由單通道等化器消除符號間的干擾。然而，當通道具有雙選擇性，傳統的接收器將不足夠還原輸入訊號。因此，越來越多的文獻著重在正交分頻多工系統中對於雙選擇性通道的研究。
在本論文中，我們考慮基於分接延遲線模型的一個雙選擇性通道模型。分接延遲線模型只需要少量的都卜勒頻率偏移參數來表示都卜勒效應。我們研究裝有均勻線性陣列的正交分頻多工系統中的都卜勒效應。我們聚焦在到達角、都卜勒頻率偏移及通道估測。首先，我們展示如何使用旋轉不變性技術的信號參數估計方法對訊號參數的估計用於都卜勒影響通道中的到達角估測。對於都卜勒頻率偏移的參數和通道的估測，我們提出了基於訓練序列的估計器和基於導頻的估計器。此外，我們開發了一種兩步驟的演算法來提高基於訓練序列的估計器的通道估測性能。我們還進行了數值模擬以證明所提出方法的性能。
在具有大量天線的均勻線性陣列中，一種稱為混和陣列的結構經常被使用來減少類比數位轉換器的數量。在本論文中，我們還研究具有交錯混合陣列的正交分頻多工系統中的分接延遲線雙選擇性通道。在這個情況下，我們展示旋轉不變性技術的信號參數估計方法仍然可以應用於到達角的估測。接下來，我們可以透過分別傳送訓練資料和已知的導頻來估測都卜勒頻率偏移及通道。數值模擬展示所提出方法具有令人滿意的性能。

關鍵字

雙選擇性通道 ； 正交多頻多工系統 ； 到達角估測 ； 都卜勒頻率估測 ； 通道估測

並列摘要

The orthogonality frequency division multiplexing (OFDM) system is one of the popular techniques in wireless communication systems. For frequency selective channels, OFDM systems can achieve inter-symbol interference (ISI) free by using one-tap equalizer. However, when the channels are not only frequency selective but also time selective, the conventional equalizer is not enough to recover the input signal. Thus, there is an increasing interest in the study for doubly selective channel in OFDM systems.
In this thesis, we consider a model of doubly selective channels based on the tapped delay line (TDL). The TDL model only needs a few parameters called Doppler frequency offsets (DFO) to express the Doppler effect. We study the Doppler effect in OFDM systems equipped with uniform linear array (ULA). We focus on the angle-of-arrival (AoA), DFO and channel estimation. First, we show how to use the estimation of signal parameters via rotational invariance techniques (ESPRIT) method for AoA estimation in Doppler affected channels. Then channel estimation problem is also studied. For DFO and channel estimation, we propose both the training sequence-based estimator and the pilot-based estimator. Furthermore, we develop a two-step algorithm to improve the channel estimation performance for training sequence-based estimator. Numerical simulations are also carried out to demonstrate the performance of the proposed methods.
In ULA with a large number of antennas, a structure called hybrid array is often used to reduce the number of analog to digital converters. In this thesis, we also study the TDL doubly selective channels in OFDM systems with interleaved hybrid array. In this case, we show that the ESPRIT method can still be applied for AoA estimation. Next, for DFO and channel estimation, we develop two methods by transmitting the training sequence and pilots respectively. Numerical simulations show that the proposed methods have satisfactory performance.

並列關鍵字

Doubly selective channel ； OFDM systems ； AoA estimation ； DFO estimation ； channel estimation

參考文獻

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