於交織正交分頻多工存取上行系統之基於修正型傳播子方法的載波頻率偏移估測

Carrier Frequency Offsets Estimation Based on Modified Propagator Methods for Interleaved OFDMA Uplink Systems

郭鴻志(Hong-Jhih Kuo)

指導教授 ： 張安成

嶺東科技大學/資訊學院/資訊科技系碩士班/碩士(2017年)

摘要

本論文係處理於交織正交分頻多工存取(Orthogonal Frequency Division Multiple Access, OFDMA)上行系統之簡單和有效的殘餘載波頻率偏移(Carrier Frequency Offset, CFO)估測，研究的目標是從估計器之目標函數的有效性和計算複雜性以及頻譜搜尋的計算複雜度來進行。基於接收資料矩陣的結構代數特性之傳播子方法(Propagator Method, PM)已經被專用於訊號源的定位，且傳播子方法(PM)已經被證實具有低的計算負載且於無雜訊或高訊號雜訊比(Signal to Noise Ratio, SNR)環境下是有效的。無論如何，傳播子方法(PM)對抗雜訊的能力並不強健。經結合順向逆向(forward-backward, FB)自相關矩陣和傳播子方法(PM)，此所提出的基於頻譜搜尋的FBPM估測器可以提高CFO的估測精準度。首先，本論文之目的係驗證使用FB自相關矩陣的LU和QR因子分解對FBPM估測器於存有雜訊的情況下是有效的。但是對於基於頻譜搜尋估測器，它們在計算負荷上也是昂貴的。因此，本論文還提出了基於多項式求根版本的處理方法，用於減少頻譜搜尋所衍生的計算負荷。同時於交織正交分頻多工存取(OFDMA)上行系統亦建議一種最大輸出功率估測方法，其基於給予某一初始值後去尋找基於一階泰勒級數展開之新的CFO向量，此一尋找新的CFO向量之問題可以被形成為廣義特徵值(generalized eigenvalue)問題的封閉解，並容易求得CFO估測值；另外，由於更精確的殘餘CFO估測可以提供更精確的殘餘CFO補償，本論文亦呈現具有較少計算負荷的疊代估測方式來增進所提估測器的性能，最後，提供了一些電腦模擬結果來說明在單一個OFDMA資料區塊下所提出的盲目估測方法的有效性。

關鍵字

交織正交分頻多工存取 ； 載波頻率偏移 ； 傳播運算子 ； LU分解 ； QR分解 ； 多項式求根 ； 泰勒級數展開 ； 廣義特徵值 ； 疊代

並列摘要

This thesis deals with simple and effective residual carrier frequency offset (CFO) estimation for interleaved orthogonal frequency division multiple access (OFDMA) uplink systems. The goal of research is proceed from the effectiveness and computational complexity of the estimator's objective function, and the computational complexity of the spectrum search. The propagator method (PM) has been dedicated to source localization which is based on the structural algebraic properties of the received data matrix. It has been shown that the PM has low computational load and is efficient in nonnoisy or high signal-to-noise ratio (SNR) environments. However, propagator is not robust to noise. In conjunction with the forward-backward (FB) autocorrelation matrix and PM, the presented searching-based FBPM estimator can improve the CFO estimate accuracy. First, this thesis aims at demonstrating the usefulness of LU and QR factorizations of the FB autocorrelation matrix for the FBPM estimators are efficient in noisy situations. But for the searching-based estimators, they are also computationally expensive. Therefore, the polynomial rooting version approaches are also presented for reducing search computational load. Meanwhile, a maximal output power estimation method is suggested which finds a new CFO vector based on first order Taylor series expansion of one initially given for interleaved OFDMA uplink systems. The problem of finding the new CFO vector is formulated as the closed form of a generalized eigenvalue problem, which allows one to readily solve it. Since raising the accuracy of residual CFO estimation can provide more accurate residual CFO compensation, this thesis also presents an iterative estimate approach with less computation load to improve the CFO estimation performance. Finally, several computer simulation results are provided for illustrating the effectiveness of the proposed blind estimate approaches under a single OFDMA data block.

並列關鍵字

interleaved OFDMA ； carrier frequency offset ； propagator method ； LU factorization ； QR factorization ； polynomial rooting ； Taylor series expansion ； generalized eigenvalue ； iterative

參考文獻

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