正交分頻多工系統最大可能性聯合載波頻率和通道估測;Joint Maximum Likelihood Estimation of Carrier Frequency Offsets and Channels in OFDM Systems

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题名:	正交分頻多工系統最大可能性聯合載波頻率和通道估測;Joint Maximum Likelihood Estimation of Carrier Frequency Offsets and Channels in OFDM Systems
作者:	邱士豪;Chiu,Shi-Hao
贡献者:	通訊工程研究所
关键词:	正交分頻多工載波頻率偏移;joint maximum likelihood estimation;carrier fre
日期:	2012-07-19
上传时间:	2012-09-11 18:49:10 (UTC+8)
出版者:	國立中央大學
摘要:	這篇論文探討了在正交分頻多工系統中利用最大可能性準則做載波頻率偏移和頻率選擇通道響應的聯合估測。首先介紹訊號模型以及聯合估測器的推導，提出的演算法可以分成兩大部分，第一部分是利用旋轉觀念初步的估測載波頻率偏移再利用頻域等化器來提升估測準確率，第二部分則是利用疊代的觀念來找到最大的頻率波峰。所提出的疊代演算法不需要做初始值的猜測，可以正確收斂至全域最大值而不是區域最大值，演算法的計算複雜度和格子搜尋法比較起來大幅度的減少，較利於硬體上的實現而且在平均錯誤平方 (MSE) 精確度上也貼近於克拉瑪 (CRB) 界線。A joint estimation method of carrier frequency offset and frequency selective channel response in orthogonal frequency division multiplexing (OFDM) systems is presented in this thesis based on the maximum likelihood (ML) criterion. The signal model is introduced and a joint estimator is derived. The proposed algorithm can be divided into two major portions. The first part is to use the rotation concept to estimate the initial CFO and design the frequency domain equalizer. The second part is making use of iterative concept to find the true frequency peak for better estimate. The proposed scheme does not require initial random guess as regular iterative algorithms, in which may suffer from the problem of the convergence to the local maximum. The proposed approach can surely converge to the global maximum for achieving the solution. The computation complexity is much less than the grid-search method and easily be implemented in hardware. The MSE performance of the proposed algorithm is close to the Cramer-Rao Lower bound which is shown in the simulation result.
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