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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/18293

Title: STBC/SFBC-OFDM系統修正之對角最大概似率解碼方法
A Modified Diagonalized Maximum Likelihood Decoder for the STBC/SFBC-OFDM
Authors: 李國瑋
Contributors: NTOU:Department of Communications Navigation and Control Engineering
Keywords: 空-時區塊編碼;空-頻區塊編碼;正交分頻多工
Date: 2008
Issue Date: 2011-07-04
Abstract: STBC-OFDM於一個fasting fading 的環境中,其正交特性被破壞,將導致系統錯誤率效能增加;同樣地,SFBC-OFDM於相鄰子載波衰減不同時,亦有相同的問題。Diagonalized Maximum Likelihood Decoder(DMLD)可於fasting fading或相鄰子載波衰減不同的環境中,保持STBC-OFDM及SFBC-OFDM的正交特性,並利用ML偵測法使其具有最大分集增益(diversity gain)及最佳錯誤率效能。本論文針對STBC/SFBC-OFDM系統,提出Modified DMLD,經由修正後的Modified DMLD將不再經由ML偵測法,因此相較於Alomuti偵測法只需要增加些微的運算複雜度。模擬結果顯示,Modified DMLD與DMLD的錯誤率效能相近,並可大幅降低運算複雜度。
The orthogonality of the two consecutive STBC-OFDM symbols are no longer valid in a fast fading channel. As a result, and the bit error rate(BER) performance will be degraded. Similarly, SFBC-OFDM suffers the same problem when the frequency response of the adjacent two subcarriers are not identical. Diagonalized Maximum Likelihood Decod-er(DMLD) has been proposed to maintain the orthogonality of the STBC-OFDM and the SFBC-OFDM under severe fading environments. DMLD uses the ML detector to achieve the maximum diversity and best BER performance. In this thesis, we propose a modified DMLD for the ST/SFBC-OFDM scheme. The proposed method avoids the need of ML calculation. Simulation results show that BER performances are very similar between the proposed modified DMLD and DMLD. Besides, the proposed method can greatly reduce the computational complexity com-pared with the DMLD.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M95670032
Appears in Collections:[通訊與導航工程學系] 博碩士論文

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