正交分頻多重存取以共同項載波頻率偏移補償以達到最小均方誤差之方法

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研究生：	賴彥亨 Yen-Heng Lai
論文名稱：	正交分頻多重存取以共同項載波頻率偏移補償以達到最小均方誤差之方法 An OFDMA System with Minimum Mean Square Error via the Common Carrier Frequency Offset Compensation
指導教授：	張大中 Dah-Chung Chang
口試委員:
學位類別：	碩士 Master
系所名稱：	資訊電機學院 - 通訊工程學系 Department of Communication Engineering
畢業學年度：	96
語文別：	中文
論文頁數：	72
中文關鍵詞：	均方誤差、載波頻率偏移、多重存取干擾、正交分頻多重存取
外文關鍵詞：	carrier frequency offset, OFDMA, minimum mean square error, multiple access interference
相關次數：	點閱：8 下載：0
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近年來正交分頻多重存取系統受到相當大的重視，被視為未來多用戶無線網路的主要技術。在這計劃中，對於正交分頻多重存取系統的載波頻率偏移提出一個新的改良架構；過去很多論文提出補償載波頻率偏移的方法，但是仍受到多重存取干擾的影響，雖然已經有消除多重存取干擾的研究可以有效降低多重存取干擾的影響，但如果整個接受端架構在時域加入共同載波頻率補償項，就可以使均方誤差最小。本計劃將探討共同載波頻率補償項的影響，並且提出一個新的方法來估測最佳共同載波頻率補償項使正交分頻多重存取系統接收端達到最小均方誤差的效能。此方法能針對特定的使用者有效的降低其錯誤率，最後模擬結果顯示出此架構能夠有效運作並且比過去既有沒有使用共同載波頻率補償項的研究有更好的性能。

In recent years, the orthogonal frequency division multiple access (OFDMA) system has been considered as an important technology for future multiuser wireless communications. An OFDMA system with a new carrier frequency offset (CFO) correction scheme is proposed in this thesis. The previous works compensating for the CFO effect at the OFDMA receiver can result in multiple access interference (MAI). Although the MAI cancellation scheme can be used to mitigate the MAI effect, the minimum mean square error (MMSE) performance depends on a common CFO value to be corrected in front of the DFT. We explore the effect of the common CFO and propose a new method to estimate the optimal common CFO at the OFDMA receiver to achieve the MMSE performance. The proposed scheme can decrease the bit error rate (BER) for particular subscribers. Simulation results show that the new algorithm combining MAI cancellation schemes outperforms the past schemes without common CFO correction.

第一章 序論	1
1	研究動機與目的	1
2	章節架構介紹	3
第二章 系統架構	4
1	OFDM 系統架構	4
1.1	正交分頻系統	4
1.2	循環字首	5
1.3	訓練符元	5
1.4	領航訊號	6
2	OFDMA系統簡介	6
2.1	多工存取	6
2.2	多重存取	7
3	OFDMA 上行傳送端架構	8
3.1	OFDMA系統傳送端架構	8
3.2	載波分配方式(Carrier Assignment Scheme, CAS)	9
第三章 載波頻率偏移在OFDMA系統上產生的問題	11
1	OFDM/OFDMA系統中載波頻率偏移的問題	11
1.1	OFDM系統中載波頻率偏移的問題	12
1.2	OFDMA系統中載波頻率偏移的問題	14
1.3	多重存取干擾分析	17
2	OFDMA上行接收機架構	19
2.1	在時域補償頻率偏移	19
2.2	在頻域補償頻率偏移	20
第四章 以共同項載波頻率偏移補償於OFDMA系統	24
1	基於HL之補償法加入前端共同項補償(CCFO)之解調	24
2	CCFO影響分析與說明	25
3	最佳CCFO估計方法	28
4	實現問題	31
4.1	共同頻率偏移補償項初始值偵測(Initial Detector)	31
4.2	MSE計算方法	32
5	Interleaved OFDMA系統以CLJL解調法之修正	35
5.1	遞迴法	35
第五章 模擬與分析	39
1	系統模擬參數與說明	39
1.1	訓練序列(Training Sequence)	40
1.2	領航(Pilot)訊號的配置	42
1.3	載波頻率偏移估計及追蹤偵測	42
1.4	通道估計	43
2	模擬結果	44
2.1	載波頻率偏移估計及追蹤偵測	44
2.2	通道估計	45
2.3	共同頻率偏移補償項初始值偵測	45
2.4	CCFO之觀察	46
3	性能比較	50
3.1	子頻帶(Subband)系統	50
3.2	交錯分配(Interleaved)系統	53
第六章 結論與未來展望	56
1	結論	56
2	未來展望	56
參考文獻	58

                                

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