以共同項載波頻率偏移補償於正交分頻多重存取系統中減少多重存取干擾之方法

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研究生：	張譽騰 Yeh-Tang Chang
論文名稱：	以共同項載波頻率偏移補償於正交分頻多重存取系統中減少多重存取干擾之方法 A Common Carrier Frequency Offset Compensation Method for Multiple Access Interference Reduction in OFDMA Systems
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：	95
語文別：	中文
論文頁數：	43
中文關鍵詞：	多重存取干擾、載波頻率偏移、正交分頻多重存取
外文關鍵詞：	CFO, mutiple access interference, carrier frequency offset, OFDMA, MAI
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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，被視為未來廣
域無線網路的主要技術，但是在此系統中，載波頻率偏移會破壞子載
波間的正交性，而造成子載波間相互干擾。且在多重存取的情況下，
無法對多個載波頻率偏移同時補償，因此造成多重存取干擾。接收機
為了避免此種干擾，需要使用多個平行系統對多位使用者各別補償，
因此使用環形迴積補償的架構被提出，但是，載波頻率不同步的影響
仍然存在。我們藉由分析多重存取干擾所產生的影響提出一個具共同
項載波頻率偏移補償的方法，並且此方法能夠基於估計所得到的載波
頻率偏移，針對特定的使用者而降低其錯誤率，最後模擬顯示出此系
統架構能夠有效運作並且提升系統的性能。

In recent years, the orthogonal frequency division multiple access (OFDMA) system has been viewed as a principal technique for future worldwide wireless networks. But in such a system, carrier frequency offset (CFO) can destroy the orthogonality among all subcarriers and induce inter-carrier interference. While in multiple accessing applications, different CFO misalignments exist in multiusers, which cannot be compensated simultaneously. This result is considered as multiple access interference (MAI). However, MAI can be reduced by using parallel compensation systems for different users at the basestation side and thus, a circular deconvolution solution has been proposed after the fast Fourier transform (FFT) operation. Since the effect of MAI is related to the value of CFO, a common CFO compensation method is studied in this paper to regulate MAI’s for a group of users whose performance may be interested in some TDMA slot. Simulation results show that the proposed method can achieve required results.

CH 1：緒論 ................................................................................................................... 1
1 研究動機.......................................................................................................... 1
2 章節架構介紹................................................................................................. 2
CH 2：OFDM 及OFDMA 系統介紹 .......................................................................... 3
1.1 正交分頻系統...................................................................................... 4
1.2 循環字首.............................................................................................. 5
1.3 訓練符元.............................................................................................. 6
1.4 領航訊號.............................................................................................. 6
2 OFDMA 系統簡介 .......................................................................................... 7
2.1 多工存取.............................................................................................. 7
2.2 多重存取.............................................................................................. 8
CH 3：OFDMA 之上行系統架構.............................................................................. 10
1 OFDMA 上行基頻系統架構 ........................................................................ 10
1.1 OFDMA 上行傳送端架構 ................................................................. 10
1.2 直序解調( Direct Method ) ............................................................... 12
2 CLJL 解調法 ................................................................................................. 13
3 消除多重存取干擾解調法........................................................................... 15
4 基於環形迴積之補償方法加入前端共同項補償之解調........................... 16
5 加入共同項補償後之訊號推導................................................................... 18
6 OFDMA 上行系統同步 ................................................................................ 21
6.1 取得模式............................................................................................ 21
6.2 追蹤模式............................................................................................ 23
7 多重存取干擾分析....................................................................................... 24
8 多重存取干擾降低....................................................................................... 27
8.1 共同頻率補償項估計........................................................................ 27
8.2 權重設定方式.................................................................................... 30
CH4：系統模擬及結果比較 ...................................................................................... 32
1 系統參數設定：........................................................................................... 32
2 模擬及結果：............................................................................................... 33
CH 5：結論 ................................................................................................................. 42
Refrences： .................................................................................................................. 43

                                

[1] IEEE Std. 802.16-2004 Standard for Local and Metropolitan Area Networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE Std. 802.16, 2004
[2] IEEE Std. 802.16e-2005 Standard for Local and Metropolitan Area Networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems-Amendment 2, IEEE Std. 802.16e, 2005
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[8] M.-O. Pun, M. Morelli and J.-J. Kuo, “Mazimum-Likelihood Synchronization and Channel Estimation for OFDMA Uplink Transmissions,” IEEE Trans. Commun., vol. 54, no. 4, pp. 726–736, April 2006.
[9] Y.-H. You, W.-G. Jeon, J.-W. Wee, S.-T. Kim, I. Hwang and H.-K. Song, “OFDMA Uplink Performance for Interactive Wireless Broadcasting, ” IEEE Trans. Broadcasting, vol. 51, no.3 , pp. 383–388 Sep. 2005

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