選擇性對應序列法在OFDM系統中對降低PAPR值效能分析

數位電視為未來的趨勢已不容置疑，現在有很多國家已設定數位電視廣播之開播時間表，並設定電視需含數位接收裝置之百分比及時間表。目前歐規數位電視廣播採用OFDM 作為傳輸規格,經過很多的測試, 均證實OFDM 是個很好的傳輸方式。由於OFDM具有抵抗頻道衰退以及抗多重路徑干擾之優點，因此4G亦正針對此一特性準備採用作為其傳輸規格。但由於OFDM之訊號為多個子載波所組成，因此其高峰值對平均值能量比便為其一大問題點。科學家們發明了各種不同理論如直接裁減、編碼方式、及改變編碼結構等；現今由於DSP之技術不斷更新，DSP運算速度越來越快,價錢也不斷的下降,因此改變編碼結構的方式越來越受到重視。本篇論文中，我們將OFDM 傳送接收系統作一些說明, 並對於減少OFDM PAPR 的技巧作簡短的討論.最後針對SLM之改變編碼結構方式，如不同的相位序列作模擬測試，另根據不同的相位序列cluster 數目討論然後分析找出最好的組合。

關鍵字

選擇性對應序列法

並列摘要

It is no doubt that the Digital Television (DTV) is the future trend. Now there are a lot of countries announced the DTV broadcasting schedule, and the schedule of import television with DTV receiver device. Now the Europe DVB-T adopted the OFDM as the transmission scheme. In Taiwan, Tatung University have fulfilled some field test to prove that the OFDM technology is better than 8-VSB when applying for mobile devices. Due to OFDM system has the following characteristic, such as anti channel fading and anti multi-path interference, 4G system also want to adopt the OFDM as it’s transmission specification. But OFDM signal is composed by several multi-carriers, it’s peak power will degrade it’s system battery life. Scientists develop several algorithms to reduce the PAPR such as clipping theory, coding technology, and scrambling algorithm. Now the SLM and PTS scrambling technology are more and more important as consequence of the improvement of DSP technology. In this thesis, an overview of OFDM system is presented. The schemes of reduction OFDM PAPR are discussed briefed. We focus on the different schemes of SLM scrambling such as different phase sequences, and we also discussed the best combination between different phase sequences and different clusters.

並列關鍵字

OFDM ； PAPR ； SLM

參考文獻

[1] Leonard J., Cimini Jr., and Nelson R. Sollenberger, “Peak-to-Average Power Ratio Reduction of an OFDM Signal Using Partial Transmit Sequences”, IEEE Comm. Letters, Vol. 4, No. 3, pp.86-88, March 2000.

[2] Imran Ali Tasadduq and Raveendra K. Rao, “Weighted OFDM with Block Codes for Wireless Communication”, in IEEE Pacific Rim Conference on Communications,Victoria BC, Canada, Aug. 26-28, 2001, pp.441-444.

[3] Pingyi Fan and Xiang-Gen Xia, “Block Coded Modulation for the Reduction of the Peak to Average Power Ratio in OFDM Systems”, Consumer Electronics, IEEE Trans. on Communication, Vol. 45, pp.1095-1099, Nov. 1999.

[4] G. Hill, M. Faulkner and J. Singh, “Cyclic Shifting and Time Inversion of Partial Transmit Sequences to Reduce the Peak-to-Average Power Ratio on OFDM”, Personal, Indoor and Mobile Radio Communication, Vol. 2, pp.18-21, Sept. 2000.

[5] C. Tellambura, “A Coding Technique for Reducing Peak-to-Average Power Ratio in OFDM”, in IEEE Global Telecommunication Conference, Vol. 5, Nov. 1998, pp.8-12.

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選擇性對應序列法在OFDM系統中對降低PAPR值效能分析

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