臺灣博碩士論文加值系統

正交分頻多工 ( Orthogonal Frequency Division Multiplexing，簡稱OFDM ) 技術有著高速資料傳輸與抵抗多路徑通道衰退的優點，因此被廣泛使用在無線通訊系統上。然而正交分頻多工技術在實際實現上仍需克服過高的峰均值功率比 ( peak-to-average power ratio，簡稱PAPR ) 的缺點，因此本論文致力於解決過高的峰均值功率比，其內容提供一個好的相位序列 ( a good phase sequence ) 概念，並使用最大長度位移暫存序列 ( Maximum-length shift-register sequence，簡稱M sequence ) 來實現此概念，然後把M序列與適應性子區塊相位權重 ( adaptive Subblock Phase Weighting，簡稱adaptive SPW ) 互相配合來達到降低PAPR的效果。電腦模擬證明我們的系統能有效率的降低PAPR，且在相同複雜度之下，我們的系統比傳統的選擇性映射 ( Selective Mapping，簡稱SLM ) 有更好的效能。

Orthogonal frequency division multiplexing ( OFDM ) has advantages of high data rate transmission and immunities to multipath fading, and so it has been widely used in wireless communication systems. A high peak-to-average power ratio ( PAPR ) is a main disadvantage of OFDM. A high value of PAPR occurrs when many signals on subchannels are coherently summed up. In this thesis, a new concept of good phase sequence is provided, and M sequences are used to realize the concept to reduce the PAPR in adaptive ( SPW ) systems. Computer simulation verified that the proposed system can effectively reduce PAPR, and it has better performance than selective mapping ( SLM ) has by means of the same complexity.

目錄

誌謝…………………………………………………………………………………....I
摘要…………………………………………………………………………………...II
Abstract……………………………………………………………………………....III
目錄…………………………………………………………………………………..IV
圖目錄………………………………………………………………………………..VI
第一章 緒論…………………………………………………………………………..1
第二章 正交分頻多工技術…………………………………………………………..3
2.1 簡介………………………………………………………………………….3
2.2 OFDM基本原理……………………………………………………………..4
2.3 保護區間與循環前置……………………………………………………….7
2.4 OFDM的優缺點……………………………………………………………..8
第三章 正交分頻多工之峰均值功率比……………………………………………..9
3.1 簡介………………………………………………………………………….9
3.2 峰均值功率比……………………………………………………………...10
3.3 峰均值功率比的分佈……………………………………………………...11
第四章 降低峰均值功率比的方法…………………………………………………15
4.1 簡介………………………………………………………………………...15
4.2 多訊號表示………………………………………………………………...15
4.3 選擇性映射………………………………………………………………...16
4.4 分部傳送序列……………………………………………………………...18
第五章 藉由隨機性相位插入降低峰均值功率比…………………………………21
5.1 簡介………………………………………………………………………...21
5.2 向量和與相位之關係……………………………………………………...21
5.3 離散OFDM訊號與相位的關係…………………………………………..27
5.3.1 各個取樣振幅與映射相位隨機分散範圍之討論…………………29
5.3.2 各個取樣振幅與等分 後的映射相位之討論…………………...32
5.3.3 映射相位對PAPR的影響………………………………………….35
5.4 相位序列與PAPR的關係…………………………………………………37
5.5 利用MSR技術降低PAPR效能與複雜度的關係………………………...38
5.6 利用M序列來降低PAPR…………………………………………………41
5.6.1 更新相位的演算法…………………………………………………41
5.6.2 傳送與接收…………………………………………………………42
5.6.3 門檻值與重複更新相位序列的次數的關係………………………43
5.6.4 模擬結果與討論……………………………………………………44
第六章 結論…………………………………………………………………………50
參考文獻……………………………………………………………………………..51





















圖目錄

圖2.1 (a)傳統多載波傳輸技術 (b)正交多載波技術………………………………..3
圖2.2 OFDM調變器………………………………………………………………….5
圖2.3 一個含有4個子載波的OFDM訊符………………………………………….5
圖3.1 OFDM訊號取樣功率圖……………………………………………………….9
圖3.2 不同的子載波在(3.8)式所產生的CCDF曲線圖…………………………...12
圖3.3 過取樣之方塊………………………………………………………………..12
圖3.4 OFDM訊號過取樣後的CDF圖……………………………………………...13
圖3.5 OFDM訊號過取樣後( )的CDF圖…………………………………….14
圖4.1 多訊號表示的方塊圖………………………………………………………..16
圖4.2 使用MSR技術PAPR的CCDF理想分佈圖………………………………...16
圖4.3 SLM的方塊圖………………………………………………………………...17
圖4.4 使用SLM技術PAPR的CCDF曲線圖……………………………………...18
圖4.5 PTS的方塊圖…………………………………………………………………18
圖4.6 在同樣使用4個IFFT數目下，PTS與SLM之PAPR的CCDF曲線圖……..20
圖5.1 128個向量之相位隨機分散在 下，做100次向量相加的結果分佈圖…...22
圖5.2 128個向量做10000次相加結果的CCDF統計圖…………………………..23
圖5.3 128個向量做10000次相加結果的CDF統計圖…………………………….23
圖5.4 兩大小一樣的向量做相加之關係特性圖…………………………………..24
圖5.5 變大與變小相位區域之示意圖……………………………………………..25
圖5.6 等分成2個相位、3個相位、4個相位及8個相位的示意圖……………..26
圖5.7 等分成16個相位、32個相位、64個相位及128個相位的示意圖………26
圖5.8 映射相位隨機分散在 時，各個取樣振幅的CCDF圖…………………….30
圖5.9 映射相位隨機分散在 時，各個取樣振幅的CCDF圖…………………….30
圖5.10 映射相位隨機分散在 時，各個取樣振幅的CCDF圖………………….31
圖5.11 映射相位隨機分散在 時，各個取樣振幅的CCDF圖…………………..31
圖5.12 等分成2個相位，從中隨機選取來當 ，各個取樣振幅CCDF圖……33
圖5.13 等分成2個相位，從中隨機選取來當 ，各個取樣振幅CDF圖……...33
圖5.14 等分成3個相位，從中隨機選取來當 ，各個取樣振幅CCDF圖……34
圖5.15 等分成 個相位，從中隨機選取來當 ，各個取樣振幅CCDF圖…...34
圖5.16 OFDM之PAPR的CCDF圖………………………………………………...36
圖5.17 OFDM之PAPR的CCDF圖………………………………………………...36
圖5.18 與 的關係圖………………………………………………………39
圖5.19 使用SLM技術所能降低的PAPR值與理想 之關係圖…………...40
圖5.20 不考慮附帶消息位元的adaptive SPW系統方塊圖……………………….40
圖5.21 長度為 的M序列……………………………………………………….41
圖5.22 更新相位的演算法示意圖…………………………………………………42
圖5.23 使PAPR降到 以下，所需 次重複更新相位序列之曲線圖……………43
圖5.24 映射方式為QPSK，其PAPR的CCDF曲線圖……………………………..44
圖5.25 映射方式為QPSK，所需 次重複更新相位序列之曲線圖………………45
圖5.26 映射方式為BPSK，其PAPR的CCDF曲線圖……………………………..45
圖5.27 映射方式為BPSK，所需 次重複更新相位序列之曲線圖……………….46
圖5.28 映射方式為16QAM，其PAPR的CCDF曲線圖…………………………...46
圖5.29 映射方式為16QAM，所需 次重複更新相位序列之曲線圖…………….47
圖5.30 在相同複雜度之下加入M序列與SLM的CCDF比較圖………………...47
圖5.31 映射方式為QPSK，其PAPR的CCDF曲線圖……………………………..48
圖5.32 映射方式為QPSK，所需 次重複更新相位序列之曲線圖………………49
圖5.33 在相同複雜度之下加入M序列與SLM的CCDF比較圖………………...49

參考文獻

[1] ETSI, “Radio broadcasting systems: Digital Audio Broadcasting ( DAB ) to mobile, portable and fixed receivers,” ETS 300 401 v1.3.2, Sept. 2000.

[2] ETSI, “Digital Video Broadcasting ( DVB ): Framing structure, channel coding and modulation for digital terrestrial television,” EN 300 744 v1.3.1, Aug. 2000.

[3] IEEE, “part 11: Wireless LAN Medium Access control ( MAC ) and Physical Layer ( PHY ) Specifications: High-speed Physical Layer in the 5 GHz Band,”IEEE Std 802.11a-1999, Sept. 1999.

[4] ANSI, “Asymmetric digital subscriber line ( ADSL ) metallic interface,” ANSI/TIEI/9J-007, Aug. 1997.

[5] R.van Nee and R. Prasad, OFDM Wireless Multimedia Communications: Artech House, 2000, pp. 229-253.

[6] G. Karam and H. Sari, “Analysis of predistortion, equalization and ISI cancellation techniques in digital radio systems with nonlinear transmit amplifiers,” IEEE Tran. on Comm., vol. 37, no. 12, pp. 1245-1253, Dec. 1989.

[7] L. C. Cimini, Jr., “Analysis and simulation of a digital mobile channel using orthogonal frequency division multiplexing,” IEEE Trans. Commun., vol. 33, no. 7, pp. 665-675, July 1985.

[8] R. W. Bauml, R. F. H. Fischer, J. B. Huber, “Reducing the peak-to-average power ratio of multicarrier modulation by selective mapping,” Electron. Lett., vol. 32, no. 22, pp. 2056-2057, Oct. 1996.

[9] S. Muller-Weinfurtner, OFDM for wilress communications: Nyquist windowing, peak-power reduction and synchronization. PhD Dissertation, Der Technischen Fakultat, der Universitat Erlangen-Nurnberg, 2000.



[10] S. H. Muller and J. B. Huber, “OFDM with reduced peak-to-average power ratio by optimum combination of partial transmit sequences,” Electron. Lett., vol. 33, no. 5, pp. 368-369, Feb. 1997.

[11] S. H. Muller and J. B. Huber, “A novel peak power reduction scheme for OFDM”. 1997 Int. Sym. on Personal, Indoor and Mobil radio comms. Proc., 1997, ( IEEE ), pp. 1090-1094.

[12] L. J. Cimini, Jr. and N. R. Sollenberger, “Peak-to-average power ratio reduction of an OFDM signal using partial transmit sequences with embedded side information,” Proc. IEEE GobeCom'00, pp. 746-750, Nov. 2000.

[13] C. C. Feng, C. Y. Wang, C. Y. Lin, and Y. H. Hung, “Protection and Transmission of Side Information for Peak-to-Average Power Ratio Reduction of an OFDM Signal Using Partial Transmit Sequences,” IEEE Vehicular Technology Conference, vol. 2, pp. 1354-1358, Oct. 2003.

[14] H. G. Ryu and K. J. Youn “A NEW PAPR REDUCTION SCHEME: SPW ( SUBBLOCK PHASE WEIGHTING ),” Consumer Electronics, IEEE Transactions on, vol. 48, pp. 81-89, Feb. 2002.

[15] R. van Nee, A. de Wild, “Reducing the peak-to-average power ratio of OFDM,” in Proceedings of VTC ’98, vol.3 pp. 2072-2076.

[16] A. D. S. Jayalath and C. R. N. Athaudage, “On the PAR Reduction of OFDM Signals Using Multiple Signal Representation,” IEEE Communications Lett., vol. 8, pp. 425-427, July 2004.