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研究生:吳芳茂
研究生(外文):Fang-Mao Wu
論文名稱:無保護區間正交分頻多工系統之通道估測研究
論文名稱(外文):A Study on Channel Estimation of OFDM Systems without Guard Interval
指導教授:陳儒雅
指導教授(外文):Ju-Ya Chen
學位類別:碩士
校院名稱:國立中山大學
系所名稱:通訊工程研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2008
畢業學年度:96
語文別:中文
論文頁數:182
中文關鍵詞:通道估測無保護區間正交分頻多工
外文關鍵詞:without guard intervalOFDMchannel estimation
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  近年來正交分頻多工(orthogonal frequency division multiplexing,OFDM)技術被廣泛的應用在高速傳輸通訊系統上。OFDM技術普及的主要原因之一是透過保護區間(guard interval,GI)的應用,使得OFDM系統在多重路徑通道底下能比其他系統展現較佳的性能。由於使用保護區間,它可將符號原先會受到符際間干擾(inter-symbol interference,ISI)的狀態轉換成不受符際間干擾的狀態。但使用不夾帶任何資訊的保護區間將會造成頻道間干擾(inter-carrier interference,ICI)。為了解決這個問題,保護區間便使用循環字首(cyclic prefix,CP)來避免從相鄰符號所造成的符際間干擾與從其他子通道所造成的頻道間干擾。但由於使用過長的保護區間將會使傳輸速率下降、降低頻譜效率(spectral efficiency)與增加訊雜比的損失(SNR loss)。假如我們選擇較短的保護區間時,通道長度也許會大於循環字首的長度,由於循環字首長度不足所造成的干擾可能會使得OFDM系統的性能嚴重衰減。為了解決此問題,通常是在OFDM傳輸系統的接收端設計一時域等化器來縮減通道長度,以此來減少符際間干擾與頻道間干擾。然而,由於複雜度的關係,最佳化設計的時域等化器是較難以去實現的
  因此我們使用時頻域交錯的重複式技術來減輕OFDM系統中由於循環字首長度不足所造成符際間干擾與頻道間干擾。並且在通道估測演算法中也加入我們的重複式技術來避免符際間干擾與頻道間干擾。重複式技術除了可以移除符際間干擾與維持循環摺積的特性。透過重複式技術的使用,我們可以改良通道估測的性能使得OFDM符號就像使用了足夠長度的循環字首。
  模擬時,我們考量最糟的情況,就是當OFDM符號傳送時,不使用保護區間。模擬結果顯示我們提出的方法可以有效地消除符際間干擾。並且將我們所提出包含通道估測與資料解調的演算法和決策回授通道估測、避免符際間干擾訓練序列通道估測與殘餘符際間干擾消除演算法比較。最後我們模擬幾種不同的通道環境來比較這些演算法面對不同通道環境時所能提供的系統性能改善情形。
  In recent year, orthogonal frequency division multiplexing (OFDM) technology has been widely used in high-speed communication systems. One primary reason for the popularity of OFDM is its ability to provide good performance in multi-path channels than the other systems through the use of Guard interval(GI). By using the Guard interval, it can convert these inter-symbol interference (ISI) channels into ISI-free channels. But Guard interval without any information will caused inter-channel interference. In order to solve this problem, a guard interval using cyclic prefix (CP) is inserted to avoid inter-symbol interference from the adjacent symbols and inter-channel interference from other sub-channels. However, using long cyclic prefix will decrease the transmission rate, reduce the spectral efficiency, and increase the signal-to-noise power ratio(SNR)loss. If we choose a shorter one, the channel length may be longer than the cyclic prefix. The interference caused by insufficient cyclic prefix can seriously degrade the performance of OFDM systems. In order to solve this problem, a time domain equalizer(TEQ)is usually used in the receiver to shorten the channel length of OFDM transmission system, and therefore minimize the ISI and ICI. However, because of its high complexity, the optimum design of TEQ is hard to realize.
  So we use an iterative channel estimation technique between time domain and frequency domain to mitigate the ISI and ICI which is caused by insufficient cyclic prefix. The iterative technique can remove ISI and hold the circular convolution property. By utilizing the iterative technique we can improve the channel estimation performance as the OFDM symbol used sufficient cyclic prefix.
  In the computer simulations, we consider the worst case that the OFDM symbol is transmitted without guard interval. The results show that our proposed method can effectively suppress residual ISI. The comparison between our proposed method including both proposed channel estimation(PCE)and proposed data demodulation(PDD), decision feedback channel estimation(DFCE), avoid ISI preamble channel estimation(AISIP), and residual ISI cancellation(RISIC)algorithm are made in this thesis. Finally, the performance improvement of the proposed algorithm under several channel conditions is considered and compared with other algorithms.
摘要 i
Abstract ii
目錄 iv
圖索引 vi
表索引 xi
第一章 簡介 1
1.1 研究背景與動機 1
1.2 文獻探討 2
1.3 各章提要 4
第二章 OFDM系統概論 5
2.1 OFDM系統架構 5
2.1.1 OFDM系統基本架構 6
2.1.2 保護區間 9
2.2 通道估測與等化 13
2.2.1 導航符號排列與設計方式 13
2.2.2 通道估測 15
2.2.3 等化器 16
2.3 符際間干擾與頻道間干擾之分析 19
2.3.1 符際間干擾 19
2.3.2 頻道間干擾 22
2.3.3 減少符際間干擾與頻道間干擾之研究 27
第三章 消除符際間干擾與頻道間干擾之演算法設計 29
3.1 系統架構 30
3.2 現有文獻探討 32
3.2.1 通道估測 32
3.2.2 干擾消除與資料解調 37
3.3 提出之演算法 38
3.3.1 通道估測 38
3.3.2 干擾消除與資料解調 44
第四章 系統模擬 45
4.1 不同程度之符際間干擾比較 45
4.1.1 觀測區間之決策 54
4.1.2 郊區通道模型 85
4.1.3 典型都會通道模型 90
4.1.4 丘陵地形通道模型 99
4.1.5 廣播通道模型 103
4.2 改變資料符號的調變方式 118
4.2.1 郊區通道模型 119
4.2.2 典型都會通道模型 122
4.2.3 丘陵地形通道模型 124
4.2.4 廣播通道模型 126
4.3  改變訓練序列與資料符號傳送比例 127
4.3.1 郊區地形通道模型 127
4.3.2 典型都會通道模型 128
4.3.3 丘陵地形通道模型 130
4.3.4 廣播通道模型 131
4.4 接收機移動速率的影響 131
4.4.1 郊區通道模型 134
4.4.2 典型都會通道模型 142
4.4.3 丘陵地形通道模型 149
4.4.4 廣播通道模型 160
第五章 結論 166
參考文獻 167
[1] J. A. Bingham, “Multicarrier modulation for data transmission: An idea whose time has com,” IEEE Commun. Mag., pp. 5-14, May 1990.
[2] European Telecommunication Standard Institute, “Radio broadcast systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers,” ETSI document, Draft prevision ETS 300 401, March 1994.
[3] European Telecommunication Standard Institute, “Digital Video Broadcasting (DVB); Framing structure channel coding and modulation for digital Terrestrial television (DVB-T),” ETSI document, Final Draft pr ETS 300 744, November. 1996.
[4] IEEE Std 802.11a-1999, PartII: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: High-speed physical layer in the 5GHz band, 1999.
[5] ITU-T, Telecommunication Standardization Sector of ITU, Recommendation G.992.1 “Asymmetric digital subscriber line (ADSL) transceivers,” Jun. 1999.
[6] H. Bolcskei, D. Gesbert, and A.-J. Paulraj, “On the capacity of OFDM-based spatial multiplexing systems,” IEEE Trans. Commun., vol. 50, pp. 225-234, Feb. 2002.
[7] J. Zhu, W. Ser, and A. Nehorai, “ Channel equalization for DMT with insufficient cyclic prefix, ”in Proc. Asilomar Conf. Signals, Systems and Computers, vol. 2, pp. 951-955, Oct. 2000.
[8] G.-R. Parsaee, H. Ebrahimzad, and A. Yarali, “MMSE-DFE equalizer design for OFDM systems with insufficient cyclic prefix, ” in Proc. IEEE 60th Veh. Technol. Conf., vol. 6, pp. 3828-3832, Sep. 2004.
[9] K. Van Acker, G.. Leus, M. Moonen, O. van de Wiel, and T. Pollet, “Per tone equalization for DMT-based system,” IEEE Trans. Commun., vol. 49, pp. 109-119, Jan. 2001.
[10] G.. Leus and M. Moonen, “Per-tone equalization for MIMO OFDM systems,” IEEE Trans. Signal Proc., vol. 51, pp. 2965-2975, Nov. 2003.
[11] N. Al Dhahir, “FIR Channel-shortening equalizers for MIMO ISI channels,” IEEE Trans. Commun., vol. 49, pp. 213-218, Feb. 2001.
[12] H. Zamiri-Jafarian , H. Khoshbin and S. Pasupathy, “Time-domain equalizer for OFDM systems based on SINR maximization,” IEEE Trans. Commun., vol. 49, pp. 1895-1900, Nov. 2001
[13] J. Zhang, W. Ser, and J. Zhu, “Effective optimisation method for channel shortening in OFDM systems,” IEE Proc. Commun., vol. 150, pp. 85-90, April 2003.
[14] R. Schur and J. Speidel, “An efficient equalization method to minimize delay spread in OFDM/DMT systems,” IEEE Int. Conf. Commun., vol. 5, pp. 1481-1485, 2001.
[15] R. Lopez-Valcarce, “Minimum delay spread TEQ design in multicarrier Systems,” IEEE Signal Processing Lett., vol. 11, pp. 682-685, Aug. 2004.
[16] S. Celebi, “Interblock Interference(IBI)Minimizing time-domain equalizer (TEQ) for OFDM,” IEEE Signal Processing Lett., vol. 10, pp. 232-234, Aug. 2003.
[17] G. Ysebaert, K. Vanbleu, G. Cuypers, and M. Moonen, “Joint window and time Domain equalizer design for bit rate maximization in DMT-receivers,” IEEE Trans. Signal Proc., vol. 53, pp. 1132-1146, Mar. 2005
[18] S.-W. Kim and K.-H. Tchah, “Performance analysis of adaptive equalizer design for OFDM wireless LAN,” IEEE Trans. Consum. Electron., vol. 5, pp. 512-514, May 2004
[19] D. Kim and G. Stuber, “Residual ISI cancellation for OFDM with applications to HDTV broadcasting,” IEEE J. Sel. Areas Commun., vol.16, pp. 1590-1599, Oct. 1998.
[20] S. Chen and C. Zhu, “ICI and ISI analysis and mitigation for OFDM systems with insufficient cyclic prefix in time-varying channels,” IEEE Trans. Consum. Electron., vol. 50, pp. 78-83, Feb. 2004.
[21] X. Wang, P. Ho, and Y. Wu , “Robust channel estimation and ISI cancellation for OFDM systems with suppressed features,” IEEE J. Sel. Areas Commun., vol. 23, pp. 963-972, May 2005.
[22] W.-R. Wu and C.-Y. Hsu, “Decision feedback IBI mitigation in OFDM Systems,” in Proc. IEEE Int. Symp. CAS, pp. 2619-2622, 23-26 May 2005.
[23] W. Zhong and Z. Mao, “Efficient time-domain residual ISI cancellation for OFDM-based WLAN systems,” IEEE Trans. Consum. Electron., vol. 52, pp. 321-326. May 2006.
[24] M. Toeltsch and A. F. Molisch, “ Efficient OFDM Transmission without cyclic prefix over frequency-selective channels,” in Proc. PIMRC, vol. 2, pp. 1363-1367, 2000.
[25] W. Zhong and Z. Mao, “Tentative decision based low complexity equalization for OFDM systems with insufficient cyclic prefix,” In Prco. Inf., Commun., Signal Processing, vol. 51, pp. 116-119, Dec. 2005.
[26] T. Keller, L. Piazzo, P. Mandarini, and L. Hanzo, “Orthogonal frequency division multiplex synchronization techniques for frequency-selective fading channels,” IEEE J. Sel. Areas Commun., vol. 19, pp. 999 –1008, June 2001.
[27] J.J. van de Beek, M. Sandell, and P.O. Borjesson, “ML estimation of time and frequency offset in OFDM systems,” IEEE Trans. Signal Proc., vol. 45, pp 1800-1805, July 1997.
[28] J.J. van de Beek, M.Sandell, M. Isaksson, and P. O. Borjesson, “Low-complex frame synchronization in OFDM systems,” IEEE Int. Conf. Commun., pp. 982-986, 1995.
[29] D. Lee and K. Cheun, “A new symbol timing recovery algorithm for OFDM systems,” IEEE Trans. Consum. Electron., vol. 43, pp. 366-367, June 1997.
[30] I. Barhumi, G. Leus, and M. Moonen, ”Optimal training design for MIMO OFDM systems in mobile wireless channels,” IEEE Trans. Signal Proc., vol. 51, no. 6, pp. 1615-1624, June 2003.
[31] S. A. Fechtel and H. Meyr, “Optimal linear interpolative channel estimation for TDMA-based personal mobile communications over frequency-selective channels, ” in Proc. IEEE 45th Veh. Technol. Conf., vol. 1, Jul. 1995, pp. 321–325.
[32] S. A. Fechtel and H. Meyr, “Optimal parametric feedforward estimation of frequency selective fading radio channels,” IEEE Trans. Commun., vol. 42, no. 2/3/4, pp. 1639–1650, Feb./Mar./Apr. 1994.
[33] V. Mignone and A. Morello, “CD3-OFDM: A novel demodulation scheme for fixed and mobile receivers,” IEEE Trans. Commun., vol. 44. pp. 1144–1151, Sep. 1996.
[34] J. Rinne and M. Renfors, “Pilot spacing in orthogonal frequency division multiplexing systems on practical channels,” IEEE Trans. Consum. Electron., vol. 42, pp. 959-962, Nov. 1996.
[35] Y. Le, “Pilot-symbol-aided channel estimation for OFDM in wireless systems,” IEEE Trans. Veh. Technol., vol. 48, pp. 1207-1215, July 2000.
[36] J. M. Cioffi and A. C. Bingham, “A data-driven multitone echo canceller,” IEEE Trans. Commun., vol. 42. pp. 2853–2869, Oct. 1994.
[37] X. Wang, Y. Wu, J. Chouinard, S. Lu, and B. Caron, “A channel characterization technique using frequency-domain pilot time domain correlation for DVB-T system,” IEEE Trans. Consum. Electron., vol. 49, no. 4, pp. 949–957, Nov. 2003.
[38] Y. Qiao, S. Yu, P. Su, and L. Zhang, “Research on an iterative algorithm of LS channel estimation in MIMO OFDM systems,” IEEE Trans. Broadcast., vol. 51, pp. 149-153, Mar. 2005.
[39] COST 207 Digital Land Mobile Radio Communications, Commission of the European Communities, Luxemburg, Belgium, 1989.
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