系統識別號 | U0002-1806200816073500 |
---|---|
DOI | 10.6846/TKU.2008.00546 |
論文名稱(中文) | 頻率選擇性通道下正交分頻多工系統之頻率同步與通道估測 : 最大概似率與最小平方估測法 |
論文名稱(英文) | Frequency Synchronization and Channel Estimation for OFDM Systems over Frequency-Selective Channels: ML and LS Approaches |
第三語言論文名稱 | |
校院名稱 | 淡江大學 |
系所名稱(中文) | 電機工程學系碩士班 |
系所名稱(英文) | Department of Electrical and Computer Engineering |
外國學位學校名稱 | |
外國學位學院名稱 | |
外國學位研究所名稱 | |
學年度 | 96 |
學期 | 2 |
出版年 | 97 |
研究生(中文) | 南尚傑 |
研究生(英文) | Shang-Chieh Nan |
學號 | 695441104 |
學位類別 | 碩士 |
語言別 | 繁體中文 |
第二語言別 | 英文 |
口試日期 | 2008-06-16 |
論文頁數 | 57頁 |
口試委員 |
指導教授
-
嚴雨田
委員 - 易志孝(chyih@ee.tku.edu.tw) 委員 - 劉鴻裕(hongyu.liu@msa.hinet.net) |
關鍵字(中) |
正交分頻多工 最大概似 都普勒偏移 頻率偏移 頻率選擇性衰退 通道頻率響應 |
關鍵字(英) |
OFDM Maximum-likelihood Doppler spread Carrier frequency offset Frequency selective fading Channel frequency response Gradient search Inter-symbol interference |
第三語言關鍵字 | |
學科別分類 | |
中文摘要 |
在本論文中,我們首先介紹正交分頻多工 (orthogonal frequency division multiplexing, OFDM) 傳輸與調變技術的基本原理。其次,我們提出一種最大概似率 (maximum-likelihood, ML) 演算法作聯合頻率偏移與通道頻率響應估測 (joint frequency synchronization and channel estimation)於頻率選擇性通道 (frequency-selective channels)中的OFDM 系統。頻率偏移可能由載波頻率不同步及都卜勒頻譜延展(Doppler frequency spread) 兩者效應所引起。我們使用適應性梯度搜尋法 (adaptive gradient search) 進行頻率偏移的估測,而通道頻率響應 (channel frequency response) 將隨頻率偏移估測後獲得。然後在矯正頻率偏移後,我們再以合理假設運用最小均 (least squares)方法求得通道估測做一比較。我們提出的各種估測法在模擬結果中有十分準確的表現。估測法的模擬結果效能與理論分析之結果十分一致。 |
英文摘要 |
In this thesis, we first introduced the basic principle of the orthogonal frequency division multiplexing (OFDM) transmission and modulation technique. Second, we present a maximum-likelihood (ML) estimation algorithm for jointly estimate frequency offset and channel frequency response (CFR) for OFDM systems in frequency selective channels. Then, with proper approximations after frequency offset correction, a least squares approach is also used for channel estimation for comparison. The frequency offset may arise from both carrier frequency mismatch and Doppler spread effect. We use adaptive gradient search to estimate the frequency offset, the channel frequency response estimation is subsequently obtained. Simulation results of our proposed estimations show great estimation accuracies and are found in excellent agreements with theoretical predictions. |
第三語言摘要 | |
論文目次 |
CONTENTS ACKNOWLEGENME I CHINESE ABSTRACT II ENGLISH ABSTRACT III CONTENTS IV LIST OF FIGURE VI CHAPTER 1 INTRODUCTION 1 CHAPTER 2 OFDM PRINCIPLE AND STRUCTURE 3 2.1 Introduction 3 2.2 Mathematical Description of an OFDM Signal and System 8 2.3 Frequency Offset 11 CHAPTER 3 MULTIPATH PROPAGATION AND FADING CHANNEL MODELS 17 3.1 Multipath Propagation 17 3.1.1 Frequency Selective and Nonselective (Flat) Fading 18 3.1.2 Slow and Fast Fading Channels 19 3.2 Fading Models 20 3.2.1 Rayleigh Fading Model 20 3.2.2 Rice Fading 22 CHAPTER 4 MAXIMUM LIKELIHOOD ESTIMATION 23 CHAPTER 5 JOINT FREQUENCY SYNCHRONIZATION AND CHANNEL ESTIMATION 27 5.1 Doppler Spread and Carrier Frequency Offset 27 5.2 The Joint Maximum Likelihood Estimation 30 5.3 A Least squares Approach for Channel Estimation 35 5.4 Channel Estimator Performances 37 CHAPTER 6 NUMERICAL RESULTS 40 CHAPTER 7 CONCLUSIONS 54 REFERENCES 55 LIST OF FIGURE Figure 2.1.1 Data transmission using multicarriers 4 Figure 2.1.2 Guard Interval protect 5 Figure 2.1.3 Concept of cyclic prefix 6 Figure 2.1.4 Illustration of a frequency selective channel………......................……..….7 Figure 2.2.1 Baseband OFDM Transmitter 9 Figure 2.2.2 Baseband OFDM Receiver (cyclic prefix removal omitted) 12 Figure 2.2.3 The OFDM system structure……………………………………………...16 Figure 6.1 Learning curve of gradient search for frequency offset estimation. 20dB SNR…………………...…….........………………………………….....…42 Figure 6.2 Learning curve of gradient search for estimate frequency offset, and SNR is 40dB. ..……………………………………………………………....……43 Figure 6.3 Estimated frequency offset vs. true frequency offset. SNR is 20. 44 Figure 6.4 Variance of the frequency offset estimator vs. SNR. 45 Figure 6.5 The ML estimate of vs. SNR and the true (solid lines) 46 Figure 6.6 The ML estimate of vs. SNR and the true (solid lines). 47 Figure 6.7 Comparison of the ML estimator variance and the theoretical LS estimator variance for . 48 Figure 6.8 Comparison of the ML estimator variance and the LS estimator variance for . ........................................................................................................49 Figure 6.9 The LS estimate of and the true (solid lines). 50 Figure 6.10 The LS estimate of and the true (solid lines). 51 Figure 6.11 Comparison of the experimental LS estimation variance and theoretical LS estimation variance for . 52 Figure 6.12 Comparison of the experimental LS estimation variance and theoretical LS estimation variance for . 53 |
參考文獻 |
[1] X. Wang; Host-Madsen, A., “Advanced Signal Processing for Wireless Multimedia Communications”, Information Technology: Coding and Computing, 2000. Proceedings. International Conference on, 27-29 March 2000, pp. 109 – 114. [2] R. van Nee, G. Awater, M. M. H. Takanashi, M. Wester, and K. Halford, “New high-rate wireless LAN standards,” IEEE Communication Magazine, vol. 37, pp. 82–88, December 1999. [3] IEEE 802.11 Task Group a, Part 11, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High-speed Physical Layer in the 5 GHz Band,” 1999. [4] M. Morelli, C.-C. Jay Kuo, Man-On Pun, “Synchronization Techniques for Orthogonal Frequency Division Multiple Access (OFDMA):A Tutorial Review” Proceeding of the IEEE, pp. 1394 – 1427, July 2007 [5] A. Peled and A. Ruiz, “Frequency domain data transmission using reduced computationally complexity algorithms,” in Proceedings of IEEE International Conference of Acoustics, Speech and Signal Processing, (Denver), pp. 964–967, April 1980. [6] X. Ma, H. Kabayashi, and S. C. Schwartz,, “Joint frequency offset and channel estimation for OFDM,” IEEE Global Telecomm. Conf. 2003, Dec. 2003, vol.3, pp. 15-19. [7] T. Roman, M. Enescu and V. Koivunen, “Joint time-domain tracking of channel and frequency offset for OFDM systems” Signal Processing Advances in Wireless Communications, 2003. June 2003, pp. 605-609. [8] H. Minn, V. K. Bhargava, and K. B. Letaief, “A combined timing and frequency synchronization and channel estimation for OFDM,” IEEE Trans. Commun., vol. 54, no. 3, pp. 416-422, Mar. 2006. [9] M.-O. Pun, M. Morelli, and C-C J. Kuo, “Maximum-likelihood synchronization and channel estimation for OFDMA uplink transmissions,” IEEE Trans. Commun., vol. 54, no. 4, pp. 726-736, Apr. 2006. [10] J. Li, G. Liao, and Q. Guo, “MIMO-OFDM Channel Estimation in the Presence of Carrier Frequency Offset” EURASIP Journal on Applied Signal Processing, Apr. 2005, pp.525-531. [11] P. H. Moose, “A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction,” IEEE Trans. Commun., vol. 42, pp. 2908–2914, Oct. 1994. [12] J. H. Yu and Y. T. Su, “Pilot-Assisted Maximum-Likelihood Frequency-Offset Estimation for OFDM Systems,” IEEE Trans. Commun., vol. 52, pp. 1997–2008, Nov. 2004. [13] I. Kalet, “The multitone channel,” IEEE Trans. Comm., vol. 37, no. 2, pp.119-125, Feb. 1989. [14] O. Edfors, M. Sandell, J-J van de Beek, S. K. Wilson, and P. O. Borjesson, “OFDM channel estimation by singular value decomposition,” IEEE Trans. Comm., vol. 46, no. 7, July 1998, pp. 931-939. [15] L. L. Scharf, Statistical Signal Processing, Reading, MA., Addison-Wesley, 1991. [16] J. G. Proakis, Digital Communications, 4th ed. New York: McGraw-Hill, 2001. [17] T. S. Rappaport, Wireless Communications, 2nd ed. Prentice Hall, 2002. [18] T. David, V. Pramod, Fundamentals of Wireless Communication, Cambridge University Press 2005. [19] K. F. Yang, A Least Squares Approach for OFDM Channel Estimation in Frequency-Selective Channels, Master’s Thesis, Tamkang University, 2008. [20] D. C. Chu, “Polyphase codes with good periodic correlation properties,” IEEE Trans. Inform. Theory., pp. 531-532, July 1972. [21] S. Haykin, Adaptive Filter Theory, 4th ed. Prentice Hall, 2002. |
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