臺灣博碩士論文加值系統

在單載波與多載波的無線通訊系統中，頻寬使用效益佔了很重要的地位。雖然保護區間（Guard Interval）或循環字首(Cyclic Prefix)的使用可以大幅的降低接收端等化的複雜度；然而，保護區間的使用也浪費了部份的頻寬。同時在無線的傳輸之下，多重路徑（Multipath）所造成的通道延遲擴散(Delay Spread)可能會超過保護區間的長度。在循環字首不足的情形下，相鄰區塊間干擾（Interblock Interference, IBI）以及相鄰符元間干擾(Intersymbol Interference, ISI)將被引進且造成系統效能嚴重衰減，故高效能的等化器是必須被開發來改善保護區間不足的問題。
本篇論文中我們為單載波頻域等化系統（SC-FDE）提出了一個有效的保護區間重建的方法。利用改良式的暫時性決策等化器（Tentative Decision-Based Equalizer），我們重建了通道的循環特性（Cyclicity）並且消除由於保護區間不足所造成的干擾。雖然我們犠牲了等化時間及些許的複雜度，但電腦模擬顯示出我們提出的方法在效能表現上優於傳統的暫時性決策等化器。

Efficiency of bandwidth utilization plays an important role in wireless communication systems such as single-carrier (SC) systems and discrete Multi-tone (DMT) systems. Although employing guard interval (GI) or cyclic prefix (CP) can greatly simplify the complexity of receiver, it also results in considerable loss in bandwidth utilization. Meanwhile, in wireless transmission, Delay spread due to multipath effect may exceed the length of cyclic prefix. When CP is insufficient, Interblock interference (IBI) and intersymbol interference (ISI) occur and that results in significant degradation on system performance. A well-designed equalizer is needed to combat IBI and ISI when CP is insufficient.
We propose an efficiency cyclic prefix reconstruction method for single-carrier systems with frequency-domain equalization (SC-FDE) in this thesis. We restore the cyclicity of the channel and eliminate the interferences by using the modification Tentative Decision-Based Equalizer. Although the system will be delayed for equalization and increase little complexity due to iteration, but we can get a better performance than conventional tentative method.

Chinese Abstract I
English Abstract II
Acknowledgement III
Contents IV
List of Tables VI
List of Figures VII

1. Introduction………………………………………………………..1

2. System Model………………………………………………………3
2.1 Single-Carrier Frequency-Domain Equalization System..........3
2.2 Single-Carrier Cyclic Prefix Modulation..................................8
2.3 SC System Model for Delay Spread Longer Than the CP…..11
2.4 Channel Model………………………………………………19
2.4.1 Modification of Jake’s Rayleigh Fading Model….....19
2.4.2 Multipath Model………………………………….....21

3. Interference Elimination Schemes for SC-FDE with Insufficient CP………………………………………………………………….24
3.1 Zero Forcing Decision Feedback Equalization (ZF-DFE)…..25
3.2 Tentative Decision-Based Equalization……………………...30
3.3 Proposed Iterative Cyclic Reconstruction for SC-FDE with Insufficient CP………………………………………………34
3.3.1 Modification of Tentative Decision-Based
Equalization Method……………………………….35
3.3.2 Optimum Weighting Coefficients for Cyclicity
Restoration………………………………………..43
3.3.3 Summarize of Proposed Equalization………….45

4. Simulation Results………………………………………………...47

5. Conclusions………………………………………………………..53

Bibliography…………………………………………………………...54

[1] Henrik Schulze and Christian Luders, Ed., Theory and Applications of OFDM and CDMA: Wideband Wireless Communications. John Wiley & Sons, Ltd., 2005.

[2] D.D. Falconer, S.L. Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson, “Frequency domain equalization for single-carrier broadband wireless systems,” IEEE Commun. Mag., vol. 40, pp. 58–66, Apr. 2002.

[3] S. Chen, C. Zhu, ”ICI and ISI analysis and mitigation for OFDM systems with insufficient cyclic prefix in time-varying channels”, IEEE Transactions on Consumer Electronics, Vol. 50, No.1, pp 78-83, Feb 2004.

[4] Naresh Sharma and Ashok A. Tikku, “Is the cyclic prefix necessary?”, IEEE ISIT 2006, Seattle, USA, July 9 14, 2006.

[5] R. K. Martin and C. R. Johnson, Jr., "Adaptive Equalization: Transitioning from Single-Carrier to Multicarrier Systems," IEEE Signal Processing Magazine, vol. 22, no. 6, November 2005, pp. 108-122.

[6] T. Hwang, Y. (G.) Li. Iterative cyclic prefix reconstruction for coded single-carrier systems with frequency-domain equalization (SC-FDE). In Proc. IEEE Vehicular Technology Conference, Korea, Apr. 2003, vol.3, pp.1841–1845.

[7] K. Hayashi and H. Sakai, ”Single Carrier Block Transmission Without Guard Interval”, IEEE PIMRC.2006, pp. 1-5, Sept. 2006.

[8] P. W. Melsa, R. C. Younce, and C. E. Rohrs, “Impulse response shortening for discrete multitone transceivers,” IEEE Trans. Commun., vol. 44, no. 12, pp. 1662–1672, Dec. 1996.

[9] J. Zhang, W. Ser, and J. S. Zhu, “Effective optimisation method for channel shortening in OFDM systems,” IEE. Communs. Proceedings, vol. 52, pp. 85–90, Apr. 2003.

[10] W. Henkel and T. Kessler, "Maximizing the channel capacity of multicarrier transmission by suitable adaptation of the time-domain equalizer," IEEE Trans. Commun., vol.48, no.12, pp.2000–2004, Dec. 2000.

[11] D. Kim and G. L. St¨uber, “Residual ISI cancellation for OFDM with application to HDTV broadcasting,” IEEE J. Sel. Areas Commun., vol.16, no. 8, pp. 1590-1599, Oct. 1998.

[12] S. Kunaruttanapruk and S. Jitapunkul, “The novel decision feedback equalizer for OFDM system with insufficient cyclic prefix,” in Proc. 2nd Annual Conf. Communication Networks and Services Research 2004, pp.19-24.

[13] G. Parsaee, H. Ebrahimzad, and A. Yarali, “MMSE-DFE equalizer design for OFDM systems with insufficient cyclic prefix,” in Proc. IEEE VTC’04-fall, Los Angeles, USA, 2004, pp. 3828–3832.

[14] W. Zhong and Z. Mao, “Tentative decision based low complexity equalization for OFDM systems with insufficient cyclic prefix,” in Proc. Int. Conf. on Inf., Commun. and Sig. Proc., Bangkok, Thailand, Dec.2005, 116–119.

[15] W. Zhong and Z. Mao, “Cyclicity Restoration Using Tentative Signals for OFDM-Based WLAN Systems”, IEEE ICCCAS.2006, vol.2, pp. 1073-1076, June 2006.

[16] K. Hayashi and H. Sakai, ”A Subtractive Interference Cancellation. Scheme for Single Carrier Block Transmission with Insufficient Cyclic. Prefix,” Proc. of WPMC2005, vol. 1, pp. 706–710, Sept. 2005.

[17] J. Louveaux, L. Vandendorpe, and T. Sartenaer, “Cyclic Prefixed Single Carrier and Multicarrier Transmission: Bit Rate Comparison,” IEEE Communications Letters, vol. 7, no. 4, pp. 180–182, April 2003.

[18] J. Tubbax, B. Come, L. Van der Perre, L. Deneire, S. Donnay, and M. Engels, "OFDM versus single carrier with cyclic prefix: A system-based comparison," IEEE Veh. Technol. Conf., vol.2, pp.1115–1119, Oct. 2001.

[19] H. Yu, M. Kim, T. Jeori and S. Lee, ”Equalization scheme for OFDM systems in long delay spread channels”, IEEE PIMRC 2004., vol. 2, pp. 1297- 1301, Sept. 2004.

[20] Y. Li, and X. Huang, “The Simulation of Independent Rayleigh Faders,” IEEE Trans. Commun., vol. 50, NO. 9, pp. 1503-1514, Sept. 2002.

[21] Zhu, J., Ser, W., and Nehorai, A., “Channel equalization for DMT with insufficient cyclic prefix,” Proc. Asilomar Conf. on Signals, Systems, and Computers 2000, Vol. 2, 2000, pp. 951-955.

[22] C. J. Park and G. H. Im, “Efficient cyclic prefix reconstruction for coded OFDM systems,” IEEE Commun. Letters, vol. 8, no. 5, pp. 274-276, May. 2004.