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標題: 應用於高階QAM通信系統之載波回復器與多模數盲蔽式等化器協同設計與分析
Design and Analysis of Joint Carrier Recovery and Multi-Modulus Blind Equalizer for High-Order QAM Systems
作者: 徐宛寧
Hsu, Wan-Ning
關鍵字: High-Order Systems;高階QAM;Blind Equalizer;Carrier Recovery;盲蔽式等化器;載波回復器
出版社: 電機工程學系所
引用: 中文參考資料 [1] 梁文軒,“應用於高階QAM調變系統之快速收斂盲蔽式等化器設計與實 作”, 國立中興大學論文, 民國96年6月 [2] 胡皓峻,“應用於高階QAM通信系統之混合廣義多模數與軟性決策快速盲蔽式等化器設計與模擬”, 國立中興大學論文, 民國98年7月 [3] 白政達,“高階QAM通信系統的盲蔽式等化器與載波回復協同設計與模擬”,國立中興大學論文,民國97年6月 英文參考資料 [4] D.Godard, “Self-Recovering Equalization and Carrier Tracking in Two-Dimensional Data Communication Systems”, IEEE Transactions on Communications, vol. 28, pp. 1867-1875, 1980. [5] K.N. Oh, and YO. Chin, , “New Blind Equalization Techniques Based on Constant Modulus Algorithm”, IEEE Conference Global Telecommunications, vol. 2, pp 865-869, 1995. [6] J. Yang, J.J. Werner and G A. Dumont, “The multimodulus blind equalization and its generalized algorithms”, IEEE Journal on Selected Areas in Communications, vol.20, no.5, pp99’7-lOl5, June 2002. [7] J. Karaoguz and S. H. A, “A Soft Decision Directed Blind Equalization Algorithm Applied to Equalization of Mobile Communication Channels,” in Proc. ICC, vol.3, pp. 343.4.1-343.4.5 ,Chicago, USA, 1992. [8] 5. Chen, ES. Chng, “Concurrent Constant Modulus Algorithm and Soft Decision Directed Scheme for Fractionally-Spaced Blind Equalization,” in: Proceedings of the ICC, vol. 4, pp. 2342-2346, Paris, France, 2004. [9] J. Yang, J. J. Werner, and G A. Dumont, “The Multimodulus Blind Equalization Algorithm,” 13th Int. Conf Digital Signal Processing, Santorini, Greece, July 1997. [10] M. Rupp and A.H. Sayed,”A time-domain feedback analysis of filtered-error adaptive gradient algorithms”, IEEE Trans. on Signal Processing, vol. 44, no.6, pp.1428 — 1439, June 1996. [11] B. Lin, R. He, X. Wang, and B. Wang,”Excess MSE analysis of the concurrent constant modulus algorithm and soft decision-directed scheme for blind equalisation”, lET Signal Processing, vol. 2, no.2, pp.147 — 155, June 2008. [12] J. Mai and A.H. Sayed ,“A feedback approach to the steady-state performance of fractionally spaced blind adaptive equalizers”, IEEE Trans. on Signal Processing, vol. 48, no.1, pp.80 —91, Jan. 2000. [13] CR Fan, WH. Liang, W. Lee, “Fast Blind Equalization with Two-Stage Single/Multilevel Modulus and DD Algorithm for High Order QAI4 Cable Systems”, IEEE International Symposium on Circuits and Systems, Seattle, USA, May 2008. [14] H.J. Hu and C.P. Fan, “Two-Stage Generalized Multilevel Modulus and Soft Decision-Directed Based Fast Blind Equalization for High-Order QAIVI Cable Systems”, IEEE Tencon, Singapore, November 2009. [15] K.Banovié,M.A.S.Khalid,E. Abdel-Raheem, “A configurable fractionally-spaced blind adaptive equalizer for QAIVI demodulators”,IEEE International Symposium on Signal Processing and Information Technology, pp. 150 — 153, Dec. 2007. [16] T. Kurakake, N. Nakamura, and K. Oyamada, “A Blind 1024-QAIVI Demodulatior for Cable Television”, Internation Zurich Seminar on Communications, Zurich, Swiss, pp.136-139, 2004. [17] C.N. Ke, C.Y. Huang and C.P. Fan, “An Adaptive Carrier Synchronizer for M-QAIVI Cable Receiver”, IEEE Transactions on Consumer Electronics, vol.49, pp.9&3-989, 2003. [18] Y.X.Zhang, L.X.Yu, “Practical Implementation of Blind Equalization, Carrier Recovery and Timing Recovery for QAM Cable Receiver Chip”, Proc. Of 5th International Conference on ASIC, vol.2, pp.886-889, Oct. 2003 [19] J. Tian, B. Shen, Z. Li, J. Su and Q. Zhang, “Joint Carreir Recovery and Adaptive Equalization for High-Order QAIVI”, IEEE International Symposium on Circuits and Systems, vol.2, pp.928-931, 2005. [20] John G Proakis, Digital Communications, Fourth edition, McGraw-Hill, 2001.
本篇論文主要應用在高階QAM調變系統中使用纜線數據機(cable modem)通道模型的環境下,藉由盲蔽式等化器估計出通道效應,將接收到的訊號進行振幅與相位的補償。盲蔽式等化器的特性在於不需要使用訊號符元(training symbol),藉由傳輸訊號的統計特性便能有效的校正受到干擾的訊號,而盲蔽式等化器相關演算法中,主要是以固定模數演算法(Constant Modulus Algorithm,CMA)為基礎,再延伸出廣義多模數演算法(Generalized Multi-Modulus Algorithm,GMMA),為了使等化器在高階QAM調變系統下也能有較低的符元錯誤率(Symbol Error Rate,SER),因此我們設計了一個兩階段式混合廣義多模數演算法及軟性決策運算(Soft Decision-Directed,SDD)的等化器演算法,其中,第一階段為結合廣義多模數演算法與軟性決策運算來提升收斂的速度,當等化器收斂到一定的程度後,在由收斂偵測器(convergence detector)將等化器從第一階段切換到第二階段,第二階段等化器使用的演算法為軟性決策運算來降低穩態的均方誤差(Mean Square Error,MSE)。
在不同QAM調變系統下,藉由數學式的分析以及Matlab的模擬,將我們所設計的演算法與其他的演算法比較後,可以得到較快的收斂速度與較低的均方誤差以及在相同的訊號雜訊比(Signal to Noise Ratio,SNR)環境下也可以得到較低的符元錯誤率,因此我們所設計的兩階段式混合廣義多模數演算法與軟性決策運算為最佳的組合方式。
接著,為了要解決通信系統中傳送與接收兩端振盪頻率不同所產生的載波偏移現象,因此我們將等化器與載波回復器(carrier recovery)整合模擬,由於廣義多模數演算法與載波回復器會互相產生干擾的現象,因此將等化器演算法改良成多階模數演算法(Multi-Level Modulus Algorithm,MLMA)。整個系統主要是由等化器消除部分的通道效應與雜訊的干擾,使載波回復器有較乾淨的環境進行載波偏移補償,最後再搭配決策回授等化器(Decision Feedback Equalizer,DFE),來得到更低的均方誤差與符元錯誤率。在整合模擬中,64QAM可補償的頻率範圍為-250kHz ~ 250kHz,256QAM可補償的頻率範圍為-150kHz ~ 200kHz,而1024QAM雖然可以收歛,不過必須先估計出載波頻率偏移約為多少的情況下,才可以有效的進行載波回復。

This thesis mainly presents the blind equalization for high-order QAM cable modem systems. By applying the blind equalization, the inverse channel impulse response can be accurately found and the amplitude and phase of the received symbols can also be corrected. Blind equalizations operate the computations and adjust equalizer coefficients without training symbols by only using received symbols. The generalized multi-modulus algorithm (Generalized Multi-Modulus Algorithm, GMMA) is an extension of the typical blind equalization algorithm, which is called the constant modulus algorithm (CMA). In order to let the equalizer have a lower symbol error rate (SER) in high-order QAM systems, we design a two-stage joint GMMA and Soft Decision-Directed (SDD) blind equalizer. In the first stage, the joint GMMA and SDD scheme is applied for the purpose of fast convergence. When the equalization approaches the threshold of convergence, the convergence detector switches the first stage equalization to the second stage equalization, where the SDD scheme is applied merely for the purpose to reduce the stable mean square error (MSE) in the second stage.
In difference QAM modulations, through the mathematical analysis and Matlab simulations, our proposed scheme can achieve faster convergence speed and lower MSE than other blind algorithms. Meanwhile, at the same signal to noise ratio (SNR) environment, our proposed equalization can also obtain lower SER than other blind algorithms.
In order to solve the carrier offset problem where the transmitter and receiver generate two different oscillation frequencies, we propose the joint adaptive equalization and carrier recovery algorithm for high-order QAM systems. Because the GMMA and the carrier recovery interfere with each other, we replace the GMMA equalization with the Multi-Level Modulus Algorithm (MLMA). By applying the MLMA equalizer to eliminate some channel effects and noise interferences, the carrier recovery loop can effectively eliminate the carrier offset, and finally a decision feedback equalizer (DFE) is also applied to obtain lower MSE and SER.
其他識別: U0005-2707201017063500
Appears in Collections:電機工程學系所

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