OFDM系统定时与频偏估计算法研究
|
摘要
OFDM技术是一种多载波传输技术,由于它具有极强的抗多径衰落能力和极高的频谱利用率,其已经被广泛应用于无线局域网等无线高速数据传输系统中,OFDM也被视为第四代移动通信的核心技术之一。
由于OFDM系统对同步误差十分敏感,同步误差的存在会使系统性能大大降低。其中定时偏差会造成符号间干扰(ISI),频率偏差会造成载波间干扰(ICI),所以精确的同步算法对OFDM系统来说是至关重要的。
首先,本文介绍了OFDM技术的发展过程、同步算法的研究背景和意义、OFDM的原理与特点,分析了定时偏差、频率偏差、采样偏差对系统性能的影响,通过仿真分析了当同步偏差存在时,系统信噪比的损失情况。
其次,本文重点研究和分析了OFDM定时同步算法,分为基于非数据辅助和数据辅助性两大类。其中非数据辅助主要研究了MLE算法,数据辅助性主要研究了S&C算法、Minn算法和Park算法。对这三种经典同步算法进行了大量的仿真,详细分析了每种算法的优缺点。针对S&C算法的峰值平台效应,本文分析和仿真了一种加窗的S&C算法,该算法能有效的消除S&C算法的平台效应。本文针对三种同步算法的缺点,在增加计算复杂度而不改变训练符号结构的思路下,对Park算法进行改进。改进的定时同步算法具有了更强相关性,通过仿真分析表明改进算法定时性有所提高,克服了S&C算法的平台效应,同时也克服了当循环前缀长度大于子载波数四分之一时Minn和Park算法所产的双峰值现象,从而提高了定时精度。
最后,本文研究和分析了OFDM频率同步算法。先分析了基于数据辅助的频率同步算法的基本理论,包括Moose算法、S&C算法和M&M算法。然后研究了基于非数据辅助的MLE频率同步算法。在理论分析的基础上对这几种频率同步算法进行大量的仿真,对比了算法的优缺点。
OFDM, a multi-carrier transmission solution, has been widely utilized in high-speed wireless data transmission systems such as wireless local area network (WLAN) due to its fairly strong anti-multipath delay capability and quite high utilization efficiency for frequency spectrum. It is also been regarded as the core technology for the fourth generation mobile communication technology.
As a result of OFDM system's high sensitivity to synchronization difference, the existence of synchronization difference would greatly low down OFDM's working efficiency. Among synchronization difference, its time difference will lead to inter-symbol interference, while its frequency difference would lead to inter-channel interference, therefore, an accurate synchronization algorithm become an extremely important part in OFDM system.
In this thesis, it firstly described the development process of OFDM technology, the research background and meaning for synchronization algorithm as well as the principal and feature for OFDM system; and then it analyzed the influence that time difference、frequency difference and sampling difference have in OFDM system, lastly, via simulation, it explained the signal to noise ratio loose condition while synchronization difference existed.
In the following, this thesis paid much attention on the research and analysis of the four types of OFDM timing synchronization algorithms. Of the four types of algorithms, MLE algorithm is based on non-data-aided, while the S&C algorithm, Minn algorithm and Park algorithm are based on the data-aided method. Through abundant of simulation, this thesis analyzed the advantage and disadvantages for each algorithm. When refer to the peak plateau-like effect for S&C algorithm, it simulated a windowing S&C algorithm that can effectively eliminate the peak plateau-like effect of S&C algorithm.In the following, it made an improvement for Park algorithm based on the idea that to increase the complexity but not change the structure for the training symbol. In the meantime, it also made the synchronization algorithm possess stronger pertinence. It was also proved through simulation analysis that the improved algorithm has only a single peak value, thus overcame the demerits of S&C algorithm, Minn algorithm and Park algorithm, which therefore improved the timing precision.
In the last, this thesis mainly researched and analyzed the OFDM frequency synchronization algorithm. It firstly analyzed the basic theory for data assistance based frequency synchronization algorithm, including Moose algorithm, S&C algorithm and M&M algorithm. Then researched the non date assistance based algorithm:MLE frequency synchronization algorithm. Basing on theory analysis, it made quite a few simulations for those three frequency synchronization algorithm and compared their advantages and disadvantages.
由于OFDM系统对同步误差十分敏感,同步误差的存在会使系统性能大大降低。其中定时偏差会造成符号间干扰(ISI),频率偏差会造成载波间干扰(ICI),所以精确的同步算法对OFDM系统来说是至关重要的。
首先,本文介绍了OFDM技术的发展过程、同步算法的研究背景和意义、OFDM的原理与特点,分析了定时偏差、频率偏差、采样偏差对系统性能的影响,通过仿真分析了当同步偏差存在时,系统信噪比的损失情况。
其次,本文重点研究和分析了OFDM定时同步算法,分为基于非数据辅助和数据辅助性两大类。其中非数据辅助主要研究了MLE算法,数据辅助性主要研究了S&C算法、Minn算法和Park算法。对这三种经典同步算法进行了大量的仿真,详细分析了每种算法的优缺点。针对S&C算法的峰值平台效应,本文分析和仿真了一种加窗的S&C算法,该算法能有效的消除S&C算法的平台效应。本文针对三种同步算法的缺点,在增加计算复杂度而不改变训练符号结构的思路下,对Park算法进行改进。改进的定时同步算法具有了更强相关性,通过仿真分析表明改进算法定时性有所提高,克服了S&C算法的平台效应,同时也克服了当循环前缀长度大于子载波数四分之一时Minn和Park算法所产的双峰值现象,从而提高了定时精度。
最后,本文研究和分析了OFDM频率同步算法。先分析了基于数据辅助的频率同步算法的基本理论,包括Moose算法、S&C算法和M&M算法。然后研究了基于非数据辅助的MLE频率同步算法。在理论分析的基础上对这几种频率同步算法进行大量的仿真,对比了算法的优缺点。
OFDM, a multi-carrier transmission solution, has been widely utilized in high-speed wireless data transmission systems such as wireless local area network (WLAN) due to its fairly strong anti-multipath delay capability and quite high utilization efficiency for frequency spectrum. It is also been regarded as the core technology for the fourth generation mobile communication technology.
As a result of OFDM system's high sensitivity to synchronization difference, the existence of synchronization difference would greatly low down OFDM's working efficiency. Among synchronization difference, its time difference will lead to inter-symbol interference, while its frequency difference would lead to inter-channel interference, therefore, an accurate synchronization algorithm become an extremely important part in OFDM system.
In this thesis, it firstly described the development process of OFDM technology, the research background and meaning for synchronization algorithm as well as the principal and feature for OFDM system; and then it analyzed the influence that time difference、frequency difference and sampling difference have in OFDM system, lastly, via simulation, it explained the signal to noise ratio loose condition while synchronization difference existed.
In the following, this thesis paid much attention on the research and analysis of the four types of OFDM timing synchronization algorithms. Of the four types of algorithms, MLE algorithm is based on non-data-aided, while the S&C algorithm, Minn algorithm and Park algorithm are based on the data-aided method. Through abundant of simulation, this thesis analyzed the advantage and disadvantages for each algorithm. When refer to the peak plateau-like effect for S&C algorithm, it simulated a windowing S&C algorithm that can effectively eliminate the peak plateau-like effect of S&C algorithm.In the following, it made an improvement for Park algorithm based on the idea that to increase the complexity but not change the structure for the training symbol. In the meantime, it also made the synchronization algorithm possess stronger pertinence. It was also proved through simulation analysis that the improved algorithm has only a single peak value, thus overcame the demerits of S&C algorithm, Minn algorithm and Park algorithm, which therefore improved the timing precision.
In the last, this thesis mainly researched and analyzed the OFDM frequency synchronization algorithm. It firstly analyzed the basic theory for data assistance based frequency synchronization algorithm, including Moose algorithm, S&C algorithm and M&M algorithm. Then researched the non date assistance based algorithm:MLE frequency synchronization algorithm. Basing on theory analysis, it made quite a few simulations for those three frequency synchronization algorithm and compared their advantages and disadvantages.
引文
[1]G A Doelz, E T Heald and D L Martin. Binary data transmission techniques for linear systems[J]. Proc. I. R.E,1957,45,656-661
[2]Saltzber B R. Performance of an efficient parallel data transmission system[J]. IEEE Transactions on Communications,1967,15 (6):805-813.
[3]R.W.Chang. Synthesis of band-limited orthogonal signals for rnulti-channel data transmission[J]. Bell System Technical Journal,1967,46:1775-1796
[4]Cimini L J. Analysis and simulation for a digital mobile channel using orthogonal frequency division multiplexing[J]. IEEE Transactions on Communications 1985, 33(7):665-675.
[5]Andalibi Z, Jamali S H, Arazm F. Complexity reduction schemes for synchronization of IEEE 2006,26:98-106
[6]Chow P S, Tu J C, Cioffi J M. Performance evaluation of a multichannel transceiver system for ADSL and VHDSL services[J]. IEEE Journal on Selected Areas in Communications,1991,9(6):909-919.
[7]B.Le Floch, R. Hatbert-Lassalle, and D. Castlain. Digital sound broadcasting to mobile receivers. IEEE Traps Consumer Electron.1989,35(3):493-503
[8]尚星.OFDM系统同步与信道估计研究[D].西安电子科技大学硕士学位论文2009：8-15.
[9]Theodore S.Rappaport著.无线通信原理与应用[M],北京：电子工业出版社,2007.
[10]啜钢,王文博等,移动通信原理与系统[M].北京：北京邮电大学出版社,16-61.
[11]Weinstein S B, Ebert P M. Data transmission by frequency division multiplexing using the discrete fourier transform[J]. IEEE Transactions on Communications,1971 19(5):628-634.
[12]王文博等,宽带无线通信OFDM技术(第二版)[M].北京：人民邮电出版社,2007：6-19
[13]Peled A, Ruiz A. Frequency domain data transmission using reduced computational complexity algorithms [J]. IEEE International Conference on Acoustics, Speech, and Signal Processing. NEW YORK:IEEE,1980.5:964-967.
[14]R. van Nee, R. Prasad. OFDM for wireless multimedia communications[M]. Artech House Publisher,2000.
[15]罗仁泽.新一代无线移动通信系统关键技术[M].北京：北京邮电大学出版社,2002：16-28.
[16]R.Boudrean, J.-Y. Chouinard, A. Yongacoghu. Exploiting doppler-diversity in flat, Fast fading channel[J]. Canadian Conference on Electerical and Computer engineering. March,2000,vol.1,270-274.
[17]夏喆,朱晓明,张海涛.改进型JAKES模型在OFDM系统中的仿真[J].电子科技2007
[18]Matthias Patzold.Statistiacl properties of Jakes'fading channel simulator[J]. IEEE Trans.Vehicular Technology conference,VCT-98,48th 1998. p712-717.
[19]Athaudage C R N. Ber sensitivity of OFDM systems to time synchronization error[J]. 8th International Conference on Communication Systems. NEW YORK:IEEE,2002. 1:42-46.
[20]王宝祥,信号与系统[M].哈尔滨：哈尔滨工业大学出版社,2000.
[21]Landstorm D S K, van de Beek J-J, Borjesson PO. Symbol time offset estimation in coherent OFDM systems[J]. IEEE Transactions on Communications,2002,50(04): 545-549.
[22]Muller Weinfutner. On the optimality of metrics for coarse frame synchronization in OFDM:AComparison[J]. IEEE International symposium,1998,2:533-537.
[23]Stefan H. Muller-Weinfurtner. On the optimality of metrics for coarse frame synchronization in OFDMA Comparison[J]. The Ninth IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications,1998(2):533-537.
[24]杨大成等.移动传播环境理论基础[M].北京：机械工业出版社,2003.
[25]Pollet T,Van Bladel M,Moeneclaey M. Ber sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise[J]. IEEE transactions on communications. 199543 (234):191-193.
[26]Timothy M Schmidl,Donald C Cox. Robust frequency and timing synchronization for OFDM[J]. IEEE Transactions on Communications,1997,45 (12):613-1621.
[27]田野.宽带无线OFDM系统同步算法的研究[D].北京邮电大学博士学位论文,2008：63-79.
[28]William D.Warner, Cyril Leung. OFDM/FM frame synchronization for mobile radio data communication[J]. IEEE Transaction on Vehicular Technology,1993,42:302-313.
[29]F. Tufvesson, O. Edfors, and M. Faulkner. Time and frequency synchronization for OFDM using PN-sequence preambles[J]. IEEE VTC' 1999, vol.4,2203-2207.
[30]Jong-Ho Lee, Jae Choong Han, Seong-Cheol Kim. Joint carrier frequency synchronization and channel estimation for OFDM systems via the EM algorithm[J]. Vehicular Technology, IEEE Transactions,2006.167-172.
[31]Viterbo E, Fazel K, How to combat long echoes in OFDM transmission schemes:sub-channel equalization or more powerful channel coding[J]. IEEE Global Telecommunications Conference. NEW YORK:IEEE,1995.3:2069-2074.
[32]王可.OFDM系统同步技术的研究[D].哈尔滨工业大学,硕士学位论文,2006：26-51
[33]H. Minn, Bhargava V.K, A simple and efficient timing offset estimation for OFDM systems[J]. IEEE Trans. VTC,2000,51-55.
[34]王胜坤OFDM同步技术的研究[D].太原理工大学,硕士学位论文,2007,50-61.
[35]Park Byungjoon, Cheon Hyunsoo, and Kang Changeon. A novel timing estimation method for OFDM systems[J]. IEEE. Comms. Letters.5 Jun.2003:239-241.
[36]丁玉美,高西全.数字信号处理(第二版)[M].西安：西安电子科技大学出版社,2002：21-63.
[37]Hanli Zou, McNair B, Daneshrad B. An integrated OFDM receiver for high-speed mobile data communications [J]. IEEE Global Telecommunications Conference, 2001,5:3090-3094.
[38]P.H. Moose, A technique for OFDM frequency offset correction[J]. IEEE Trans. Comm, vol.42,pp.2908-2914, October 1994.
[39]张宁炜,基于OFDM系统同步算法的研究[D],哈尔滨工程大学硕士学位论文,2008.
[40]Y H.Kim, Y K.Hahm, H.J.Jung. An efficient frequency offset estimator for timing and frequency synchronization in OFDM systems[J]. Communications, Computers and Signal Processing, IEEE Pacific Rim Conference on,1999,580-583.
[41]Tufvesson F, Fualkner M, Hoeher P, Edfors O. OFDM time and frequency synchronization by spread spectrum pilot technique[J]. Communication Theory Mini-Conference[C].NEWYORK:IEEE,1999.115-119.
[42]贺永坤OFDM同步问题的研究[D].昆明理工大学硕士学位论文,2007：34-47.
[43]李旭等,一种在OFDM系统中提高同步估计性能的方法[J].北京交通大学学报,2009, NO.5 vol.33:1-4.
[44]王梅梅,OFDM系统的同步算法研究[D].重庆大学硕士学位论文,2009：37-46.
[45]Jan-Jaap van de Beek,Magnus Sandell, ML estimation of time and frequency offset in OFDM systems[J]. IEEE Trans.Signal Processing,1997,45,800-1805.
[46]Jan-Jaap van de Beek, Magnus Sandell, Mikael Isaksson, Per Ola Borjesson. Low-complex frame synchronization in OFDM systems [J]. IEEE ICUPC,1995:982-986.
[47]李绪诚OFDM传输系统中同步问题研究[D],贵州大学硕士学位论文,2007,36-38.
[48]韩艳春.OFDM系统的同步技术研究[D].重庆大学博士学位论文,2007,77-99.
[49]R.Boudrean, J.-Y. Chouinard, A. yongacoghu. exploiting doppler-diversity in flat, fast fading channel[J]. Canadian Conference on Electerical and Computer engineering. March,2000,1,270-274.
[50]Michele Morelli,Umberto Mengali. An improved frequency offset estimator for OFDM applications[J]. IEEE Communications Letters,1999,3(3):75-77
[51]F.Classen, H.Meyr. Frequency synchronization algorithms for OFDM systems suitable for communication over frequency-selective fading channels[J]. IEEE Vehicle Technology Conference,1994,3:1655-1659.
[2]Saltzber B R. Performance of an efficient parallel data transmission system[J]. IEEE Transactions on Communications,1967,15 (6):805-813.
[3]R.W.Chang. Synthesis of band-limited orthogonal signals for rnulti-channel data transmission[J]. Bell System Technical Journal,1967,46:1775-1796
[4]Cimini L J. Analysis and simulation for a digital mobile channel using orthogonal frequency division multiplexing[J]. IEEE Transactions on Communications 1985, 33(7):665-675.
[5]Andalibi Z, Jamali S H, Arazm F. Complexity reduction schemes for synchronization of IEEE 2006,26:98-106
[6]Chow P S, Tu J C, Cioffi J M. Performance evaluation of a multichannel transceiver system for ADSL and VHDSL services[J]. IEEE Journal on Selected Areas in Communications,1991,9(6):909-919.
[7]B.Le Floch, R. Hatbert-Lassalle, and D. Castlain. Digital sound broadcasting to mobile receivers. IEEE Traps Consumer Electron.1989,35(3):493-503
[8]尚星.OFDM系统同步与信道估计研究[D].西安电子科技大学硕士学位论文2009：8-15.
[9]Theodore S.Rappaport著.无线通信原理与应用[M],北京：电子工业出版社,2007.
[10]啜钢,王文博等,移动通信原理与系统[M].北京：北京邮电大学出版社,16-61.
[11]Weinstein S B, Ebert P M. Data transmission by frequency division multiplexing using the discrete fourier transform[J]. IEEE Transactions on Communications,1971 19(5):628-634.
[12]王文博等,宽带无线通信OFDM技术(第二版)[M].北京：人民邮电出版社,2007：6-19
[13]Peled A, Ruiz A. Frequency domain data transmission using reduced computational complexity algorithms [J]. IEEE International Conference on Acoustics, Speech, and Signal Processing. NEW YORK:IEEE,1980.5:964-967.
[14]R. van Nee, R. Prasad. OFDM for wireless multimedia communications[M]. Artech House Publisher,2000.
[15]罗仁泽.新一代无线移动通信系统关键技术[M].北京：北京邮电大学出版社,2002：16-28.
[16]R.Boudrean, J.-Y. Chouinard, A. Yongacoghu. Exploiting doppler-diversity in flat, Fast fading channel[J]. Canadian Conference on Electerical and Computer engineering. March,2000,vol.1,270-274.
[17]夏喆,朱晓明,张海涛.改进型JAKES模型在OFDM系统中的仿真[J].电子科技2007
[18]Matthias Patzold.Statistiacl properties of Jakes'fading channel simulator[J]. IEEE Trans.Vehicular Technology conference,VCT-98,48th 1998. p712-717.
[19]Athaudage C R N. Ber sensitivity of OFDM systems to time synchronization error[J]. 8th International Conference on Communication Systems. NEW YORK:IEEE,2002. 1:42-46.
[20]王宝祥,信号与系统[M].哈尔滨：哈尔滨工业大学出版社,2000.
[21]Landstorm D S K, van de Beek J-J, Borjesson PO. Symbol time offset estimation in coherent OFDM systems[J]. IEEE Transactions on Communications,2002,50(04): 545-549.
[22]Muller Weinfutner. On the optimality of metrics for coarse frame synchronization in OFDM:AComparison[J]. IEEE International symposium,1998,2:533-537.
[23]Stefan H. Muller-Weinfurtner. On the optimality of metrics for coarse frame synchronization in OFDMA Comparison[J]. The Ninth IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications,1998(2):533-537.
[24]杨大成等.移动传播环境理论基础[M].北京：机械工业出版社,2003.
[25]Pollet T,Van Bladel M,Moeneclaey M. Ber sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise[J]. IEEE transactions on communications. 199543 (234):191-193.
[26]Timothy M Schmidl,Donald C Cox. Robust frequency and timing synchronization for OFDM[J]. IEEE Transactions on Communications,1997,45 (12):613-1621.
[27]田野.宽带无线OFDM系统同步算法的研究[D].北京邮电大学博士学位论文,2008：63-79.
[28]William D.Warner, Cyril Leung. OFDM/FM frame synchronization for mobile radio data communication[J]. IEEE Transaction on Vehicular Technology,1993,42:302-313.
[29]F. Tufvesson, O. Edfors, and M. Faulkner. Time and frequency synchronization for OFDM using PN-sequence preambles[J]. IEEE VTC' 1999, vol.4,2203-2207.
[30]Jong-Ho Lee, Jae Choong Han, Seong-Cheol Kim. Joint carrier frequency synchronization and channel estimation for OFDM systems via the EM algorithm[J]. Vehicular Technology, IEEE Transactions,2006.167-172.
[31]Viterbo E, Fazel K, How to combat long echoes in OFDM transmission schemes:sub-channel equalization or more powerful channel coding[J]. IEEE Global Telecommunications Conference. NEW YORK:IEEE,1995.3:2069-2074.
[32]王可.OFDM系统同步技术的研究[D].哈尔滨工业大学,硕士学位论文,2006：26-51
[33]H. Minn, Bhargava V.K, A simple and efficient timing offset estimation for OFDM systems[J]. IEEE Trans. VTC,2000,51-55.
[34]王胜坤OFDM同步技术的研究[D].太原理工大学,硕士学位论文,2007,50-61.
[35]Park Byungjoon, Cheon Hyunsoo, and Kang Changeon. A novel timing estimation method for OFDM systems[J]. IEEE. Comms. Letters.5 Jun.2003:239-241.
[36]丁玉美,高西全.数字信号处理(第二版)[M].西安：西安电子科技大学出版社,2002：21-63.
[37]Hanli Zou, McNair B, Daneshrad B. An integrated OFDM receiver for high-speed mobile data communications [J]. IEEE Global Telecommunications Conference, 2001,5:3090-3094.
[38]P.H. Moose, A technique for OFDM frequency offset correction[J]. IEEE Trans. Comm, vol.42,pp.2908-2914, October 1994.
[39]张宁炜,基于OFDM系统同步算法的研究[D],哈尔滨工程大学硕士学位论文,2008.
[40]Y H.Kim, Y K.Hahm, H.J.Jung. An efficient frequency offset estimator for timing and frequency synchronization in OFDM systems[J]. Communications, Computers and Signal Processing, IEEE Pacific Rim Conference on,1999,580-583.
[41]Tufvesson F, Fualkner M, Hoeher P, Edfors O. OFDM time and frequency synchronization by spread spectrum pilot technique[J]. Communication Theory Mini-Conference[C].NEWYORK:IEEE,1999.115-119.
[42]贺永坤OFDM同步问题的研究[D].昆明理工大学硕士学位论文,2007：34-47.
[43]李旭等,一种在OFDM系统中提高同步估计性能的方法[J].北京交通大学学报,2009, NO.5 vol.33:1-4.
[44]王梅梅,OFDM系统的同步算法研究[D].重庆大学硕士学位论文,2009：37-46.
[45]Jan-Jaap van de Beek,Magnus Sandell, ML estimation of time and frequency offset in OFDM systems[J]. IEEE Trans.Signal Processing,1997,45,800-1805.
[46]Jan-Jaap van de Beek, Magnus Sandell, Mikael Isaksson, Per Ola Borjesson. Low-complex frame synchronization in OFDM systems [J]. IEEE ICUPC,1995:982-986.
[47]李绪诚OFDM传输系统中同步问题研究[D],贵州大学硕士学位论文,2007,36-38.
[48]韩艳春.OFDM系统的同步技术研究[D].重庆大学博士学位论文,2007,77-99.
[49]R.Boudrean, J.-Y. Chouinard, A. yongacoghu. exploiting doppler-diversity in flat, fast fading channel[J]. Canadian Conference on Electerical and Computer engineering. March,2000,1,270-274.
[50]Michele Morelli,Umberto Mengali. An improved frequency offset estimator for OFDM applications[J]. IEEE Communications Letters,1999,3(3):75-77
[51]F.Classen, H.Meyr. Frequency synchronization algorithms for OFDM systems suitable for communication over frequency-selective fading channels[J]. IEEE Vehicle Technology Conference,1994,3:1655-1659.