MIMO-OFDM系统中信道估计的关键技术研究
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摘要
无线通信与个人通信在短短几十年经历了从模拟通信到数字通信、从FDMA到CDMA的巨大发展,目前又出现了以MIMO-OFDM为核心的第四代移动通信技术。第四代移动通信系统是多功能集成的宽带移动通信系统,它将以带宽、接入因特网、具有多种综合功能的系统形态出现。在中国FUTURE项目以及欧盟WINNER项目中,以MIMO-OFDM为物理层基础的下一代移动通信系统的研究正在如火如荼的展开。
本文第一章首先回顾了移动通信的发展历程,介绍了3G技术的进展以及B3G或4G的发展现状,重点分析了目前B3G或4G的物理层存在的问题和难点,为接下来的论叙提供了研究背景。
第二章首先分别介绍OFDM的基本理论、MIMO技术的基本理论,接着介绍了移动通信中的无线移动信道的衰落特性,然后给出了无线信道模型的计算机仿真以及MIMO-OFDM系统的结构模型和原理。
第三章对MIMO-OFDM系统的信道估计进行了初步研究。给出了各种插值算法的均方误差(MSE)限,并利用仿真进行了验证。
第四章我们提出了基于频域插入梳状导频的三种不同的信道估计算法,一个在频域实行,其它两个在时域实行。基于梳状导频的算法比使用块状导频的算法能提供更高的带宽效率。仿真结果表明,这三种估计算法有同样好的性能,而时域方法能提供相对简单的结构。
第五章提出了在MIMO-OFDM系统中减弱导频位置处限幅噪声的一种新方法,其基本原理是插入导频前在频域内把导频位置的限幅噪声直接滤除。仿真结果表明这种新的方法能有效的改善信道估计和系统的性能。
最后对全文进行了总结,并给出了B3G或4G可能的未来研究课题。
Nowadays, the 4~(th) generation mobile communications, which base on the MIMO-OFDM technology, has emerged just shortly after several decades' development of wireless and personal conununication, which has burgeoned from analog to digital and from FDMA to CDMA. It is an integrated communication system including broadband, Internet access and many other integrated functions. Now, China's Future Technology for Universal Radio Environment (FUTURE) project and Europe's Wireless World Initiative New Radio (WINNER) project also accept MIMO-OFDM as the base of physical layer.
In the first chapter, the progress of the mobile communications is reviewed. The current progress of 3G、B3G/4G is introduced. The key techniques and the problems lying in B3G/4G are denoted.
In the second chapter we introduced the principle of OFDM and MIMO and the structure and principle of MIMO-OFDM system at first. Secondly, introduced the characteristic of the wireless mobile channel in mobile communication, and the fading effect caused. Then analyzed the model of the wireless channel and then simulated it. And a real MIMO-OFDM system was shown in the last part.
In the third chapter, the channel estimation in MIMO-OFDM systems is investigated initially. The Mean Square Error (MSE) bound of various interpolations is derived and verified by simulation.
In the fourth chapter, we propose three different channel estimation algorithms based on specially designed comb type pilots inserted in frequency domain. One of our proposed algorithms is performed in frequency domain and the other two are performed in time domain. Such comb type pilot based algorithms can provide higher bandwidth efficiency than common significant-tap-catching algorithm using training block pilots. Numerical analyzes and computational simulation show that our proposed estimation schemes have the same good performance while the time domain methods have relatively simple structure.
In the fifth chapter, we provides a new technique to mitigate the clipping noise on pilot symbols in MIMO-OFDM systems. The basic principle is to directly filter the clipping noise on the positions of pilots in the frequency domain before the insertion of pilots .Simulation results show that the new technique can effectively improve channel estimation and system performance.
At last, conclusions are remarked and the possible research issues in B3G/4G are shown.
本文第一章首先回顾了移动通信的发展历程,介绍了3G技术的进展以及B3G或4G的发展现状,重点分析了目前B3G或4G的物理层存在的问题和难点,为接下来的论叙提供了研究背景。
第二章首先分别介绍OFDM的基本理论、MIMO技术的基本理论,接着介绍了移动通信中的无线移动信道的衰落特性,然后给出了无线信道模型的计算机仿真以及MIMO-OFDM系统的结构模型和原理。
第三章对MIMO-OFDM系统的信道估计进行了初步研究。给出了各种插值算法的均方误差(MSE)限,并利用仿真进行了验证。
第四章我们提出了基于频域插入梳状导频的三种不同的信道估计算法,一个在频域实行,其它两个在时域实行。基于梳状导频的算法比使用块状导频的算法能提供更高的带宽效率。仿真结果表明,这三种估计算法有同样好的性能,而时域方法能提供相对简单的结构。
第五章提出了在MIMO-OFDM系统中减弱导频位置处限幅噪声的一种新方法,其基本原理是插入导频前在频域内把导频位置的限幅噪声直接滤除。仿真结果表明这种新的方法能有效的改善信道估计和系统的性能。
最后对全文进行了总结,并给出了B3G或4G可能的未来研究课题。
Nowadays, the 4~(th) generation mobile communications, which base on the MIMO-OFDM technology, has emerged just shortly after several decades' development of wireless and personal conununication, which has burgeoned from analog to digital and from FDMA to CDMA. It is an integrated communication system including broadband, Internet access and many other integrated functions. Now, China's Future Technology for Universal Radio Environment (FUTURE) project and Europe's Wireless World Initiative New Radio (WINNER) project also accept MIMO-OFDM as the base of physical layer.
In the first chapter, the progress of the mobile communications is reviewed. The current progress of 3G、B3G/4G is introduced. The key techniques and the problems lying in B3G/4G are denoted.
In the second chapter we introduced the principle of OFDM and MIMO and the structure and principle of MIMO-OFDM system at first. Secondly, introduced the characteristic of the wireless mobile channel in mobile communication, and the fading effect caused. Then analyzed the model of the wireless channel and then simulated it. And a real MIMO-OFDM system was shown in the last part.
In the third chapter, the channel estimation in MIMO-OFDM systems is investigated initially. The Mean Square Error (MSE) bound of various interpolations is derived and verified by simulation.
In the fourth chapter, we propose three different channel estimation algorithms based on specially designed comb type pilots inserted in frequency domain. One of our proposed algorithms is performed in frequency domain and the other two are performed in time domain. Such comb type pilot based algorithms can provide higher bandwidth efficiency than common significant-tap-catching algorithm using training block pilots. Numerical analyzes and computational simulation show that our proposed estimation schemes have the same good performance while the time domain methods have relatively simple structure.
In the fifth chapter, we provides a new technique to mitigate the clipping noise on pilot symbols in MIMO-OFDM systems. The basic principle is to directly filter the clipping noise on the positions of pilots in the frequency domain before the insertion of pilots .Simulation results show that the new technique can effectively improve channel estimation and system performance.
At last, conclusions are remarked and the possible research issues in B3G/4G are shown.
引文
[1]T.S.Rappaport.Wireless communications:principle& practice[J].Prentice Hall,1996,3(3):15-34.
[2]郭梯云,杨家玮,李建东.数字移动通信(修订本)[M].北京:人民邮电出版社,2001:7-29.
[3]曹志刚,钱亚生.现代通信原理[M].北京:清华大学出版社,1999:4-19.
[4][奥]Andreas F.Molisch.宽带无线数字通信[M].北京:电子工业出版社,2002:6-15.
[5]A.J.Viterbi.CDMA principles of spread spectrum communication[J].Addison-Wesley,1995,2(5):5-16.
[6]Proakis,John G.Digital communications 3rd edition[M].Beijing:Publishing House of Electronics industry,1998,Chapter 14:14-21.
[7]Bingham,J.A.C.Multicarrier modulation for data transmission:an idea whose time has come[J].IEEE Communications Magazine,1990,5(28):5-14.
[8]N.Yee,J.P.Linnarz,G.Fettweis.Multi-carrier CDMA in indoor wireless radio networks[J].Proceedings IEEE International Symposium on Personal,Indoor and Mobile Radio Commun.,1993,9(15):109-113.
[9]V.DaSilva,E.S.Sousa.Performance of orthogonal CDMA codes for quasi-synchronous communication systems[J].In Proceedings IEEE International Conference on Universal Personal Communications,Ottawa,Canada,1993,10(10):995-999.
[10]L.Vandendorpe.Multitude direct sequence CDMA system in an indoor wireless environment[J].In Proceedings IEEE First Symposium of Communications and Vehicular Technology,Delft,1993,10(10):411-418.
[11]S.Kaise.OFDM-CDMA versus DS-CDMA,Performance evaluation for fading channels[J].In Proceedings IEEE International Conference on Communications,Seattle,USA,1995,6(6):1722-1726.
[12]S.Hara,R.Prasad.Overview of multicarrier CDMA[J].IEEE Communications Magazine,1997,12(35):126-133.
[13]Chong,L.L.,Milsteir,L.13 Comparing DS-CDMA and multicarrier CDMA with imperfect:channel estimation[J].Statistical Signal Processing,2001,4(12):385-388.
[I4]K.Fazel,L.Papke.On the performance of convolutionally-coded CDMA/OFDM for mobile communication system[J].Yokohama,Japan,1993,9(17):68-472.
[15]王颖,孟嗣仪.MIMO-OFDM系统中的信道估计方法分析[J].中国数 据通信,2005,6(1):122-125.
[16]Atarashi,H.,Abeta,S.,Sawahashi,M..Broadband packet wireless access appropriate for high-speed and high-capacity throughput[J].Vehicular Technology Conference,2001,1(1):566-570.
[17]I.E.Telatar.Capacity of multi-antenna Gaussian channels[J].Eur.Trans.Telecommun.,1999,9(10):585-595.
[18]G.J.Foschini.Layered space-time architecture for wireless communication in a fading environment when using multielement antennas[J],Bell Labs Tech.J.,1996,8(16):41-59.
[19]谢显中,等.基于TDD的第四代移动通信技术[M].北京:电了工业出版社,2005:75-116.
[20]吴伟陵、牛凯.移动通信原理[M].北京:电了工业出版社,2005:252-262.
[21]H.B olcskei,D.Gesbert,and A.J.Paulraj,On the capacity of OFDM-based spatial multiplexing systems[J].Trans,on Comm.,2002,12(23):75-82.
[22]Agrawal,D.;Tarokh,V.;Naguib,A.;Seshadri,N.;Space-time coded OFDM for high data-rate wireless communication over wideband channels[J].IEEE VTC 98.,1998,5(3):2232-2236.
[23]Witzke,M.,Baro,S.,Schreckenbach,F.,Hagenauer,J.Iterative detection of MIMO signals with linear detectors,2002[J].Conference Record of the Thirty-Sixth Asilomar Conference,Systems and Computers,2002,9(1):289-293.
[24]Rappaport T S.无线通信原理与应用[M].北京:电子工业出版社,1999:5-50.
[25]E.Biglieri,J.Proakis.Fading channels Information-theoretic and communications aspects[J].IEEE Trans.Info.Theory,1998,5(15):1-12.
[26]S.M.Alamouti.A simple transmit diversity technique for wirelesson communications[J],IEEE.Journal Select Areas.Commun.,1998,8(16):1451-1458.
[27]V Tarokh,N.Seshadri,Space-time codes for high data rate wireless communication:performance criteria and code construction[J].IEEE Tran.s.Information Theory,1998,3(44):744-765.
[28]佟学俭,罗涛.OFDM移动通信技术原理与应用[M].北京:人民邮电出版社,2003:165-210.
[29]W.C.Y Lee,Mobile Communications Engineering:Theory and Applications[M].New York:McGraw-Hill,1998:210-350.
[30]裴昌幸,聂敏等译,Gordon,L.Stuber著.移动通信原理(第二版)[M].北京:人民邮电出版社,2004:25-130.
[31]蔡涛,李旭,杜振民译,Theodore S.Rappaport著.无线通信原理与应用[M].北京:电子工业出版社,1999:15-78.
[32]杨大成.移动传播环境理论基础、分析方法和建模技术[M].北京:机械工业出版社,2003:33-215.
[33]J.K.Cavers.An anlysis fo pilot symbol assisted modulation for Rayleigh fading channels[J],IEEE Trans.Vehic.Technol.,1991,9(40):686-693.
[34]董艳男、朱琦.基于IEEE 802.16a MIMO-OFDM系统的信道估计方法研究[J].南京:南京邮电学院学报,2006,25(2):62-66.
[35]柴关华,徐友云,蔡越明.MIMO-OFDM无线传输系统中的信道估计研究[J].江苏:江苏省通信学会论文集,2005,6(12):200-205.
[36]G.Auer,Analysis of pilot-symbol aided channel estimation for OFDM systems with multiple transmit antennas[J],2004 IEEE International Conference on Communications,2004,9(6):3221-3225.
[37]Y.Li.Simplified channel estimation for OFDM systems[J].IEEE Transmit antennas Transactions on Wireless Communications,2002,12(1):67-75.
[38]I.Barhumi,G.Leus,and M.Moonen.Optimal training design for MIMO OFDM systems in mobile wireless channels[J].IEEE Transactions on Signal Processing,2003,7(51):1615-1624.
[39]H.Zhang,J.M.Chen,Y.X.Tang,S.Q.Li.Analysis of pilot-symbol aided channel estimation for MIMO-OFDM systems[J].2004International Conference on Communications,Circuits and Systems,2004,7(1):299-303.
[40]王东明,高西奇,尤肖虎,韩冰.宽带MIMO-OFDM系统信道估计算法研究[J].电子学报,2005,7(7):1254-1257.
[41]S.Verdu,.Multiuser Detection,Cambridge University Press,1998[J].Workshop Process.Adv.Wireless Commun.,2001,3(22):42-55.
[42]王文博,等.宽带无线通信OFDM技术[M].北京:人民邮电出版社,2003:46-56.
[43]H.K.Song,Y.H.You.Error performance analysis of STBC-OFDM systems with parameter imbalances[J].IEEE Trans.Broadcasting,2004,3(23):76-82.
[44]W.G.Song,J.T.Lim.Pilot-symbol aided channel estimation for OFDM with fast fading channels[J].IEEE Trans.Broadcasting,2003,12(49):56-67.
[45]刘刚,郭漪,葛建华.MIMO-OFDM系统中的信道估计[J],华中科技大学学报,2005,9(59):26-29.
[46]S.J.Kang,M.J.Kim.Simplified channel estimation for OFDM systems with multiple transmit antennas[J].IEEE Trans.Wireless Commun.,January 2002,1(1):235-250.
[47]M.Li,J.Tan,W.Zhang.A channel estimation method based on frequency-domain pilots and time-domain processing for OFDM systems[J],IEEETrans.ConsumerElectronics,2004,9(50):504-520.
[48]H.Chen,A.M.Haimovich.Iterative estimation and cancellation of clipping noise for OFDM signals[J].IEEE Commun., 2003,7(7):305-307.
[49] X.Lei,Y.Tang,S.Li,Y.Li.A minimum clipping power loss scheme for mitigating the clipping noise in OFDM[J]. Proc.IEEE Global Telecommunication Conf.,2003,5(10):6-9.
[50] M. Garcia, J. Paez-Borrallo, S. Zazo.DFT-based channel estimation in 2D-pilot-symbol-aided OFDM wireless systems[J].Proc. IEEE Vehicular Technology Conf., 2001,11(37): 810-814.
[51] Z. J. Wang, Z. Han, K. J. R. Liu, A MIMO-OFDM channel estimation approach using time of arrivals[J],IEEE Trans. Wireless Commun., 2005,5(4):1207-1213.
[52] Yue Xiao,Shaoqian Li. Clipping Noise Mitigation for Channel Estimation in OFDM Systems [J],IEEE Communcations Leters, 2006,7(10):1050-1065.
[2]郭梯云,杨家玮,李建东.数字移动通信(修订本)[M].北京:人民邮电出版社,2001:7-29.
[3]曹志刚,钱亚生.现代通信原理[M].北京:清华大学出版社,1999:4-19.
[4][奥]Andreas F.Molisch.宽带无线数字通信[M].北京:电子工业出版社,2002:6-15.
[5]A.J.Viterbi.CDMA principles of spread spectrum communication[J].Addison-Wesley,1995,2(5):5-16.
[6]Proakis,John G.Digital communications 3rd edition[M].Beijing:Publishing House of Electronics industry,1998,Chapter 14:14-21.
[7]Bingham,J.A.C.Multicarrier modulation for data transmission:an idea whose time has come[J].IEEE Communications Magazine,1990,5(28):5-14.
[8]N.Yee,J.P.Linnarz,G.Fettweis.Multi-carrier CDMA in indoor wireless radio networks[J].Proceedings IEEE International Symposium on Personal,Indoor and Mobile Radio Commun.,1993,9(15):109-113.
[9]V.DaSilva,E.S.Sousa.Performance of orthogonal CDMA codes for quasi-synchronous communication systems[J].In Proceedings IEEE International Conference on Universal Personal Communications,Ottawa,Canada,1993,10(10):995-999.
[10]L.Vandendorpe.Multitude direct sequence CDMA system in an indoor wireless environment[J].In Proceedings IEEE First Symposium of Communications and Vehicular Technology,Delft,1993,10(10):411-418.
[11]S.Kaise.OFDM-CDMA versus DS-CDMA,Performance evaluation for fading channels[J].In Proceedings IEEE International Conference on Communications,Seattle,USA,1995,6(6):1722-1726.
[12]S.Hara,R.Prasad.Overview of multicarrier CDMA[J].IEEE Communications Magazine,1997,12(35):126-133.
[13]Chong,L.L.,Milsteir,L.13 Comparing DS-CDMA and multicarrier CDMA with imperfect:channel estimation[J].Statistical Signal Processing,2001,4(12):385-388.
[I4]K.Fazel,L.Papke.On the performance of convolutionally-coded CDMA/OFDM for mobile communication system[J].Yokohama,Japan,1993,9(17):68-472.
[15]王颖,孟嗣仪.MIMO-OFDM系统中的信道估计方法分析[J].中国数 据通信,2005,6(1):122-125.
[16]Atarashi,H.,Abeta,S.,Sawahashi,M..Broadband packet wireless access appropriate for high-speed and high-capacity throughput[J].Vehicular Technology Conference,2001,1(1):566-570.
[17]I.E.Telatar.Capacity of multi-antenna Gaussian channels[J].Eur.Trans.Telecommun.,1999,9(10):585-595.
[18]G.J.Foschini.Layered space-time architecture for wireless communication in a fading environment when using multielement antennas[J],Bell Labs Tech.J.,1996,8(16):41-59.
[19]谢显中,等.基于TDD的第四代移动通信技术[M].北京:电了工业出版社,2005:75-116.
[20]吴伟陵、牛凯.移动通信原理[M].北京:电了工业出版社,2005:252-262.
[21]H.B olcskei,D.Gesbert,and A.J.Paulraj,On the capacity of OFDM-based spatial multiplexing systems[J].Trans,on Comm.,2002,12(23):75-82.
[22]Agrawal,D.;Tarokh,V.;Naguib,A.;Seshadri,N.;Space-time coded OFDM for high data-rate wireless communication over wideband channels[J].IEEE VTC 98.,1998,5(3):2232-2236.
[23]Witzke,M.,Baro,S.,Schreckenbach,F.,Hagenauer,J.Iterative detection of MIMO signals with linear detectors,2002[J].Conference Record of the Thirty-Sixth Asilomar Conference,Systems and Computers,2002,9(1):289-293.
[24]Rappaport T S.无线通信原理与应用[M].北京:电子工业出版社,1999:5-50.
[25]E.Biglieri,J.Proakis.Fading channels Information-theoretic and communications aspects[J].IEEE Trans.Info.Theory,1998,5(15):1-12.
[26]S.M.Alamouti.A simple transmit diversity technique for wirelesson communications[J],IEEE.Journal Select Areas.Commun.,1998,8(16):1451-1458.
[27]V Tarokh,N.Seshadri,Space-time codes for high data rate wireless communication:performance criteria and code construction[J].IEEE Tran.s.Information Theory,1998,3(44):744-765.
[28]佟学俭,罗涛.OFDM移动通信技术原理与应用[M].北京:人民邮电出版社,2003:165-210.
[29]W.C.Y Lee,Mobile Communications Engineering:Theory and Applications[M].New York:McGraw-Hill,1998:210-350.
[30]裴昌幸,聂敏等译,Gordon,L.Stuber著.移动通信原理(第二版)[M].北京:人民邮电出版社,2004:25-130.
[31]蔡涛,李旭,杜振民译,Theodore S.Rappaport著.无线通信原理与应用[M].北京:电子工业出版社,1999:15-78.
[32]杨大成.移动传播环境理论基础、分析方法和建模技术[M].北京:机械工业出版社,2003:33-215.
[33]J.K.Cavers.An anlysis fo pilot symbol assisted modulation for Rayleigh fading channels[J],IEEE Trans.Vehic.Technol.,1991,9(40):686-693.
[34]董艳男、朱琦.基于IEEE 802.16a MIMO-OFDM系统的信道估计方法研究[J].南京:南京邮电学院学报,2006,25(2):62-66.
[35]柴关华,徐友云,蔡越明.MIMO-OFDM无线传输系统中的信道估计研究[J].江苏:江苏省通信学会论文集,2005,6(12):200-205.
[36]G.Auer,Analysis of pilot-symbol aided channel estimation for OFDM systems with multiple transmit antennas[J],2004 IEEE International Conference on Communications,2004,9(6):3221-3225.
[37]Y.Li.Simplified channel estimation for OFDM systems[J].IEEE Transmit antennas Transactions on Wireless Communications,2002,12(1):67-75.
[38]I.Barhumi,G.Leus,and M.Moonen.Optimal training design for MIMO OFDM systems in mobile wireless channels[J].IEEE Transactions on Signal Processing,2003,7(51):1615-1624.
[39]H.Zhang,J.M.Chen,Y.X.Tang,S.Q.Li.Analysis of pilot-symbol aided channel estimation for MIMO-OFDM systems[J].2004International Conference on Communications,Circuits and Systems,2004,7(1):299-303.
[40]王东明,高西奇,尤肖虎,韩冰.宽带MIMO-OFDM系统信道估计算法研究[J].电子学报,2005,7(7):1254-1257.
[41]S.Verdu,.Multiuser Detection,Cambridge University Press,1998[J].Workshop Process.Adv.Wireless Commun.,2001,3(22):42-55.
[42]王文博,等.宽带无线通信OFDM技术[M].北京:人民邮电出版社,2003:46-56.
[43]H.K.Song,Y.H.You.Error performance analysis of STBC-OFDM systems with parameter imbalances[J].IEEE Trans.Broadcasting,2004,3(23):76-82.
[44]W.G.Song,J.T.Lim.Pilot-symbol aided channel estimation for OFDM with fast fading channels[J].IEEE Trans.Broadcasting,2003,12(49):56-67.
[45]刘刚,郭漪,葛建华.MIMO-OFDM系统中的信道估计[J],华中科技大学学报,2005,9(59):26-29.
[46]S.J.Kang,M.J.Kim.Simplified channel estimation for OFDM systems with multiple transmit antennas[J].IEEE Trans.Wireless Commun.,January 2002,1(1):235-250.
[47]M.Li,J.Tan,W.Zhang.A channel estimation method based on frequency-domain pilots and time-domain processing for OFDM systems[J],IEEETrans.ConsumerElectronics,2004,9(50):504-520.
[48]H.Chen,A.M.Haimovich.Iterative estimation and cancellation of clipping noise for OFDM signals[J].IEEE Commun., 2003,7(7):305-307.
[49] X.Lei,Y.Tang,S.Li,Y.Li.A minimum clipping power loss scheme for mitigating the clipping noise in OFDM[J]. Proc.IEEE Global Telecommunication Conf.,2003,5(10):6-9.
[50] M. Garcia, J. Paez-Borrallo, S. Zazo.DFT-based channel estimation in 2D-pilot-symbol-aided OFDM wireless systems[J].Proc. IEEE Vehicular Technology Conf., 2001,11(37): 810-814.
[51] Z. J. Wang, Z. Han, K. J. R. Liu, A MIMO-OFDM channel estimation approach using time of arrivals[J],IEEE Trans. Wireless Commun., 2005,5(4):1207-1213.
[52] Yue Xiao,Shaoqian Li. Clipping Noise Mitigation for Channel Estimation in OFDM Systems [J],IEEE Communcations Leters, 2006,7(10):1050-1065.