室内MIMO系统信道容量的改善
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摘要
随着多媒体移动通信等新业务的发展,频谱资源日益紧张。人们持续增长的需求与有限频谱资源之间的矛盾成为研究高频谱利用率技术的动力和挑战。众多新技术中,基于多天线的多输入多输出无线通信结构已显示出无尽的潜力,成为充分利用空间资源的必然途径。它可以不需增加带宽和发射功率,大幅度地提高无线通信系统的信息容量和传输速率,从而提供远高于传统单天线系统的频带利用率。
室内多输入多输出系统,即MIMO(Multiple-Input Multiple-Output)系统,如使用无指向性天线作为基站天线,由于存在大量墙壁散射,送信电力损失比较大。本文提出应用指向性天线作为室内MIMO系统的基站天线,从而改善系统的信道容量。通过EEM-RTM软件仿真与Matlab软件计算信道容量,接收端采用最小均方差算法,即MMSE(Minimum MeanSquare Error)算法,与最大似然检测算法,即MLD(Maximum LikelihoodDetection)算法,进行信号处理。计算结果表明指向性天线作为基站天线时,较之无指向性天线相比,系统信道容量能够得到很大提高,从而系统的性能得到改善。本文还进一步研究了如何通过合理地配置基站天线系数,改善系统的信道容量。仿真与计算结果表明在从四根终端天线中选择两根作为接收器的情况下,基站天线参数设置为波瓣角度差φ_B∶90°,方向系数φ_(HP)=60°时,系统信道容量最佳。
此外,为了提高系统的通信性能,降低系统的成本,本文探讨了MIMO系统终端天线的选择方式,仿真结果表明依据最大信道容量选择接收天线时,使用多根终端天线并从中选择两根作为接收天线是最有效的。
MIMO (Multiple-Input Multiple-Output) system attracts much attention and has been put into a practical use. It makes high-speed wireless communications possible by using plural antennas for each station without extending frequency bandwidth.
As well know, the channel capacity is low using omni antennas as the base station antennas because of useless radiation. As to improve the channel capacity, this paper proposes that channel capacity of the indoor MIMO system can be improved using directional antennas rather than omni antennas. Using EEM-RTM software to simulate, Matlab software to calculate the channel capacity, and signal processing algorithms of terminal: MMSE(Minimum Mean Square Error) and MLD(Maximum Likelihood Detection) algorithms to process signal, the results prove that channel capacity of the indoor MIMO system can be improved using directional antennas rather than omni antennas. Moreover, the effects of directivity and beam direction of base station antennas on the system capacity are evaluated, it is proved that whenφ_B = 90°andφ_(HP) = 60°, we can achieve the maximum channel capacity. As to improve the performance of MIMO system and reduce the cost of system, this paper also discusses the way of selecting the terminal antennas with good characters. Selecting terminal antennas is according to the maximum channel capacity, it can be said that using two receivers with many terminal antennas is very effective.
室内多输入多输出系统,即MIMO(Multiple-Input Multiple-Output)系统,如使用无指向性天线作为基站天线,由于存在大量墙壁散射,送信电力损失比较大。本文提出应用指向性天线作为室内MIMO系统的基站天线,从而改善系统的信道容量。通过EEM-RTM软件仿真与Matlab软件计算信道容量,接收端采用最小均方差算法,即MMSE(Minimum MeanSquare Error)算法,与最大似然检测算法,即MLD(Maximum LikelihoodDetection)算法,进行信号处理。计算结果表明指向性天线作为基站天线时,较之无指向性天线相比,系统信道容量能够得到很大提高,从而系统的性能得到改善。本文还进一步研究了如何通过合理地配置基站天线系数,改善系统的信道容量。仿真与计算结果表明在从四根终端天线中选择两根作为接收器的情况下,基站天线参数设置为波瓣角度差φ_B∶90°,方向系数φ_(HP)=60°时,系统信道容量最佳。
此外,为了提高系统的通信性能,降低系统的成本,本文探讨了MIMO系统终端天线的选择方式,仿真结果表明依据最大信道容量选择接收天线时,使用多根终端天线并从中选择两根作为接收天线是最有效的。
MIMO (Multiple-Input Multiple-Output) system attracts much attention and has been put into a practical use. It makes high-speed wireless communications possible by using plural antennas for each station without extending frequency bandwidth.
As well know, the channel capacity is low using omni antennas as the base station antennas because of useless radiation. As to improve the channel capacity, this paper proposes that channel capacity of the indoor MIMO system can be improved using directional antennas rather than omni antennas. Using EEM-RTM software to simulate, Matlab software to calculate the channel capacity, and signal processing algorithms of terminal: MMSE(Minimum Mean Square Error) and MLD(Maximum Likelihood Detection) algorithms to process signal, the results prove that channel capacity of the indoor MIMO system can be improved using directional antennas rather than omni antennas. Moreover, the effects of directivity and beam direction of base station antennas on the system capacity are evaluated, it is proved that whenφ_B = 90°andφ_(HP) = 60°, we can achieve the maximum channel capacity. As to improve the performance of MIMO system and reduce the cost of system, this paper also discusses the way of selecting the terminal antennas with good characters. Selecting terminal antennas is according to the maximum channel capacity, it can be said that using two receivers with many terminal antennas is very effective.
引文
[1]龚耀寰.多输入多输出智能天线技术.中兴通信技术,2002,6:19—21
[2]付景兴.MIMO—无线高速数据传输的关键技术.通信世界,2003,10:56—57
[3]E.Teletar,"Capacity of multi-antenna Gaussian channels," European Transactions on Telecommunications,vol.10,no.6,Nov./Dec.1999,pp.585-595
[4]Sokthai Chan,Mitoshi Fujimoto and Toshikazu Hori,"Novel Configuration for Indoor Wireless LAN Base Station Applied to SDMA System," Proc.Of ISAP2005,Seoul,Korea,August 2005,pp.253-256
[5]G.J.Foschini and M.J.Gans,"On limits of wireless communications in a fading environment when using multiple antennas," Wireless Personal Communications,Feb.2001,pp.178-187
[6]G.J.Foschini,"Layered space-time architecture for wireless communication in a fading environment when using multiple antennas," Bell Labs.Tech.J.,vol.1,no.2,1996,pp.41-59
[7]叶卓映,吴伟陵.MIMO无线新技术研究.数据通信,2004,3:6-7
[8]D.Gesbert,M.Shafi,D.Shiu,et al.,"From theory to practice:An overview of MIMO space-time coded wireless systems,"IEEE J.Select.Areas Commun.,vol.21,no.3,Apr.2003,pp.281-302
[9]S.M.Alalnouti,"A simple transmit diversity technique for wireless communications,"IEEE J.Selected Areas Commun.,vol.16,no.8,Oct.1998,pp.1451-1458
[10]V.Tarokh,N.Seshadri,and A.R.Calderbank,"Space-time codes for high data rate wireless communication:performance criterion and code construction," IEEE Trans.Inform.Theory,vol.44,no.2,March 1998,pp.744-765
[11]A.van Zelst and T.C.W.Schenk,"Implementation of a MIMO OFDM-based wireless LAN system," IEEE Trans.Signal Processing,vol.52,no.2,Feb.2004,pp.483-494
[12]G.D.Golden,G.J.Foschini,R.A.valensuela,and P.W.Wolniansky,"Detection algorithm and initial laboratory results using V-BLAST space-time communication architecture,"Electron.Lett.,vo.35,no.1,Jan.1999,pp.14-16
[13]E.Viterbo and J.Bouros,"A universal lattice code decoder for fading channels," IEEE Trans.Inform.Theory,vol.45,no.5,July 1999,pp.1639-1642
[14]M.O.Damen,A.Chkeif,and J.C.Belfiore,"Lattice codes decoder for space-time codes,"IEEE Commun.Lett.,vol.4,no.5,May 2000,pp.161-163
[15]M.O.Damen,H.E1 Gamel,and G.Caire,"On maximum-likelihood detection and the search for the closest lattice point," IEEE Trans.Inform.Theory,vol.49,no.10,Oct.2003,pp.2389-2402
[16]K.J.Kim and R.A.Iltis,"Joint detection and channel estimation algorithms for QS-CDMA signals over time-varying channels," IEEE Trans.Commun.,vol.50,no.5,May 2002,pp.845-855
[17]谢新梅.基于TDD的第四代移动通信技术.北京:电子工业出版社,2003,2:22-23
[18]王君.平坦衰落环境中多输入多输出系统衰落相关与信道容量研究.电子与信息学 报,2006,28(2):193-197
[19]程型清.相关瑞利信道在速率调整与分集合并下的容量研究.北京电子科技学院学报,2004,12(4):24-25
[20]D.Samardzija and N.Mandayam,"Pilot-assisted estimation of MIMO fading channel response and achievable data rates," IEEE Trans.Signal Processing,vol.51,no.11,Nov.2003,pp.2882-2890
[21]V.Lau,L.Youjian,and T.A.Chen,"On the design of MIMO block-fading channels with feedback-link capacity constraint," IEEE Trans.Commun.,vol.52,no.1,Jan.2004,pp.62-70
[22]程型清.相关瑞利分集系统容量的研究.无线电工程,2004,34(:7)1-2
[23]张贤达.通信信号处理.北京:国防工业出版社,2000,6:45-47
[24]彭林.第二代移动通信技术.北京:电子工业出版社,2003,8:65-67
[25]Masahiro Chuta,Mitoshi Fujimoto and Toshikazu Hori,"Antenna Configuration for Indoor MIMO System Using Directional Antennas," 2006 Korea-Japan Joint Conference on AP/EMCJ/EMT,Sept.2006,P-AP-4
[26]K.Liu,V.Raghavan,and A.Sayeed,"Capacity scaling and spectral efficiency in wide-band correlated MIMO channels,"IEEE Trans.Infonn.Theory,vol.49,no.10,Oct.2003,pp.2504-2526
[27]R.Clarke,"A statistical theory of mobile-radio reception,"Bell Syst.Tech.J.Jul.-Aug.1968,pp.957-1000
[28]汪晋.空间白适应信号处理.沈阳:东北大学出版社,2003,10:45-48
[29]孙俊.MIMO传输中的信道相关性影响:[学位论文].武汉:华中科技大学,2004:13-14
[30]Molisch A.E宽带无线数字通信.许希彬等泽.北京:电子工业出版社,2002,4:19-20
[31]]P.A.Dighe,R.K.Mallik,and S.R.Jamuar,"Analysis of transmit-receive diversity in Rayleigh fading," Proc.IEEE GLOBECOM '2001,Nov.2001,pp.1132-1136
[32]B.Hassibi and B.Hochwald,"How much training is needed in multiple-antenna wireless links,"IEEE Trans.Inform.Theory,vol.49,no.4,Apr.2003,pp.951-963
[33]H.Bolsckei,M.Borgmann,and A.Paulraj,"Impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM,"IEEE J.Select.Areas Commun,vol.21,no.3,Apr.2003,pp.427-439
[2]付景兴.MIMO—无线高速数据传输的关键技术.通信世界,2003,10:56—57
[3]E.Teletar,"Capacity of multi-antenna Gaussian channels," European Transactions on Telecommunications,vol.10,no.6,Nov./Dec.1999,pp.585-595
[4]Sokthai Chan,Mitoshi Fujimoto and Toshikazu Hori,"Novel Configuration for Indoor Wireless LAN Base Station Applied to SDMA System," Proc.Of ISAP2005,Seoul,Korea,August 2005,pp.253-256
[5]G.J.Foschini and M.J.Gans,"On limits of wireless communications in a fading environment when using multiple antennas," Wireless Personal Communications,Feb.2001,pp.178-187
[6]G.J.Foschini,"Layered space-time architecture for wireless communication in a fading environment when using multiple antennas," Bell Labs.Tech.J.,vol.1,no.2,1996,pp.41-59
[7]叶卓映,吴伟陵.MIMO无线新技术研究.数据通信,2004,3:6-7
[8]D.Gesbert,M.Shafi,D.Shiu,et al.,"From theory to practice:An overview of MIMO space-time coded wireless systems,"IEEE J.Select.Areas Commun.,vol.21,no.3,Apr.2003,pp.281-302
[9]S.M.Alalnouti,"A simple transmit diversity technique for wireless communications,"IEEE J.Selected Areas Commun.,vol.16,no.8,Oct.1998,pp.1451-1458
[10]V.Tarokh,N.Seshadri,and A.R.Calderbank,"Space-time codes for high data rate wireless communication:performance criterion and code construction," IEEE Trans.Inform.Theory,vol.44,no.2,March 1998,pp.744-765
[11]A.van Zelst and T.C.W.Schenk,"Implementation of a MIMO OFDM-based wireless LAN system," IEEE Trans.Signal Processing,vol.52,no.2,Feb.2004,pp.483-494
[12]G.D.Golden,G.J.Foschini,R.A.valensuela,and P.W.Wolniansky,"Detection algorithm and initial laboratory results using V-BLAST space-time communication architecture,"Electron.Lett.,vo.35,no.1,Jan.1999,pp.14-16
[13]E.Viterbo and J.Bouros,"A universal lattice code decoder for fading channels," IEEE Trans.Inform.Theory,vol.45,no.5,July 1999,pp.1639-1642
[14]M.O.Damen,A.Chkeif,and J.C.Belfiore,"Lattice codes decoder for space-time codes,"IEEE Commun.Lett.,vol.4,no.5,May 2000,pp.161-163
[15]M.O.Damen,H.E1 Gamel,and G.Caire,"On maximum-likelihood detection and the search for the closest lattice point," IEEE Trans.Inform.Theory,vol.49,no.10,Oct.2003,pp.2389-2402
[16]K.J.Kim and R.A.Iltis,"Joint detection and channel estimation algorithms for QS-CDMA signals over time-varying channels," IEEE Trans.Commun.,vol.50,no.5,May 2002,pp.845-855
[17]谢新梅.基于TDD的第四代移动通信技术.北京:电子工业出版社,2003,2:22-23
[18]王君.平坦衰落环境中多输入多输出系统衰落相关与信道容量研究.电子与信息学 报,2006,28(2):193-197
[19]程型清.相关瑞利信道在速率调整与分集合并下的容量研究.北京电子科技学院学报,2004,12(4):24-25
[20]D.Samardzija and N.Mandayam,"Pilot-assisted estimation of MIMO fading channel response and achievable data rates," IEEE Trans.Signal Processing,vol.51,no.11,Nov.2003,pp.2882-2890
[21]V.Lau,L.Youjian,and T.A.Chen,"On the design of MIMO block-fading channels with feedback-link capacity constraint," IEEE Trans.Commun.,vol.52,no.1,Jan.2004,pp.62-70
[22]程型清.相关瑞利分集系统容量的研究.无线电工程,2004,34(:7)1-2
[23]张贤达.通信信号处理.北京:国防工业出版社,2000,6:45-47
[24]彭林.第二代移动通信技术.北京:电子工业出版社,2003,8:65-67
[25]Masahiro Chuta,Mitoshi Fujimoto and Toshikazu Hori,"Antenna Configuration for Indoor MIMO System Using Directional Antennas," 2006 Korea-Japan Joint Conference on AP/EMCJ/EMT,Sept.2006,P-AP-4
[26]K.Liu,V.Raghavan,and A.Sayeed,"Capacity scaling and spectral efficiency in wide-band correlated MIMO channels,"IEEE Trans.Infonn.Theory,vol.49,no.10,Oct.2003,pp.2504-2526
[27]R.Clarke,"A statistical theory of mobile-radio reception,"Bell Syst.Tech.J.Jul.-Aug.1968,pp.957-1000
[28]汪晋.空间白适应信号处理.沈阳:东北大学出版社,2003,10:45-48
[29]孙俊.MIMO传输中的信道相关性影响:[学位论文].武汉:华中科技大学,2004:13-14
[30]Molisch A.E宽带无线数字通信.许希彬等泽.北京:电子工业出版社,2002,4:19-20
[31]]P.A.Dighe,R.K.Mallik,and S.R.Jamuar,"Analysis of transmit-receive diversity in Rayleigh fading," Proc.IEEE GLOBECOM '2001,Nov.2001,pp.1132-1136
[32]B.Hassibi and B.Hochwald,"How much training is needed in multiple-antenna wireless links,"IEEE Trans.Inform.Theory,vol.49,no.4,Apr.2003,pp.951-963
[33]H.Bolsckei,M.Borgmann,and A.Paulraj,"Impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM,"IEEE J.Select.Areas Commun,vol.21,no.3,Apr.2003,pp.427-439
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