MIMO-OFDM通信系统中自适应技术的研究
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摘要
高速率、高可靠性的数据传输以及端到端的服务质量是下一代移动通信系统的首要目标,多入多出(MIMO,Multi-InputMulti-Output)技术、正交频分复用(OFDM,Orthogonal FrequencyDivision Multiplexing)技术和自适应传输已经被广泛认为是未来移动通信系统中的主要候选技术。MIMO技术通过采用多个发射天线和接收天线可以显著提高无线通信系统的信道容量,增强数据传输的可靠性。OFDM技术可以把频率选择性衰落的信道转化成一组正交的平坦衰落的信道,因此将MIMO技术与OFDM技术相结合的多入多出—正交频分复用(MIMO-OFDM)技术成为未来移动通信系统设计的主选架构。
本文首先对无线信道进行了分析,对其参数多径效应和多普勒效应进行了研究,并引入MIMO-OFDM的系统概念,并重点介绍和分析波束成型技术,以及自适应调制的三大关键技术。
其次,通过对波束成型技术的介绍,引入并推出多用户情况下的子载波分配方案,分别对基于正确信道信息和非精确信道信息的情况进行了讨论。其中,在正确信道信息的系统模型下,推出以最大特征值为分配准则的子载波分配方案,通过仿真结果表明,这种分配方案可以有效获取多用户的分集效果。接着对非精确信道信息的
实际系统进行了讨论,并提出了信道预测模型,该模型通过各个用户信道的相关系数来均衡信道时延的影响,仿真结果表面该模型能够有效减小信道信息时延所造成的性能损失。
本文最后对注水分配法基本原理进行了研究,讨论了最常用的比特数和误码率上限不变时发射功率最小化算法,然后提出了基于变步长的比特功率分配算法,该算法对于步长选择进行优化,和比特数和误码率上限不变时发射功率最小化算法相比,在系统复杂度方面有了明显的降低,同时两者性能非常接近,而且通过仿真可知其多用户时性能将更好,因此可以很好的应用于多用户的MIMO-OFDM系统。
High data-rate, high reliable transmission and guarantee end-to-end Qos are required to be provided for the next generation mobile communication. MIMO, OFDM, and adaptive transmission have been comprehensively considered as the major candidate techniques for future radio communication systems. MIMO technology can increase the channel capability notably and enhance reliability of data-transmission with the help of multi-send antenna and multi-receive antenna. OFDM has the ability of transforming the frequency-selective channel into a collection of parallel flat-fading sub channels. Therefore combination of MIMO and OFDM is regarded as the potential architecture for the future communication system.
In this paper, wireless channel, the parameters of multi-path effect and Doppler Effect were analyzed firstly, and then mainly focus on introduction and analysis of Beam-Forming, and 3 key technology of adaptive modulation.
Based on the Beam-Forming technology, multi-carrier allocation programs was introduced, and it was discussed based on the correct channel information and non-accurate information of channel. Among two different circumstance, in the correct channel information system model, the greatest eigenvalue distribution criteria for the subcarrier allocation program was introduced, and the simulation results show that the distribution program can be effective multi-user access to the diversity effect. Then channel for non-precision actual information systems were discussed and a channel prediction model was proposed, the model balance the channel Delay through multi-users' correlation coefficient, and the simulation result shows that this model effectively reduce the loss caused by channel information Delay.
Finally, the basic principles of water-filling method was studied, and then discussed the most commonly used unchanged-bit number and bit error rate when minimize the transmitting power method. Then the power allocation algorithm which is based on the variable step-bit was proposed, the algorithm optimize the choice of step, and compared with the former algorithm, this power allocation algorithm based on the variable step-bit can decrease the complexity of the system while the performance are quite close to each other. Through simulation, the performance of the multi-user will be better, so it can be good for the multi-user MIMO-OFDM system.
本文首先对无线信道进行了分析,对其参数多径效应和多普勒效应进行了研究,并引入MIMO-OFDM的系统概念,并重点介绍和分析波束成型技术,以及自适应调制的三大关键技术。
其次,通过对波束成型技术的介绍,引入并推出多用户情况下的子载波分配方案,分别对基于正确信道信息和非精确信道信息的情况进行了讨论。其中,在正确信道信息的系统模型下,推出以最大特征值为分配准则的子载波分配方案,通过仿真结果表明,这种分配方案可以有效获取多用户的分集效果。接着对非精确信道信息的
实际系统进行了讨论,并提出了信道预测模型,该模型通过各个用户信道的相关系数来均衡信道时延的影响,仿真结果表面该模型能够有效减小信道信息时延所造成的性能损失。
本文最后对注水分配法基本原理进行了研究,讨论了最常用的比特数和误码率上限不变时发射功率最小化算法,然后提出了基于变步长的比特功率分配算法,该算法对于步长选择进行优化,和比特数和误码率上限不变时发射功率最小化算法相比,在系统复杂度方面有了明显的降低,同时两者性能非常接近,而且通过仿真可知其多用户时性能将更好,因此可以很好的应用于多用户的MIMO-OFDM系统。
High data-rate, high reliable transmission and guarantee end-to-end Qos are required to be provided for the next generation mobile communication. MIMO, OFDM, and adaptive transmission have been comprehensively considered as the major candidate techniques for future radio communication systems. MIMO technology can increase the channel capability notably and enhance reliability of data-transmission with the help of multi-send antenna and multi-receive antenna. OFDM has the ability of transforming the frequency-selective channel into a collection of parallel flat-fading sub channels. Therefore combination of MIMO and OFDM is regarded as the potential architecture for the future communication system.
In this paper, wireless channel, the parameters of multi-path effect and Doppler Effect were analyzed firstly, and then mainly focus on introduction and analysis of Beam-Forming, and 3 key technology of adaptive modulation.
Based on the Beam-Forming technology, multi-carrier allocation programs was introduced, and it was discussed based on the correct channel information and non-accurate information of channel. Among two different circumstance, in the correct channel information system model, the greatest eigenvalue distribution criteria for the subcarrier allocation program was introduced, and the simulation results show that the distribution program can be effective multi-user access to the diversity effect. Then channel for non-precision actual information systems were discussed and a channel prediction model was proposed, the model balance the channel Delay through multi-users' correlation coefficient, and the simulation result shows that this model effectively reduce the loss caused by channel information Delay.
Finally, the basic principles of water-filling method was studied, and then discussed the most commonly used unchanged-bit number and bit error rate when minimize the transmitting power method. Then the power allocation algorithm which is based on the variable step-bit was proposed, the algorithm optimize the choice of step, and compared with the former algorithm, this power allocation algorithm based on the variable step-bit can decrease the complexity of the system while the performance are quite close to each other. Through simulation, the performance of the multi-user will be better, so it can be good for the multi-user MIMO-OFDM system.
引文
[1]陈宏,中国无线电,2006/10,57-58.
[2]I.E.Telatar.Capacity of Multi-Antenna Gaussian Channels.European Trans Telecommunication,1999,10(6):585-596.
[3]G.J.Foschini,Jr.and M.J.Gans.On limits of wireless communication in a fading environment when using multiple antennas.Wireless Personal Commun.,1998,6:311-335.
[4]V.Tarokh,N.Seshadri,and A.R.Calderbank.Space-time codes for high data ratewireless communication:Performance criterion and code construction.IEEE Trans.Inform.Theory,1998,44:744-765.
[5]V.Tarokh,H.Jafarkhani and A.R.Calderbank.Space-time block codes from orthogonal designs.IEEE Trans.Inform.Theory,1999,45:1456-1467.
[6]Jafar S.A.;Goldsmith A.Transmitter optimization and optimality of beam-forming for multiple antenna systems.IEEE Transactions on Wireless Communications,2004,3:1165-1175.
[7]G.J.Foschini.Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas.Bell Labs Tech.J.,1996:41-59.
[8]G.J.Foschini,G.D.Golden,P.W.Wolniansky,and R.A.Valenzuela.Simplified processing for wireless communication at high spectral efficiency.IEEE J.Select.Areas Commun.-Wireless Commun.Series,1999,17:1841-1852.
[9]J.Ha et al.LDPC-coded OFDM with Alamouti/SVD Diversity Technique.Wireless Pers.Commtm.,2002,23(1):183-194.
[10]L.Zheng and D.Tse.Diversity and Multiplexing:A Fundamental Tradeoff in Multiple Antenna Channels.IEEE Transactions on Information Theory,2002,48(2):359-383.
[11]Hongwei Yang.A road to future broadband wireless access:MIMO-OFDM-based air interface.IEEE commun.Magazine,2005,43:53-60.
[12]C.Y.Wong,R.S.Cheng,K.B.Letaief,R.D.Murch.Multiuser OFDM with Adaptive Subcarrier,Bit,and Power Allocation.IEEE Journal on Selected Areas in Comm,1999-10,17:1747-1758.
[13]C.Y.Wong.C.Y.Tsui,R.S.Cheng,K.B.Letaief.A Real-time Subearrier Allocation Scheme for Multiple Access Downlink OFDM Transmission.IEEE,1999:1124-1128.
[14]Ytmg-Fang Chen,Jean-Wei Chen,Chih-Peng Li.A fast suboptimal subearrier,bit,and power allocation algorithm for multiuser OFDM-based systems.IEEE ICC,2004,6:3212-3216.
[15]S.Pietrzyk,G.J.M.Janssen.Multiuser subcarrier allocation for QoS provision in the OFDMA systems.IEEE VTC 2002,2:1077-1081.
[16]W.Rhee,J.M.Cioffi.Increase in Capacity of Multiuser OFDM System Using Dynamic Subchannel Allocation.IEEE VTC 2000,2:1085-1089.
[17]J.Jang and K B.Lee.Transmit Power Adaptation for Multiuser OFDM Systems.IEEE J.Selected Areas Comm.,2003,21:171-178.
[18]Rbee W,Cionffi J M.Increase in capacity of multiuser OFDM System using dynamic subchannel allocation.In:Proc.IEEE Vehicular Teehnology Conf.,2000:1085-1089.
[19]Inhyoung Kim,Hre Leem Lee,et al.On the use of linear programming for dynamic subehannel and bit allocation in multiuser OFDM.《IEEE Global Telecommunications Conference 》 Kim Inhyoung Kim Beomsup Kim Beomsup 2001,6:3648-3652.
[20]TENG Y,NAGAOSA T,MORI K,et al.Proposal of adaptive subchannel and bit allocation method for OFDM access wireless LAN systems[A].Proceeding IEEE VTC 03 Volume 2[C].Jeju:IEEE,2003:910-914.
[21]Daniel Perez,Javier R,Fonollosa.Practical Algorithm for a Family of Waterfilling Solution.IEEE Transaction on Signal Processing,2005,21(53):686-695.
[22]贺志强,王晓湘,吴伟陵。一种新的时变衰落信道下MIMO系统的功率分配和自适应调制算法[J]。电子学报,2004,9(32):1556-1559.
[23]P S Chow,J M Cioffi,J A Bingham.A practical discrete multitone transceiver loading algorithm for data transmission over speetrally shaped channels[J].IEEE Trans Comm,1995,43:773-775.
[24]R F H Fischer,J B Huber.A New loading algorithm for discrete multitone transmission[A].Proe IEEE Globecom[C].1996:724-728.
[25]B S Krongold,K Ramchandran,D L Jones.Computationally efficient optimal power allocation algorithm for multicarrier communication system [A].ICC[C].1998:1018-1022.
[26]J Campello.A practical bit loading for DMT[A].ICC[C].1999:801-805.
[27]Joon Hyun Sung.Transmitter Strategies for Closed-Loop MIMO-OFDM.2004.OCLC(Online Computer Library Center)Number:56569115,2005,3:27-30.
[28]Jinsock Lee and Kojiro Hamabe.Adaptive modulation switching level control in high speed downlink packet access transmission.3G Mobile Communication Technologies,Conference Publication No.489.IEE.2002:156-159.
[29]H.Viswanathan,X.Li,and R.Krishnamoorthy.Adaptive coded modulation over slow frequency selective fading channels.IEEE,1999,Vol.3:2388-2392.
[30]H.Cheon,B.Park,and D.Hong.Adaptive multicarrier system with reduced feedback information in wideband radio channels.IEEE,VTC1999,Vol.5:2880-2884.
[31]G.D.Golden,G.J.Foschini,R.A.Valenzuela,and P.W.Wolniansky.Detection algorithm and initial laboratory results using the V-BLAST space-time communication architecture.Electronics Letters,1999,35(1):14-15.
[32]T.Keller and L.Hanzo.Adaptive modulation technique for duplex OFDM transmission.IEEE Transactions on Vehicular Technology,2000,49:1893-1906.
[33]T.S.Rappaport.Whreless Communications:Principles and Practice.Englewood Cliffs,N J:Prentice-Hall,1996:342-346.
[34]张贤达.矩阵分析与应用.清华大学出版社,2004:453-490.
[35]K.Wong,R.Cheng,K.Letaief and R.Murch.Adaptive antennas at the mobile and base stations in an OFDM/TDMA system.IEEE Transaction on Communications,2001,49(1):195-206.
[36]W.Jakes.Microwave Mobile Communications.New York:Wiley,1974.:341-389.
[37]王永学等.非精确信道信息下的自适应MIMO-OFDM系统性能分析.北京.电子与信息学报.2006.3:433-436.
[38]T.Cormen,C.Leiserson,R.Rivest,and C.Stein.Introduction to Algorithms.2nd ed.Cambridge,MA:MIT Press,2001:Sections 16.1-16.3.
[39]A.J.Goldsmith and S.Chua.Degrees of freedom in adaptive modulation:a unified view.IEEE Trans.Commun.,2001,49:1561-1571.
[40]J.Yuan,Z.Chen,B.Vucetic and W.Firmanto,Performance and design of space-time coding in flat fading channels,IEEE Trans.Commun.,Dec.2003,vol.51:1991-1996.
[41]Sigen Ye,Rick S.Blum,Leonard J.Cimini,"Adaptive Modulation for Variable-Rate OFDM Systems with Imperfect Channel Information," EECS Univ.,2002:52-57.
[42]T.Keller and L.Hanzo,"Adaptive Multicarrier Modulation:a convenient framework for time-frequency processing in wireless communications," IEEE Proc.,2000,Vol.88:611-640.
[43]Forney G D Jr.Combined equalization and coding using precoding[J].IEEE Communication Magazine,1991,29(12):25-34.
[44]Campello J.Optimal discrete bit loading for multicarrier modulation systems.In Proc.of ISIT,Cambrige,USA,1998:193-193.
[2]I.E.Telatar.Capacity of Multi-Antenna Gaussian Channels.European Trans Telecommunication,1999,10(6):585-596.
[3]G.J.Foschini,Jr.and M.J.Gans.On limits of wireless communication in a fading environment when using multiple antennas.Wireless Personal Commun.,1998,6:311-335.
[4]V.Tarokh,N.Seshadri,and A.R.Calderbank.Space-time codes for high data ratewireless communication:Performance criterion and code construction.IEEE Trans.Inform.Theory,1998,44:744-765.
[5]V.Tarokh,H.Jafarkhani and A.R.Calderbank.Space-time block codes from orthogonal designs.IEEE Trans.Inform.Theory,1999,45:1456-1467.
[6]Jafar S.A.;Goldsmith A.Transmitter optimization and optimality of beam-forming for multiple antenna systems.IEEE Transactions on Wireless Communications,2004,3:1165-1175.
[7]G.J.Foschini.Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas.Bell Labs Tech.J.,1996:41-59.
[8]G.J.Foschini,G.D.Golden,P.W.Wolniansky,and R.A.Valenzuela.Simplified processing for wireless communication at high spectral efficiency.IEEE J.Select.Areas Commun.-Wireless Commun.Series,1999,17:1841-1852.
[9]J.Ha et al.LDPC-coded OFDM with Alamouti/SVD Diversity Technique.Wireless Pers.Commtm.,2002,23(1):183-194.
[10]L.Zheng and D.Tse.Diversity and Multiplexing:A Fundamental Tradeoff in Multiple Antenna Channels.IEEE Transactions on Information Theory,2002,48(2):359-383.
[11]Hongwei Yang.A road to future broadband wireless access:MIMO-OFDM-based air interface.IEEE commun.Magazine,2005,43:53-60.
[12]C.Y.Wong,R.S.Cheng,K.B.Letaief,R.D.Murch.Multiuser OFDM with Adaptive Subcarrier,Bit,and Power Allocation.IEEE Journal on Selected Areas in Comm,1999-10,17:1747-1758.
[13]C.Y.Wong.C.Y.Tsui,R.S.Cheng,K.B.Letaief.A Real-time Subearrier Allocation Scheme for Multiple Access Downlink OFDM Transmission.IEEE,1999:1124-1128.
[14]Ytmg-Fang Chen,Jean-Wei Chen,Chih-Peng Li.A fast suboptimal subearrier,bit,and power allocation algorithm for multiuser OFDM-based systems.IEEE ICC,2004,6:3212-3216.
[15]S.Pietrzyk,G.J.M.Janssen.Multiuser subcarrier allocation for QoS provision in the OFDMA systems.IEEE VTC 2002,2:1077-1081.
[16]W.Rhee,J.M.Cioffi.Increase in Capacity of Multiuser OFDM System Using Dynamic Subchannel Allocation.IEEE VTC 2000,2:1085-1089.
[17]J.Jang and K B.Lee.Transmit Power Adaptation for Multiuser OFDM Systems.IEEE J.Selected Areas Comm.,2003,21:171-178.
[18]Rbee W,Cionffi J M.Increase in capacity of multiuser OFDM System using dynamic subchannel allocation.In:Proc.IEEE Vehicular Teehnology Conf.,2000:1085-1089.
[19]Inhyoung Kim,Hre Leem Lee,et al.On the use of linear programming for dynamic subehannel and bit allocation in multiuser OFDM.《IEEE Global Telecommunications Conference 》 Kim Inhyoung Kim Beomsup Kim Beomsup 2001,6:3648-3652.
[20]TENG Y,NAGAOSA T,MORI K,et al.Proposal of adaptive subchannel and bit allocation method for OFDM access wireless LAN systems[A].Proceeding IEEE VTC 03 Volume 2[C].Jeju:IEEE,2003:910-914.
[21]Daniel Perez,Javier R,Fonollosa.Practical Algorithm for a Family of Waterfilling Solution.IEEE Transaction on Signal Processing,2005,21(53):686-695.
[22]贺志强,王晓湘,吴伟陵。一种新的时变衰落信道下MIMO系统的功率分配和自适应调制算法[J]。电子学报,2004,9(32):1556-1559.
[23]P S Chow,J M Cioffi,J A Bingham.A practical discrete multitone transceiver loading algorithm for data transmission over speetrally shaped channels[J].IEEE Trans Comm,1995,43:773-775.
[24]R F H Fischer,J B Huber.A New loading algorithm for discrete multitone transmission[A].Proe IEEE Globecom[C].1996:724-728.
[25]B S Krongold,K Ramchandran,D L Jones.Computationally efficient optimal power allocation algorithm for multicarrier communication system [A].ICC[C].1998:1018-1022.
[26]J Campello.A practical bit loading for DMT[A].ICC[C].1999:801-805.
[27]Joon Hyun Sung.Transmitter Strategies for Closed-Loop MIMO-OFDM.2004.OCLC(Online Computer Library Center)Number:56569115,2005,3:27-30.
[28]Jinsock Lee and Kojiro Hamabe.Adaptive modulation switching level control in high speed downlink packet access transmission.3G Mobile Communication Technologies,Conference Publication No.489.IEE.2002:156-159.
[29]H.Viswanathan,X.Li,and R.Krishnamoorthy.Adaptive coded modulation over slow frequency selective fading channels.IEEE,1999,Vol.3:2388-2392.
[30]H.Cheon,B.Park,and D.Hong.Adaptive multicarrier system with reduced feedback information in wideband radio channels.IEEE,VTC1999,Vol.5:2880-2884.
[31]G.D.Golden,G.J.Foschini,R.A.Valenzuela,and P.W.Wolniansky.Detection algorithm and initial laboratory results using the V-BLAST space-time communication architecture.Electronics Letters,1999,35(1):14-15.
[32]T.Keller and L.Hanzo.Adaptive modulation technique for duplex OFDM transmission.IEEE Transactions on Vehicular Technology,2000,49:1893-1906.
[33]T.S.Rappaport.Whreless Communications:Principles and Practice.Englewood Cliffs,N J:Prentice-Hall,1996:342-346.
[34]张贤达.矩阵分析与应用.清华大学出版社,2004:453-490.
[35]K.Wong,R.Cheng,K.Letaief and R.Murch.Adaptive antennas at the mobile and base stations in an OFDM/TDMA system.IEEE Transaction on Communications,2001,49(1):195-206.
[36]W.Jakes.Microwave Mobile Communications.New York:Wiley,1974.:341-389.
[37]王永学等.非精确信道信息下的自适应MIMO-OFDM系统性能分析.北京.电子与信息学报.2006.3:433-436.
[38]T.Cormen,C.Leiserson,R.Rivest,and C.Stein.Introduction to Algorithms.2nd ed.Cambridge,MA:MIT Press,2001:Sections 16.1-16.3.
[39]A.J.Goldsmith and S.Chua.Degrees of freedom in adaptive modulation:a unified view.IEEE Trans.Commun.,2001,49:1561-1571.
[40]J.Yuan,Z.Chen,B.Vucetic and W.Firmanto,Performance and design of space-time coding in flat fading channels,IEEE Trans.Commun.,Dec.2003,vol.51:1991-1996.
[41]Sigen Ye,Rick S.Blum,Leonard J.Cimini,"Adaptive Modulation for Variable-Rate OFDM Systems with Imperfect Channel Information," EECS Univ.,2002:52-57.
[42]T.Keller and L.Hanzo,"Adaptive Multicarrier Modulation:a convenient framework for time-frequency processing in wireless communications," IEEE Proc.,2000,Vol.88:611-640.
[43]Forney G D Jr.Combined equalization and coding using precoding[J].IEEE Communication Magazine,1991,29(12):25-34.
[44]Campello J.Optimal discrete bit loading for multicarrier modulation systems.In Proc.of ISIT,Cambrige,USA,1998:193-193.