MIMO系统有限反馈预编码技术研究
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摘要
多入多出(Multiple Input Multiple Output, MIMO)技术凭借在提高频谱利用率方面的极大优势成为未来无线通信系统的一项关键技术。在多用户多入多出(Multi-user MIMO, MU-MIMO)系统中,基站在相同的时频资源块和多个用户传递信息,在成倍地提高系统频谱资源利用率的同时不可避免地引入了用户及子数据流间的干扰。预编码正是通过发射端的预处理消除空间信号干扰的一种有效措施。下行链路预编码技术的应用一方面大大简化了用户终端信号处理难度,另一方面极大地提高了系统的可靠性。
本文针对多入多出系统中的有限反馈预编码技术做了如下研究：
1.研究了无线信道特点、多入多出系统传输模型及系统容量的推导,总结了现有系统的反馈方案,针对典型预编码算法的基本原理、实现流程及优缺点进行了深入分析。
2.针对目前主流的模代数预编码,提出了只反馈信道方向信息的改进方案,该方案无需反馈幅度信息,大大节省了反馈量。研究了该方案下基于矢量量化反馈及标量量化反馈的模代数预编码具体实现流程,并对基于量化反馈的模代数预编码系统容量进行了推导,通过理论及仿真对该方案的有效性进行了验证。
3.研究了时分复用系统利用上下行信道间的互易性进行模代数预编码的方案,分析了信道时变性、信道估计误差、射频器件不对称、上行探测信号带宽受限等四种影响信道互易性的因素并研究了对应的补偿方案,最后通过仿真评估了信道时变性及射频器件不对称两个因素对信道互易性及模代数预编码算法性能的影响。
With the significant advantage in improving spectrum efficiency, multiple-input multiple-output (MIMO) technology becomes one of the key technologies of next generation wireless communication system. In multi-user multiple-input multiple-output (MU-MIMO) downlink, a base station communicates with several co-channel users simultaneously in the same frequency and time slots, the spectrum resource utilization is multiplied but co-channel interference (CCI) is also introduced inevitably, including interference between users and sub-streams. Precoding is just the effective measure which can eliminate space signal interference by some pre-processing at the transmitting side. The application of precoding technology greatly reduces the complexity of the receiver on one hand and significantly improves the reliability of the system on the other hand.
This paper focuses on the limited feedback precoding schemes in MIMO system. The main contents include following aspects:
1. Investigate on the characteristic of radio channel, transmission model of MIMO systems and derivation of system capacity. Research on the existing feedback schemes and precoding techniques. Do in-depth analysis on the basic principles, implementation process, advantages and disadvantages of some typical precoding schemes.
2. Aimed at Tomlinson-Harashima Precoding (THP), an optimized scheme which only needs feeding back channel direction information is proposed. Amplitude information is not necessary for the new scheme. It has significantly reduced the feedback bits. Implementation process of the proposed THP scheme based on both vector quantization and scalar quantization is studied. Also system capacity is derived. The effectiveness of the scheme is certified both by theory and simulation.
3. Deeply research on THP scheme in time division duplex (TDD) system which obtains channel state information by reciprocity between downlink and uplink. Factors that affect reciprocity, including time-variance of channel, estimation error of channel, asymmetry of RF devices, bandwidth limit of uplink reference signal and etc., are investigated and the corresponding compensation schemes are proposed. The impact of time-variance and RF devices' asymmetry to channel reciprocity and THP performance is evaluated by simulation.
本文针对多入多出系统中的有限反馈预编码技术做了如下研究：
1.研究了无线信道特点、多入多出系统传输模型及系统容量的推导,总结了现有系统的反馈方案,针对典型预编码算法的基本原理、实现流程及优缺点进行了深入分析。
2.针对目前主流的模代数预编码,提出了只反馈信道方向信息的改进方案,该方案无需反馈幅度信息,大大节省了反馈量。研究了该方案下基于矢量量化反馈及标量量化反馈的模代数预编码具体实现流程,并对基于量化反馈的模代数预编码系统容量进行了推导,通过理论及仿真对该方案的有效性进行了验证。
3.研究了时分复用系统利用上下行信道间的互易性进行模代数预编码的方案,分析了信道时变性、信道估计误差、射频器件不对称、上行探测信号带宽受限等四种影响信道互易性的因素并研究了对应的补偿方案,最后通过仿真评估了信道时变性及射频器件不对称两个因素对信道互易性及模代数预编码算法性能的影响。
With the significant advantage in improving spectrum efficiency, multiple-input multiple-output (MIMO) technology becomes one of the key technologies of next generation wireless communication system. In multi-user multiple-input multiple-output (MU-MIMO) downlink, a base station communicates with several co-channel users simultaneously in the same frequency and time slots, the spectrum resource utilization is multiplied but co-channel interference (CCI) is also introduced inevitably, including interference between users and sub-streams. Precoding is just the effective measure which can eliminate space signal interference by some pre-processing at the transmitting side. The application of precoding technology greatly reduces the complexity of the receiver on one hand and significantly improves the reliability of the system on the other hand.
This paper focuses on the limited feedback precoding schemes in MIMO system. The main contents include following aspects:
1. Investigate on the characteristic of radio channel, transmission model of MIMO systems and derivation of system capacity. Research on the existing feedback schemes and precoding techniques. Do in-depth analysis on the basic principles, implementation process, advantages and disadvantages of some typical precoding schemes.
2. Aimed at Tomlinson-Harashima Precoding (THP), an optimized scheme which only needs feeding back channel direction information is proposed. Amplitude information is not necessary for the new scheme. It has significantly reduced the feedback bits. Implementation process of the proposed THP scheme based on both vector quantization and scalar quantization is studied. Also system capacity is derived. The effectiveness of the scheme is certified both by theory and simulation.
3. Deeply research on THP scheme in time division duplex (TDD) system which obtains channel state information by reciprocity between downlink and uplink. Factors that affect reciprocity, including time-variance of channel, estimation error of channel, asymmetry of RF devices, bandwidth limit of uplink reference signal and etc., are investigated and the corresponding compensation schemes are proposed. The impact of time-variance and RF devices' asymmetry to channel reciprocity and THP performance is evaluated by simulation.
引文
[1]肖扬,MIMO多天线无线通信系统.2009,人民邮电出版社.
[2]Zheng L. Tse DNC, Diversity and multiplexing:A fundamental tradeoff in multiple-antenna channels. IEEE Transactions on Information Theory,2003, vol.49, no.5, pp.1073-1096.
[3]G.J. Foschini, M.J. Gans, On limits of wireless communication in a fading environment when using multiple antennas. Wireless Personal Commun, Mar.1998, pp.311-335.
[4]I.E. Telatar, Capacity of multi-antenna Gaussian channels. European Trans. Telecomm, vol.10, no.6, Nov./Dec.1999, pp.585-595.
[5]Q.H. Spencer, A.L. Swindlehurst, H. Martin, Zero-forcing Methods for Downlink Spatial Multiplexing in Muitiuser MIMO Channels. IEEE Transactions on Signal Processing, vol.52, no.2, Feb.2004, pp.461-471.
[6]H. Sampth, P. Storica, A. Paulraj, Genralized Linear Precoder and Decoder Design for MIMO Channels Using the Weighted MMSE Criterion. IEEE Transactions on Commun., vol.49, no.12, Dec.2001, pp.2198-2206.
[7]A. Scaglione, P. Stoica, S. Barbarossa, et. al, Optimal designs for space-time linear precoders and equalizers. IEEE Transaction on Signal Processing, vol.50, no.5, May 2002, pp.1051-1064.
[8]Q.H. Spencer, M. Haardt, Capacity and downlink transmission algorithms for a multiuser MIMO channel. Conference on Signals, Systems and Computers,2002, pp.1384-1388.
[9]M. Sadek, A. Tarighat, A. H. Sayed. A Leakage Based Precoding Scheme for Downlink Multi-user MIMO Channels. IEEE Transactions on Wireless Commun, vol.6, no.5,2007, pp.1711-1721.
[10]M. Costa, Writing on dirty paper. IEEE Transaction on Information Theory, vol. IT-29, May 1983, pp.439-441.
[11]M. Tomlinson, New automatic equalizer employing modulo arithmetic. Electronies Letters, vol.7, no.5,1971, pp.138-139.
[12]H. Harashima, H. Miyakawa, Matched-transmission technique for channels with inter-symbol interference. IEEE Transactions on Commun., vol.20, no.4,1972, pp.774-780.
[13]C. Windpassinger, R. F. H. Fischer, T. Vencel, et. al, Precoding in multiantenna and multiuser communications. IEEE Transactions on Wireless Commun.,vol.3, no.4, Jul.2004,pp.1305-1315.
[14]Liu Jia, A.K. Witold, A Novel Nonlinear Joint Transmitter Receiver Processing Algorithm for the Downlink of Multi-User MIMO Systmes. IEEE Transactions on Vehicular Technology, vol.57, no.4,2008, pp.2189-2204.
[15]D.J. Love, R.W. Heath, W. Santipach, et. al, What is the value of limited feedback for MIMO channels". IEEE Communications Magazine, vol.42, no.10, Oct.2004, pp.54-59.
[16]D. J. Love, R.W. Heath, V.K.N. Lau, et. al, An overview of limited feedback in wireless communication systems. IEEE J. Select. Area Commun., vol.26, no.8, Oct. 2008,pp.1341-1365.
[17](美)拉帕波特(RappaportT.S.)著,周文安等译,无线通信原理与应用(第二版).2006,电子工业出版社.
[18]J. Winters, On the capacity of radio communication systems with diversity in a Rayleigh fading environment. IEEE J. Select. Areas Commun., vol.5, no.5, Jun.1987, pp.871-878.
[19]G.J. Foschini, Layered space-time architecture for wireless communication in fading environments when using multi-element antennas. Bell Labs Tech. J.,1996, pp. 41-59.
[20]E. Telatar, Capacity of multi-antenna Gaussian channels. Eur. Trans. Telecomm. ETT, vol.10, no.6, Nov.1999, pp.585-596.
[21]G. Caire and S. Shamai, On the achievable throughput of a multi-antenna Gaussian broadcast channel. Submitted IEEE Trans. Inform. Theory, Jury 2001.
[22]G. Caire and S.Shamai, On achievable rates in a multi-antenna broadcast channel. In Proceedings of IEEE Int. Symp. Inform. Theory,2001, pp.147.
[23]S. Vishwanath, N. Jindal, and A. Goldsmith, Duality achievable rates and sum rate capacity of Gaussian MIMO broadcast channels. IEEE Transactions on Information Theory, vol.49,2003, pp.2658-2668.
[24]T.M. Cover and J.A. Thomas, Elements of Information Theory. New York: Wiley,1991.
[25]On achievable rates in a multi-antenna broadcast downlink, in Proc.38th Annual Allerton Conf. Commununications, Control, Computing, Oct.2000, pp.1188-1193.
[26]N. Jindal, MIMO broadcast channels with finite-rate feedback. IEEE Transactions on Information Theory, vol.52,2006, pp.5045-5060.
[27]3GPP R1-071510, Details of Zero-forcing MU-MIMO for DL EUTRA, Freescale Semiconductor,3GPP TSG RAN WG1 #48b, St. Julian's, Malta,2007.
[28]A. Tarighat, M. Sadek, and A.H. Sayed, A multi user beamforming scheme for downlink MIMO channels based on maximizing signal-toleakage ratios, in Proc. IEEE International Conference on Acoustics, Speech, and Signal Processing, vol.3, Philadelphia, PA,2005, pp.1129-1132.
[29]M. Sadek, A. Tarighat, and A.H. Sayed, Active antenna selection in multi-user MIMO communications, IEEE Trans. Signal Processing, vol.55, no.4, Apr.2007, pp.1498-1510.
[30]M. Schubert and H. Boche, Solution of the multiuser downlink beamforming problem with individual SINR constraints, IEEE Trans. Veh. Technol., vol.53, no.l, Jan.2004, pp.18-28.
[31]C.B. Peel, On dirty-paper coding. IEEE Signal Processing Magazine, vol.20, 2003, pp.112-113.
[32]G.D. J. Forney, M.V. Eyuboglu, Combined equalization and coding using precoding. IEEE Communications Magazine, vol.29,1991, pp.25-34.
[33]R.F.H. Fischer, C. Windpassinger, A. Lampe, et al., Space-time transmission using Tomlinson-Harashima precoding, ITG FACHBERICHT,2002, pp.139-148.
[34]Liu Jia, A.W. Kizymien, Improved Tomlinson-Harashima precoding for the downlink of multi-user MIMO systems. Canadian Journal of Electrical and Computer Engineering, vol.32,2007, pp.133-144.
[35]W. Yu, D.P. Varodayan, and J.M. Cioffl, Trellis and convolutional precoding for transmitter-based interference presubtraction. IEEE Transactions on Communications, vol.53,2005, pp.1220-1230.
[36]M. Huang, S. Zhou, and J. Wang, Analysis of Tomlinson-Harashima precoding in multiuser MIMO systems with imperfect channel state information. IEEE Transactions on Vehicular Technology, vol.57,2008, pp.2856-2867.
[37]C. Yan and H. Kayama, Limited Feedback Scheme Using Constant Amplitude Codebook for Tomlinson-Harashima Precoding in Multi-User MIMO Systems,2011, pp.1-5.
[38]Z. Shi, Q. Wang, J. Jin, D. Jiang, et al., Achievability of the channel reciprocity and its benefit in TDD system.2010, pp.1-4.
[39]G. Chunyan, M. Enescu, and C. Xiang Guang, On the Feasibility of SVD-based Downlink Precoding in Future TDD Systems, in Personal, Indoor and Mobile Radio Communications,2007. PIMRC 2007. IEEE 18th International Symposium on,2007, pp.1-5.
[40]G. Lebrun, J. Gao, and M. Faulkner, MIMO transmission over a time-varying channel using SVD. IEEE Transactions on Wireless Communications, vol.4,2005, pp. 757-764.
[41]K. Schober and R. Wichman, MIMO-OFDM Channel Estimation with Eigenbeamforming and User-Specific Reference Signals, in Vehicular Technology Conference,2009. VTC Spring 2009. IEEE 69th,2009, pp.1-5.
[42]M. Guillaud, D.T.M. Slock, and R. Knopp, A practical method for wireless channel reciprocity exploitation through relative calibration, in Signal Processing and Its Applications,2005. Proceedings of the Eighth International Symposium on,2005, pp.403-406.
[43]F. Kaltenberger, J. Haiyong, M. Guillaud, and R. Knopp, Relative channel reciprocity calibration in MIMO/TDD systems, in Future Network and Mobile Summit,2010, pp.1-10.
[44]F. Dietrich, R. Hunger, M. Joham, and W. Utschick, Linear precoding over time-varying channels in TDD systems, in Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP'03).2003 IEEE International Conference on, vol.5, 2003, pp.117-120.
[45]M. Petermann, D. Wubben, and K. D. Kammeyer, Evaluation of encoded MU-MISO-OFDM systems in TDD mode with non-ideal channel reciprocity.2010 International ITG Conference on Source and Channel Coding (SCC),2010, pp.1-6.
[2]Zheng L. Tse DNC, Diversity and multiplexing:A fundamental tradeoff in multiple-antenna channels. IEEE Transactions on Information Theory,2003, vol.49, no.5, pp.1073-1096.
[3]G.J. Foschini, M.J. Gans, On limits of wireless communication in a fading environment when using multiple antennas. Wireless Personal Commun, Mar.1998, pp.311-335.
[4]I.E. Telatar, Capacity of multi-antenna Gaussian channels. European Trans. Telecomm, vol.10, no.6, Nov./Dec.1999, pp.585-595.
[5]Q.H. Spencer, A.L. Swindlehurst, H. Martin, Zero-forcing Methods for Downlink Spatial Multiplexing in Muitiuser MIMO Channels. IEEE Transactions on Signal Processing, vol.52, no.2, Feb.2004, pp.461-471.
[6]H. Sampth, P. Storica, A. Paulraj, Genralized Linear Precoder and Decoder Design for MIMO Channels Using the Weighted MMSE Criterion. IEEE Transactions on Commun., vol.49, no.12, Dec.2001, pp.2198-2206.
[7]A. Scaglione, P. Stoica, S. Barbarossa, et. al, Optimal designs for space-time linear precoders and equalizers. IEEE Transaction on Signal Processing, vol.50, no.5, May 2002, pp.1051-1064.
[8]Q.H. Spencer, M. Haardt, Capacity and downlink transmission algorithms for a multiuser MIMO channel. Conference on Signals, Systems and Computers,2002, pp.1384-1388.
[9]M. Sadek, A. Tarighat, A. H. Sayed. A Leakage Based Precoding Scheme for Downlink Multi-user MIMO Channels. IEEE Transactions on Wireless Commun, vol.6, no.5,2007, pp.1711-1721.
[10]M. Costa, Writing on dirty paper. IEEE Transaction on Information Theory, vol. IT-29, May 1983, pp.439-441.
[11]M. Tomlinson, New automatic equalizer employing modulo arithmetic. Electronies Letters, vol.7, no.5,1971, pp.138-139.
[12]H. Harashima, H. Miyakawa, Matched-transmission technique for channels with inter-symbol interference. IEEE Transactions on Commun., vol.20, no.4,1972, pp.774-780.
[13]C. Windpassinger, R. F. H. Fischer, T. Vencel, et. al, Precoding in multiantenna and multiuser communications. IEEE Transactions on Wireless Commun.,vol.3, no.4, Jul.2004,pp.1305-1315.
[14]Liu Jia, A.K. Witold, A Novel Nonlinear Joint Transmitter Receiver Processing Algorithm for the Downlink of Multi-User MIMO Systmes. IEEE Transactions on Vehicular Technology, vol.57, no.4,2008, pp.2189-2204.
[15]D.J. Love, R.W. Heath, W. Santipach, et. al, What is the value of limited feedback for MIMO channels". IEEE Communications Magazine, vol.42, no.10, Oct.2004, pp.54-59.
[16]D. J. Love, R.W. Heath, V.K.N. Lau, et. al, An overview of limited feedback in wireless communication systems. IEEE J. Select. Area Commun., vol.26, no.8, Oct. 2008,pp.1341-1365.
[17](美)拉帕波特(RappaportT.S.)著,周文安等译,无线通信原理与应用(第二版).2006,电子工业出版社.
[18]J. Winters, On the capacity of radio communication systems with diversity in a Rayleigh fading environment. IEEE J. Select. Areas Commun., vol.5, no.5, Jun.1987, pp.871-878.
[19]G.J. Foschini, Layered space-time architecture for wireless communication in fading environments when using multi-element antennas. Bell Labs Tech. J.,1996, pp. 41-59.
[20]E. Telatar, Capacity of multi-antenna Gaussian channels. Eur. Trans. Telecomm. ETT, vol.10, no.6, Nov.1999, pp.585-596.
[21]G. Caire and S. Shamai, On the achievable throughput of a multi-antenna Gaussian broadcast channel. Submitted IEEE Trans. Inform. Theory, Jury 2001.
[22]G. Caire and S.Shamai, On achievable rates in a multi-antenna broadcast channel. In Proceedings of IEEE Int. Symp. Inform. Theory,2001, pp.147.
[23]S. Vishwanath, N. Jindal, and A. Goldsmith, Duality achievable rates and sum rate capacity of Gaussian MIMO broadcast channels. IEEE Transactions on Information Theory, vol.49,2003, pp.2658-2668.
[24]T.M. Cover and J.A. Thomas, Elements of Information Theory. New York: Wiley,1991.
[25]On achievable rates in a multi-antenna broadcast downlink, in Proc.38th Annual Allerton Conf. Commununications, Control, Computing, Oct.2000, pp.1188-1193.
[26]N. Jindal, MIMO broadcast channels with finite-rate feedback. IEEE Transactions on Information Theory, vol.52,2006, pp.5045-5060.
[27]3GPP R1-071510, Details of Zero-forcing MU-MIMO for DL EUTRA, Freescale Semiconductor,3GPP TSG RAN WG1 #48b, St. Julian's, Malta,2007.
[28]A. Tarighat, M. Sadek, and A.H. Sayed, A multi user beamforming scheme for downlink MIMO channels based on maximizing signal-toleakage ratios, in Proc. IEEE International Conference on Acoustics, Speech, and Signal Processing, vol.3, Philadelphia, PA,2005, pp.1129-1132.
[29]M. Sadek, A. Tarighat, and A.H. Sayed, Active antenna selection in multi-user MIMO communications, IEEE Trans. Signal Processing, vol.55, no.4, Apr.2007, pp.1498-1510.
[30]M. Schubert and H. Boche, Solution of the multiuser downlink beamforming problem with individual SINR constraints, IEEE Trans. Veh. Technol., vol.53, no.l, Jan.2004, pp.18-28.
[31]C.B. Peel, On dirty-paper coding. IEEE Signal Processing Magazine, vol.20, 2003, pp.112-113.
[32]G.D. J. Forney, M.V. Eyuboglu, Combined equalization and coding using precoding. IEEE Communications Magazine, vol.29,1991, pp.25-34.
[33]R.F.H. Fischer, C. Windpassinger, A. Lampe, et al., Space-time transmission using Tomlinson-Harashima precoding, ITG FACHBERICHT,2002, pp.139-148.
[34]Liu Jia, A.W. Kizymien, Improved Tomlinson-Harashima precoding for the downlink of multi-user MIMO systems. Canadian Journal of Electrical and Computer Engineering, vol.32,2007, pp.133-144.
[35]W. Yu, D.P. Varodayan, and J.M. Cioffl, Trellis and convolutional precoding for transmitter-based interference presubtraction. IEEE Transactions on Communications, vol.53,2005, pp.1220-1230.
[36]M. Huang, S. Zhou, and J. Wang, Analysis of Tomlinson-Harashima precoding in multiuser MIMO systems with imperfect channel state information. IEEE Transactions on Vehicular Technology, vol.57,2008, pp.2856-2867.
[37]C. Yan and H. Kayama, Limited Feedback Scheme Using Constant Amplitude Codebook for Tomlinson-Harashima Precoding in Multi-User MIMO Systems,2011, pp.1-5.
[38]Z. Shi, Q. Wang, J. Jin, D. Jiang, et al., Achievability of the channel reciprocity and its benefit in TDD system.2010, pp.1-4.
[39]G. Chunyan, M. Enescu, and C. Xiang Guang, On the Feasibility of SVD-based Downlink Precoding in Future TDD Systems, in Personal, Indoor and Mobile Radio Communications,2007. PIMRC 2007. IEEE 18th International Symposium on,2007, pp.1-5.
[40]G. Lebrun, J. Gao, and M. Faulkner, MIMO transmission over a time-varying channel using SVD. IEEE Transactions on Wireless Communications, vol.4,2005, pp. 757-764.
[41]K. Schober and R. Wichman, MIMO-OFDM Channel Estimation with Eigenbeamforming and User-Specific Reference Signals, in Vehicular Technology Conference,2009. VTC Spring 2009. IEEE 69th,2009, pp.1-5.
[42]M. Guillaud, D.T.M. Slock, and R. Knopp, A practical method for wireless channel reciprocity exploitation through relative calibration, in Signal Processing and Its Applications,2005. Proceedings of the Eighth International Symposium on,2005, pp.403-406.
[43]F. Kaltenberger, J. Haiyong, M. Guillaud, and R. Knopp, Relative channel reciprocity calibration in MIMO/TDD systems, in Future Network and Mobile Summit,2010, pp.1-10.
[44]F. Dietrich, R. Hunger, M. Joham, and W. Utschick, Linear precoding over time-varying channels in TDD systems, in Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP'03).2003 IEEE International Conference on, vol.5, 2003, pp.117-120.
[45]M. Petermann, D. Wubben, and K. D. Kammeyer, Evaluation of encoded MU-MISO-OFDM systems in TDD mode with non-ideal channel reciprocity.2010 International ITG Conference on Source and Channel Coding (SCC),2010, pp.1-6.