盲自适应多用户检测技术研究
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摘要
围绕着CDMA无线蜂窝移动通信系统中的多址干扰(MAI)抵消问题，本论文在现有盲自适应多用户检测技术基础上，提出了一种新的基于干扰空间线性MMSE盲自适应多用户检测器及其相应的基于干扰自相关矩阵C_1跟踪算法。数学分析和仿真结果表明：该检测器具有实现复杂度低、跟踪速度快和健壮性强的优点。
随着CDMA移动通信系统容量增大，同频信道中同时处于通信状态的用户数增多，单用户检测器抗多址干扰能力急剧下降。传统多用户检测在单用户检测技术基础上，充分利用造成多址干扰的所有用户的信息进行联合检测，从而具有良好的抗多址干扰能力，但存在一些缺陷：(1)不仅要求知道期望用户的地址PN码及其定时信息，还要求其他干扰用户的地址PN码及其定时信息；(2)不能消除其他相邻小区的多址干扰对本小区的影响；(3)不能直接应用在CDMA移动通信系统中的下行链路。在传统多用户检测技术基础上，自适应多用户检测利用训练序列在仅知道期望用户地址PN码及其定时信息条件下就可以进行检测，不足的就是训练序列占用了额外的频率资源。
研究结果表明：盲自适应多用户检测可以不需要训练序列，在仅知道期望用户地址PN码及其定时信息条件下自适应跟踪信道中用户地址PN码的变化，更有效地抵消小区内和小区间多址干扰，很方便地应用在上行和下行链路。
为实现盲自适应检测，通常采用对接收信号样本矩阵进行特征值分解(EVD)或奇异值分解(SVD)后进行跟踪，由此带来的子空间秩跟踪使得实现复杂度很高；另一方面，在跟踪算法中考虑一些实际情况而作出近似处理，从而引起误差积累和正交性误差，导致每次跟踪开始阶段跟踪速度变慢。为此，本论文提出基于干扰空间线性MMSE盲自适应多用户检测器及其相应的基于干扰自相关矩阵C_1跟踪算法。仿真结果还表明，该检测器具有很好的健壮性。
In this paper, a new Interference-space-Based blind adaptive MMSE linear detector and the corresponding tracking algorithm based interference correlation matrix is proposed for MAI in CDMA wireless celluar communication system. Analysis and simulation illustrate that the proposed blind multiuser detector has lower computational complexity, faster convergence and stronger robust with respect to imprecise knowledge of the received signature waveform of user of interest.
With the increase of active user numbers in CDMA channels, single user detector cannot effectively suppress MAI. Traditional multiuser detector make good use of all signals which resuilt in multiple access interference so that it provides optimum MAI resistance. (1) Nevertheless, it assumes that the receiver can acquire the signature waveform and timing of desired user and the interfering users ; (2) It has no ability to suppress intercell multiple access interference; (3) It cannot be applied in downlink channels. Adaptive multiuser detector eliminates the need to know the signature waveforms and the timing of the interferes and has to need training data sequences for every active user. But the frequent use of training sequence is certainly a waste of channel bandwidth.
Research shows that with the prior knowledge of only the signature waveform and timing of the user of interest, blind adaptive multiuser detector can effectively detect data symbol of the desired user without training data sequence for every active user . It is especially attractive for the downlinks and suppressing intercell MAI.
When multiuser detector is adapted in blind mode, it usually adopts eignvalue decomposition or singularvalue decomposition of received sample correlation matrix and tracking alrithgms, which result in high computational complexity. At the same time, approximation computation in tracking alrithgms also result in slow convergence. To overcome these shortcomes, a Interference-Space-Based blind adaptive MMSE linear detector and the corresponding tracking algorithm based interference correlation matrix is proposed. Simulation also show that the detector has strong robust.
随着CDMA移动通信系统容量增大，同频信道中同时处于通信状态的用户数增多，单用户检测器抗多址干扰能力急剧下降。传统多用户检测在单用户检测技术基础上，充分利用造成多址干扰的所有用户的信息进行联合检测，从而具有良好的抗多址干扰能力，但存在一些缺陷：(1)不仅要求知道期望用户的地址PN码及其定时信息，还要求其他干扰用户的地址PN码及其定时信息；(2)不能消除其他相邻小区的多址干扰对本小区的影响；(3)不能直接应用在CDMA移动通信系统中的下行链路。在传统多用户检测技术基础上，自适应多用户检测利用训练序列在仅知道期望用户地址PN码及其定时信息条件下就可以进行检测，不足的就是训练序列占用了额外的频率资源。
研究结果表明：盲自适应多用户检测可以不需要训练序列，在仅知道期望用户地址PN码及其定时信息条件下自适应跟踪信道中用户地址PN码的变化，更有效地抵消小区内和小区间多址干扰，很方便地应用在上行和下行链路。
为实现盲自适应检测，通常采用对接收信号样本矩阵进行特征值分解(EVD)或奇异值分解(SVD)后进行跟踪，由此带来的子空间秩跟踪使得实现复杂度很高；另一方面，在跟踪算法中考虑一些实际情况而作出近似处理，从而引起误差积累和正交性误差，导致每次跟踪开始阶段跟踪速度变慢。为此，本论文提出基于干扰空间线性MMSE盲自适应多用户检测器及其相应的基于干扰自相关矩阵C_1跟踪算法。仿真结果还表明，该检测器具有很好的健壮性。
In this paper, a new Interference-space-Based blind adaptive MMSE linear detector and the corresponding tracking algorithm based interference correlation matrix is proposed for MAI in CDMA wireless celluar communication system. Analysis and simulation illustrate that the proposed blind multiuser detector has lower computational complexity, faster convergence and stronger robust with respect to imprecise knowledge of the received signature waveform of user of interest.
With the increase of active user numbers in CDMA channels, single user detector cannot effectively suppress MAI. Traditional multiuser detector make good use of all signals which resuilt in multiple access interference so that it provides optimum MAI resistance. (1) Nevertheless, it assumes that the receiver can acquire the signature waveform and timing of desired user and the interfering users ; (2) It has no ability to suppress intercell multiple access interference; (3) It cannot be applied in downlink channels. Adaptive multiuser detector eliminates the need to know the signature waveforms and the timing of the interferes and has to need training data sequences for every active user. But the frequent use of training sequence is certainly a waste of channel bandwidth.
Research shows that with the prior knowledge of only the signature waveform and timing of the user of interest, blind adaptive multiuser detector can effectively detect data symbol of the desired user without training data sequence for every active user . It is especially attractive for the downlinks and suppressing intercell MAI.
When multiuser detector is adapted in blind mode, it usually adopts eignvalue decomposition or singularvalue decomposition of received sample correlation matrix and tracking alrithgms, which result in high computational complexity. At the same time, approximation computation in tracking alrithgms also result in slow convergence. To overcome these shortcomes, a Interference-Space-Based blind adaptive MMSE linear detector and the corresponding tracking algorithm based interference correlation matrix is proposed. Simulation also show that the detector has strong robust.
引文
[1] 李勇强．CDMA系统中的多用户检测算法及其与智能天线相结合的研究[硕士学位论文]．重庆．重庆邮电学院．2001．
[2] 周科理．CDMA多用户检测技术研究[硕士学位论文]．重庆．重庆大学．2002．
[3] 王庆扬，张青，韦岗．CDMA移动通信系统中的多用户检测技术．移动通信．2000年第2期．pp．41-45．
[4] Lee Jhong Sam，Miller Leonard E著．许希斌，周世东，赵明等译．CDMA系统过程手册．北京．人民邮电出版社．2001．
[5] Ramjee Prassad著．朱旭红，卢学军，卓天真等译．宽带CDKA：第三代移动通信技术．北京．人民邮电出版社．2001．
[6] 黎海涛，徐继麟．多用户检测算法及其在IMT-2000中的应用．无线通信技术．2001年第2期．pp．1-6．
[7] Michael Honig, Upamanyu Madhow and Sergio Verdu , "Blind Adaptive Detection" , IEEE Transactions on Information Theory, Vol.41, No.4, July 1995.
[8] Xiaodong Wang,Andets and Host-Madsen , "Group-Blind Multiuser Detection for Uplink CDMA", IEEE Journal on Selected Areas in Communication, Vol.17, No.11, Nov. 1999.
[9] Xiaodong Wang and H.Vincent Poor, "Blind Multiuser Detection: A Subspace Approach", IEEE Transactions on Information Theory, Vol.44, No.2, March 1998.
[10] 郑建忠，焦李成，郝继升．一种新的最小二乘盲空时多用户检测．西安电子科技大学学报(自然科学版)．Vol．28．No．6 Dec．2001．
[11] Peter Strobach , "Bi-iteration SVD Subspace Tracking Algorithms" , IEEE Transactions on Signal Processing, Vol.45, No.5, May 1997.
[12] Benoit Champagne and Qing-Quang Liu, "Plane Rotation-based EVD Updating Schemes for Efficient Subspace Tracking", IEEE Transactions on Signal Processing, Vol.46, No.7, July 1998.
[13] Jyh-Horng Wen and Chao-Kai Wen, "Adaptive Recursive Algorithms for Commplementary Subspace-Based Blind Multiuser Detection" , IEEE Transactions on Circuits and Systems-Ⅱ:Analog and Digital Signal Processing, Vol.48, No.12, Dec. 2001.
[14] Miao.Y and Hua.Y , "Fast Subspace Tracking and Neural Network Learning by a Novel Information Criterion", IEEE Transactions on Signal Proccessing, Vol.46, No.3, July 1998.
[15] A．J．维特比著．李世鹤，鲍刚，彭容等译．CDMA扩频通信原理．北京．人民邮电出版社．1997．
[16] 沈允春．扩频技术．北京国防工业出版社．1995．
[17] Michael.L, Scott L.Miller, mark J.Shensa and Lawrence B.Milstein, "Performance of Adaptive Linear Interference Suppression in the Presence of Dynamic Fading", IEEE transactions on Communications, Vol.49, No.4, April 2001.
[18] Scott L.Miller, Michael L.Honig and Laurence B.Milstein, "Performance Analysis of MMSE Receivers for DS-CDMA in Frequency-Selective Fading Channels", IEEE Transactions on Communications, Vol.48, No.11, Nov. 2000.
[19] Daryl Reynolds and Xiaodong Wang , "Adaptive Group-Blind Detection Based on a New Subspace Tracking Algorithm", IEEE Transactions on Communications , Vol.49, No.7, July 2001.
[20] Vijay K.Garg著．于鹏，白春霞等译．第三代移动通信系统原理与工程设计：IS-95 CDMA和cdma2000．北京．电子工业出版社．2001．
[21] Jitendra K.Tuyait , "Blind Space-Time Detection in Asynchronouns Multipath CDMA Channels", IEEE Journal on Selected Areas in Communications, Vol.19, No.8, Aug. 2001.
[22] Qingchong Liu, Robert A.Scholtz and Zhen Zhang, "Complexity of Verdu Optimum Multiuser Detection Algorithm in Multicharmel CDMA Systems", IEEE Transactions on Communications, Vol.47, No.12, Dec. 1999.
[23] S.Verdu , "Computational Complexity of Optimum Multiuser Detection", Algorithmica , pp.303-312,1989.
[24] 王立宁等，MATLAB与通信仿真，人民邮电出版社，2000．
[25] Ojanpera, T.K.Rikkinen, H.Hakkinen K.Pehkonen, A. Hottinen and J. Lilleberg, "Design of a 3rd Generation Multirate CDMA System with Multiuser Detection, MUD-CDMA", Proceedings of ISSTA'96 Vol.1, Mainz, Germany, pp.334-338, Sept. 1996.
[26] Guoqiang Xue, Jiangfeng Weng, Tho Le-Ngoc and Sofiene Thahar, "Multiuser Detection Techniques:An Overview", Department of Electrical and Computer Engineering, Concordia University, pp.4-16, October 1998.
[27] Zheng C. and M.Barton, "The Performance of Near-Far Resisant CDMA Detectors in the Presence of Synchronization Errors", IEEE Transactions on Communication, Vol.43 , pp.3037-3045, Dec. 1995.
[28] Zheng C and M.Daulkner, "Power Control Requirements in Linear Decorrelating Detector for CDMA", Proceeding of VTC'97.Arizona. USA, pp.213-217, May 1997.
[29] Stefano Buzzi, Marco Lops and Antonia M.Tulino, "A New Family of MMSE Miltiuser Receivers for Interfernce Suppression in DS/CDMA Syetems Employing BPSK Modulation", IEEE Transactions on Communications, Vol.49, Jan. 2001.
[30] U.Madhow and M.Honig, "MMSE Interference Suppression for Direct Sequence Spread
Spectrum CDMA" , IEEE Transactions on Communications , Vol.42 , pp.3178-3188 , Dec. 1994.
[31] P.Rapajic and B.Vucetic, "A Linear Adaptive Fractionally Spaced Single User Receiver for Asynchronous CDMA Systems", in IEEE Int. Syrup. on Information Theory(San Antonio, TX, Jan. 1993), p.45.
[32] M.Abdulrahman,D.D.Falconer and A.U.H.Sheikh, "Equalization for Interference Cancellation in Spread Spectrum Multiple Access Systems", in Proc. IEEE Vehicular Technology Conf. (Denver, CO, May 1992).
[33] M.Honig, U.Madhow and S.Verdu, "Blind Multiuser Detection", IEEE Transactions Information Theory, Vol.41, pp.944-960, July 1995.
[34] L.Xu, "Least Mean Square Error Reconstruction Principle for Selforhanizing Neural Nets", Neural Networks, Vol.6, pp.627-648,1993.
[35] B.Yang, "Projection Approximation Subspace Tracking", IEEE Transactions on Signal Processing, Vol.43, pp.95-107, Jan. 1995.
[36] Yongfeng Miao and Yingbo Hun, "Fast Subspace Tracking and Neural Network Learning by a Novel Information Criterion", IEEE Transactions on Signal Processing, Vol.46, No.7 , July 1998.
[37] B Yang, "An Extension of the PASTd Algorithm to Both Rank and Subspace Tracking", IEEE Signal Processing Let., Vol.2, pp.179-182, Sept. 1995.
[38] H.V.Poor and X.Wang, "Code-aided Interference Suppression for DS/CDMA Communications—Part Ⅱ :Parallel Blind Adapative Implementations", IEEE Transactions on Signal Processing, Vol.45, pp.1112-1122, Sept. 1997.
[39] Wanshi.Chen and Urbashi.Mitra, "An Improved Blind Adaptive MMSE Receiver for Fast Fading DS-CDMA Channels" , IEEE Journal on Selected Areas in Communications , Vol.19 ,No.8, August 2001.
[40] Ruxandra Lupas and Sergio Verdu, "Near-Far Resistance of Multiuser Detector in Asynchronous Channels, IEEE Transactions on Communications, Vol.38, No.4, April 1990.
[2] 周科理．CDMA多用户检测技术研究[硕士学位论文]．重庆．重庆大学．2002．
[3] 王庆扬，张青，韦岗．CDMA移动通信系统中的多用户检测技术．移动通信．2000年第2期．pp．41-45．
[4] Lee Jhong Sam，Miller Leonard E著．许希斌，周世东，赵明等译．CDMA系统过程手册．北京．人民邮电出版社．2001．
[5] Ramjee Prassad著．朱旭红，卢学军，卓天真等译．宽带CDKA：第三代移动通信技术．北京．人民邮电出版社．2001．
[6] 黎海涛，徐继麟．多用户检测算法及其在IMT-2000中的应用．无线通信技术．2001年第2期．pp．1-6．
[7] Michael Honig, Upamanyu Madhow and Sergio Verdu , "Blind Adaptive Detection" , IEEE Transactions on Information Theory, Vol.41, No.4, July 1995.
[8] Xiaodong Wang,Andets and Host-Madsen , "Group-Blind Multiuser Detection for Uplink CDMA", IEEE Journal on Selected Areas in Communication, Vol.17, No.11, Nov. 1999.
[9] Xiaodong Wang and H.Vincent Poor, "Blind Multiuser Detection: A Subspace Approach", IEEE Transactions on Information Theory, Vol.44, No.2, March 1998.
[10] 郑建忠，焦李成，郝继升．一种新的最小二乘盲空时多用户检测．西安电子科技大学学报(自然科学版)．Vol．28．No．6 Dec．2001．
[11] Peter Strobach , "Bi-iteration SVD Subspace Tracking Algorithms" , IEEE Transactions on Signal Processing, Vol.45, No.5, May 1997.
[12] Benoit Champagne and Qing-Quang Liu, "Plane Rotation-based EVD Updating Schemes for Efficient Subspace Tracking", IEEE Transactions on Signal Processing, Vol.46, No.7, July 1998.
[13] Jyh-Horng Wen and Chao-Kai Wen, "Adaptive Recursive Algorithms for Commplementary Subspace-Based Blind Multiuser Detection" , IEEE Transactions on Circuits and Systems-Ⅱ:Analog and Digital Signal Processing, Vol.48, No.12, Dec. 2001.
[14] Miao.Y and Hua.Y , "Fast Subspace Tracking and Neural Network Learning by a Novel Information Criterion", IEEE Transactions on Signal Proccessing, Vol.46, No.3, July 1998.
[15] A．J．维特比著．李世鹤，鲍刚，彭容等译．CDMA扩频通信原理．北京．人民邮电出版社．1997．
[16] 沈允春．扩频技术．北京国防工业出版社．1995．
[17] Michael.L, Scott L.Miller, mark J.Shensa and Lawrence B.Milstein, "Performance of Adaptive Linear Interference Suppression in the Presence of Dynamic Fading", IEEE transactions on Communications, Vol.49, No.4, April 2001.
[18] Scott L.Miller, Michael L.Honig and Laurence B.Milstein, "Performance Analysis of MMSE Receivers for DS-CDMA in Frequency-Selective Fading Channels", IEEE Transactions on Communications, Vol.48, No.11, Nov. 2000.
[19] Daryl Reynolds and Xiaodong Wang , "Adaptive Group-Blind Detection Based on a New Subspace Tracking Algorithm", IEEE Transactions on Communications , Vol.49, No.7, July 2001.
[20] Vijay K.Garg著．于鹏，白春霞等译．第三代移动通信系统原理与工程设计：IS-95 CDMA和cdma2000．北京．电子工业出版社．2001．
[21] Jitendra K.Tuyait , "Blind Space-Time Detection in Asynchronouns Multipath CDMA Channels", IEEE Journal on Selected Areas in Communications, Vol.19, No.8, Aug. 2001.
[22] Qingchong Liu, Robert A.Scholtz and Zhen Zhang, "Complexity of Verdu Optimum Multiuser Detection Algorithm in Multicharmel CDMA Systems", IEEE Transactions on Communications, Vol.47, No.12, Dec. 1999.
[23] S.Verdu , "Computational Complexity of Optimum Multiuser Detection", Algorithmica , pp.303-312,1989.
[24] 王立宁等，MATLAB与通信仿真，人民邮电出版社，2000．
[25] Ojanpera, T.K.Rikkinen, H.Hakkinen K.Pehkonen, A. Hottinen and J. Lilleberg, "Design of a 3rd Generation Multirate CDMA System with Multiuser Detection, MUD-CDMA", Proceedings of ISSTA'96 Vol.1, Mainz, Germany, pp.334-338, Sept. 1996.
[26] Guoqiang Xue, Jiangfeng Weng, Tho Le-Ngoc and Sofiene Thahar, "Multiuser Detection Techniques:An Overview", Department of Electrical and Computer Engineering, Concordia University, pp.4-16, October 1998.
[27] Zheng C. and M.Barton, "The Performance of Near-Far Resisant CDMA Detectors in the Presence of Synchronization Errors", IEEE Transactions on Communication, Vol.43 , pp.3037-3045, Dec. 1995.
[28] Zheng C and M.Daulkner, "Power Control Requirements in Linear Decorrelating Detector for CDMA", Proceeding of VTC'97.Arizona. USA, pp.213-217, May 1997.
[29] Stefano Buzzi, Marco Lops and Antonia M.Tulino, "A New Family of MMSE Miltiuser Receivers for Interfernce Suppression in DS/CDMA Syetems Employing BPSK Modulation", IEEE Transactions on Communications, Vol.49, Jan. 2001.
[30] U.Madhow and M.Honig, "MMSE Interference Suppression for Direct Sequence Spread
Spectrum CDMA" , IEEE Transactions on Communications , Vol.42 , pp.3178-3188 , Dec. 1994.
[31] P.Rapajic and B.Vucetic, "A Linear Adaptive Fractionally Spaced Single User Receiver for Asynchronous CDMA Systems", in IEEE Int. Syrup. on Information Theory(San Antonio, TX, Jan. 1993), p.45.
[32] M.Abdulrahman,D.D.Falconer and A.U.H.Sheikh, "Equalization for Interference Cancellation in Spread Spectrum Multiple Access Systems", in Proc. IEEE Vehicular Technology Conf. (Denver, CO, May 1992).
[33] M.Honig, U.Madhow and S.Verdu, "Blind Multiuser Detection", IEEE Transactions Information Theory, Vol.41, pp.944-960, July 1995.
[34] L.Xu, "Least Mean Square Error Reconstruction Principle for Selforhanizing Neural Nets", Neural Networks, Vol.6, pp.627-648,1993.
[35] B.Yang, "Projection Approximation Subspace Tracking", IEEE Transactions on Signal Processing, Vol.43, pp.95-107, Jan. 1995.
[36] Yongfeng Miao and Yingbo Hun, "Fast Subspace Tracking and Neural Network Learning by a Novel Information Criterion", IEEE Transactions on Signal Processing, Vol.46, No.7 , July 1998.
[37] B Yang, "An Extension of the PASTd Algorithm to Both Rank and Subspace Tracking", IEEE Signal Processing Let., Vol.2, pp.179-182, Sept. 1995.
[38] H.V.Poor and X.Wang, "Code-aided Interference Suppression for DS/CDMA Communications—Part Ⅱ :Parallel Blind Adapative Implementations", IEEE Transactions on Signal Processing, Vol.45, pp.1112-1122, Sept. 1997.
[39] Wanshi.Chen and Urbashi.Mitra, "An Improved Blind Adaptive MMSE Receiver for Fast Fading DS-CDMA Channels" , IEEE Journal on Selected Areas in Communications , Vol.19 ,No.8, August 2001.
[40] Ruxandra Lupas and Sergio Verdu, "Near-Far Resistance of Multiuser Detector in Asynchronous Channels, IEEE Transactions on Communications, Vol.38, No.4, April 1990.