FDD系统中基于DOA估计的下行波束形成技术研究
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摘要
智能天线技术是第三代移动通信系统中的关键技术之一。智能天线技术引入了空分多址(Space Division Multiple Access，SDMA)方式，利用信号不同的空间传输路径，可以将相同频率、相同时隙、相同地址码的信号区分开来，并能够与其他多址技术相结合，使得通信资源由时间域、频率域和码域扩展到了空间域，从而有效地增大了系统容量，最大限度地利用了有限的频谱资源。在频分双工(FDD)系统中，由于上、下行载波的频率差大于相干频带，上、下行信道衰落是不相关的，而且阵列响应也与信号的载波频率有关，因此，上行信道不能直接用来估计下行信道，故智能天线应用于下行链路是一个难点。但是，如果上、下行载波频率间隔不是太大，下行波束形成可以利用上行链路的DOA信息来实现。本文选择智能天线中DOA估计算法进行研究。
本文主要工作概括如下：
1．建立上下行链路信道模型，据此获得FDD系统中DCCM的计算公式。
2．MUSIC等高分辨率算法在估计DOA时需要进行协方差矩阵的特征分解运算，但是传统的矩阵特征分解方法计算量都非常大，不适合实时运算。另外，MUSIC算法不能很好地估计出弱信号的DOA，通过仿真结果证明确实是这样。
3．本文提出了基于改进PCA的DOA估计方法，在原有MUSIC算法的基础土引入了迭代估计信号子空间的方法，代替了原算法中通过特征值分解获得信号子空间的部分。仿真表明，本文提出的算法在估计弱信号时性能比较好，而且与MUSIC算法相比，计算复杂度有所降低，这可以从学习曲线上看出。
4．在DOA估计的基础上，本文首先综合了文献[47-50]中的主要思想，然后对其进行了详细的数学推导，之后，据此得到了下行发射波束形成的初始权值。在此基础上以最小化阵列发射功率为目标对初始权值进行优化得到了优化权值。最后通过仿真验证比较了初始权值和优化权值应用于下行波束赋形对方向图的影响。
Smart antenna technology is one of the key technologies of the thirdgeneration mobile communication system. And it introduces space divisionmultiple access which makes use of different transmission paths ofdifferent signals to differentiate the signals from the same frequency, thesame time slot and the same code. Moreover, space division multiple accesscan also be combined with other multiple access technologies, such as timedivision multiple access, code division multiple access, and so on. Smartantenna technology makes the range of communication resource extendfrom time region, frequency region and code region to space region. Thussmart antenna can remarkably increase the capacity of communicationsystem, and sufficiently exploit limited frequencY spectrum resource. In anFDD wireless system, the duplex spacing between uplink and downlink islarger than the coherence bandwidth of the mobile radio channel, thus theuplink and the downlink small-scale fading is uncorrelated. Moreover, thearray response is correlated with the frequency of the signal carrier. So it isimpossible to resue the uplink weights for downlink beamforming. As aresult, the application of smart antenna for the downlink is a difficult problem. However, if the duplex spacing between the uplink and thedownlink isn't large enough, the uplink channel parameters like thedirections-of-arrival can be used for the downlink beamforming. This paperplaces its importance on the research of DOA estimation algorithms.
The major works of this paper can be summarized as follows:
1. This paper establishes the uplink and downlink channel model.According to this model, it knows how to calculate DCCM.
2. Many high resolution subspace-based methods like MUSIC andESPRIT estimate the direction of arrival of plane waves impinging on anantenna array via eigendecomposition in array signal processing. However,high computational burden for eigendecomposition makes them unsuitablefor real time processing. Moreover, MUSIC algrithom can't estimate weaksignals very well, and it is verified through the simulation.
3. This paper presents a DOA estimation method based on a novelprincipal component analysis technique. It introduces an iterative approachfor estimating the signal subspace to MUSIC algorithm, which substitutesthe steps that obtain signal subspace via eigendecomposition in originalalgorithm. Simulation results show that the proposed algorithm has betterperformance than MUSIC algorithm when estimating weak signals and itscomputational complexity is smaller, which can be seen from the learningcurves.
4. On the basis of DOA estimation, this paper integrates the mainideas in literatures[47-50] firstly, and then deduces them in detail, after thatthis paper achieves the initial weight according to those results deduced.Based on these works finished before, aiming to minimize the arraytransmission power, it optimizes the initial weight and gains optimized weight. In the end, through the simulation this paper compares their effectson the beam pattern when initial weight and optimized weight are used forthe downlink beamforming.
本文主要工作概括如下：
1．建立上下行链路信道模型，据此获得FDD系统中DCCM的计算公式。
2．MUSIC等高分辨率算法在估计DOA时需要进行协方差矩阵的特征分解运算，但是传统的矩阵特征分解方法计算量都非常大，不适合实时运算。另外，MUSIC算法不能很好地估计出弱信号的DOA，通过仿真结果证明确实是这样。
3．本文提出了基于改进PCA的DOA估计方法，在原有MUSIC算法的基础土引入了迭代估计信号子空间的方法，代替了原算法中通过特征值分解获得信号子空间的部分。仿真表明，本文提出的算法在估计弱信号时性能比较好，而且与MUSIC算法相比，计算复杂度有所降低，这可以从学习曲线上看出。
4．在DOA估计的基础上，本文首先综合了文献[47-50]中的主要思想，然后对其进行了详细的数学推导，之后，据此得到了下行发射波束形成的初始权值。在此基础上以最小化阵列发射功率为目标对初始权值进行优化得到了优化权值。最后通过仿真验证比较了初始权值和优化权值应用于下行波束赋形对方向图的影响。
Smart antenna technology is one of the key technologies of the thirdgeneration mobile communication system. And it introduces space divisionmultiple access which makes use of different transmission paths ofdifferent signals to differentiate the signals from the same frequency, thesame time slot and the same code. Moreover, space division multiple accesscan also be combined with other multiple access technologies, such as timedivision multiple access, code division multiple access, and so on. Smartantenna technology makes the range of communication resource extendfrom time region, frequency region and code region to space region. Thussmart antenna can remarkably increase the capacity of communicationsystem, and sufficiently exploit limited frequencY spectrum resource. In anFDD wireless system, the duplex spacing between uplink and downlink islarger than the coherence bandwidth of the mobile radio channel, thus theuplink and the downlink small-scale fading is uncorrelated. Moreover, thearray response is correlated with the frequency of the signal carrier. So it isimpossible to resue the uplink weights for downlink beamforming. As aresult, the application of smart antenna for the downlink is a difficult problem. However, if the duplex spacing between the uplink and thedownlink isn't large enough, the uplink channel parameters like thedirections-of-arrival can be used for the downlink beamforming. This paperplaces its importance on the research of DOA estimation algorithms.
The major works of this paper can be summarized as follows:
1. This paper establishes the uplink and downlink channel model.According to this model, it knows how to calculate DCCM.
2. Many high resolution subspace-based methods like MUSIC andESPRIT estimate the direction of arrival of plane waves impinging on anantenna array via eigendecomposition in array signal processing. However,high computational burden for eigendecomposition makes them unsuitablefor real time processing. Moreover, MUSIC algrithom can't estimate weaksignals very well, and it is verified through the simulation.
3. This paper presents a DOA estimation method based on a novelprincipal component analysis technique. It introduces an iterative approachfor estimating the signal subspace to MUSIC algorithm, which substitutesthe steps that obtain signal subspace via eigendecomposition in originalalgorithm. Simulation results show that the proposed algorithm has betterperformance than MUSIC algorithm when estimating weak signals and itscomputational complexity is smaller, which can be seen from the learningcurves.
4. On the basis of DOA estimation, this paper integrates the mainideas in literatures[47-50] firstly, and then deduces them in detail, after thatthis paper achieves the initial weight according to those results deduced.Based on these works finished before, aiming to minimize the arraytransmission power, it optimizes the initial weight and gains optimized weight. In the end, through the simulation this paper compares their effectson the beam pattern when initial weight and optimized weight are used forthe downlink beamforming.
引文
[1] Liberti J．C．著，马凉等译，无线通信中的智能天线：IS-95和第3代CDMA应用，北京，北京机械工业出版社，2002
[2] 汪晓光，智能天线技术与波达方向估计研究，[学位论文]，西安，西安电子科技大学，2002
[3] 单志龙，智能天线中的波达方向估计研究，[学位论文]，广州，华南理工大学，2004
[4] 陈莉娜，FDD模式下的智能天线下行波束形成技术，[学位论文]，哈尔滨，哈尔滨工业大学，2004
[5] 吴伟陵，移动通信中的关键技术，北京，北京邮电大学出版社，2000，pp．257-286
[6] Gertach. D, Praulraj. A, Base station transmitter antenna arrays with mobile to base feedback, In 27th Asilomar Conference on Signals, Systems and Computers, 1993, pp.1432-1436
[7] Gerlaeh. D, Praulraj.A, Adaptive transmitting antenna with feedback, IEEE Signal Processing Letters, 1994, 1(10), pp.150-152
[8] Per Zetterberg, Ottersten.B, The spectrum efficiency of a base station antenna array system for spatially selective transmission, IEEE trans, on Vehicular Technology, 1995, 44(3), pp.651-660
[9] Guanghan Xu, Hui Liu, An effective transmission beamforming scheme for frequency-division-duplex digital wireless communication systems, IEEE, 1995, pp.1729-1732
[10] 葛利嘉，路鸣，蜂窝通信的空分多址：概念、算法和性能，通信学报，1999，20(8)，pp．52-62
[11] 徐建，基于子波分解的DOA估计研究与应用，[学位论文]，北京，北京交通大学，2005
[12] R. O. Schmidt, Multiple emitter location and signal parameter estimation, IEEE trans, on Antennas Propagation, 1986, 34(3), pp.276-280
[13] Roy. R, Paulraj.A, Kailath.T, ESPRIT—A subspace rotation approach to estimation of parameters of cisoids in noise, IEEE trans, on Acoustics, Speech and Signal Processing, 1986, 34(5), pp.1340-1342
[14] R. Pan, C. L. Nikias, Harmonic decomposition methods in cumulant domains, in Proc. ICASSP'88, 1988, pp.2356-2359
[15] H. H. Chiang, C. L. Nikias, The Esprit Algorithm with Higher-order Statistics, Proceedings of Workshop on Higher order spectral analysis, 1989, pp. 163-168
[16] N. Yuen, B.Friedlander, DOA estimation in multipath: an approach using fourth-order cumulants, IEEE trans, on Signal Processing, 1997, 45(5), pp. 1253-1263
[17] S. V. Schell, R. A. Calabretta, W.A.Gardner, etc., Cyclic MUSIC algorithms for signal-selective direction estimation, 1989 International Conference on Acoustics, Speech, and Signal Processing, ICASSP-89, 1989, 4, pp.2278-2281
[18] G. Xu, T. Kailath, Direction-of-arrival estimation via explotation of cyclostationarity-A combination of temporal and spatial processing, IEEE transactions on Signal Processing, 1992, 40(7), pp. 1775-1785
[19] P. Charge, Y. Wang, J.Saillard, An extended cyclic MUSIC algorithm, IEEE trans. on Signal Processing, 2003, 51 (7), pp. 1695-1701
[20] A. F. Naguib, A. Paulraj, T. Kailath, Capacity Improvement with Base Station Antenna Arrays in Cellular CDMA, IEEE trans, on Vehicular Technology, 1994, 43(3), pp.691-698
[21] 李国通，仇佩亮，徐绿洲，FDD-CDMA的下行链路的波束形成，电子学报，1999，27(12)，pp．76-79
[22] 王安义，保铮，廖桂生，下行波束形成与上行Rake接收机的联合处理技术，通信学报，2001，22(3)，pp．124-128
[23] G. G. Raleigh, S. N. Diggavi, V. K. Jones, etc., A Blind Adaptive Transmit Antenna Algorithm for Wireless Communication, IEEE International Conference on Communications, ICC'95, 1995, 3, pp. 1494-1499
[24] Xu guanghan, Liu Hui, An effective transmitting beamforming scheme for frequency-division-duplex digital wireless communication system, ICASSP, 1995, 3, pp.1729-1732
[25] T. Aste, P. Forster, L.Fety, etc., Downlink Beamforming Avoiding DOA Estimation for Cellular Mobile Communications, IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP'98, 1998, 6, pp.3313-3316
[26] 徐卫，智能天线研究，[学位论文]，西安，西安电子科技大学，2003
[27] 张贤达，保铮，通信信号处理，北京，国防工业出版社，2000
[28] 国炜，FDD-CDMA系统下行链路波束形成的研究，[学位论文]，大连，大连理工大学，2005
[29] A. Paulraj,. C. B. Papadias, Space-time processing for wireless communication, IEEE Signal Processing Magazine, 1997, 14(6), pp.49-83
[30] 杨秋萍，智能天线发射波束形成技术研究，[学位论文]，西安，西安电子科技大学，2004
[31] P. Hoeher, A Statistical Discrete-Time Model for the WSSUS Multipath Channel, IEEE trans, on Vehicular Technology, 1992, 41 (4), pp. 461-468
[32] Lal Chand Godara, Smart Antennas, Boca Raton, Florida, CRC Press, 2004
[33] 贺宁蓉，吕善伟，子空间跟踪PASTd算法的改进及其应用，现代雷达，2005，27(11)，pp．75-78
[34] 张贤达，现代信号处理，第二版，北京，清华大学出版社，2002
[35] G. Adams, M. F. EGriffm, G.W.Stewart, Direction-of-arrival estimation using the rank-revealing URV decomposition, IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP-91, 1991, 2, pp.1385-1388
[36] P. Stoica, A. Eriksson, T. Soderstrom, Subspace-based algorithms without eigendeco-mposition for array signal processing, IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP-93, 1993, 4, pp.33-36
[37] 张媛，张燕平，一种PCA算法及其应用，微机发展，2005，15(2)，pp．67-72
[38] 唐懿芳，钟达夫，主成分分析方法对数据进行预处理，广西师范大学学报，2002，3(1)，pp．223-225
[39] Hiroshi Sawada, Ryo Mukai, Shoji Makino, Direction of Arrival Estimation for Multiple Source Signals Using Independent Component Analysis, NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237, Japan
[40] Yongfeng Miao, Yingbo Hua, Fast subspace tracking and neural network learning by a novel information criterion, IEEE transactions on Signal Processing, 1998, 46(7), pp.1967-1979
[41] Martin T．Hagan，Howard B．Demuth，Mark H．Beale著，戴葵等译，神经网络设计，北京，机械工业出版社，2004
[42] Bin Yang, Projection approximation subspace tracking, IEEE transactions on Signal Processing, 1995, 43(1), pp.95-107
[43] 张贤达，信号处理中的线性代数，北京，科学出版社，1997
[44] 周旦，王翠萍，一种新的子空间跟踪方法在DOA估计中的应用，无线通信，2005，pp．66-70
[45] 余继周，陈定昌，一种DOA估计的快速子空间算法，微电子技术，2005，12，pp．90-92
[46] 陈洪光，沈振康，郭天天，一种基于PCA分析的DOA估计算法，系统工程与电子技术，2005，27(8)，pp．1376-1378
[47] Christof Farsakh, Josef A. Nossek, Spatial Covariance Based Downlink beamforming in an SDMA Mobile Radio System, IEEE transactions on communications, 1998, 46(11), pp.1497-1506
[48] G. G. Raleigh, S.N.Diggavi, V.K.Jones, etc., A blind adaptive transmit antenna algorithm for wireless communication, in Proc.Int.Symp.Comm. (ICC'95), 1995, pp. 1494-1499
[49] P.Zetterberg, A comparison of two systems for downlink communication with antenna arrays at the base, in Proc.IEEE Wireless Commun.Syst.Symposium, 1995, 48 (5), pp.1356-1370
[50] Christof Farsakh, Josef A.Nassek, Channel Allocation and Downlink Beamforming in an SDMA Mobile Radio System, IEEE, Personal, Indoor and Mobile Radio Communications(PIMRC'95), 1995, pp.687-691
[51] 李丽君，智能天线数字自适应波束形成器的研究，[学位论文]，太原，太原理工大学，2005
[52] A. Kuchar, M.Tafemer, M.Tangemann,etc., A Robust DOA-based Smart Antenna Processor for GSM Base Stations, 1999 IEEE International Conference on Comm., 1999, pp.11-16
[53] 马静，CDMA系统的下行波束形成算法研究，[学位论文]，西安，西安电子科技大学，2003
[54] 谷学涛，智能天线波束形成技术的研究，[学位论文]，哈尔滨，哈尔滨工程大学，2004
[2] 汪晓光，智能天线技术与波达方向估计研究，[学位论文]，西安，西安电子科技大学，2002
[3] 单志龙，智能天线中的波达方向估计研究，[学位论文]，广州，华南理工大学，2004
[4] 陈莉娜，FDD模式下的智能天线下行波束形成技术，[学位论文]，哈尔滨，哈尔滨工业大学，2004
[5] 吴伟陵，移动通信中的关键技术，北京，北京邮电大学出版社，2000，pp．257-286
[6] Gertach. D, Praulraj. A, Base station transmitter antenna arrays with mobile to base feedback, In 27th Asilomar Conference on Signals, Systems and Computers, 1993, pp.1432-1436
[7] Gerlaeh. D, Praulraj.A, Adaptive transmitting antenna with feedback, IEEE Signal Processing Letters, 1994, 1(10), pp.150-152
[8] Per Zetterberg, Ottersten.B, The spectrum efficiency of a base station antenna array system for spatially selective transmission, IEEE trans, on Vehicular Technology, 1995, 44(3), pp.651-660
[9] Guanghan Xu, Hui Liu, An effective transmission beamforming scheme for frequency-division-duplex digital wireless communication systems, IEEE, 1995, pp.1729-1732
[10] 葛利嘉，路鸣，蜂窝通信的空分多址：概念、算法和性能，通信学报，1999，20(8)，pp．52-62
[11] 徐建，基于子波分解的DOA估计研究与应用，[学位论文]，北京，北京交通大学，2005
[12] R. O. Schmidt, Multiple emitter location and signal parameter estimation, IEEE trans, on Antennas Propagation, 1986, 34(3), pp.276-280
[13] Roy. R, Paulraj.A, Kailath.T, ESPRIT—A subspace rotation approach to estimation of parameters of cisoids in noise, IEEE trans, on Acoustics, Speech and Signal Processing, 1986, 34(5), pp.1340-1342
[14] R. Pan, C. L. Nikias, Harmonic decomposition methods in cumulant domains, in Proc. ICASSP'88, 1988, pp.2356-2359
[15] H. H. Chiang, C. L. Nikias, The Esprit Algorithm with Higher-order Statistics, Proceedings of Workshop on Higher order spectral analysis, 1989, pp. 163-168
[16] N. Yuen, B.Friedlander, DOA estimation in multipath: an approach using fourth-order cumulants, IEEE trans, on Signal Processing, 1997, 45(5), pp. 1253-1263
[17] S. V. Schell, R. A. Calabretta, W.A.Gardner, etc., Cyclic MUSIC algorithms for signal-selective direction estimation, 1989 International Conference on Acoustics, Speech, and Signal Processing, ICASSP-89, 1989, 4, pp.2278-2281
[18] G. Xu, T. Kailath, Direction-of-arrival estimation via explotation of cyclostationarity-A combination of temporal and spatial processing, IEEE transactions on Signal Processing, 1992, 40(7), pp. 1775-1785
[19] P. Charge, Y. Wang, J.Saillard, An extended cyclic MUSIC algorithm, IEEE trans. on Signal Processing, 2003, 51 (7), pp. 1695-1701
[20] A. F. Naguib, A. Paulraj, T. Kailath, Capacity Improvement with Base Station Antenna Arrays in Cellular CDMA, IEEE trans, on Vehicular Technology, 1994, 43(3), pp.691-698
[21] 李国通，仇佩亮，徐绿洲，FDD-CDMA的下行链路的波束形成，电子学报，1999，27(12)，pp．76-79
[22] 王安义，保铮，廖桂生，下行波束形成与上行Rake接收机的联合处理技术，通信学报，2001，22(3)，pp．124-128
[23] G. G. Raleigh, S. N. Diggavi, V. K. Jones, etc., A Blind Adaptive Transmit Antenna Algorithm for Wireless Communication, IEEE International Conference on Communications, ICC'95, 1995, 3, pp. 1494-1499
[24] Xu guanghan, Liu Hui, An effective transmitting beamforming scheme for frequency-division-duplex digital wireless communication system, ICASSP, 1995, 3, pp.1729-1732
[25] T. Aste, P. Forster, L.Fety, etc., Downlink Beamforming Avoiding DOA Estimation for Cellular Mobile Communications, IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP'98, 1998, 6, pp.3313-3316
[26] 徐卫，智能天线研究，[学位论文]，西安，西安电子科技大学，2003
[27] 张贤达，保铮，通信信号处理，北京，国防工业出版社，2000
[28] 国炜，FDD-CDMA系统下行链路波束形成的研究，[学位论文]，大连，大连理工大学，2005
[29] A. Paulraj,. C. B. Papadias, Space-time processing for wireless communication, IEEE Signal Processing Magazine, 1997, 14(6), pp.49-83
[30] 杨秋萍，智能天线发射波束形成技术研究，[学位论文]，西安，西安电子科技大学，2004
[31] P. Hoeher, A Statistical Discrete-Time Model for the WSSUS Multipath Channel, IEEE trans, on Vehicular Technology, 1992, 41 (4), pp. 461-468
[32] Lal Chand Godara, Smart Antennas, Boca Raton, Florida, CRC Press, 2004
[33] 贺宁蓉，吕善伟，子空间跟踪PASTd算法的改进及其应用，现代雷达，2005，27(11)，pp．75-78
[34] 张贤达，现代信号处理，第二版，北京，清华大学出版社，2002
[35] G. Adams, M. F. EGriffm, G.W.Stewart, Direction-of-arrival estimation using the rank-revealing URV decomposition, IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP-91, 1991, 2, pp.1385-1388
[36] P. Stoica, A. Eriksson, T. Soderstrom, Subspace-based algorithms without eigendeco-mposition for array signal processing, IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP-93, 1993, 4, pp.33-36
[37] 张媛，张燕平，一种PCA算法及其应用，微机发展，2005，15(2)，pp．67-72
[38] 唐懿芳，钟达夫，主成分分析方法对数据进行预处理，广西师范大学学报，2002，3(1)，pp．223-225
[39] Hiroshi Sawada, Ryo Mukai, Shoji Makino, Direction of Arrival Estimation for Multiple Source Signals Using Independent Component Analysis, NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237, Japan
[40] Yongfeng Miao, Yingbo Hua, Fast subspace tracking and neural network learning by a novel information criterion, IEEE transactions on Signal Processing, 1998, 46(7), pp.1967-1979
[41] Martin T．Hagan，Howard B．Demuth，Mark H．Beale著，戴葵等译，神经网络设计，北京，机械工业出版社，2004
[42] Bin Yang, Projection approximation subspace tracking, IEEE transactions on Signal Processing, 1995, 43(1), pp.95-107
[43] 张贤达，信号处理中的线性代数，北京，科学出版社，1997
[44] 周旦，王翠萍，一种新的子空间跟踪方法在DOA估计中的应用，无线通信，2005，pp．66-70
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