MIMO中的空时编码技术研究
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摘要
MIMO(Multi-Input Multi-Output,多输入多输出系统)泛指采用多发射、多接收天线的无线通信系统,它可以在有限的频谱资源、不增加发射功率前提下,以较小的系统复杂度换来性能的大幅提升,因此MIMO技术成为当今无线通信研究的热点,也是未来无线通信的发展趋势。
空时编码技术是MIMO中的关键技术,能够改善系统的BER性能、实现数据高速传输。BLAST空时复用技术属于空时编码技术的一个分支,充分利用多径信道的容量,是真正可以实现频谱高效利用的新一代无线通信技术。大名鼎鼎的Turbo码因其逼近香农限的性能,自1993年提出以来一直是信道编码技术的研究热点。迭代译码的思想也被广泛采纳,很多被人们疏漏的编码方案也因此被重新研究,并取得了优异的性能,如乘积码和LDPC码。由于BLAST系统的高速传输需要建立在可靠通信的前提下,所以BLAST与这些性能优异的信道编码级联的通信系统理所当然的成为热门课题。传统的BLAST检测技术和译码判决分离的系统,由于不能充分利用软信息,所以误码性能较差。受TCM技术的启发,联合检测技术越来越广泛的在收端被用来恢复原始信息,并给系统性能带来可观的提升。论文讨论了V-BLAST的多种检测技术,包括ML(Maximum Likelihood,最大似然)算法、ZF(Zero Forcing,迫零)算法、MMSE(Minimum Mean Square Error,最小均方误差)算法、IIC(Iterative Interference Cancelling,迭代干扰消除)算法,还有SD(Sphere Decoding,球译码)算法和软输出SD算法等。基于栅格理论的SD算法是一种次优算法,在保证接近ML算法性能的同时,降低检测复杂度;软输出SD算法通过在球形域保留多个栅格点来计算接收矢量的软信息,从而避免了硬判决SD中软信息的丢失,改善系统性能。重点研究了采用IJDD(Iterative Joint Detection and Decoding,联合迭代检测译码)的Turbo和V-BLAST级联系统,将软输出SD检测和Turbo的迭代MAP译码相结合,实现了较传统的检测判决分离系统更优的性能。
空时编码的另一个分支以取得分集增益为目的,包括STTC(空时格码)和STBC(空时块码)。STTC将网格编码技术(TCM)与发射分集技术相结合,可以获得满分集增益和编码增益,抗衰落性能最优,但STTC好码搜索较困难,译码复杂度也较高。STBC作为性能与复杂度折中的一种编码方案,利用正交设计原理,可以在保证满分集增益的同时大大降低译码复杂度,它的译码仅为简单的线性合并。论文简单讨论了STTC、STBC编译码的基本理论,并对一些简单的空时码级联系统进行了研究。STTC、STBC与BLAST的级联系统,也是研究的热门课题。
MIMO(Multi-Input Multi-Output) refers to any wireless communication systems adopting multi-transmit antennas and multi-receive antennas. It can greatly enhance communication system performance with a little more system complexity, requiring no more frequency band and higher transmit power. Due to these advantages, MIMO is the focus nowadays and also the trend in future of wireless communication.
Space-Time Coding, which is the key technique for MIMO, can provide better BER performance and highly improve the data rating of communication systems. BLAST(Bell LAyered Space Time), which is a branch of STC, is a kind of Space-Time multiplexing technique using multi-path fading to highly improve the data rating and is indeed a method to achieve a high frequency spectrum efficiency. Since advanced in 1993, Turbo coding, well known for its near Shannon performance, has always been the focus of channel coding research. Iterative decoding is also widely adopted, using which to achieve better performance, by other channel codes such as LDPC, TPC etc. Due to the fact that high data rating is based on reliable transmission, BLAST systems cascaded with these high performance channel code is deeply studied. Detecting and decoding separated BLAST system is always poor in BER performance for its loss of soft information. So Iterative Joint Detection and Decoding technique is used more and more to recover the original information. In this paper, we discuss varieties of detection techniques for V-BLAST, such as ML, ZF, MMSE, IIC, SD, soft SD, and so on. SD is a kind of sub-optimal detection algorithm based on Trellice theory, which can highly decrease the detection complexity achieving a near-ML performance. Soft-output SD detection computes the soft information of the received vector by reserving some small-weight trellice points in the given sphere to improve system performance. Finally we focus on the IJDD system of Turbo cascaded with V-BLAST, using soft-SD detection and iterative MAP decoding. In addition, we simulate a TPC, V-BLAST cascaded system as a reference.
The other branch of Space-Time coding, STTC and STBC, aims at achieving diversity gain. STTC is the combination of TCM and transmission diversity, achieving full diversity gain and high coding gain but with high code searching and decoding complexity. We simply introduce the basic principles of STTC, STBC coding and decoding. Then STTC, STBC and BLAST cascaded systems are studied.
空时编码技术是MIMO中的关键技术,能够改善系统的BER性能、实现数据高速传输。BLAST空时复用技术属于空时编码技术的一个分支,充分利用多径信道的容量,是真正可以实现频谱高效利用的新一代无线通信技术。大名鼎鼎的Turbo码因其逼近香农限的性能,自1993年提出以来一直是信道编码技术的研究热点。迭代译码的思想也被广泛采纳,很多被人们疏漏的编码方案也因此被重新研究,并取得了优异的性能,如乘积码和LDPC码。由于BLAST系统的高速传输需要建立在可靠通信的前提下,所以BLAST与这些性能优异的信道编码级联的通信系统理所当然的成为热门课题。传统的BLAST检测技术和译码判决分离的系统,由于不能充分利用软信息,所以误码性能较差。受TCM技术的启发,联合检测技术越来越广泛的在收端被用来恢复原始信息,并给系统性能带来可观的提升。论文讨论了V-BLAST的多种检测技术,包括ML(Maximum Likelihood,最大似然)算法、ZF(Zero Forcing,迫零)算法、MMSE(Minimum Mean Square Error,最小均方误差)算法、IIC(Iterative Interference Cancelling,迭代干扰消除)算法,还有SD(Sphere Decoding,球译码)算法和软输出SD算法等。基于栅格理论的SD算法是一种次优算法,在保证接近ML算法性能的同时,降低检测复杂度;软输出SD算法通过在球形域保留多个栅格点来计算接收矢量的软信息,从而避免了硬判决SD中软信息的丢失,改善系统性能。重点研究了采用IJDD(Iterative Joint Detection and Decoding,联合迭代检测译码)的Turbo和V-BLAST级联系统,将软输出SD检测和Turbo的迭代MAP译码相结合,实现了较传统的检测判决分离系统更优的性能。
空时编码的另一个分支以取得分集增益为目的,包括STTC(空时格码)和STBC(空时块码)。STTC将网格编码技术(TCM)与发射分集技术相结合,可以获得满分集增益和编码增益,抗衰落性能最优,但STTC好码搜索较困难,译码复杂度也较高。STBC作为性能与复杂度折中的一种编码方案,利用正交设计原理,可以在保证满分集增益的同时大大降低译码复杂度,它的译码仅为简单的线性合并。论文简单讨论了STTC、STBC编译码的基本理论,并对一些简单的空时码级联系统进行了研究。STTC、STBC与BLAST的级联系统,也是研究的热门课题。
MIMO(Multi-Input Multi-Output) refers to any wireless communication systems adopting multi-transmit antennas and multi-receive antennas. It can greatly enhance communication system performance with a little more system complexity, requiring no more frequency band and higher transmit power. Due to these advantages, MIMO is the focus nowadays and also the trend in future of wireless communication.
Space-Time Coding, which is the key technique for MIMO, can provide better BER performance and highly improve the data rating of communication systems. BLAST(Bell LAyered Space Time), which is a branch of STC, is a kind of Space-Time multiplexing technique using multi-path fading to highly improve the data rating and is indeed a method to achieve a high frequency spectrum efficiency. Since advanced in 1993, Turbo coding, well known for its near Shannon performance, has always been the focus of channel coding research. Iterative decoding is also widely adopted, using which to achieve better performance, by other channel codes such as LDPC, TPC etc. Due to the fact that high data rating is based on reliable transmission, BLAST systems cascaded with these high performance channel code is deeply studied. Detecting and decoding separated BLAST system is always poor in BER performance for its loss of soft information. So Iterative Joint Detection and Decoding technique is used more and more to recover the original information. In this paper, we discuss varieties of detection techniques for V-BLAST, such as ML, ZF, MMSE, IIC, SD, soft SD, and so on. SD is a kind of sub-optimal detection algorithm based on Trellice theory, which can highly decrease the detection complexity achieving a near-ML performance. Soft-output SD detection computes the soft information of the received vector by reserving some small-weight trellice points in the given sphere to improve system performance. Finally we focus on the IJDD system of Turbo cascaded with V-BLAST, using soft-SD detection and iterative MAP decoding. In addition, we simulate a TPC, V-BLAST cascaded system as a reference.
The other branch of Space-Time coding, STTC and STBC, aims at achieving diversity gain. STTC is the combination of TCM and transmission diversity, achieving full diversity gain and high coding gain but with high code searching and decoding complexity. We simply introduce the basic principles of STTC, STBC coding and decoding. Then STTC, STBC and BLAST cascaded systems are studied.
引文
[1] E.Telatar,“Capacity of mufti-antenna Gaussian channels”, AT&T Bell Labs Internal Tech., Jun., 1995
[2] Foschini.G.J. and Gars.M.J.,“On limits of wireless communications in a fading environment when using multiple antennas, Wireless Personal Communications”, Wireless Personal Communications, 1998, Vol.6, No.3, pp.311-335
[3] Gerard.J.Foschini,“Layered Space-Time Architecture for Wire1ess Communication in a Fading Environment When using Multi-Element Antennas”, Bell Labs Technical Journal, Autumn 1996, pp.41-59
[4] Vahid Tarokh, Namib Seshadri, and A.R.Calderbank,“Space-Time Codes for High Data Rate Wireless Communications: Performance Criterion and Code Construction”,IEEE Transactions on Information Theory, Mar., 1998, Vol.44, pp.74 4-765
[5] S.M.Alamout,“A simple transmit diversity technique for wireless communications”, IEEE J. Selec. Area Commun., Oct., 1998, vol.16, pp.1451-1458
[6] Vahid Tarokh, Namib Seshadri, and A.R.Calderbank,“Space-Time Block Codes from Orthogonal Designs”, IEEE Transactions on Information Theory, Jul., 1999, Vol. 45, pp.1456-1467
[7] Wonjong R. and John.M.C,“On the capacity of multiuser wireless Channels with multiple antennas”, IEEE Transaction on Information Theory, 2003, Vo1.49, No. 10, pp.2580-2595
[8]杨大成等,“移动传播环境理论基础、分析方法和建模技术”,机械工业出版社,2003
[9] Prasad, N. and Varanast M.IC.,“Optimizing the performance of D-BLAST lattice fading channels”, IEEE International Conference on Personal Wireless Communications, 2002, pp.61-65
[10] Hamid J.,“A Quasi-Orthogonal Spare-Time Block Code”, IEEE Trans. On Communications, 2001,Vo1.49, No.l, pp.l-4
[11] Bertrand M.H., Thomas L.M., etc., "Systematic Design of Unitary Space-Time Constellations", IEEE Trans. on Information Theory, 2000, Vo1.46, No.6, pp.1962-1973
[12] Hochwald B.M., "Differential Unitary Space-Time Modulation", IEEE Trans. On Communications, 2000, Vol.4, No.12, pp.2041-2052
[13] Youjian L., Michael P.F. and Oscar Y.T., "Full Rate Space-Time Turbo Codes",IEEE JSAC, 2001, Vol.19, No.5, pp.969-980
[14] V.M.DaSilva and E.S.Sousa, "Fading-Resistant Modulation Using Several Transmitter Antennas", IEEE Trans. on Communications, 1997, Vol.45, No.10, pp. 1236-1244
[15] J.J.Bautras and E.Viterbo,“Signal Space Diversity: a power and bandwidth efficient diversity technique for the ltayleigh fading channel”, IEEE Trans. on Information Theory, 1988, Vol.44, No.4, pp.1453-1467
[16] B.Hassibi and B.M.Hochwald,“High-Rate Codes that are Linear in Space and Time”, IEEE Trans. on Information Theory, 2002, Vol.48, No.7, pp.1804-1824
[17] Jean-Claude B.,Ghaya R. and Emanuele V.,“The golden code: a 2X2 full-rate space-time code with non-vanishing determinants”, IEEE Trans. on Information Theory, 2005, Vo1.51, No.4, pp.1432-1436
[18] N.Gresset, "New Space-Time Coding Techniques with Bit-Interleaved Coded Modulations”, Ph.D. thesis, http://www.comelec.enst.fr/boatros/coding
[19] Daniel P.P., John M.C. and Miguel A.L.,“Joint Tx-Rx Bearmforming Design for Multicarrier MIMO channels: a Unified Framework for Convex Optimization”, lEEE Trans. on Signal Processing, 2003, Vol.51, No.9, pp.2381-2400
[20] Taesang Y. and Goldsmith A.,“On the optimality of muitiantenna broadcast using zero-forcing beamforming”, IEEE JSAC, 2006, Vo1.24, No.3, pp.528-541
[21] Blum R.S, Winters J.H.,“On optimum MIMO with antenna selection”, IEEE Communication letters, 2002, Vol.24, No.3, pp.322-324
[22] Theodre S.Rappaport,“Wireless Communications Principles and Practice”, U.S., pp.50-97
[23]John G.Proakis,“Digital Communications”, Fourth Edition, Publishing House of Electronics Industry, 2006, pp.577-636
[24] E.Telatar,“Capacity of Multi-antenna Gaussion Channels”, European Trans. on Telecommunications, Nov./Dec., 1999, Vol.10, No.6, pp.585-595
[25] D.M.Ionescu,“New Results on Space-Time Code Design Criteria”, IEEE WCNC’99, 1999, Vol.2, pp.684-687
[26] A.R.Jr.Hammons, and H.EI Gamal,“On the theory of space-time codes for PSK modulation”, IEEE Trans. Inform. Theory, Mar., 2000, Vol.46, No.2, pp.524-542
[27] M.Tao and R.S.Cheng,“Improved design criteria and new trellis codes for space-time coded modulation in slow flat fading channels”, IEEE Commun. Lett., Jul. 2001, Vol.5, No.7, pp.301-303
[28]Z.Chen, J.Yuan and B.Vucetic,“An improved space-time trellis coded modulationscheme on slow Rayleigh fading channels”, IEEE ICC’01, Jun. 2001, pp.1110-1116
[29] S.Baro, G.Bauch, and A.R.Jr.Hammons,“Improved codes for space-time trellis-coded modulation”, IEEE Commun. Lett., Jan., 2000, Vol.4, No.1, pp.20-22
[30] Q.Yan and R.S.Blum,“Optimum space-time convolutional codes”, IEEE WCNC’00, Sep., 2000, pp.1351-1355
[31] H.Huang, M.Sandell and H.Viswanathan,“Achieving high data rates on the UMTS downlink shared channel using multiple antennas”, 3G Mobile Communication Technologies, 2001, pp.373-377
[32] P.W.Wolniansky, G.J.Foschini, G.D.Golden,“V-BLAST: An architecture for realizing very high data rates over the rich-scattering wireless channel”,ISSSE’1998, pp.295-300
[33] Vahid Tarokh, Hamid Jafarkhani and A.R.Calderbank,“Space-Time Block Coding for Wireless Communications: Performance Results”, IEEE Journal on Selected Areas in Communications, Mar., 1999, Vol. 17x, pp.20-22
[34] Bertrand M.Hochwald and Stephan ten Brink,“Achieving Near-Capacity on a Multiple-Antenna Channel”, IEEE Transactions on Communications, Mar., 2003, Vol.51, No.3, pp.389-399
[35] Joseph Boutros, Nicolas Gresset, and Marc Fossorier,“Soft-input soft-output lattice sphere decoder for linear channels”, IEEE Globecom, 2003, pp.1583-1587
[36]邬钢,“移动通信中的空时编码和发射分集技术的研究”,Southeast University Ph.D. Thesis, 2002
[37] W.C.Jr.Jakes,“Microwave Mobile Communications”, AT&T IMP Corp, IEEE Press, 1994
[38] Shu Lin, Daniel J.Costello,“Error Control Coding”, Second Edition, China Machine Press, Jun., 2007, pp.505-560
[39] Claude Berrou, Alain Glavieux and Punya Thitimajshima,“NEAR SHANNON LIMTT ERROR CORRECTING CODING AND DECODING: TURBO-CODES”, IEEE Trans., 1993, pp.1064-1070
[40]D.Divsalar and M.K.Simon,“The design of trellice coded MPSK for fading channel: Performance criteria”, IEEE Trans. Commun., Sep., 1988, Vol.36, No.9, pp.1004-1012
[41]D.Divsalar and M.K.Simon,“The design of trellice coded MPSK for fading channel: Set partitioning for optimum code design”, IEEE Trans. Commun., Sep., 1988, Vol.36, No.9, pp.1013-1021
[2] Foschini.G.J. and Gars.M.J.,“On limits of wireless communications in a fading environment when using multiple antennas, Wireless Personal Communications”, Wireless Personal Communications, 1998, Vol.6, No.3, pp.311-335
[3] Gerard.J.Foschini,“Layered Space-Time Architecture for Wire1ess Communication in a Fading Environment When using Multi-Element Antennas”, Bell Labs Technical Journal, Autumn 1996, pp.41-59
[4] Vahid Tarokh, Namib Seshadri, and A.R.Calderbank,“Space-Time Codes for High Data Rate Wireless Communications: Performance Criterion and Code Construction”,IEEE Transactions on Information Theory, Mar., 1998, Vol.44, pp.74 4-765
[5] S.M.Alamout,“A simple transmit diversity technique for wireless communications”, IEEE J. Selec. Area Commun., Oct., 1998, vol.16, pp.1451-1458
[6] Vahid Tarokh, Namib Seshadri, and A.R.Calderbank,“Space-Time Block Codes from Orthogonal Designs”, IEEE Transactions on Information Theory, Jul., 1999, Vol. 45, pp.1456-1467
[7] Wonjong R. and John.M.C,“On the capacity of multiuser wireless Channels with multiple antennas”, IEEE Transaction on Information Theory, 2003, Vo1.49, No. 10, pp.2580-2595
[8]杨大成等,“移动传播环境理论基础、分析方法和建模技术”,机械工业出版社,2003
[9] Prasad, N. and Varanast M.IC.,“Optimizing the performance of D-BLAST lattice fading channels”, IEEE International Conference on Personal Wireless Communications, 2002, pp.61-65
[10] Hamid J.,“A Quasi-Orthogonal Spare-Time Block Code”, IEEE Trans. On Communications, 2001,Vo1.49, No.l, pp.l-4
[11] Bertrand M.H., Thomas L.M., etc., "Systematic Design of Unitary Space-Time Constellations", IEEE Trans. on Information Theory, 2000, Vo1.46, No.6, pp.1962-1973
[12] Hochwald B.M., "Differential Unitary Space-Time Modulation", IEEE Trans. On Communications, 2000, Vol.4, No.12, pp.2041-2052
[13] Youjian L., Michael P.F. and Oscar Y.T., "Full Rate Space-Time Turbo Codes",IEEE JSAC, 2001, Vol.19, No.5, pp.969-980
[14] V.M.DaSilva and E.S.Sousa, "Fading-Resistant Modulation Using Several Transmitter Antennas", IEEE Trans. on Communications, 1997, Vol.45, No.10, pp. 1236-1244
[15] J.J.Bautras and E.Viterbo,“Signal Space Diversity: a power and bandwidth efficient diversity technique for the ltayleigh fading channel”, IEEE Trans. on Information Theory, 1988, Vol.44, No.4, pp.1453-1467
[16] B.Hassibi and B.M.Hochwald,“High-Rate Codes that are Linear in Space and Time”, IEEE Trans. on Information Theory, 2002, Vol.48, No.7, pp.1804-1824
[17] Jean-Claude B.,Ghaya R. and Emanuele V.,“The golden code: a 2X2 full-rate space-time code with non-vanishing determinants”, IEEE Trans. on Information Theory, 2005, Vo1.51, No.4, pp.1432-1436
[18] N.Gresset, "New Space-Time Coding Techniques with Bit-Interleaved Coded Modulations”, Ph.D. thesis, http://www.comelec.enst.fr/boatros/coding
[19] Daniel P.P., John M.C. and Miguel A.L.,“Joint Tx-Rx Bearmforming Design for Multicarrier MIMO channels: a Unified Framework for Convex Optimization”, lEEE Trans. on Signal Processing, 2003, Vol.51, No.9, pp.2381-2400
[20] Taesang Y. and Goldsmith A.,“On the optimality of muitiantenna broadcast using zero-forcing beamforming”, IEEE JSAC, 2006, Vo1.24, No.3, pp.528-541
[21] Blum R.S, Winters J.H.,“On optimum MIMO with antenna selection”, IEEE Communication letters, 2002, Vol.24, No.3, pp.322-324
[22] Theodre S.Rappaport,“Wireless Communications Principles and Practice”, U.S., pp.50-97
[23]John G.Proakis,“Digital Communications”, Fourth Edition, Publishing House of Electronics Industry, 2006, pp.577-636
[24] E.Telatar,“Capacity of Multi-antenna Gaussion Channels”, European Trans. on Telecommunications, Nov./Dec., 1999, Vol.10, No.6, pp.585-595
[25] D.M.Ionescu,“New Results on Space-Time Code Design Criteria”, IEEE WCNC’99, 1999, Vol.2, pp.684-687
[26] A.R.Jr.Hammons, and H.EI Gamal,“On the theory of space-time codes for PSK modulation”, IEEE Trans. Inform. Theory, Mar., 2000, Vol.46, No.2, pp.524-542
[27] M.Tao and R.S.Cheng,“Improved design criteria and new trellis codes for space-time coded modulation in slow flat fading channels”, IEEE Commun. Lett., Jul. 2001, Vol.5, No.7, pp.301-303
[28]Z.Chen, J.Yuan and B.Vucetic,“An improved space-time trellis coded modulationscheme on slow Rayleigh fading channels”, IEEE ICC’01, Jun. 2001, pp.1110-1116
[29] S.Baro, G.Bauch, and A.R.Jr.Hammons,“Improved codes for space-time trellis-coded modulation”, IEEE Commun. Lett., Jan., 2000, Vol.4, No.1, pp.20-22
[30] Q.Yan and R.S.Blum,“Optimum space-time convolutional codes”, IEEE WCNC’00, Sep., 2000, pp.1351-1355
[31] H.Huang, M.Sandell and H.Viswanathan,“Achieving high data rates on the UMTS downlink shared channel using multiple antennas”, 3G Mobile Communication Technologies, 2001, pp.373-377
[32] P.W.Wolniansky, G.J.Foschini, G.D.Golden,“V-BLAST: An architecture for realizing very high data rates over the rich-scattering wireless channel”,ISSSE’1998, pp.295-300
[33] Vahid Tarokh, Hamid Jafarkhani and A.R.Calderbank,“Space-Time Block Coding for Wireless Communications: Performance Results”, IEEE Journal on Selected Areas in Communications, Mar., 1999, Vol. 17x, pp.20-22
[34] Bertrand M.Hochwald and Stephan ten Brink,“Achieving Near-Capacity on a Multiple-Antenna Channel”, IEEE Transactions on Communications, Mar., 2003, Vol.51, No.3, pp.389-399
[35] Joseph Boutros, Nicolas Gresset, and Marc Fossorier,“Soft-input soft-output lattice sphere decoder for linear channels”, IEEE Globecom, 2003, pp.1583-1587
[36]邬钢,“移动通信中的空时编码和发射分集技术的研究”,Southeast University Ph.D. Thesis, 2002
[37] W.C.Jr.Jakes,“Microwave Mobile Communications”, AT&T IMP Corp, IEEE Press, 1994
[38] Shu Lin, Daniel J.Costello,“Error Control Coding”, Second Edition, China Machine Press, Jun., 2007, pp.505-560
[39] Claude Berrou, Alain Glavieux and Punya Thitimajshima,“NEAR SHANNON LIMTT ERROR CORRECTING CODING AND DECODING: TURBO-CODES”, IEEE Trans., 1993, pp.1064-1070
[40]D.Divsalar and M.K.Simon,“The design of trellice coded MPSK for fading channel: Performance criteria”, IEEE Trans. Commun., Sep., 1988, Vol.36, No.9, pp.1004-1012
[41]D.Divsalar and M.K.Simon,“The design of trellice coded MPSK for fading channel: Set partitioning for optimum code design”, IEEE Trans. Commun., Sep., 1988, Vol.36, No.9, pp.1013-1021