Zero-forcing methods for downlink spatial multiplexing in multiuser MIMO channels

The use of space-division multiple access (SDMA) in the downlink of a multiuser multiple-input, multiple-output (MIMO) wireless communications network can provide a substantial gain in system throughput. The challenge in such multiuser systems is designing transmit vectors while considering the co-channel interference of other users. Typical optimization problems of interest include the capacity problem - maximizing the sum information rate subject to a power constraint-or the power control problem-minimizing transmitted power such that a certain quality-of-service metric for each user is met. Neither of these problems possess closed-form solutions for the general multiuser MIMO channel, but the imposition of certain constraints can lead to closed-form solutions. This paper presents two such constrained solutions. The first, referred to as "block-diagonalization," is a generalization of channel inversion when there are multiple antennas at each receiver. It is easily adapted to optimize for either maximum transmission rate or minimum power and approaches the optimal solution at high SNR. The second, known as "successive optimization," is an alternative method for solving the power minimization problem one user at a time, and it yields superior results in some (e.g., low SNR) situations. Both of these algorithms are limited to cases where the transmitter has more antennas than all receive antennas combined. In order to accommodate more general scenarios, we also propose a framework for coordinated transmitter-receiver processing that generalizes the two algorithms to cases involving more receive than transmit antennas. While the proposed algorithms are suboptimal, they lead to simpler transmitter and receiver structures and allow for a reasonable tradeoff between performance and complexity.

[1]  Max H. M. Costa,et al.  Writing on dirty paper , 1983, IEEE Trans. Inf. Theory.

[2]  Charles R. Johnson,et al.  Matrix analysis , 1985, Statistical Inference for Engineers and Data Scientists.

[3]  Richard D. Gitlin,et al.  The impact of antenna diversity on the capacity of wireless communication systems , 1994, IEEE Trans. Commun..

[4]  M. J. Gans,et al.  On Limits of Wireless Communications in a Fading Environment when Using Multiple Antennas , 1998, Wirel. Pers. Commun..

[5]  Reinaldo A. Valenzuela,et al.  V-BLAST: an architecture for realizing very high data rates over the rich-scattering wireless channel , 1998, 1998 URSI International Symposium on Signals, Systems, and Electronics. Conference Proceedings (Cat. No.98EX167).

[6]  John M. Cioffi,et al.  Spatio-temporal coding for wireless communication , 1998, IEEE Trans. Commun..

[7]  A. L. Swindlehurst,et al.  MIMO environmental capacity sensitivity , 2000, Conference Record of the Thirty-Fourth Asilomar Conference on Signals, Systems and Computers (Cat. No.00CH37154).

[8]  Khaled Ben Letaief,et al.  Optimizing the spectral efficiency of multiuser MIMO smart antenna systems , 2000, 2000 IEEE Wireless Communications and Networking Conference. Conference Record (Cat. No.00TH8540).

[9]  Q. H. Spencer,et al.  Some results on channel capacity when using multiple antennas , 2000, Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152).

[10]  Reinaldo A Valenzuela,et al.  Link-optimal BLAST processing with multiple-access interference , 2000, Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152).

[11]  Mary Ann Ingram,et al.  Power-controlled capacity for interfering MIMO links , 2001, VTC Fall.

[12]  David Tse,et al.  Asymptotically optimal water-filling in vector multiple-access channels , 2001, IEEE Trans. Inf. Theory.

[13]  Zhigang Cao,et al.  Spatial multiuser access with MIMO smart antennas for OFDM systems , 2001, IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211).

[14]  A.J. Paulraj,et al.  Multiuser diversity for MIMO wireless systems with linear receivers , 2001, Conference Record of Thirty-Fifth Asilomar Conference on Signals, Systems and Computers (Cat.No.01CH37256).

[15]  Rick S. Blum,et al.  On the capacity of cellular systems with MIMO , 2002, IEEE Communications Letters.

[16]  David Tse,et al.  Sum capacity of the multiple antenna Gaussian broadcast channel , 2002, Proceedings IEEE International Symposium on Information Theory,.

[17]  Brian G. Agee.  Exploitation of Internode MIMO Channel Diversity in Spatially Distributed Multipoint Communication Networks , 2002 .

[18]  Holger Boche,et al.  Optimum sir balancing using extended 1-norm beamforming optimization , 2002, 2002 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[19]  Leandros Tassiulas,et al.  Joint transmitter receiver diversity for efficient space division multiaccess , 2002, IEEE Trans. Wirel. Commun..

[20]  Holger Boche,et al.  An efficient algorithm for optimum joint downlink beamforming and power control , 2002, Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367).

[21]  Kung Yao,et al.  Multiuser spatio-temporal coding for wireless communications , 2002, 2002 IEEE Wireless Communications and Networking Conference Record. WCNC 2002 (Cat. No.02TH8609).

[22]  Mats Bengtsson.  A pragmatic approach to multi-user spatial multiplexing , 2002, Sensor Array and Multichannel Signal Processing Workshop Proceedings, 2002.

[23]  D. Popescu,et al.  Interference avoidance for multiaccess vector channels , 2002, Proceedings IEEE International Symposium on Information Theory,.

[24]  Shlomo Shamai,et al.  On the achievable throughput of a multiantenna Gaussian broadcast channel , 2003, IEEE Transactions on Information Theory.

[25]  Rick S. Blum.  MIMO capacity with interference , 2003, IEEE J. Sel. Areas Commun..

[26]  Andrea J. Goldsmith,et al.  Duality, achievable rates, and sum-rate capacity of Gaussian MIMO broadcast channels , 2003, IEEE Trans. Inf. Theory.

[27]  Wei Yu,et al.  Sum capacity of Gaussian vector broadcast channels , 2004, IEEE Transactions on Information Theory.