Journal of the Institute of Electronics Engineers of Korea TC (대한전자공학회논문지TC)

The Institute of Electronics and Information Engineers (대한전자공학회)
권호 표지

New Beamforming Schemes with Optimum Receive Combining for Multiuser MIMO Downlink Channels

다중사용자 다중입출력 하향링크 시스템을 위한 최적 수신 결합을 이용한 새로운 빔 형성 기법

  • Received : 2011.01.03
  • Accepted : 2011.08.17
  • Published : 2011.08.25
Download PDF
⟨ Previous Next ⟩

Abstract

In this paper, we present a new beamforming scheme for a downlink of multiuser multiple-input multipleoutput (MIMO) communication systems. Recently, a block-diagonalization (BD) algorithm has been proposed for the multiuser MIMO downlink where both a base station and each user have multiple antennas. However, the BD algorithm is not efficient when the number of supported streams per user is smaller than that of receive antennas. Since the BD method utilizes the space based on the channel matrix without considering the receive combining, the degree of freedom for beamforming cannot be fully exploited at the transmitter. In this paper, we optimize the receive beamforming vector under a zero forcing (ZF) constraint, where all inter-user interference is driven to zero. We propose an efficient algorithm to find the optimum receive vector by an iterative procedure. The proposed algorithm requires two phase values feedforward information for the receive combining vector. Also, we present another algorithm which needs only one phase value by using a decomposition of the complex general unitary matrix. Simulation results show that the proposed beamforming scheme outperforms the conventional BD algorithm in terms of error probability and obtains the diversity enhancement by utilizing the degree of freedom at the base station.

본 논문에서 우리는 다중사용자 다중입출력 하향링크 통신 시스템을 위한 새로운 빕 형성 기법을 제시한다. 최근 block-diagonalization (BD) 알고리즘이 기지국과 각 사용자들이 다중 안테나는 가지는 다중사용자 다중입출력 하향링크를 위해 제안되고 있다. 그러나, BD 알고리즘은 유저당 제공되는 스트림의 개수가 수신기의 개수보다 작은 경우에는 효율적이지 않다. BD 방법이 수신단의 결합을 고려하지 않고 채널 행렬에 기반한 space를 활용하기 때문에, 빔 형성을 위한 자유도는 수신측에서 전부 얻지 못한다. 본 논문에서 우리는 모든 사용자간의 간섭이 0이 되는 zero forcing (ZF) 조건 하에 수신 빔 형성 벡터를 최적화 한다. 우리는 반복적인 과정에 의해 최적 수신 벡터를 찾는 효율적인 알고리즘을 제안한다. 제안된 알고리즘은 수신 결합 벡터를 위해 전방향 정보인 두 phase 값을 요구한다. 또한, 우리는 일반적인 복소 단위 행렬의 분해를 이용하여 단지 한 phase 값만 필요한 또 다른 알고리즘을 제시한다. 시뮬레이션 결과는 에러 확률 관점에서 제안된 빔 형성 기법이 기존 BD 알고리즘보다 성능이 낫고 기지국에서 자유도를 이용함으로써 다이버시티 증가를 획듬함을 보여준다.

Keywords

References

  1. G. J. Foschini and M. Gans, "On Limits of Wireless Communications in a Fading Environment when Using Multiple Antennas," Wireless Personal Communications, vol. 6, pp. 311-335, March 1998. https://doi.org/10.1023/A:1008889222784
  2. G. Caire and S. Shamai, "On the achievable throughput of a multiantenna Gaussian broadcast channel," IEEE Transactions on Information Theory, vol. 49, pp. 1691-1706, July 2003. https://doi.org/10.1109/TIT.2003.813523
  3. 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, pp. 2658-2668, October 2003. https://doi.org/10.1109/TIT.2003.817421
  4. P. Viswanath and D. N. C. Tse, "Sum capacity of the vector Gaussian broadcast channel and uplink-downlink duality," IEEE Transactions on Information Theory, vol. 49, pp. 1912-1921, August 2003. https://doi.org/10.1109/TIT.2003.814483
  5. W. Yu and J. M. Cioffi, "Sum Capacity of Gaussian Vector Broadcast Channels," IEEE Transactions on Information Theory, vol. 50, pp. 1875-1892, September 2004. https://doi.org/10.1109/TIT.2004.833336
  6. M. Costa, "Writing on dirty paper," IEEE Transactions on Information Theory, vol. 29, pp. 439-441, May 1983. 22 https://doi.org/10.1109/TIT.1983.1056659
  7. C. B. Peel, B. M. Hochwald, and A. L. Swindelhurst, "A vector-perturbation technique for near-capacity multiantenna multiuser communication-part I: channel inversion and regularization," IEEE Transactions on Communications, vol. 53, pp. 195-202, January 2005. https://doi.org/10.1109/TCOMM.2004.840638
  8. B. M. Hochwald, C. B. Peel, and A. L. Swindelhurst, "A vector-perturbation technique for near-capacity multiantenna multiuser communication-part II: perturbation," IEEE Transactions on Communications, vol. 53, pp. 537-544, March 2005. https://doi.org/10.1109/TCOMM.2004.841997
  9. Q. H. Spencer, A. L. Swindelhurst, and M. Haardt, "Zero-forcing methods for downlink spatial multiplexing in multiuser MIMO channels," IEEE Transactions on Signal Processing, vol. 52, pp. 461-471, February 2004. https://doi.org/10.1109/TSP.2003.821107
  10. P. U. Sripathi and J. S. Lehnert, "Optimizing ZF Precoders for MIMO Broadcast Systems," in Proc. Wireless Communications and Networking Conference, pp. 1874-1880, April 2006.
  11. H. Lee, S. Park, and I. Lee, "A New MIMO Beamforming Technique Based on Rotation Transformations," Proc. ICC '07, June 2007.
  12. D. Chizhik, J. Ling, P. W. Wolniansky, R. A. Valenzuela, N. Costa, and K. Huber, "Multiple-input-multiple-output measurements and modeling in Manhattan," IEEE Journal on Selected Areas in Communications, vol. 21, pp. 321-331, April 2003. https://doi.org/10.1109/JSAC.2003.809457
  13. A. L. Moustakas, S. H. Simon, and A. M. Sengupta, "MIMO capacity through correlated channels in the presence of correlated interferers and noise: a (not so) large N analysis," IEEE Transactions on Information Theory, vol. 49, pp. 2545-2561, Oct. 2003. https://doi.org/10.1109/TIT.2003.817427