Improved Code Timing Estimator for DS-CDMA Systems Using Correlated Antennas in Time-Varying Fading Channels

시변 페이딩 채널에서 상관관계가 있는 안테나를 사용하는 DS-CDMA 통신 시스템을 위한 개선된 최대가능도 코드 타이밍 추정기

  • Published : 2006.05.01

Abstract

We consider the problem of estimating a code-timing of DS-CDMA signal in antenna array systems in the presence of flat fading channels and near-far environments. We derive an approximate maximum likelihood algorithm of estimating the code-timing of a desired user for DS-CDMA systems to better utilize the time-varying characteristics of the fading process. In the development of code timing estimator, the given observation bits are divided into many sets of sub-windows with each sufficiently large. The proposed method uses sub-windows with equal size associated with the coherence time of channel fading. The alternative approach is that without the estimation of the fading rate, the sufficiently given observation bits are simply separated into two consecutive sets of sub-windows. The derivation of the proposed algorithms is based on multiple antennas partially correlated in space. The impacts of spatial fading correlation on acquisition and men acquisition time performance of the proposed algorithms are also examined.

본 논문에서는 평탄 페이딩과 근거리/원거리 현상이 존재할 때 안테나 어레이를 사용하는 DS-CDMA 신호의 코드 타이밍을 추정하는 문제를 다루고자 한다. 페이딩 과정의 시변 페이딩 특성을 보다 잘 활용할 수 있도록 DS-CDMA 시스템에 대한 희망하는 사용자의 코드 타이밍을 추정하는 최대가능성 알고리즘을 유도한다. 코드 타이밍 추정기의 개발에 있어서 주어진 관찰 비트들을 포함하는 윈도우를 각각의 부-윈도우가 충분히 큰 길이를 갖도록 나눈다. 제안된 방법은 채널 페이딩의 일관성 시간과 연관된 똑같은 크기를 가지는 부-윈도우들을 이용한다. 또한 페이딩 속도를 추정하지 않고 충분히 긴 관찰 비트들을 두 개의 연속적 인 부-윈도우로 나누는 방법을 대안으로 제시한다. 알고리즘의 유도과정은 공간적으로 상관성이 있는 다중안테나를 바탕으로 한다. 공간적인 페이딩 상관성이 제안된 알고리즘의 동기 획득 및 평균 동기 획득 성능에 미치는 영향을 분석한다.

Keywords

References

  1. U. Madhow and M. B. Pursley, 'Acquisition in direct-sequence spread-spectrum communication networks : an asymptotic analysis,' IEEE Trans. Information Theory, vol. 39, no. 3, pp. 903-912, May 1993 https://doi.org/10.1109/18.256498
  2. D. Zheng, J. Li, S. L. Miller, and E. G. Strom, 'An efficient code-timing estimator for DS-CDMA signals,' IEEE Trans. Signal Processing, vol. 45, pp. 82-89, Jan. 1997 https://doi.org/10.1109/78.552207
  3. T. Ristaniemi and J. Joutsensalo, 'Code timing acquisition for DS-CDMA in fading channels by differential correlation,' IEEE Trans. Commun., vol. 49, no. 5, pp. 899-910, May 2001 https://doi.org/10.1109/26.923813
  4. H. Li, J. Li and S. L. Miller, 'Decoupled multiuser code-timing estimation for code-division multiple-access communication systems,' IEEE Trans. Commun., vol. 49, pp.1425-1436, Aug.2001 https://doi.org/10.1109/26.939881
  5. K. AmIeh and H. Li, 'An algebraic approach to blind carrier offset and code timing estimation for DS-CDMA systems,' IEEE Signal Processing Letters, vol. 10, no. 2, pp. 32-34, Feb. 2003 https://doi.org/10.1109/LSP.2002.807874
  6. J. H. Winters, J. Salz, and R. D. Gitlin, 'The impact of antenna diversity on the capacity of wireless communication systems,' IEEE Trans. Commun., vol. 42, nos. 2, 3, and 4, pp. 1740-1750, Feb./Mar./Apr. 1994 https://doi.org/10.1109/TCOMM.1994.582882
  7. M. Dell'Anna and A. H. Aghvami, 'Performance of optimum and suboptimum combining at the antenna array of a W-CDMA system,' IEEE JSAC, vol. 17, no. 12, pp.2123-2137, Dec.1999
  8. S. Tanaka, A. Harada, M. Sawahashi and F. Adachi, 'Experiments on coherent adaptive antenna array diversity for wideband DS-CDMA mobile radio,' IEEE JSAC, vol. 18, no.8, pp. 1495-1504, Aug. 2000
  9. D. Gesbert, M. Shafi, D. Shiu, P. J. Smith and A. Naguib, 'From theory to practice: an overview of MIMO space-time coded wireless systems,' IEEE JSAC, vol. 21, no. 3, pp. 281-302, April 2003
  10. W. Ryu, M. Park and S. Oh, 'Code acquisition schemes using antenna arrays for DS-SS systems and their performance in spatially correlated fading channels,' IEEE Trans. Connnun., vol. 50, no. 8, pp. 1337-1347, Aug. 2002 https://doi.org/10.1109/TCOMM.2002.801462
  11. O. Shin and K. B. Lee, 'Use of multiple antennas for DS/CDMA code acquisition,' IEEE Trans. Wireless Connnun., vol. 2, no. 3, pp. 424-430, May 2003 https://doi.org/10.1109/TWC.2003.811187
  12. S. Kim, 'Acquisition performance of CDMA systems with multiple antennas,' IEEE Trans. Veh. Tech., vol. 53, no.5, pp.1341-1353, Sept.2004 https://doi.org/10.1109/TVT.2004.832360
  13. S. Kim, 'Improved MUSIC algorithm for the code-timing estimation of DS-CDMA multipath fading channels in multiantenna systems,' IEEE Trans. Veh. Tech., vol. 53, no. 5, pp. 1354-1369, Sept. 2004 https://doi.org/10.1109/TVT.2004.832414
  14. Z. Liu, J. Li, and S. L. Miller, 'An efficient code-timing estimator for receiver diversity DS-CDMA systems,' IEEE Trans. Commun., vol. 46, no. 6, pp. 826-835, June 1998 https://doi.org/10.1109/26.681424
  15. S. Kim, 'Approximate maximum likelihood approach for code acquisition in DS-CDMA systems with multiple antennas,' IEICE Trans. Commun., vol. E88-B, no. 3, pp. 1054-1065, Mar.2005 https://doi.org/10.1093/ietcom/e88-b.3.1054
  16. J. P. Kermoal, L. Schumacher, K. I. Pedersen, P. E. Mogensen and F. Frederiksen, 'A stochastic MIMO radio channel model with experimental validation,' IEEE JSAC, vol. 20, no. 6, pp. 1211-1226, Aug. 2002
  17. K. I. Pedersen, J. B. Andersen, J. P. Kermoal and P. E. Mogensen, 'A stochastic multiple-input multiple-output radio channel model for evaluation of space-time coding algorithm,' Proc. of VTC, Boston, MA, pp. 893-897, Sept. 2000
  18. L. Schumacher, K. I. Pedersen and P. E. Mogensen, 'From antenna spacings to theoretic capacities-guidelines for simulating MIMO systems,' Proc. of PIMRC, pp. 587-592,vol. 2, Sept. 2002
  19. J. Fuhl, A. F. Molsch and E. Bonek, 'Unified channel model for mobile radio systems with smart antennas,' IEE Proc.-Radar, Sonar Navig., vol. 145, no. 1, pp. 32-41, Feb. 1998 https://doi.org/10.1049/ip-rsn:19981750
  20. A. Jakobsson, A. L. Swindlehurst and P. Stoica, 'Subspace-based estimation of time delays and Doppler shifts,' IEEE Trans. Signal Processing, vol. 46, no. 9, pp. 2472-2483, Sept. 1998 https://doi.org/10.1109/78.709535
  21. M. D. Austin and G. L. Stuber, 'Velocity adaptive handoff algorithms for microcelluar systems,' IEEE Trans. Veh. Tech., vol. 43, no. 3, pp. 549-561, Aug. 1994 https://doi.org/10.1109/25.312791
  22. T. S. Rappaport, Wireless Communications: Principles and Practice, Prentice Hall, NJ, 1996
  23. A. N. Barbosa and S. L. Miller, 'Adaptive detection of DS/CDMA signals in fading channels,' IEEE Trans. Cornmun., vol. 46, no. 1, pp. 115-124, Jan. 1998 https://doi.org/10.1109/26.655409