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

The Institute of Electronics and Information Engineers (대한전자공학회)
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Decision-directed Channel Estimation for QAM-modulated OFDM Systems

QAM 변조방식의 OFDM 시스템을 위한 결정지향 채널추정 방법

  • Rim, Min-Joong (Department of Information and Communication Engineering, Dongguk University) ;
  • Ahn, Jae-Min (School of Electrical and Computer Engineering, Chungnam National University) ;
  • Kim, Yeon-Soo (Service Development Lab., Korea Telecom)
  • 임민중 (東國大學校 情報通信工學科) ;
  • 안재민 (忠南大學校 情報通信工學部) ;
  • 김연수 (韓國通信 서비스開發硏究所)
  • Published : 2002.11.01
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Abstract

When decision-directed channel estimation is used for QAM-OFDM systems, the optimal shape of the two-dimensional filter depends on the amplitudes of the modulated symbols as well as the channel characteristics such as delay spread, Doppler frequency, and signal-to-noise ratio. While most conventional channel estimation methods did not consider the amplitudes of the modulated symbols because of the large computational complexity, we propose a simple channel estimation method for multi-level-amplitude-modulated systems. The proposed method can effectively reduce the noise variance of the estimates with small-sized filtering and there is a possibility of reducing the implementation cost and producing better results by avoiding the bias due to large filter sizes.

QAM-OFDM 시스템에서 결정지향 채널추정을 위해 사용하는 2차원 필터의 최적의 크기와 모양은 도플러 주파수, 신호의 지연확산, 신호 대 잡음비 등 채널의 특성과 함께 송신 심벌의 크기에 의해서 결정된다. 기존의 채널 추정방법들은 QAM 변조 방식에서의 송신 심벌의 크기의 다양성을 고려하지 않고 채널 특성만을 고려한 고정된 형태의 필터를 취하는 데 반해서 이 논문에서는 단순하면서도 송신 심벌의 크기의 다양성을 고려한 필터를 제안한다. 제안된 채널추정방법은 작은 크기의 필터로 예측잡음을 효과적으로 줄일 수 있으므로 구현 복잡도를 줄일 수 있는 가능성을 가질 뿐만 아니라 채널의 변화에 의한 성능 감소 효과도 적어 더 우수한 성능을 나타낼 수 있다.

Keywords

References

  1. Z. Wang, G. B. Giannakis, 'Wireless Multicarrier Communications,' IEEE Signal Processing Magazine, May 2000 https://doi.org/10.1109/79.841722
  2. Y. Li, N. R. Sollenberger, 'Adaptive Antenna Arrays for OFDM Systems with Cochannel Interference,' IEEE Trans. On Communication, pp. 217-229, February 1999 https://doi.org/10.1109/26.752127
  3. J-J. van de Beek, O. Edfors, M. Sandell, S. K. Wilson, and P. O. Borjesson, 'On channel estimation in OFDM systems,' in Proc. IEEE Vehicular Technology Conf., pp. 815-819, July 1995 https://doi.org/10.1109/VETEC.1995.504981
  4. O. Edfors, M. Sandel, J-J. van de Beek, S. K. Wildon, and P. O. Borjesson, 'OFDM Channel Estimation by Singular Value Decomposition,' IEEE Trans. On Communication, pp. 931-939, July 1998 https://doi.org/10.1109/26.701321
  5. Y. Li, L. J. Cimini, N. R. Sollenberger, 'Robust Channel Estimation for OFDM Systems with Rapid Dispersive Fading Channels,' IEEE Trans. On Communication, pp. 902-915, July 1998 https://doi.org/10.1109/26.701317
  6. Y. LI, N. Seshadri, S. Ariyavisitakul, 'Channel Estimation for OFDM Systems with Transmitter Diversity in Mobile Wireless Channels,' IEEE Journal on Selected Areas in Communication, pp. 461-471, March 1999 https://doi.org/10.1109/49.753731
  7. Y. Li, 'Pilot-Symbol-Aided Channel Estimation for OFDM in Wireless Systems,' IEEE Trans. On Vehicular Technology, pp. 1207-1215, July 2000 https://doi.org/10.1109/25.875230
  8. J. Rinne and M. Renfors, 'Pilot Spacing in Orthogonal Frequency Division Multiplexing Systems on Practical Channels,' IEEE Trans. On Consumer Electronics, November 1996 https://doi.org/10.1109/30.555792
  9. R. Nilsson, O. Edfors, M. Sandell, P. O. Borjesson, 'An Analysis of Two-Dimensional Pilot-Symbol Assisted Modulation for OFDM,' ICPWC, 1997 https://doi.org/10.1109/ICPWC.1997.655481
  10. P. K. Frenger, N. A. B. Svensson, 'Decision-Directed Coherent Detection in Multicarrier Systems on Rayleigh Fading Channels,' IEEE Trans. On Vehicular Technology, pp. 490-498, March 1999 https://doi.org/10.1109/25.752573
  11. A. Chini, Y. Wu, M. El-Tanany, and S. Mahmoud, 'Filtered Decision Feedback Channel Estimation for OFDM-based Terrestrial Broadcasting System,' IEEE Trans. On Broadcasting, pp. 2-11, March 1998 https://doi.org/10.1109/11.713051
  12. L. L. Scharf, Statistical Signal Processing, Addison-Wisely, 1991
  13. G. Li, Y. Jin, 'A Speed Estimation Based Two-Stage Symbol Aided Channel Estimator for Frequency Nonselective Variant Fading Channel,' Personal Wireless Communications, pp. 109-113, 2000 https://doi.org/10.1109/ICPWC.2000.905783
  14. H.J. Oh, J.M. Cioffi, 'An Adaptive Channel Estimation Scheme for DS-CDMA Systems,' VTC, pp. 2839-2843, 2000 https://doi.org/10.1109/VETECF.2000.886837
  15. 이영용, 배광석, 안재민, 임민중, 최형진, '속도 추정기를 갖는 WCDMA 역방향 링크 수신기를 위한 비대칭 직접 판별 채널 추정기,' pp. 391-394, JCCI, 2001