The Journal of Korean Institute of Communications and Information Sciences (한국통신학회논문지)

The Korean Institute of Commucations and Information Sciences (한국통신학회)
권호 표지

Residual ISI cancellation and EM-based channel estimation for STBC/SFBC OFDM with insufficient cyclic prefix

불충분한 주기적 프리픽스를 갖는 STBC/SFBC OFDM 시스템을 위한 잔재 ISI 제거 기법 및 EM 기반 채널 추정 기법

  • 원희철 (대구대학교 정보통신대학 컴퓨터.IT공학부)
  • Published : 2007.11.30
Download PDF
⟨ Previous Next ⟩

Abstract

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response. In order to prevent a loss of bandwidth efficiency due to the use of a CP, residual intersymbol interference cancellation (RISIC) method has recently been developed. In this paper, we first apply the RISIC algorithm to the space-time block coded (STBC) OFDM and the space-frequency block coded (SFBC) OFDM with insufficient CP. It is shown that in the STBC OFDM, tail cancellation as well as cyclic restoration of the RISIC should be repeated. Second, we propose iterative channel estimation method for the RISIC in the STBC OFDM system with insufficient CP. Based on the expectation-maximization (EM) algorithm, the proposed estimation method exploits the extrinsic probabilities of the channel decoder iteratively. The performance of the proposed method is evaluated by computer simulation in a multipath fading environment.

OFDM 시스템은 채널 충격 응답보다 긴 길이의 주기적 프리픽스를 사용해야 하므로 주파수 효율이 감소된다. 주기적 프리픽스 사용에 따른 주파수 효율 감소를 막기 위하여 잔재 ISI 제거 기법이 최근에 개발되었다. 본 논문에서는 잔재 ISI 제거 기법을 불충분한 주기적 프리픽스를 갖는 시공간 블록 부호 (STBC) OFDM과 주파수 공간 블록 부호 (SFBC) OFDM 시스템에 적용한다. SFBC OFDM과 달리, STBC OFDM에서는 잔재 ISI 제거 기법의 주기성 복원 과정 뿐만 아니라 꼬리 제거 과정도 반복되어야 함을 확인할 수 있다. 또한, 불충분한 주기적 프리픽스를 사용하는 STBC OFDM 시스템에서의 잔재 ISI 제거 기법을 위한 채널 추정 방법을 제안한다. 제안된 채널 추정 방법은 EM 알고리즘을 이용한 반복적 추정을 특징으로 하고, 잔재 ISI가 제거된 신호를 통해 얻어지는 채널 디코더의 외부 확률 값을 활용한다. 제안된 방법의 성능은 다중 경로 페이딩 환경에서 컴퓨터 시뮬레이션을 통해 확인한다.

Keywords

References

  1. J. A. C. Bingham, 'Multicarrier modulation for data transmission: An idea whose time has come,' IEEE Commun. Mag., vol. 28, pp. 5-14, May 1990 https://doi.org/10.1109/35.54342
  2. ETSI ETS 300 401,, 'Radio broadcasting systems: digital audio broadcasting (DAB) to mobile, portable and fixed receivers,' ETSI, Tech. Rep., Feb. 1995
  3. ETSI ETS 300 744,, 'Digital video broadcasting (DVB); frame structure, channel coding and modulation for digital terrestrial television (DVB-T),' ETSI, Tech. Rep., March 1997
  4. R. V. Nee, G. Awater, M. Morikura, H. Takanashi, M. Webster, and K. W. Halford,, 'New high-rate wireless LAN standards,' IEEE Commun. Mag., vol. 37, pp. 82-88, Dec. 1999
  5. IEEE Std 802.16e-2005,, 'IEEE Standard for Local and metropolitan area networks - Part 16 : Air interface for Fixed and Mobile broadband wireless access systems,' Feb. 2006
  6. A. Ghosh, D. Wolter, J. Andrews, and R. Chen,, 'Broadband Wireless Access with WiMax/802.16: Current Performance Benchmarks and Future Potential,' IEEE Commun. Mag., vol. 43, no. 2, pp. 129-136, Feb. 2005
  7. T. Kwon, H. Lee, S. Choi, J. Kim, D. Cho, S. Cho, S. Yun, W. Park, and K. Kim,, 'Design and Implementation of a Simulator based on a Cross-Layer Protocol between MAC and PHY Layers in a WiBro Compatible IEEE 802.16e OFDMA System,' IEEE Commun. Mag., vol.43, no. 12, pp. 136-146, Dec. 2005
  8. D. Kim and G. L. Stuber,, 'Residual ISI cancellation for OFDM with application to HDTV broadcasting,' IEEE J. Select. Areas Commun., vol. 16, no. 8, pp. 1590-1599, Oct. 1998 https://doi.org/10.1109/49.730464
  9. C. J. Park and G. H. Im,, 'Efficient cyclic prefix reconstruction for coded OFDM systems,' IEEE Commun. Letters, vol. 8, no. 5, pp. 274-276, May 2004 https://doi.org/10.1109/LCOMM.2004.827439
  10. S. Alamouti,, 'A simple transmit diversity technique for wireless communications,' IEEE J. Select. Areas Commun., vol. 16, no. 8, pp. 1451-1458, Oct. 1998 https://doi.org/10.1109/49.730453
  11. V. Tarokh, H. Jafarkhani, and A. Calderbank,, 'Space-time block codes from orthogonal designs,' IEEE Trans. on Information Theory, vol. 45, no. 5, pp. 1456-1467, July 1999 https://doi.org/10.1109/18.771146
  12. J. Beek, O. Edfors, and M. Sandell,, 'On channel estimation in OFDM systems,' 45th IEEE Vehicular Technology Conference (VTC), pp. 815-819, July 1995
  13. Y. Li,, 'Simplified channel estimation for OFDM systems with multiple transmit antennas,' IEEE Trans. Wireless Commun., vol. 1, no. 1, pp. 67-75, Jan. 2002 https://doi.org/10.1109/7693.975446
  14. G. Al-Rawi, T. Al-Naffouri, A. Bahai, and J. Cioffi,, 'Exploiting error-control coding and cyclic-prefix in channel estimation for coded OFDM systems,' IEEE Commun. Letters, vol. 7, no. 7, pp. 388-390, July 2003 https://doi.org/10.1109/LCOMM.2003.814712
  15. T. K. Moon,, 'The expectation -maximization algorithm,' IEEE Signal Processing Mag., no. 1, pp. 47-60, Nov. 1996
  16. P. Robertson, E. Villebrun, and P. Hoeher,, 'A comparison of optimal and sub-optimal MAP decoding algorithms operating in the log domain,' IEEE International Conference of Communications, vol. 2, pp. 1009-1013, June 1995
  17. A. Oppenheim and R. Schafer, Discrete-time Signal Processing, Prentice-Hall, 1989
  18. COST 207 TD(86)51-REV 3 (WG1), 'Proposal on channel transfer function to be used in GSM tests late 1986,' Sept. 1986