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

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

DOI QR Code

A New Decision-Directed Equalization with Improved Blind Convergence Properties by Error Scaling

오차 스케일링에 의해 블라인드 수렴 특성을 개선한 새로운 판정의거 등화

  • Oh, Kil Nam (Dept. of Optical Commun. Eng., Gwangju Univ.)
  • Received : 2015.01.12
  • Accepted : 2015.03.11
  • Published : 2015.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

The Decision-directed (DD) algorithm is known to be not effective to initialize a blind equalizer in the channel conditions when the eye diagram of received signals is completely closed because it can not open the eye diagram enough. In this paper, we propose a new error to replace the error of the conventional DD algorithm. The new DD error is the conventional DD error scaled by the modulus of symbol decision, new DD algorithm using this error is effective to open the closed eye diagram in early stage of equalization unlike the conventional DD. The new DD algorithm appling the new error is showed excellent convergence characteristics as compared to the CMA widely used in blind initialization, particularly, is useful for equalization of signals having multimodulus. The performance of the new DD algorithm is verified through the simulation for the higher-order QAM signals.

판정의거(decision-directed: DD) 등화는 수신 신호의 눈모형이 완전히 닫힌 채널 조건에서는 눈모형을 충분히 열지 못하여 블라인드 등화기를 초기화하는 데는 효과적이지 않은 것으로 알려져 있다. 본 논문에서는 기존 DD 알고리즘의 오차를 대체하는 새로운 오차를 제안한다. 새로운 DD 오차는 신호점 판정의 모듈러스를 기존 DD 오차에 스케일링한 것으로, 이를 적용한 새로운 DD 알고리즘은 기존 DD와는 달리 등화 초기의 닫힌 눈모형을 여는데 효과적이다. 새로운 오차를 적용한 DD 알고리즘은 블라인드 초기화에 널리 쓰이는 CMA에 비해 우수한 수렴 특성을 보이며, 특히 다중 모듈러스를 가지는 신호 등화에 유용하다. 고차 QAM 신호에 대한 모의실험을 통해 새로운 DD 알고리즘의 성능을 검증하였다.

Keywords

References

  1. A. W. Azim, S. Abrar, A. Zerguine, and A. K. Nandi, "Steady-state performance of multimodulus blind equalizers," Signal Processing, vol. 108, pp. 509-520, Mar. 2015. https://doi.org/10.1016/j.sigpro.2014.10.020
  2. M.T.M. Silva and J. Arenas-Garcia, "A soft-switching blind equalization scheme via convex combination of adaptive filters," IEEE Trans. Signal Processing, vol. 61, no. 5, pp. 1171-1182, Mar. 2013. https://doi.org/10.1109/TSP.2012.2236835
  3. K. Banovic, E. Abdel-Raheem, and M. A. S. Khalid, "Hybrid methods for blind adaptive equalization: new results and comparisons," in Proc. ISCC, pp. 275-280, Jun. 2005.
  4. J. Arenas-Garcia and A. R. Figueiras-Vidal, "Improved blind equalization via adaptive combination of constant modulus algorithms," in Proc. IEEE ICASSP, vol. 3, May 2006.
  5. S. Chen and E. S. Chng, "Concurrent constant modulus algorithm and soft decision directed scheme for fractionally-spaced blind equalization," in Proc. IEEE ICC, vol. 4, pp. 2342-2346, Paris, France, Jun. 2004.
  6. O. Macchi and E. Eweda, "Convergence analysis of self-adaptive equalizers," IEEE Trans. Inform. Theory, vol. IT-30, pp. 161-176, Mar. 1984.
  7. S. Haykin, Unsupervised adaptive filtering volume 2: Blind deconvolution, John Wiley & Sons, New York, 2000.
  8. G. Picchi and G. Prati, "Blind equalization and carrier recovery using a "Stop-and-Go" decision-directed algorithm," IEEE Trans. Commun., vol. COM-43, pp. 877-887, Sept. 1987.