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

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

A Parallel Equalization Algorithm with Weighted Updating by Two Error Estimation Functions

두 오차 추정 함수에 의해 가중 갱신되는 병렬 등화 알고리즘

  • Oh, Kil-Nam (Dept. of Optical Communications Engineering, Gwangju University)
  • 오길남 (광주대학교 광통신공학과)
  • Received : 2012.02.09
  • Accepted : 2012.07.17
  • Published : 2012.07.25
Download PDF
⟨ Previous Next ⟩

Abstract

In this paper, to eliminate intersymbol interference of the received signal due to multipath propagation, a parallel equalization algorithm using two error estimation functions is proposed. In the proposed algorithm, multilevel two-dimensional signals are considered as equivalent binary signals, then error signals are estimated using the sigmoid nonlinearity effective at the initial phase equalization and threshold nonlinearity with high steady-state performance. The two errors are scaled by a weight depending on the relative accuracy of the two error estimations, then two filters are updated differentially. As a result, the combined output of two filters was to be the optimum value, fast convergence at initial stage of equalization and low steady-state error level were achieved at the same time thanks to the combining effect of two operation modes smoothly. Usefulness of the proposed algorithm was verified and compared with the conventional method through computer simulations.

다중경로 전파에 의한 수신 신호의 심벌간 간섭을 제거하기 위해, 두 오차 추정 함수를 사용하는 병렬 등화(parallel equalization) 알고리즘을 제안한다. 제안 알고리즘에서는 다치레벨 이차원 신호를 등가 이진 신호로 간주하고, 등화 초기에 효과적인 시그모이드 함수와 정상상태 성능이 우수한 임계 함수를 사용하여 각각 오차를 추정한다. 이때 두 오차 추정의 상대적 정확도에 따라 두 오차를 가중 처리하여 두 필터를 서로 다르게 갱신하도록 하였다. 결과적으로 결합된 두 필터의 출력이 최적한 값이 되도록 하였으며, 두 동작 모드를 완만하게 결합하는 효과로 등화 초기의 빠른 수렴과 정상상태에서의 낮은 오차 레벨을 동시에 달성하였다. 제안 알고리즘의 유용성을 모의실험을 통해 기존 방식과 비교, 검증하였다.

Keywords

References

  1. Y. Sato, "A method for self-recovering equalization for multilevel amplitude-modulation system," IEEE Trans. Commun., vol. COM-23, pp. 679-682, June 1975.
  2. A. Benveniste and M. Goursat, "Blind equalizers," IEEE Trans. Commun., vol. COM-32, no. 8, pp. 871-883, Aug. 1984.
  3. D.N. Godard and P.E. Thirion, "Method and device for training an adaptive equalizer by means of an unknown data signal in a quadrature amplitude modulation transmission system," US Patent 4227152, Oct. 7, 1980.
  4. D.N. Godard, "Self-recovering equalization and carrier tracking in two-dimensional data communication systems," IEEE Trans. Commun., vol. COM-28, pp. 1867-1875, Nov. 1980.
  5. J.R. Treichler and B.G. Agee, "A new approach to multipath correction of constant modulus signals," IEEE Trans. Acoust., Speech, Signal Processing, vol. ASSP-31, pp. 459-472, Apr. 1983.
  6. C.A.R. Fernandes, G. Favier, and J.C.M. Mota, "Decision directed adaptive blind equalization based on the constant modulus algorithm," Signal, Image and Video Processing, vol. 1, no. 4, pp. 333-346, 2007. https://doi.org/10.1007/s11760-007-0027-2
  7. 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, Sep. 1987.
  8. V. Weerackody and S.A. Kassam, "Dual-mode type algorithms for blind equalization," IEEE Trans. Commun., vol. COM-42, pp. 22-28, Jan. 1994.
  9. F.C.C. De Castro, M.C.F. De Castro, and D.S. Arantes, "Concurrent blind deconvolution for channel equalization," Proc. IEEE ICC, vol. 2, pp. 366-371, Helsinki, June 2001.
  10. K. Banovic, E. Abdel-Raheem, and M.A.S. Khalid, "A novel radius-adjusted approach for blind adaptive equalization," IEEE Signal Processing Letters, vol. 13, no. 1, pp. 37-40, Jan. 2006. https://doi.org/10.1109/LSP.2005.860544
  11. S. Haykin, Adaptive filter theory, 4th Ed., Prentice Hall, New Jersey, 2002.
  12. J. Karaoguz and S.H. Ardalan, "A soft decision-directed blind equalization algorithm applied to equalization of mobile communication channels," Proc. IEEE ICC, vol. 3, pp. 343.4.1-343.4.5, Chicago, 1992.
  13. O. Shalvi and E. Weinstein, "New criteria for blind deconvolution of nonminimum phase systems (channels)," IEEE Trans. Inform. Theory, vol. IT-36, no. 2, pp. 312-321, Mar. 1990.