Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
권호 표지
DOI QR코드

DOI QR Code

A Study on The Correction of The Channel Equalizer Decision Error Using Channel Estimator

채널추정기를 이용한 등화기 결정오류 정정 알고리즘에 관한 연구

  • 김선웅 (한국폴리텍대학교 남인천캠퍼스 스마트전자과)
  • Received : 2017.07.03
  • Accepted : 2017.08.17
  • Published : 2017.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

The process of transmitting messages through a medium with a limited bandwidth or channel dispersion inevitably involves signal distortion and noise influxes, resulting in the degradation of transmission quality due to the inter-symbol interference and additional noise, which increases the error rate of the received symbols. The main role of the equalizer is to remove the channel distortion and noise from the received signal to recover the transmitted messages. A number of studies on the equalizer composed of a combination of linear filter and error control coding have shown that they played a key role in enhancing the transmission efficiency, which is essential for digital communication. This paper proposes a new algorithm to correct the residual symbol errors in the message signal. In general, equalizer performance improvement algorithms were developed to improve the initial convergence speed or steady-state error. In this paper, however, the equalizer input signal was reconstructed using the equalizer decision symbols and the channel estimates to directly correct the decision errors by analyzing the statistical characteristics of the difference signal between the actual received signal and the reconstructed signal.

대역이 제한되거나 채널분산이 존재하는 매체를 통해 메시지를 전송하는 과정은 불가피하게 신호왜곡과 잡음유입을 수반하며 결과적으로 심볼간 간섭과 부가잡음에 의해 전송품질이 열화 되어 수신심볼 오율을 증가시키게 된다. 적응 등화기의 역할은 전송 메시지를 복원하기 위해 등화기 수신단에 입력되는 수신신호로부터 채널왜곡 성분과 잡음을 제거하는 일이다. 이를 위해 일반적으로 선형필터부와 심볼 결정기의 조합으로 구성되는 등화기에 관한 연구가 많이 이루어져 왔고 전방향 오류정정부호화과 결합하여 디지털 정보통신 분야에 필수적인 전송효율 제고에 핵심적인 역할을 하고 있다. 본 논문에서는 등화기 출력인 메시지 심볼에 잔존하는 심볼오류를 추가적으로 정정할 새로운 알고리즘을 제안하였는데 일반적으로 등화기 성능개선 알고리즘들이 등화 초기 수렴속도나 정상상태오차를 개선하는 방향으로 진행되어 오고 있는 반면, 본 논문에서는 등화기 결정심볼과 전송채널 추정값을 이용하여 등화기 입력신호를 재구성하고 실제 입력신호와의 오차신호를 구한 후 이에 대한 통계적 특성을 분석해 직접적으로 오류정정을 수행하는 새로운 알고리즘을 제안하였다.

Keywords

References

  1. Godard, D. N., "Self-recovering equalization and carrier tracking in two-dimensional data communication systems," IEEE Trans. on Communications, vol. 28, no. 11, pp. 1867-1875, 1980. DOI: https://doi.org/10.1109/TCOM.1980.1094608
  2. B. Jellonek, D. Boss, K. D. Kammeyer, "Generalized eigen vector algorithm for blind equalization" EURASIP Signal Processing, pp. 237-264, 1997.
  3. O Shalvi, E Weinstein, "New criteria for blind deconvolution of nonminimum phase systems (channels)," IEEE Transactions Information Theory, vol. 36, no. 2, pp. 312-321, 1990. DOI: https://doi.org/10.1109/18.52478
  4. Nandi, A.K., Anfinsen, S. N., "Blind equalization with recursive filter structures," Elsevier, signal Processing, vol. 80, no.10, pp. 2151-2167, 2000. https://doi.org/10.1016/S0165-1684(00)00074-8
  5. L. Tong, D. Liu, "Blind predictive decision-feedback equalization via the constant modulus algorithm" Proceedings of the ICASSP'97, Munich, Germany, pp. 3901-3904, Apr. 1997. DOI: https://doi.org/10.1109/ICASSP.1997.604755
  6. K. Itoh, T. Shimamura, H. Yashima, J. Suzuki, "IIR Adaptive Equalizer Using Channel Estimator," Proc. Singapore Int. Conf. Communication Systems/Int. Symp. Information Theory and Its Applications, pp. 755-759, 1992. DOI: https://doi.org/10.1109/ICCS.1992.255162
  7. Mi-Kyung Oh, Yeong-Hyeon Kwon, Dong-Jo Park, " Novel Blind Adaptive Equalization over Doubly-Selective Fading Channels," IEICE Transactions vol. 89-B, no. 12, pp. 3463-3466, 2006. DOI: https://doi.org/10.1093/ietcom/e89-b.12.3463
  8. Ibrahim Shaahin Varnosfaderani, Mohamad Faarzan Sabahi, Mohammad Ataei, "Joint blind equalization and detection in chaotic communication systems using simulation-based methods," AEU-International Journal of Electronics and Communications, Vol. 69, Issue 10, pp. 1445-1452, 2015. DOI: https://doi.org/10.1016/j.aeue.2015.06.013
  9. Zhili Zhou, Yiji Zahn, Xiukai Ruan, Qibo Cai, Guihua Cui, Guijun Zhu,"A double-DD blind equalizer for Polmux QAM optical coherent systems," Optic Communications, vol. 382, pp. 342-347, 2017. https://doi.org/10.1016/j.optcom.2016.08.005
  10. Ali W. Azim, Shafayat Abrar, Azzedine Zerguine, Asoke K. Nandi, "Performance analysis of a family of adaptive blind equalization algorithms for square-QAM," Digital Signal Processing Vol. 48, pp.163-177, 2016. DOI: https://doi.org/10.1016/j.dsp.2015.09.002
  11. Rajan Narasimha, Nirmal Warke, Naresh R. Shanbhag," Impact of DFE Error Propagation on FEC-Based High-Speed I/O Links," GLOBECOM 2009.
  12. J. Ashley, B. M. M. Blaum, and C. Melas, "Performance and error propagation of two DFE channels," IEEE Transactions on Magnetics, vol. 33, no. 5, pp. 2773-2775, 1997. DOI: https://doi.org/10.1109/20.617726
  13. S.A. Sheikh and P. Fan, "Improved square contour algorithm for blind equalization of QAM signals," in Proc. INMIC, December 2006, pp. 116-119, 2006. DOI: https://doi.org/10.1109/INMIC.2006.358147
  14. X. Li and T. F. Wong, "Turbo equalization with nonlinear Kalman filtering for time-varying frequency-selective fading channels," IEEE Transactions on Wireless Communications, vol. 6, pp. 691-700, 2007. DOI: https://doi.org/10.1109/TWC.2007.05352
  15. M. Kumar, K. Yurtseven and A. Rahrooh, "Design and performance analysis of an adaptive FIR Kalman equalizer," Journal of Ihe Franklm lnstitute, vol. 330, pp. 929-938, 1993.