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Performance Comparison of Acoustic Equalizers using Adaptive Algorithms in Shallow Water Condition

천해환경에서 적응 알고리즘을 이용한 음향 등화기의 성능 비교

  • Chuai, Ming (Dept. of Information and Communications Engineering, Pukyong National University) ;
  • Park, Kyu-Chil (Dept. of Information and Communications Engineering, Pukyong National University)
  • Received : 2018.01.19
  • Accepted : 2018.01.29
  • Published : 2018.02.28

Abstract

The acoustic communication channel in shallow underwater is typically shown as time-varying multipath fading channel characteristics. The received signal through channel transmission cause inter-symbol interference (ISI) owing to multiple components of different time delay and amplitude. To compensate for this, several techniques have been used, and one of them is acoustic equalizer. In this study, we used four equalizers - feed forward equalizer (FFE), decision directed equalizer (DDE), decision feedback equalizer (DFE) and combination DDE with DFE to compensate ISI. And we applied two adaptive algorithms to adjust coefficient of equalizers - normalized least mean square algorithm and recursive least square algorithm. As result, we found that it has a significant performance improvement over 6 dB on SNR in nonlinear equalizer. By combination of DFE and DDE has almost best performance in any case.

천해 환경에서의 수중 음향 통신 채널은 전형적으로 시변 다중 경로 페이딩 채널 특성을 나타낸다. 이러한 채널 전송을 통해 수신된 신호는 시간 지연 및 진폭의 중첩에 의해 심볼 간 간섭을 유발한다. 이를 보완하기 위해 여러 기술이 사용되었으며, 그 중 하나가 음향 등화기이다. 본 연구에서는 심볼 간 간섭을 보상하기 위해 feed-forward equalizer (FFE), decision direct equalizer (DDE), decision feedback equalizer (DFE) 및 DFE와 결합된 DDE의 4 종류의 등화기와 등화기의 계수를 조정하기 위해 normalized least mean square (NLMS) 알고리즘과 recursive least square (RLS) 알고리즘의 2 종류의 알고리즘을 적용하였다. 그 결과 비선형 등화기에서는 신호 대 잡음비 6 dB 이상에서 상당한 성능 향상을 발견할 수 있었으며, DFE와 DDE의 조합은 어떤 경우에도 최고의 성능을 발휘하였다.

Keywords

References

  1. T. C. Yang, "Properties of underwater acoustic communication channels in shallow water," Journal of the Acoustical Society of America, vol. 131, no. 1, pp. 129-145, Jan. 2012. https://doi.org/10.1121/1.3664053
  2. Y. H. Yoon and A. Zielinski, "Simulation of the equalizer for shallow water acoustic communication," in Proceeding of OCEANS 1995, San Diego, CA, pp. 1197-1203, Oct. 1995.
  3. W.-B. Yang and T. C. Yang, "High-frequency channel characterization for M-ary frequency-shift-keying underwater acoustic communications," Journal of the Acoustical Society of America, vol. 120, no. 5, pp. 2615-2626, Nov. 2006. https://doi.org/10.1121/1.2346133
  4. K.-C. Park and J. R. Yoon, "Performance Evaluation of the Complex-Coefficient Adaptive Equalizer Using the Hilbert Transform," Journal of information and communication convergence engineering, vol. 14, pp. 78-83, Jun. 2016. https://doi.org/10.6109/jicce.2016.14.2.078
  5. J. R. Yoon, K.-C. Park, and J. Park, "Performance comparison between packet and continuous data transmission using two adaptive equalizers in shallow water," Japanese Journal of Applied Physics, vol. 54, article ID: 07HG05, May, 2015.
  6. H.-J. Kim, T.-G. Gwun, Y.-I. Joo, and D.-H. Seo, "A study on implementation of background subtraction algorithm using LMS algorithm and performance comparative analysis," Journal of the Korean Society of Marine Engineering, vol. 39, pp. 94-98, Jan. 2015. https://doi.org/10.5916/jkosme.2015.39.1.94
  7. E. Camelia, P. Constantin, A. D. Robert, C. Silviu, and B. Jacob , "An RLS algorithm for the identification of bilinear forms," 2017 IEEE 23rd International Symposium for Design and Technology in Electronic Packaging (SIITME), pp. 292-295, Oct. 2017.
  8. J.-H. Son and K.-M. Kim,"Tap-length Optimization of Decision Feedback Equalizer Using Genetic Algorithm," Journal of the Korea Institute of Information and Communication Engineering, vol. 19, pp. 1765-1772, Aug. 2015. https://doi.org/10.6109/jkiice.2015.19.8.1765
  9. T.-H. Kim and J.-W. Jung, "Optimum Turbo Equalization Method based on Layered Space Time Codes in Underwater Communications," Journal of the Korea Institute of Information and Communication Engineering, vol. 18, pp. 1042-1050, May, 2014. https://doi.org/10.6109/jkiice.2014.18.5.1042
  10. L. Rugini, P. Banelli, and G. Leus, "Simple equalization of time-varying channels for OFDM," IEEE Journal of Commun. Lett. Vol. 9, pp. 619-621, July, 2005. https://doi.org/10.1109/LCOMM.2005.1461683
  11. J.-S. Lim and Y.-G. Pyeon, "Low Complexity Gauss Newton Variable Forgetting Factor RLS for Time Varying System Estimation," Journal of Korea Information and Communications Society, vol. 41, pp. 1141-1145, Sep. 2016. https://doi.org/10.7840/kics.2016.41.9.1141
  12. K, Kim, S. Oh, K. Yun, D.-H. Choi, "Travel Distance Estimation Method based on TSSI(Transmitted Signal Strength Indication) in Wireless Communication using LED," Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology, vol. 7, pp. 895-902, May, 2017.
  13. Y.-H. Song, H.-W. Park, and M.-J. Bae, "A Study on SNR Estimation of Continuous Speech Signal," The Journal of the Acoustical Society of Korea, vol. 28, pp. 1-9, Apr. 2009.
  14. S.-A. Kim and H.-G. Ryu, "Adaptive Modulation System Using SNR Estimation Method Based on Correlation of Decision Feedback Signal," The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 22, pp. 282-291, Mar. 2011. https://doi.org/10.5515/KJKIEES.2011.22.3.282
  15. C.-W. Seo, G.-S. Yoon, S. Portugal, and I.-T. Hwang, "New SNR Estimation Algorithm using Preamble and Performance Analysis," Journal of the Institute of Electronics and Information Engineers, vol. 48, pp. 6-12, Mar. 2011.
  16. K.-N. Seo, S.-W. Choi, and C.-H. Kim, "A SNR Estimation Algorithm for Digital Satellite Transponder," The Journal of Korean Institute of Communications and Information Sciences, vol. 35, pp. 729-734, Sep. 2010.
  17. H.-W. Park and M.-J. Bae, "IMBE Model Based SNR Estimation of Continuous Speech Signals," The Journal of the Acoustical Society of Korea, vol. 29, pp. 148-153, Feb. 2010.
  18. H. Kim, J. Seo, J. Kim, S. Kim, and J. Chung, "Equalizer Mode Selection Method for Improving Bit Error Performance of Underwater Acoustic Communication Systems," The Journal of the Acoustical Society of Korea, vol. 31, pp. 1-10, Jan. 2012. https://doi.org/10.7776/ASK.2012.31.1.001