Performance analysis of joint equalizer and phase-locked loop in underwater acoustic communications

Seunghwan Kim; In Soo Kim; Dae-Won Do; Seokjun Ko

doi:10.7776/ASK.2022.41.2.166

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2022 Vol.41, Issue 2 Preview Page Next Page

Research Article

Performance analysis of joint equalizer and phase-locked loop in underwater acoustic communications 수중 음향통신에서 위상고정루프와 결합된 등화기의 성능분석

31 March 2022. pp. 166-173

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Abstract

In this paper, the performance of joint equalizer and phase-locked loop in underwater communications is analyzed. In the channel where the Doppler frequency exists, it is difficult to recover the transmitted data only by the equalizer. To compensate for the Doppler frequency, the phase-locked loop is used. For removing the time-varying multipath and the Doppler frequency simultaneously, the equalizer and the phase-locked loop operate jointly. Also, if the initial Doppler frequency error obtained by Fast Fourier Transform (FFT) is compensated, the convergence speed of the joint equalizer and phase-locked loop can be improved. To verify the performance, lake and sea experiments were conducted. As a result, it was showed that the joint equalizer and phase-locked loop converges sufficiently in the preamble (known data) period regardless of whether the Doppler frequency is compensated or not. And, the bit error in random data period is not occurred. However, we can increase the convergence speed of the equalizer more than twice through the compensation of Doppler frequency.

Keywords

Underwater acoustic communication

Doppler frequency

Multipath

Decision feedback equalizer

Phase locked loop

본 논문에서는 수중 음향통신에서 데이터 복구를 위한 위상고정루프와 결합된 등화기의 성능을 분석하였다. 도플러 주파수가 존재하는 채널환경에서는 등화기 동작만으로는 데이터 복구가 어렵다. 도플러 주파수를 복구하기 위해 등화기는 위상고정루프를 결합하여 사용한다. 등화기와 위상고정루프는 각각 채널의 다중경로와 도플러 주파수를 보상하면서 맞물려 동작하게 된다. 또한, 고속 푸리에 변환을 통해 얻은 초기 주파수 오차를 보상하면, 위상고정루프와 결합된 등화기의 수렴속도를 향상시킬 수 있다. 성능 검증을 위해 호수실험과 해상실험을 진행하였다. 결과적으로, 도플러 주파수의 보상 유무와 상관없이 위상고정루프와 결합된 등화기는 프리엠블 구간에서 충분히 수렴하며, 랜덤 데이터 구간에서 비트오류는 발생하지 않았다. 그러나, 도플러 주파수의 보상을 통해 등화기의 수렴 속도를 2배 이상 증가시킬 수 있었다.

키워드

수중 음향통신

도플러 주파수

다중경로

판정 궤환 등화기

위상고정루프

References

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M. Stojanovic, J. A. Catipovic, and J. G. Proakis, "Phase-coherent digital communications for underwater acoustic channels," IEEE J. Ocean. Eng. 19, 100-111 (1994). 10.1109/48.289455

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Information

Publisher :The Acoustical Society of Korea
Publisher(Ko) :한국음향학회
Journal Title :The Journal of the Acoustical Society of Korea
Journal Title(Ko) :한국음향학회지
Volume : 41
No :2
Pages :166-173
Received Date : 2022-01-17
Revised Date : 2022-02-28
Accepted Date : 2022-03-08
DOI :https://doi.org/10.7776/ASK.2022.41.2.166

The Journal of the Acoustical Society of KoreaISSN:1225-4428(Print) 2287-3775(Online)한국음향학회

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