Performance analysis of underwater experiments results for turbo equalized frequency phase shift keying signals based on soft decision demodulation

Ye-Gwon Hong; Ji-Won Jung

doi:10.7776/ASK.2026.45.4.418

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2026 Vol.45, Issue 4 Preview Page Next Page

Performance analysis of underwater experiments results for turbo equalized frequency phase shift keying signals based on soft decision demodulation 연판정 복조 기반 터보 등화된 주파수 위상 변조 신호의 수중 실험 성능 결과 분석

31 July 2026. pp. 418-425

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Abstract

In underwater acoustic communications, the M-ary Frequency/N-ary Phase Shift Keying (MF/NPSK) modulation scheme, which combines M-ary Frequency Shift Keying (MFSK) and N-ary Phase Shift Keying (NPSK) modulations, improves performance and data transmission rates through an appropriate ratio of M and N. In MF/NPSK, Conventional MFSK signal demodulator employ hard decision method which selects the symbol with the highest energy among the M frequencies. However, to improve performance through the internal and external iterations of a turbo decoder, turbo coded MF/NPSK symbols must be inputted as soft decision symbols after demodulation. Therefore, this paper proposes a structure that improves performance through iterative equalization and decoding by enabling soft decision output for the Frequency Shift Keying (FSK) allocated symbols among the demodulated MF/NPSK symbols. To compare and analyze the performance of the conventional demodulation method and the proposed method, simulations and underwater experiments were conducted using a fixed 4FSK/2PSK modulation scheme, and the proposed demodulation method demonstrated superior performance compared to the conventional method.

Keywords

Underwater wireless acoustic communications

Frequency Phase Shift Keying (FPSK)

Turbo equalizer

Linear mean square decision feedback equalizer

Iterative equalization and decoding

수중 음향 통신에서 M-ary frequency shift keying(MFSK) 변조와 N-ary Phase Shift Keying(NPSK) 변조를 결합한 M-ary Frequency/N-ary Phase Shift Keying(MF/NPSK) 변조 방식은 M과 N의 적절한 비율을 통하여 성능 및 전송률을 향상시키는 방식이다. MF/NPSK에서 MFSK 신호의 기존 복조 방식은 M개 주파수 대역 중 에너지가 가장 큰 대역을 강판정으로 복조한다. 그러나 터보 부호화된 MF/NPSK 심볼은 복조 후 연판정된 심볼을 입력해야만 터보 복호기의 내부 반복 및 외부 반복을 통해서 성능을 향상시킬 수 있다. 따라서 본 논문에서는 MF/NPSK 복조 심볼 중 Frequency Shift Keying(FSK) 할당 심볼을 연판정 출력이 가능하게 하여 등화기와 복호기의 반복을 통하여 성능을 향상시키는 연판정 복조 기반의 터보 등화 구조를 제안한다. 기존 복조 방식과 제안한 방식의 성능 비교 분석하기 위해 4FSK/2PSK 변조 방식을 고정하여 시뮬레이션 및 수중 실험을 수행하였으며, 제안한 복조 방식이 기존 방식에 비해 우수한 성능을 보였다.

키워드

수중 음향 통신

주파수 위상변조(Frequency Phase Shift Keying, FPSK)

터보 등화기

선형 최소 제곱 결정 피드백 등화기

반복 등화 및 복호

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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 : 45
No :4
Pages :418-425
Received Date : 2026-06-05
Revised Date : 2026-07-08
Accepted Date : 2026-07-08
DOI :https://doi.org/10.7776/ASK.2026.45.4.418

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

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