scholarly journals Experimental Results of Underwater Acoustic Communication with Nonlinear Frequency Modulation Waveform

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7194
Author(s):  
Jeongha An ◽  
Hyungin Ra ◽  
Changhyun Youn ◽  
Kiman Kim
Keyword(s):  
Conventional Method ◽  
Frequency Modulation ◽  
Spread Spectrum ◽  
Multipath Channels ◽  
Underwater Acoustic Communication ◽  
Nonlinear Frequency ◽  
Underwater Acoustic ◽  
Sea Trial ◽  
Chirp Spread Spectrum ◽  
Average Bit Error Rate

In this paper, we propose underwater acoustic (UWA) communications using a generalized sinusoidal frequency modulation (GSFM) waveform, which has a distinct ambiguity function (AF) and correlation function characteristic. For these reasons, it is more robust in multipath channels than the conventional chirp spread spectrum (CSS) with a linear frequency modulation (LFM) waveform. Four types of GSFM waveforms that are orthogonal to each other are applied for each symbol in the proposed method. To evaluate the performance of the proposed method, we compared the performances of the proposed method and conventional method by conducting diverse experiments: simulations, lake trials and sea trials. In the simulation results, the proposed method shows better performance than the conventional method. The lake trial was conducted with a distance of 300~400 m between the transmitter and receiver. As a result of the experiment, the average bit error rate (BER) of the proposed method is 3.52×10−2 and that of the conventional method is 3.52×10−1, which shows that the proposed method is superior to the conventional method. The sea trial was conducted at a distance of approximately 20 km between the transmitter and receiver at a depth of 1500 m, and the receiver was composed of 16 vertical line arrays (VLAs) with a hydrophone. The proposed method had a BER of 0.3×10−2 in one channel and was error free in the other.

Underwater acoustic communication using nonlinear frequency modulation waveform with low side-lobe characteristics

2021 ◽  
Vol 263 (6) ◽  
pp. 689-697
Author(s):  
Jeongha An ◽  
Hyoungin Ra ◽  
Changhyun Youn ◽  
Kiman Kim
Keyword(s):  
Frequency Modulation ◽  
Spread Spectrum ◽  
Channel Model ◽  
Average Power ◽  
Side Lobe ◽  
Effective Bandwidth ◽  
Underwater Acoustic Communication ◽  
Nonlinear Frequency ◽  
Underwater Acoustic ◽  
Time Frequency

In fluctuating underwater acoustic (UWA) communication, reducing the interference caused by multi-path propagation is important to get better performance. For this reason, Chirp Spread Spectrum (CSS), which has insensitive Doppler effect and having effective bandwidth, using Linear Frequency Modulation (LFM) waveform was used in UWA communication before. But LFM waveform has high auto-correlation function sidelobes it becomes interference and gets worse performance in reverberation environment. This presentation proposes an UWA communication using Generalized Sinusoidal Frequency Modulation (GSFM) waveform which is generalized form of sinusoidal FM. GSFM waveform usually attains much higher spectral efficiency and lower peak-to-average power ratio than LFM while maintaining same bandwidth and pulse duration. GSFM waveform has various types and we use two GSFM pulses that is a Forward type in time-frequency domain and a time reversing type of Forward type in this presentation. Each type represents binary values '0' and '1', respectively. Each of pulses occupy same band of frequency and each of GSFM pulses have nearly orthogonality. Simulation results in various underwater channel environments with noise will be presented. A Bellhop-based underwater channel model is used for simulation. The proposed method will be analyzed compared to the conventional CSS method with LFM waveform.

scholarly journals M-ary nonlinear sine chirp spread spectrum for underwater acoustic communication based on virtual time-reversal mirror method

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Songzuo Liu ◽  
Habib Hussain Zuberi ◽  
Yi Lou ◽  
Muhmmad Bilal Farooq ◽  
Shahabuddin Shaikh ◽  
...  
Keyword(s):  
Acoustic Communication ◽  
Time Reversal ◽  
Spread Spectrum ◽  
Underwater Acoustic Communication ◽  
Half Cycle ◽  
Spreading Factor ◽  
Underwater Acoustic ◽  
Virtual Time ◽  
Chirp Spread Spectrum ◽  
Time Reversal Mirror

AbstractLinear chirp spread spectrum technique is widely used in underwater acoustic communication because of their resilience to high multipath and Doppler shift. Linear frequency modulated signal requires a high spreading factor to nearly reach orthogonality between two pairs of signals. On the other hand, nonlinear chirp spread spectrum signals can provide orthogonality at a low spreading factor. As a result, it improves spectral efficiency and is more insensitive to Doppler spread than the linear counterpart. To achieve a higher data rate, we propose two variants (half cycle sine and full cycle sine) of the M-ary nonlinear sine chirp spread spectrum technique based on virtual time-reversal mirror (VTRM). The proposed scheme uses different frequency bands to transmit chirp, and VTRM is used to improve the bit error rate due to high multipath. Its superior Doppler sensitivity makes it suitable for underwater acoustic communication. Furthermore, the proposed method uses a simple, low-power bank of matched filters; thus, it reduces the overall system complexity. Simulations are performed in different underwater acoustic channels to verify the robustness of the proposed scheme.

scholarly journals Multiuser Chirp Spread Spectrum Transmission in an Underwater Acoustic Channel Applied to an AUV Fleet

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1527
Author(s):  
Christophe Bernard ◽  
Pierre-Jean Bouvet ◽  
Antony Pottier ◽  
Philippe Forjonel
Keyword(s):  
Spread Spectrum ◽  
Multiple Access ◽  
Autonomous Underwater Vehicle ◽  
Matched Filter ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic Channel ◽  
Underwater Acoustic ◽  
Acoustic Channel ◽  
Chirp Spread Spectrum ◽  
Code Division Multiple

The objective of this paper is to provide a multiuser transmission technique for underwater acoustic communication in the framework of an Autonomous Underwater Vehicle (AUV) fleet. By using a variant of a Hyperbolically Frequency-Modulated (HFM) signal, we describe a new family of transmission techniques called MultiUser Chirp Spread Spectrum (MU-CSS), which allows a very simple matched-filter-based decoding. These techniques are expected to provide good resilience against multiuser interference while keeping good robustness to Underwater Acoustic (UWA) channel impairments like Doppler shift. Their implementation for the UWA scenario is described, and the performance results over a simulated shallow-water UWA channel are analyzed and compared against conventional Code-Division Multiple Access (CDMA) and Time-Division Multiple Access (TDMA) transmission. Finally, the feasibility and robustness of the proposed methods are verified over the underWater AcousTic channEl Replay benchMARK (Watermark), fed by several channel responses from sounding experiments performed in a lake.

scholarly journals Parallel Resampling of OFDM Signals for Fluctuating Doppler Shifts in Underwater Acoustic Communication

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Shingo Yoshizawa ◽  
Takashi Saito ◽  
Yusaku Mabuchi ◽  
Tomoya Tsukui ◽  
Shinichi Sawada
Keyword(s):  
Conventional Method ◽  
Acoustic Communication ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Error Rates ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic ◽  
Parallel Resampling

Reliable underwater acoustic communication is demanded for autonomous underwater vehicles (AUVs) and remotely operated underwater vehicles (ROVs). Orthogonal frequency-division multiplexing (OFDM) is robust with multipath interference; however, it is sensitive to Doppler. Doppler compensation is given by two-step processing of resampling and residual carrier frequency offset (CFO) compensation. This paper describes the improvement of a resampling technique. The conventional method assumes a constant Doppler shift during a communication frame. It cannot cope with Doppler fluctuation, where relative speeds between transmitter and receiver units are fluctuating. We propose a parallel resampling technique that a resampling range is extended by measured Doppler standard deviation. The effectiveness of parallel resampling has been confirmed in the communication experiment. The proposed method shows better performance in bit error rates (BERs) and frame error rates (FERs) compared with the conventional method.

Sign in / Sign up

Export Citation Format

Share Document