scholarly journals Research on Degree Distribution Optimization of LT Codes

2020 ◽  
Vol 38 (3) ◽  
pp. 627-633
Author(s):  
Yachen Liu ◽  
Pengcheng Wang ◽  
Dehong Tian ◽  
Haixin Sun ◽  
Jie Qi ◽  
...  
Keyword(s):  
Acoustic Communication ◽  
Channel Coding ◽  
Degree Distribution ◽  
Orthogonal Frequency Division Multiplexing ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic ◽  
Sea Trial ◽  
Stable Performance ◽  
Lt Code ◽  
Short Code

LT code, as a channel coding scheme with good adaptability to the channel, has a stable performance in data transmission of underwater acoustic communication. In the case of large decoding overhead, the LT code can reach the ideal bit error rate(BER), but when the length of the encoded data is short, its coding and decoding performance is not ideal. LT code was applied to underwater acoustic communication by combining with orthogonal frequency division multiplexing (OFDM), and a LT-OFDM system was constructed. To improve the performance of LT code in the case of short code length, a method for degree distribution optimization was proposed on the objective of minimizing BER and minimizing average coding degree. Simulation and sea trial results show that under the same BER this method can optimize the system, transform 7%-22% conversion, and reduce the complexity of coding and decoding.

Implementation of an Impulse Noise Suppression Method in OFDM Underwater Acoustic Communication System

2011 ◽  
Vol 268-270 ◽  
pp. 1537-1542
Author(s):  
Wen Han Ma ◽  
Xiao Yi Hu ◽  
Li Yang Bai
Keyword(s):  
Shallow Water ◽  
Acoustic Communication ◽  
Communication System ◽  
Orthogonal Frequency Division Multiplexing ◽  
Impulse Noise ◽  
Underwater Acoustic Communication ◽  
Ofdm System ◽  
Underwater Acoustic ◽  
Sea Trial ◽  
Ber Performance

This paper describes the characteristics of the impulse noise in the shallow water acoustic channel, and its influence on the bit error rate (BER) performance of the Orthogonal Frequency Division Multiplexing (OFDM) system. The simulation has been carried out to analyze the performance of the joint suppression of impulse noise in time and frequency domain in OFDM underwater acoustic communication system. Data processing of the actual sea trial in Xiamen Harbor shows that the method has some impressive effect on impulse noise in shallow water acoustic OFDM system, and improves the BER performance on different levels.

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.

scholarly journals Efficient On-Off Keying Underwater Acoustic Communication for Seafloor Observation Networks

2020 ◽  
Vol 10 (6) ◽  
pp. 1986
Author(s):  
Yan Yao ◽  
Yanbo Wu ◽  
Min Zhu ◽  
Dong Li ◽  
Jun Tao
Keyword(s):  
Acoustic Communication ◽  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Convolutional Code ◽  
High Reliability ◽  
Underwater Acoustic Communication ◽  
Decision Threshold ◽  
Underwater Acoustic ◽  
Seafloor Observation ◽  
Observation Networks

In the cableless seafloor observation networks (SONs), the links among network nodes rely on underwater acoustic communication (UAC). Due to the energy constraint and the high-reliability requirement of the cableless SONs, the noncoherent UAC has been a preferred choice, even though a noncoherent UAC scheme generally suffers from low spectral efficiency. In this paper, we propose a high-spectral-efficiency noncoherent UAC transmission scheme which is implemented as an orthogonal frequency-division multiplexing (OFDM) system adopting the on-off keying (OOK) modulation. To simultaneously achieve high performance at a low energy consumption, an irregular recursive convolutional code (IrCC) is employed and an accumulator (ACC) is introduced to achieve a modulation with memory at the transmitter side. The ACC enables a turbo iteration between the soft demapper called the ACC-OOK demapper and the soft decoder on the receiver side, and also reduces the decoding error floor. To account for the unknown signal-to-noise ratio (SNR), an iterative threshold estimation (ITE) algorithm is proposed to determine a proper decision threshold for the ACC-OOK demapper. The IrCC is designed to match the extrinsic information transfer (EXIT) curve of the ACC-OOK demapper, lowering the SNR threshold of the aforementioned turbo iteration. Simulations and experimental results verify the superiority of the proposed noncoherent UAC scheme over conventional ones.

Experimental Study of Long-Range Shallow Water Acoustic Communication Based on OFDM-Modem

2012 ◽  
Vol 546-547 ◽  
pp. 1308-1313 ◽  
Author(s):  
Gang Qiao ◽  
Song Zuo Liu ◽  
Feng Zhou ◽  
Zong Xin Sun
Keyword(s):  
Experimental Study ◽  
Acoustic Communication ◽  
Channel Equalization ◽  
Underwater Acoustic Communication ◽  
Frequency Diversity ◽  
Shallow Sea ◽  
Underwater Acoustic ◽  
Sea Trial ◽  
Communication Distance ◽  
Compensation Channel

In this paper, we focus on the need for remote and robust underwater acoustic(UWA) communication in shallow sea. A set of OFDM underwater acoustic communication algorithm is designed including the techniques of Doppler estimation and compensation, channel equalization and frequency diversity. This algorithm is realized in the DSP and successfully applied on the OFDM-Modem platform. In Da- Lian shallow sea trial, the horizontal communication distance is 36 kilometers under the condition of QPSK modulation, 1/2 rate convolution code, bandwidth between 4 and 8kHz. The communication rate of the OFDM-Modem can reach 426bps and the ultimate BER is less than 10-3.

scholarly journals A Comparative Study on Channel Coding Scheme for Underwater Acoustic Communication

2021 ◽  
Author(s):  
Mustafa Sami Ahmed ◽  
Nor Shahida Mohd Shah
Keyword(s):  
Computational Complexity ◽  
Acoustic Communication ◽  
Channel Coding ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic ◽  
Coding Schemes ◽  
Main Challenge ◽  
Polar Coding ◽  
Shift Keying ◽  
T Distribution

Abstract There are various challenges in underwater acoustic communication (UWA) however bit error rate (BER) is considered as the main challenge as it significantly affects the UWA communication. In this paper, different coding schemes such as Convolution, Turbo, LDPC, and Polar coding based on the t-distribution noise channel are investigated, and binary phase-shift keying (BPSK) modulation with a code rate of 1/2 has considered in the evaluation and analyses. The evaluation of these channel coding schemes is performed based on BER, computational complexity as well as latency. The results have shown the outperform of polar coding in UWA over other channel coding schemes as it has lower BER and lower computational complexity.

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