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An OFDM (Orthogonal Frequency Division Multiplexing) underwater acoustic communication method with high spectral efficiency under a time-varying double-spread channel condition

A channel condition, underwater acoustic communication technology, applied in the field of OFDM underwater acoustic communication with high spectral efficiency, can solve the problems of low receiver detection performance, pilot-data interference, inter-symbol interference, etc., to achieve resistance to underwater acoustic channel fading, The effect of suppressing interference and improving reliability

Active Publication Date: 2019-05-10
三亚哈尔滨工程大学南海创新发展基地
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that the detection performance of the receiver is low when the OFDM signal without guard interval is transmitted in the time-varying double-spread underwater acoustic channel with long multi-channel spread and large Doppler spread, and proposes a time-varying double spread OFDM Underwater Acoustic Communication Method with High Spectrum Efficiency under Expanded Channel Conditions
The present invention adopts OFDM signal without guard interval and superimposed pilot signal to realize reliable communication and has high spectral efficiency, and the proposed receiver can solve inter-symbol interference ISI, inter-carrier interference ICI, pilot-data interference and computational complexity low-level problems and has high detection performance

Method used

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  • An OFDM (Orthogonal Frequency Division Multiplexing) underwater acoustic communication method with high spectral efficiency under a time-varying double-spread channel condition
  • An OFDM (Orthogonal Frequency Division Multiplexing) underwater acoustic communication method with high spectral efficiency under a time-varying double-spread channel condition
  • An OFDM (Orthogonal Frequency Division Multiplexing) underwater acoustic communication method with high spectral efficiency under a time-varying double-spread channel condition

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specific Embodiment approach 1

[0092] A high spectral efficiency OFDM underwater acoustic communication method under a time-varying dual-spread channel condition, comprising the steps of:

[0093] Step 1. After the sending end performs LDPC encoding, interleaving and BPSK mapping on the original data, the data information is modulated onto parallel subcarriers through OFDM modulation, and then a known pilot signal is superimposed on the data signal for transmission. The superimposed signal at the end is used for the estimation of the time-varying double-spread channel;

[0094] Step 2, the transmission signal of step 1 reaches the communication receiving end after passing through the channel, and performs signal processing on the received signal r(k), the specific steps are as follows:

[0095] Step 2.1, the front-end processing module, the received analog signal r(k) is band-pass filtered, converted into a digital signal by ADC, down-converted, and low-pass filtered to obtain a baseband signal

[0096] ...

specific Embodiment approach 2

[0133] Specific implementation mode two: according to figure 1 Describe this embodiment, the specific operation steps of step 1 of this embodiment are as follows:

[0134] Step 1.1, performing LDPC encoding on the data source, namely the binary information stream b, to obtain the encoded binary bit stream c;

[0135] Step 1.2, interleaving the encoded binary bit stream to obtain the interleaved encoded binary bit stream d;

[0136] Step 1.3, carrying out BPSK mapping to the binary bit stream that step 1.2 obtains obtains the baseband symbol sequence e;

[0137] Step 1.4, performing serial-to-parallel conversion and IFFT (Inverse Fast Fourier Transformation) transformation on the baseband symbol sequence, that is, OFDM modulation, to obtain the modulated OFDM symbol sequence s;

[0138] Step 1.5, superimposing the known pilot signal on the OFDM symbol sequence obtained in step 1.4, the superimposed pilot signal at the receiving end is used for the estimation of the time-varyi...

specific Embodiment approach 3

[0141] Specific implementation mode three: As described in step 2.5 of this implementation mode, considering that the underwater acoustic channel can be considered to be sparse in the time domain and frequency domain, and thus considering the sparsity in the delay-Doppler domain, after compensating for the average multiple After Doppler, the OMP-DCD or Orthogonal Matching Pursuit-Dichotomous Coordinate Descent algorithm is used to jointly estimate the delay-Doppler-amplitude for the signal with residual Doppler that has experienced the dual-spread channel.

[0142] Orthogonal matching pursuit OMP algorithm is a greedy algorithm. Its basic idea is to regard the observed signal as a linear combination of some atoms in the redundant original character library, and seek the optimal solution or local optimum through a certain number of iterations. The solution makes the residual error between the estimated signal and the original signal smaller and smaller, and finally realizes the ...

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Abstract

The invention discloses an OFDM (Orthogonal Frequency Division Multiplexing) underwater acoustic communication method with high spectral efficiency under a time-varying double-spread channel condition, and belongs to the technical field of underwater acoustic communication. The method comprises the following steps: carrying out band-pass filtering on a received signal r (k), carrying out front-endprocessing such as ADC (Analog to Digital Converter) conversion into a digital signal, carrying out down-conversion and low-pass filtering, estimating average Doppler by utilizing a fuzzy function method, carrying out resampling and frequency correction, multiplexing the signal, carrying out time domain equalization and frequency domain equalization, carrying out diversity combination, and then adopting the OMP-DCD algorithm to perform residual Doppler compensation. an iterative signal processing technology is adopted, an LDPC decoder and an equalizer are cascaded through soft-in soft-out mapping / demapping and an interleaver / deinterleaver, close information interaction is achieved in the two modules, soft information transmitted in a reciprocating mode is fully utilized, and interferenceof a time-varying double-spread channel is effectively resisted. According to the method, the complexity and the performance can be well compromised, and serious inter-symbol interference, inter-carrier interference and pilot frequency-pilot frequency interference in the transmission process are efficiently solved. And the method is low in complexity and can be realized on the DSP in real time.

Description

technical field [0001] The invention belongs to the technical field of underwater acoustic communication, and in particular relates to an OFDM underwater acoustic communication method with high spectral efficiency under the condition of time-varying double-spreading channels. Background technique [0002] OFDM is a multi-carrier transmission scheme. Its main idea is to divide the available bandwidth into a large number of sub-bands with carrier frequency, convert high-speed serial data to parallel orthogonal sub-channels for transmission through serial-to-parallel conversion, and increase symbols The period can effectively offset the influence of intersymbol interference, and at the same time, its way of processing signals in the frequency domain reduces the complexity of the implementation of the equalizer at the receiving end. It has strong anti-multipath ability, high frequency band utilization, fast communication rate and low implementation complexity. Etc. The OFDM und...

Claims

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Application Information

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IPC IPC(8): H04B13/02H04L27/26
Inventor 张友文刘志鹏李俊轩黄福朋
Owner 三亚哈尔滨工程大学南海创新发展基地
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