Symbol synchronization and Doppler compensation method for mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal

A technology of Doppler compensation and symbol synchronization, which is applied in the direction of multi-frequency code system, shaping network in transmitter/receiver, baseband system components, etc., can solve the problem of low accuracy of Doppler compensation, unfavorable real-time Problems such as poor decoding effect

Active Publication Date: 2013-01-09
THE 715TH RES INST OF CHINA SHIPBUILDING IND CORP
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Problems solved by technology

The above method needs to save a complete frame of signal, takes up a lot of memory, is not conducive to real-time implementation, and uses an approximate processing method, the accuracy of Doppler compensation is not high, and the decoding effect is not good

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  • Symbol synchronization and Doppler compensation method for mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal
  • Symbol synchronization and Doppler compensation method for mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal
  • Symbol synchronization and Doppler compensation method for mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal

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[0038] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific implementation examples.

[0039] The symbol synchronization and Doppler compensation method of mobile OFDM underwater acoustic communication signal of the present invention, this method mainly comprises the following steps:

[0040] 1. Transmission signal generation method

[0041] The first part of each frame of the underwater acoustic OFDM communication signal is a frame header signal, which is used for the coarse synchronization of the first symbol. The frame header signal can be a linear frequency modulation LFM or a pseudo-random phase modulation signal, followed by a period of idle protection time, and then is an OFDM communication signal.

[0042] An OFDM symbol can be expressed as:

[0043] x ( t ) = Re { Σ k ...

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Abstract

The invention relates to a symbol synchronization and Doppler compensation method for a mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal. The method comprises the following steps of: obtaining rough estimation of a first OFMD symbol start position according to a frame header signal, extracting a symbol, then obtaining Doppler expansion rough estimation of the symbol according to a frequency measurement simple-frequency signal in the symbol, converting the symbol to a frequency domain according to Chirp-z conversion, searching a precise start moment and a Doppler expansion amount of the symbol by taking a pilot of the frequency domain and a relevant value of a local pilot as cost functions, presuming the start position of the next symbol according to the start position of the current symbol, extracting the next symbol, and repeating the operations till the end of a frame of signal. According to the Doppler measurement and compensation method, based on the Chirp-z conversion, the measurement and compensation precision is high; the Chirp-z conversion is implemented according to fast Fourier transformation (FFT); the practicability is high; according to the Doppler expansion search method which is in a manner that large step length is superior to small step length, so that the search efficiency is high; a Doppler measurement range is not limited; and the method can be used for constant-speed motion and variable-speed motion.

Description

technical field [0001] The invention relates to the field of underwater acoustic communication, more precisely, relates to an orthogonal frequency division multiplexing underwater acoustic communication method, mainly a symbol synchronization and Doppler compensation method for mobile OFDM underwater acoustic communication signals. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) has good anti-frequency selective fading performance and high bandwidth utilization, and can be used for multi-channel serious underwater high-speed acoustic communication. However, OFDM has its own determinant disadvantage that the receiving performance is sensitive to symbol synchronization deviation and frequency deviation. [0003] In underwater acoustic communication, since it usually works at low frequency and the speed of sound is much lower than that of radio, when there is Doppler, it will affect the performance of OFDM system more seriously than radio. Dopple...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26H04L25/03
Inventor 张宏滔王忠康谢哲岳志杰
Owner THE 715TH RES INST OF CHINA SHIPBUILDING IND CORP
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