Orthogonal multi-carrier M-element chaotic phase modulation spread spectrum underwater acoustic communication method

Abstract

The invention discloses an orthogonal multi-carrier M-element chaotic phase modulation spread spectrum underwater acoustic communication method. The method comprises the following steps of: 1) dividing an input information sequence sent by an information source into K groups of information sequences with the length of a + 2 by a transmitting end, respectively feeding the information sequences into K grouping devices; using each grouping device to carry out M-element chaotic phase modulation spread spectrum mapping on the previous a bits to obtain a chaotic phase modulation spread spectrum code, performing QPSK modulation on two rear bits, performing spread spectrum modulation by using the obtained chaotic phase modulation spread spectrum code to obtain baseband signals, and respectively mapping K groups of baseband signals to subcarriers of OFDM symbols to perform OFDM modulation to obtain a digital signal to be transmitted and transmitting the digital signal to be transmitted; and 2) enabling the receiving end to adopt a section of chaotic phase modulation spread spectrum signal in OFDM symbols as a pilot signal, performing time-frequency two-dimensional search on the received digital signal to complete time-frequency synchronization, then performing OFDM demodulation to obtain K groups of baseband signals, and inputing the K groups of baseband signals into K combiners to complete despreading and QPSK demodulation to obtain a binary sequence.

Description

Technical field [0001] The invention relates to the technical field of underwater acoustic communication, in particular to an orthogonal multi-carrier M-ary chaotic phase modulation spread spectrum underwater acoustic communication method. Background technique [0002] The underwater acoustic channel is a time-varying, space-changing and frequency-varying channel with limited bandwidth, complicated multi-path interference, and serious background noise. The complexity of the channel severely limits the communication performance of underwater acoustic communication. Spread-spectrum communication has good anti-noise and anti-multipath interference characteristics due to the spread-spectrum gain, and is widely used in the field of remote underwater acoustic communication. However, due to the limitation of the underwater acoustic channel bandwidth, the communication rate of spread spectrum communication is relatively low, which can only meet the transmission rate of tens of bits or ev...

AI Technical Summary

Problems solved by technology

However, the above time-domain spread spectrum scheme has limited improvement in the efficiency of spread spectrum communication, and the communication performance is limited under underwater acoustic conditions with complex channel structures.

In addition, the pseudo-random (Pseudo-Noise, PN) sequence used in the traditional spread spectrum modulation has obvious periodicity and binary characteristics. Once the signal is intercepted, the corresponding characteristics such as chip rate and code period are easy to be extracted by the enemy. and use, leading to information leakage, not confidential

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