Burst hybrid spread spectrum underwater sound covert communication method

Abstract

The invention relates to a burst hybrid spread spectrum underwater sound covert communication method. The method is characterized by comprising the steps that step 1, information to be sent is divided into three groups, BPSK spread-spectrum modulation, CSK spread-spectrum modulation and MFSK spread-spectrum modulation are conducted on the three groups of information respectively, and three signals are mixed and modulated on frequency orthogonal carrier waves; step 2, the mixed and modulated signals are randomly sent in a pulsing mode; step 3, the signals are captured and tracked by a receiving end through a time-frequency two-dimensional search algorithm; step 4, the synchronized signals are demodulated, parallel-serial conversion is conducted on demodulated data, and therefore the sent information is obtained.

Description

Technical field [0001] The invention relates to a concealed communication method of burst hybrid spread spectrum underwater sound. Background technique [0002] With the rapid development of marine development and marine military fields in various countries in the world, how to realize robust and concealed underwater acoustic communication has become a new research focus. The underwater acoustic channel is a time-varying, frequency-varying and space-varying channel with limited bandwidth, multiple channels and strong noise interference. The complexity and variability of the underwater acoustic channel severely limits the performance of underwater acoustic communication. Spread spectrum communication has the advantages of anti-interference ability, strong anti-channel fading ability and low interception rate. It is widely used in underwater acoustic remote, reliable and covert communication. [0003] In order to realize the covert communication with low detection probability, the s...

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Problems solved by technology

[0003] In order to realize covert communication with low detection probability, the simplest method is to adopt the method of direct sequence spread spectrum, and adopt technologies such as RAKE receiver and space diversity to improve the receiving signal-to-noise ratio, so as to achieve the purpose of reducing the sound source level and the probability of interception. Although direct sequence spread spectrum can work at a very low signal-to-noise ratio, it is difficult to be detected in the time domain, but due to the use of fixed carrier frequency modulation, the method of frequency domain detection is easy to be found; the frequency hopping communication method is in the direct sequence On the basis of spread spectrum, PN spread spectrum code is used to control the periodic change of carrier frequency, which makes it difficult to intercept and reduces the probability of interception, while the bandwidth occupied by frequency hopping communication is relatively wide, and the frequency band utilization rate is low

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