Research On Underwater Acoustic Communication Based On Digital Watermarking

For human beings,the ocean is a huge treasure house and our exploration and development of the ocean are becoming more frequent.Due to the characteristics of low propagation loss and long transmission distance of sound waves in the ocean,the development of underwater acoustic communication signals is unstoppable.Since underwater acoustic channels are complex and changeable,the development of underwater acoustic communication signals is inseparable from the research of underwater acoustic information countermeasures.In order to resist the enemy's attack and interference on our communication signals,we need to distinguish the received communication signals.Digital watermarking technology can add watermark signals without affecting the original signal,which has the characteristics of low load and low power consumption,and can be applied to signal identification.Therefore,the use of digital watermarking technology in underwater acoustic communication signals can bring great convenience.After comparing various watermark embedding technologies,this thesis fully considers the characteristics of strong anti-multipath ability and high spectrum utilization of underwater acoustic communication signals,and adopts time-domain scrambling technology and time-reversal mirror technology to embed the watermark respectively.Combined with digital signal processing technology and digital watermarking technology,this thesis firstly proposes a watermark embedding technology of constant envelope underwater acoustic communication signal based on time-domain scrambling.This technology embeds the watermark through the time-domain scrambling technology,and uses the correlation between the signal after inverse scrambling and the original signal to set a threshold,thereby extracting the watermark.Thus,the information embedding and extraction of the constant envelope communication signal are realized.The simulation result shows that the algorithm does not change the signal constant envelope characteristics,solves the watermark embedding problem of constant envelope communication signals,and verifies the robustness of the watermark at the same time.Secondly,aiming at the problem of transmission of hidden information,using OFDM signal as the carrier of message transmission,combined with digital watermarking technology,a method of transmission of hidden information based on OFDM signal is proposed.This method uses the OFDM signal as the carrier signal.When information needs to be sent,the OFDM signal with a period of time length ? is intercepted in real time,and the time reversal mirror technology is used to time-reverse the signal and send it again with a delay.The receiving end intercepts two segments of the signal from the received signal for convolution,uses the Neyman-Pearson criterion to determine the result of the convolution,and extracts the watermark information.Experiment shows that this method uses the OFDM signal as the carrier signal to embed the watermark.The implementation method is simple,and the influence of the channel is weakened.The watermark can still be extracted completely under low signal-to-noise ratio.The two applications in underwater acoustic communication signals are analyzed from two aspects: time domain and bit error rate.The results show that the two watermark embedding schemes are both concealed and robust.