Research On Reliability Of Underwater Mobile Node Communication

The marine resources are abundant and the ocean is the key area for countries to compete for and explore.China is a big maritime country,and the development of the ocean and the protection of resources have risen to the strategic level.Therefore,research on emerging technologies related to the ocean is imminent.Acoustic communication technology is essential for the detection and development of the ocean.Limited by the characteristics of underwater acoustic channels,underwater acoustic communication technology will be affected by noise interference,propagation loss,multipath effect and Doppler effect.In particular,the multipath effect and the Doppler effect are issues that must be considered when studying the reliability of underwater acoustic communication.To this end,this thesis studies the multipath effect and Doppler effect in underwater acoustic communication,analyzes its generation mechanism and methods to eliminate its interference.The main work of this thesis is as follows:Firstly,this thesis researches and analyzes the underwater acoustic communication channel.The factors affecting the reliability of underwater mobile communication are summarized,and the multipath effect and Doppler effect are analyzed particularly.Then this thesis introduces several theoretical models for underwater acoustic field and uses the BELLHOP tool to model the underwater acoustic channel to solve the impulse response of specific waters.Next,the impulse response is used to obtain the mathematical model of underwater mobile communication transmission which is the foundation of following study.Secondly,the mechanism of multipath effect of underwater acoustic communication is analyzed.Classical channel equalization algorithm in terrestrial wireless communication is applied to study the multipath effect of underwater acoustic communication.According to the characteristics of time-varying and spatial variation of the actual underwater acoustic channel,an improved variable-step LMS algorithm is proposed to improve the stability of classical channel equalization algorithm.The simulation results show that the improved algorithm has fast convergence,excellent performance and high stability,which can equalize the distortion of the channel and improve the reliability of the underwater acoustic communication.Next,Doppler effect of underwater acoustic mobile communication is taken into account.A mathematical model is established for the Doppler shift,and the influence of Doppler shift on the communication system is simulated.Then analyzed the accuracy of deficiencies of the existing Pisarenko harmonic decomposition algorithm in estimation.By improving the autocorrelation order,an improved Pisarenko harmonic algorithm is proposed.The simulation results show that the improved algorithm has higher estimation accuracy,less computation and practical significance.Can improve the reliability of communication.Finally,the channel equalization algorithm and the Doppler estimation algorithm were co-simulated.Since the multipath effect affects the estimation accuracy of the Doppler estimation algorithm,the improved variable-step size LMS algorithm proposed in this thesis is introduced to solve the multipath effect.In this context,the channel equalization and Doppler estimation are jointly simulated.The results show that the communication system with equalization and Doppler compensation under the same conditions has the lowest bit error rate and the highest reliability.