Research On Underwater Acoustic Communication Channel Modeling

Occupying 71.8%of the earth’s total area,there are many ocean routes and rich reserves.The research on how to operate in the ocean and transmit information in the sea can be traced back to very early human history.Underwater acoustic communication(UWAC)is a technology for sending and receiving information underwater.It is a key technology in the current marine military and one of the important tools for exploring and studying the ocean.The characteristics of UWAC technology are mainly determined by the characteristics of the underwater acoustic(UWA)channel:the UWA channel has complex multipath propagation,serious Doppler effect.limited bandwidth,and outstanding non-stationarity characteristics.Due to these characteristics of the UWA channel,the UWAC technology has the characteristics of low transmission rate,large delay,high bit error rate,low reliability,and high power dissipation,which makes communication in the UWA channel very challenging.The starting point of the research on UWAC technology is to overcome the imperfection of the UWA channel.A channel model is indispensable.The main purpose of this thesis is to summarize and analyze the characteristics of the UWA channel,establish an UWA channel model with high accuracy,low complexity and good flexibility,and study the important statistical characteristics of the UWA channel.This dissertation first describes the concept of channel modeling,and summarizes and analyzes the propagation characteristics of UWA channels and the characteristics of different scenarios.The marine environment is extremely complex,and the scenarios of UWA communication are also very complex and diverse.Moreover,the UWA channel is a parametric channel,and its characteristic parameters will change randomly with the changes of space,time and frequency.According to the characteristics of seawater as a transmission medium,this thesis analyzes the statistical characteristics of UWA channels under the influence of shallow water scenes and deep water scenes,different boundary conditions,and different environmental factors.Then,various modeling methods of UWA channel are comprehensively analyzed,and the advantages and disadvantages of different methods are expounded.Then,based on the summary and analysis of the characteristics of UWA channels,this thesis proposes an improved three-dimensional(3D)geometry-based stochastic model(GBSM),and establishes the wideband non-stationary channel model in medium-long-distance shallow water scenes of the order of 100 meters to kilometers.This modeling method can achieve a good compromise between complexity and accuracy,and can make up for the gap of the current 3D water channel model to a certain extent.Combined with the characteristics of the UWA channel,this thesis expands and improves the reference model from the 3D scene construction,the position of the cluster,and the relationship between the arrival angle and the departure angle,and considers the influence of the scatterers in the water,making the model more realistic and accurate.Then,according to the proposed 3D GBSM,the key statistical properties of the UWA channel model,such as time autocorrelation function(T-ACF),power delay profile(PDP),average delay and root mean square delay spread(RMS-DS),are studied.The channel model is simulated,analyzed and verified.Simulation results show that the proposed channel model can characterize the non-stationary characteristics of UWA channels in time and frequency domains.The simulation results of the statistical properties of the model have very similar trends or very close values to the measured data,which positively verifies the reliability of the model.Finally,this thesis proposes a modified time-varying UWA channel model based on the BELLHOP beam tracking model.Based on the BELLHOP beam tracking model,the influence of the seabed reflection coefficient determined by the incident angle and the material of the seafloor sediments is added,and the influence of the channel time-varying caused by the relative motion of the transmitter and receiver is considered.A time-varying UWA channel model based on BELLHOP model is established to meet the simulation requirements of timevarying UWA channel under the condition of accuracy of deterministic model.The impulse response of UWA channel is analyzed according to the proposed time-varying channel model.The simulation results show that the proposed channel model can represent the time-varying characteristics of UWA channel,and the simulation results are compared with the proposed 3D geometric random model to verify the reliability of the model.To sum up,based on the direction of UWA channel modeling has carried on the thorough research,shallow water scene is set up using different modeling method of UWA channel model,analyzed the different channel characteristics,this work can for UWA communication system design,evaluation and testing to provide the reference and theoretical support.