Direct Adaptive Equalization Combined With Channel Estimation Algorithm In Underwater Acoustic Communications

In recent years,our country has put forward the strategy of a maritime power and the goal of realizing the marine informatization.In this process,it is inseparable from the support of high-speed and high-reliability communication systems.At present,the most effective information carrier for underwater wireless communication technology is still acoustic waves.The transmission of acoustic waves in the underwater acoustic channel is bound to be affected by the environmental factors of the underwater acoustic channel,such as time-varying,multipath interference,Doppler Effect,and complex background noise.Underwater acoustic signals experience channel fading,which will increase the error rate of the communication system.Turbo equalization technology adopts the iterative exchange of soft information,which can greatly improve the reliability of the communication system and is widely used in the underwater acoustic communication system.Turbo equalization technology requires a trade-off between performance and complexity,especially in a complex underwater acoustic environment,where both reliability and real-time communication are required.How to find a method with lower complexity and meeting communication requirements is of great significance to underwater acoustic communication.This paper studies and analyzes the application of Turbo equalization technology in underwater acoustic communication.The main contents are as follows:1.By studying the characteristics of the underwater acoustic channel,understand the reasons for the different characteristics of the channel and the influence on the signal,and further understand the underwater acoustic channel.On this basis,mathematical modeling is performed and common channel estimation algorithms are introduced.2.Introduce the single carrier transmission model in the underwater acoustic communication system,and add Turbo equalization structure on this basis.For this system,the specific process of Turbo equalization is introduced,and two commonly used Turbo equalization methods are described,channel estimation based Turbo equalizer and direct adaptation based Turbo equalizer.In addition,the common algorithms of these two equalization methods are deduced and analyzed.3.According to the advantages and disadvantages of the above two Turbo equalization methods,a direct adaptive equalization algorithm combined with channel estimation suitable for single-carrier transmission systems is proposed.Partial combination is used to ensure the calculation simplicity of the equalization process,and at the same time make the algorithm have the characteristics of rapid convergence.After the simulation of the simulated underwater acoustic channel,it is preliminarily verified that the algorithm has a good bit error rate and effectiveness under different underwater acoustic channels.4.Optimize and improve the algorithm proposed above,starting from both the complexity and performance,and point out the areas where the algorithm can be improved and the improvement measures.And combined with the actual hardware platform,the actual communication scenarios are tested in indoor pools and off-site lakes.Through analysis and verification,it is shown that the algorithm has reliable performance and good communication quality in a single-carrier underwater acoustic transmission system,and has certain practical application value.