Simulation Research Of RAKE Receiver In Underwater Acoustic Spread Spectrum Communication

In recent years,with the growth of naval military activities and marine development and utilization,underwater acoustic communication has gradually become an indispensable member of underwater acoustic technology.In the 1980 s and 1990 s,although wireless communication technology was very mature,underwater acoustic communication technology still developed slowly because of its many specificities compared to terrestrial wireless communication.With the improvement of the level of science and technology and the research of generations of scientists,the underwater acoustic communication technology has made great progress and achievements,and will gradually shift from the unmatchable military field to the civilian development,extending to many people's lives.The field has brought many changes and conveniences to our lives.The greatest specificity in underwater acoustic communication is also the biggest technical problem,namely the multi-path effect of water sound.Properly solving the multipath effect in the underwater acoustic channel has always been the key to achieving efficient,reliable and secure communication in underwater acoustic communication systems.With the rapid development of modern signal processing technology,the technologies widely accepted for processing multipath effects mainly include adaptive beamforming,adaptive equalization,spread spectrum,diversity,and array processing.Among them,spread spectrum technology,especially direct sequence spread spectrum technology,is simple and effective,and it is the only technology that can complete communication in a negative SNR environment.Diversity technology can efficiently use multipath energy to improve input signal noise at the demodulator side.Than,resist signal fading and reduce the bit error rate.The RAKE receiver is actually a new type of communication system combining spread spectrum and diversity,which can effectively overcome the multipath effect in the underwater acoustic channel and realize safe and reliable communication under water.The main contents of the thesis include:1.Theoretical analysis of the working principle of spread spectrum technology and the feasibility of overcoming multipath effects.2.Theoretical analysis of the basic principle and structural block diagram of the RAKE receiving technique,as well as the synchronization techniques,channel estimation and signal combining involved in the RAKE receiver.3.The remote underwater acoustic communication system simulation model based on DSSS+BPSK modulation method and RAKE receiving technology is built on Simulink platform,and different path selection methods,different tap numbers and different spreading codes are simulated and analyzed.The effect on the system bit error rate under the length and different merge modes.4.Experiment with underwater acoustic communication equipment to verify the reliability of the underwater communication of the RAKE receiving system.