Simulation Research On RAKE Receiver Technology In Underwater Acoustic Spread Spectrum Communication

In recent years, with the need of naval defense construction and marine research anddevelopment and the rapid development of modern signal processing techniques, theapplication of underwater acoustic communication is constantly expanding, the study ofUnderwater acoustic communication became the hot spot of the study of Underwater acoustictechnology. Multi-path effects of underwater acoustic channel make signal severe fadingeffect, which became The main obstacle of underwater high-speed and highly reliablecommunications.In order to make the hazards of the digital communications brought by multipathfading channel be controlled at a minimum. Recently, direct-sequence spread spectrumcommunication system has been widely used in digital communications, the combination ofDiversity reception technology and direct-sequence spread spectrum communication system.The core of direct sequence spread spectrum is to let the system transmission bandwidth muchlarger than the information bandwidth,in exchange for a gain on the signal to noise ratio, toachieve reliable communication under conditions of low SNR.RAKE receiver technology isactually a diversity multipath receiver technology based on spread spectrum, it differs fromthe traditional space, frequency and time diversity technique, no need to increase thetransducer or other receiving equipment, it is a typical signal design and signal processingtechnology that implicit the role of diversity in the signal transmission among the hiddendiversity. Minor multipath signal can be time-resolved, it is the demodulation of signalreceived by each road, then superimposed on the output to enhance the purpose of reception.The paper mainly studies the application of direct sequence spread spectrum technologyin underwater acoustic communication system, especially through the RAKE receiver toimprove system reliability. Mainly cover the following:1. Completion of the application of the simulation model structures of direct sequencespread spectrum underwater communication system simulation model. Including spreadspectrum modulation, channel coding, carrier modulation, pulse shaping and Dopplerestimation and compensation.2. Study the RAKE receiver. First, discuss the basic principles and performanceadvantages of the diversity technique and the RAKE receiver. Then, RAKE receiver in thesystem path search and channel estimation and signal combining algorithms are analyzedtheoretically. 3. Computer simulation. Verify the interference of the multipath signal and RAKEreceiver to improve system performance. Analyzed and compared impact on systemperformance by different path selection method, different number of taps, different PN codelength, different combining method, different number of taps, different PN code length anddifferent combining methods. Tank experiments verify the performance of the RAKEreceiver.