Adaptive Equalizer In Underwater Acoustic Communication Studies

In recent years, the underwater acoustic communication (UAC) is very important both in military and civil. As the value of UAC is urgently needed by military and civilian, the research on UAC has become the hotspot in research of domestic and international communication, and more and more people attach great importance to it. The terminal target of research on UAC is to establish UAC system, or the UAC network which is similar to the current land Internet network. And make UAC fully applied to the communication between a submerged submarine and another submerged submarine, the communication between a submerged submarine and surface ships, the sea telemetry about marine environment by stuff and so on. The technologies of UAC are used to guarantee the accuracy of data record, image data, and voice data during transmission, which was collected by submerged Measuring Equipment. Also used in other areas for Marine resources development and utilizationBecause of the complexity of the Marine environment, namely high noise, low usable carrier frequency, low available bandwidth, and large propagation delay of UAC channel, this thesis adds an equalizer to reduce the serious inter-symbol interference (ISI) caused by the multipath effect of UAC in order to improve the quality of UAC. The research on UAC adaptive Equalizer is including two parts, one part is the adaptive equalization algorithm of equalizer, the other part is the structure of equalizer. According to adaptive equalizer composed of two parts, this thesis studies three category of UAC adaptive equalizer. These equalizers respective are:1,The UAC LMS adaptive equalizers. At first, introduces theoretical research on the traditional LMS adaptive equalizer and its modified LMS adaptive equalizers, then the simulation research on the application performance of the LMS adaptive equalizers in UAC system. The simulation results demonstrate that it is feasible to use UAC LMS adaptive equalizer to overcome UAC's serious ISI in UAC system.2,The UAC RLS adaptive equalizers. Firstly, introduces theoretical research on the traditional RLS adaptive equalizer and its modified RLS adaptive equalizers, then the simulation research on the application performance of the RLS adaptive equalizers in UAC system. The simulation results demonstrate that it is feasible to use UAC RLS adaptive equalizer to overcome UAC's serious ISI in UAC system. UAC RLS adaptive equalizer is applied in processing a group of collecting data files from one lake experiment of Chinese science research institute of acoustics in 2008.The known conditions are listed below. The sender and the receiver are static. The underwater depth of the receiver and the sender is 3m. The straight distance between the sender and the receiver is lkm.The transmitted signal is a gray image. The size of gray image is 64 pixels x 64 pixels, which has 8 gray levels. The grayscale value of the gray image is from 0 to 127. Receiving data from received file is equalized by RLS adaptive equalizer, then recover the received image, which shows this practical UAC process accurately realized the transmission of information between the sender and the receiver. Both simulation and actual data processing demonstrate that it is feasible to use UAC RLS adaptive equalizer to overcome UAC's serious ISI in UAC system.3,The UAC least squares (LS) lattice adaptive equalizers. At first, introduces theoretical research on the traditional LS lattice adaptive equalizer and its modified LS lattice adaptive equalizers, then the simulation research on the application performance of the LS lattice adaptive equalizers in UAC system. The simulation results demonstrate that it is feasible to use UAC LS lattice adaptive equalizer to overcome UAC's serious ISI in UAC system.In addition, the thesis simulates the whole UAC process, researches the application performance of UAC adaptive equalizer by applied it to the simulation of acoustic communication system. The theoretical research,results of simulation and results of actual data processing show that the application of underwater acoustic communications equalizer greatly reduced error rate mainly caused by ISI, and greatly improved the quality of UAC. And demonstrate that it is feasible to use UAC adaptive equalizer to overcome UAC's serious ISI in UAC system. The research on UAC adaptive equalizers in the thesis aims to establish a comprehensive theory and application system architecture of UAC equalizer for further developing of'UAC experiment data processing and simulation'system software platform. It is to avoid repetition of the research work, and guarantees to the development of'UAC experiment data processing and simulation'system software platform goes smoothly.