Underwater Acoustic Channel Encoding And Decoding Technology Based On Turbo Code And Its FPGA Implementation

Ocean acoustic channel is such a complex environment that it varies in space, time and frequency, and has characteristics such as narrow band, high multipath interference and severe signal fading. How to transmit information reliably and in high data rate in underwater environment is a worldwide research problem. Besides advanced modulation and demodulation and channel equalization techniques, high performance error-correction coding technique must be use in underwater acoustic communication to ensure the reliability of information transmission and to reduce its bit error rate.Turbo code is an excellent channel coding scheme, it is a novel combination of iterative decoding with Soft-Input/Soft-Output (SISO) algorithms and recursive systematic convolutional (RSC) codes in parallel connected by an interleaver. Turbo codes can approach to Shannon limit and perform very well in AWGN channel. It is an important achievement in the field of channel coding theory.This paper aims to improve the reliability of transmit information in underwater acoustic channel and study a lot in the characteristics of underwater acoustic channel, underwater communication principle and technology, turbo coding and iterative decoding principle and how to use hardware description language to implement turbo decoder.First, the characteristics of underwater acoustic channel and its research status are introduced in the paper. Because of random errors and burst errors are both exist and most of the errors are intensive burst errors when transmit information, turbo code is proposed as the channel error correction coding scheme in the underwater acoustic communication.Second, on the basis of large number of channel coding relevant reference material, turbo code encoder and decoder of the structure, decoding guidelines, SOVA (Soft Output Viterbi Algorithm) is in-depth studied, and simulation is did on SOVA in matlab with different frame length, constraint length, iteration times, code rate, interleaver and some other parameters.Third, after considering the simulation results, integration performance, system delay, implementation complexity, system compatibility and all other factors, a turbo coding and decoding scheme for CycloneⅡimplementation is proposed in the paper, and the scheme also is detailed as a whole as well as its individual components, and the way to reduce implementation complexity and decoding delay is also introduced.Finally, the underwater acoustic sensor network platform is introduced and the way to improve communication performance in the design of underwater acoustic communication nodes is also explained, and then, the entire article are summarized.