The Study Of Underwater Laser LDPC Communication System’s Characteristic

With the development of science and technology,the exploration of the oceans is more and more depth. It is inevitable for the underwater laser communication’s development. With the superiority of its communication characteristics,so,more and more researchers are pay the attention to the underwater communication transmission,especially in submarine communication.The 21st century is the world of the ocean, compared to the developed countries,China’s underwater laser communication system started a little late,in the whole,it is still fall behind with others,especially in some key technologies,the disparity is very obvious.In this paper,we discuss the characteristics and model of underwater channel in depth.As the complexity of the underwater channel,after the transmission of underwater channel,in the receiving end,the original will have errors.So,the encoding and decoding technology is one of the key technologies to be solved.Now,there are many accepted encoding methods at the international level,among these,it has been widespread concern that the LDPC code has good characteristics, has simple structure, low storage,itself has anti-error codes,so the error rate of information is greatly reduced. We studied the basic theory, the parity check matrix, and other coding and decoding methods of the LDPC code,and we know the LDPC code in the whole.In the text part of this paper,I make the LDPC code encode an decode through the MATLAB simulation,and study the properties of it. We use a laser diode and a photomultiplier tube equipped with underwater communication link system, and verify its transmission feasibility.Finally, we compare the three experimental groups, studied the performance of underwater laser LDPC communication system,mainly about the error rate of the communication wiht the LDPC code.Through the experiment we can see that,the error rate of underwater communication system has been significantly reduced with the LDPC code,especially in the case of poor water quality.At the end of this paper, we propose a direction for research.