The Study On Underwater Laser Communication System Based On LDPC Codes

This paper aims to improve the performance of laser communication to submarine,through the study of the key issues, such as the high-performance encoding-decodingtechnology and the propagation characteristics of the laser in seawater medium. Itproposes an underwater laser communication system that based on low-densityparity-check codes, and it analyzes the underwater optical channel with the Monte Carlomethod, the results was proved that it can improve the performance of the LSC systemremarkably with this method. The main contents of this paper are as follows:Firstly, through the analysis on the basic concepts, domestic and internationaldevelopment status, trends as well as key technologies of the laser communications, Igot the significance of this research, and then I introduced the main contents of this paper.Secondly, it introduces the basic knowledge about the LDPC code, describing deeplyseveral common construction methods and the decoding methods of the LDPC code.Thirdly, according to the underwater laser communication systems that based onLDPC codes, I analyzed the BER characteristics of the system through the MATLABsimulation, and then I compared the performance of the BER characteristics between thecommunication system based on LDPC codes and the uncoded communication system. Bycomparing, we can get the result that the LDPC encoding-decoding technology caneffectively improve the anti-jamming capability and reduce the bit error rate of the system.Furthermore, in order to analyze the characteristics of the seawater optical channel,the aim directly at the practical communication systems, and it was also combined withsome design parameters, we can get the space and time characteristics of the laser pulse,and analyze the broadening situation with the Monte Carlo method. At last, we proposeusing the Monte Carlo method to calculate the values of the pulse width. This method isnot only close to the reality and has a certain degree of innovation, but also it has practicalsignificance on design of the communication system.Finally, it makes a conclusion and research prospect at the end of this article.