Performance Research Of LDPC Codes In Free Space Optical Communication Based On OFDM

Free space optical communication(FSO), as a new type of broadband wireless access method, receives much attention. It uses laser as the carrier of information transmission and has the characteristics of large transmission capacity and strong anti-interference ability in short distance, it is considered as the practical solution of "last mile" problem. But FSO system takes the atmosphere as the transmission medium, it is easy to be disturbed by atmospheric turbulence and other factors, and will have an impact on the quality of communication. Low density parity check code(LDPC) and orthogonal frequency division multiplexing(OFDM) are the key techniques to improve the quality of information transmission in wireless communication, and have been widely used in many fields. The combination of OFDM and FSO system to set up the FSO-OFDM system simulation model can be used to make full use of the advantages of FSO system and analyze the influence of different scintillation index, sub carrier modulation mode and sub carrier number on the error performance of FSO-OFDM system under atmospheric turbulence. In order to further improve the communication effect, the LDPC codes with superior error correction performance are applied to the FSO-OFDM communication system, simulate and study the error characteristics of the LDPC codes in different code length, different bit rate and different number of iteration and analyze the influence of different parameters on the system performance. Research shows that the communication method of using OFDM and LDPC codes in the FSO system has good transmission performance, through the analysis of the simulation results can get reasonable parameters of LDPC codes scheme and the design of communication system has practical guidance.