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分析了在Gamma-Gamma信道下基于脉冲位置调制(PPM)的多输入多输出自由空间光通信(MIMO-FSO)系统模型。理论上分析LT码原理,研究了不同湍流环境下LDPC码与LT码对MIMO-FSO系统性能的影响,同时比较不同度分布时的LT码对该系统性能的影响。通过仿真实验验证了在不同湍流环境下,LT码对于该系统的性能有较大的提升,且在强湍流环境下,采用修正转移鲁棒孤子分布(ISRSD)的LT码能有效地降低译码开销,进一步提升该系统的性能。
The model of MIMO-FSO based on pulse position modulation (PPM) under Gamma-Gamma channel is analyzed. The principle of LT code is theoretically analyzed, and the influence of LDPC code and LT code on the performance of MIMO-FSO system under different turbulent environments is studied. Meanwhile, the influence of LT codes with different degrees of distribution on the performance of the system is compared. Simulation results show that under different turbulent environments, the LT code has a great improvement on the performance of the system. In strong turbulence environment, the LT code with modified transfer robust soliton distribution (ISRSD) can effectively reduce the coding Overhead, to further enhance the system’s performance.