FSO 中基于 LDPC 码的编码多级调制方式研究

为降低自由空间光(FSO: Free Space Optical)通信系统中由大气湍流引起的误码率影响, 提出基于低密度 奇偶校验(LDPC: Low-Density Parity-Check) 码的编码多级调制方式, 该方式将 LDPC 码与二进制相移键控 (BPSK: Binary Phase-Shift Keying)和脉冲位置调制(PPM: Pulse Position Modulation)复用的调制方式相结合, 以 提升 FSO 系统的性能。 设计了基于 PPM-BPSK-LDPC 编码多级调制方式的发射机以及接收机系统模型。 通过 在弱湍流信道和平均功率约束下的仿真证明, 所提的 PPM-BPSK-LDPC 编码多级调制方式与基础的PPM-LDPC 编码调制方式相比, 其频带利用率更高, 平均误码率性能更好。

Research on Coded Multilevel Modulation Technology Based on LDPC Codes for Free Space Optical

In order to reduce the bit error rate caused by atmospheric turbulence in FSO (Free Space Optical) communication system,a coded multilevel modulation scheme based on LDPC (Low-Density Parity-Check) codes is proposed.This scheme employs the combination of BPSK(Binary Phase-Shift Keying) and PPM (Pulse Position Modulation) with LDPC codes to improve the performance of the FSO system.The transmitter and receiver models are designed based on PPM-BPSK-LDPC coded multilevel modulation scheme.The numerical results indicate that the bandwidth utilization and the bit error rate performance of the proposed PPM-BPSK-LDPC coded multilevel modulation scheme are always better than ordinary PPM-LDPC coded modulation scheme under weak turbulence channel with average power constraint.