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空时网格码具有编码增益与频谱利用率高的特点,针对强度调制直接检测(Intensity modulation/direct detection,IM/DD)方式,提出了一种适合于大气激光通信的空时网格编码方案。该方案运用快速傅里叶逆变换(IFFT)的对称性以及加直流分量的方法解决了空时网格编码信号无法直接用于IM/DD链路传输MPSK信号的问题。之后,通过蒙特卡洛方法分析了该方案在不同大气闪烁条件下的误码性能,并对调制阶数和天线数对系统误码性能的影响进行了分析。结果表明:所提方案能够有效抵御大气湍流所产生的闪烁效应,其性能随天线数的增加而得到明显的改善,并且在强湍流条件下表现出了更好的性能。
Space-time trellis codes have the characteristics of high coding gain and spectrum utilization. Aiming at the IMDM (Intensity modulation / direct detection) method, a space-time trellis coding scheme suitable for atmospheric laser communication is proposed . The scheme uses the symmetry of IFFT (Inverse Fast Fourier Transform) and the method of adding DC component to solve the problem that space-time trellis coded signal can not be directly used to transmit MPSK signal on IM / DD link. After that, the error performance of this scheme under different atmosphere flicker conditions was analyzed by Monte Carlo method. The influence of modulation order and number of antennas on system error performance was also analyzed. The results show that the proposed scheme can effectively resist the flicker effect caused by atmospheric turbulence, and its performance is obviously improved with the increase of the number of antennas. The proposed scheme shows better performance under strong turbulent flow conditions.