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为了减小大气衰减效应和大气湍流效应对自由空间光通信的影响,采用了多输入多输出技术。假定自由空间光通信系统采用开关键控强度调制直接探测,信道独立同分布、无记忆平稳遍历并且具有加性高斯白噪声,在发射端和接收端都可以获取理想信道状态信息;建立了综合大气效应下多输入多输出信道模型和系统模型,推导了等增益分集合并下自由空间光通信系统的遍历容量和中断概率闭合表达式,仿真分析了各种天气条件和大气湍流对空间光通信链路的影响,结果显示随着发射孔径和接收孔径的数目增多,大气效应的影响逐渐减小,通信系统性能随之提高。从系统复杂度及性能提高程度综合考虑,选择2个发射孔径、2个接收孔径较为合适。
In order to reduce the effects of atmospheric attenuation and atmospheric turbulence on free space optical communications, a multiple-input multiple-output technique was used. It is assumed that the free-space optical communication system uses on-off keying intensity modulation to detect directly, the channels are independent and identically distributed, memoryless smooth traversal and additive white Gaussian noise can obtain ideal channel state information both at the transmitting end and the receiving end. An integrated atmosphere Effect and multi-input multiple-output channel model and system model, the ergodic capacity and discontinuity closed-form expressions of free space optical communication system under equal gain diversity combining are deduced. The simulation analysis of various weather conditions and atmospheric turbulence to space optical communication link The results show that as the number of transmitting apertures and receiving apertures increases, the effect of the atmospheric effect gradually decreases and the performance of the communication system increases accordingly. Considering the complexity of system and the improvement of performance, two transmitting apertures and two receiving apertures are appropriate.