2.6 本章小结
首先，介绍了光无线通信的链路配置和强度调制直接检测系统的基本原理，说明了光无线信道和 RF通信信道特性的不同。其次，介绍了LOS信道和常用的几种漫射信道模型。然后，基于迭代法计算漫射信道冲激响应，对信道冲激响应时间离散化，提出了建立离散多径信道模型的整体思路和方法。
信道建模的时间起点是首先需要解决的问题。在室内单发单收系统，提出将光信号从LED光源到检测器的传输延迟作为多径信道建模的时间起点。在多光源的MIMO系统，提出将光信号经过LED阵列几何中心和检测器阵列几何中心连线的时间延迟作为多径信道建模的时间起点。定义从信道建模时间起点开始，路径延迟大于符号周期一半的光信号引起符号间干扰，得到信道离散时间间隔。从建模时间起点开始，将离散时间间隔之间的各次反射信号的时域冲激响应之和作为多径信道各路径增益。
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