激光通信中的分集检测技术

在大气弱湍流模型下,应用Monte Carlo方法,通过产生符合光信号的对数幅度联合概率分布的数据,近似模拟计算了分集接收机的逐符号最大似然检测算法的似然比.研究了减少Monte Carlo方法中仿真点的个数对逐符号最大似然检测的分集接收机检测性能估计的影响.随后提出一种基于训练序列的分集检测方法.该方法在未知衰落分布相关信息的情况下,利用每帧内引入的一定长度的训练序列提供了某一较短时间间隔内的大气湍流信道的信息,基于与似然比表达式结构相似的算法获得改善的检测效果.仿真结果表明在各个分集接收机之间存在较强相关性的情况下,该算法仍可实现有效的检测.

Diversity detection algorithms in laser communications

The likelihood ratio function in symbol-by-symbol maximum likelihood detection was calculated with the Monte Carlo method for the atmosphere laser communication systems under the weak turbulence condition.Discrete points were mass-generated according to the marginal distribution for the turbulence-induced fading.Then the accuracy of estimating the diversity performance with a relatively less number of discrete points was discussed.A practical diversity detection algorithm was presented based on an algorithm similar to the likelihood ratio function's structure and the training sequence.This algorithm was designed to operate without any knowledge of turbulence-induced fading channel in advance.The training sequence introduced in each frame can provide the atmosphere turbulence-fading channel information for the following information sequence's detection.Simulations were taken,and the results show the validity of this newly introduced algorithm even when strong correlation exists.