Free-space optical communication links experience atmospheric turbulent light intensity fluctuation fading, which requires accurate channel parameter estimation to ensure stable communication. In this paper, the maximum likelihood (ML) method is proposed to estimate composite Gamma–Gamma fading channel parameters. The ML estimation expression based on the expectation maximization (EM) to compute unknown parameters is derived. Newton–Raphson (N–R) and generalized moment method (GMM) are used to compare EM algorithm with the estimation performance. We used the Cramer–Rao Bound (CRB) to evaluate these estimation algorithms. Each estimator’s performance is compared using simulation data as well as experimental measurements under different meteorological conditions. It is found that the proposed technique has better estimation performance for fading parameters of atmospheric turbulence channel.

自由空间光通信链路会经历大气湍流光强度波动的衰减，这需要精确的信道参数估计以确保稳定的通信。在本文中，提出了最大似然（ML）方法来估计复合Gamma–Gamma衰落信道参数。推导基于期望最大化（EM）的ML估计表达式，以计算未知参数。牛顿-拉夫森（N-R）和广义矩法（GMM）用于将EM算法与估计性能进行比较。我们使用了Cramer-Rao Bound（CRB）来评估这些估计算法。使用模拟数据以及在不同气象条件下的实验测量结果来比较每个估算器的性能。