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.