Adaptive transmission schemes for free-space optical channel

Scintillation can be a major issue for free space optical communication (FSO) links even under clear sky condition. In this paper, adaptive techniques are proposed as a means to combat the scintillation. We first consider adaptive symbol-rate in which the symbol duration varies according to the channel condition. Join adaptation of both the symbol-rate and power is then investigated. The adaptation algorithm in each case is formed as an optimization problem with the objective of maximizing the throughput of the system. The performance of the system with a bandwidth constrained detector is also evaluated. Results showed that significant improvement over the fixed transmission system can be obtained.