Optimization of the settings of the adaptive distributed frame repetition to the time-changing transmission line conditions

In order to stably achieve high throughputs in the satellite-to-ground free space optical communication systems, suppression of the influence of the fading due to atmospheric turbulence is an important technical subject to be overcome. Our group has proposed the use of Adaptive Distributed Frame Repetition (ADFR) as a countermeasure of this problem, which enables the seamless switching between the features of high-speed transmission and high tolerant link connection in response to the transmission link conditions. We have developed the test equipment of the functions whose interface was 10GbE, and demonstrated the improvements of the packet error ratio and the throughput against the varieties of the fading patterns. The settings of the ADFR should be carefully determined with the considerations of several trade-offs. The efficient suppression of PER enabled by the excess repetition and interval sacrifice the transmission bandwidth and the system latency, respectively. In this time, we develop a function that extracts the fading characteristics of the moment from the decimated signals after transmission, and, by using this information, realize the continuous optimizations of the ADFR settings to the time-changing fading patterns. The details of the estimation method and the demonstrations with this technique will be presented at the conference.