Tracking based on Control Information and Beam Divergence Control in FSO with Moving Nodes toward 6G

When free-space optics (FSO) is applied to moving objects, it is necessary for the transmitter and receiver to estimate each other's positions and continue to adjust their beam directions so that they face each other correctly. For some objects such as drones without a scheduled trajectory, we propose a method to acquire the operator's control information and use it for tracking. In this method, the transmission distance measurement is also required for accurate adjustment of beam directions. If there is an estimation error in the transmission distance, the beam direction deviates from the ideal one. To address this problem, we also propose directivity control against the error on the transmission distance and evaluate the effect on the improvement of available communication time. By expanding the beam divergence angle, the communicable time is increased by 60%.