Adaptive bandwidth for satellite optical communication

Abstract

Satellites in free space suffer from periods of high displacement amplitude vibrations. Most of the vibration is caused by satellite internal subsystems (such as thruster firing or solar array drive mechanism) and controlled by the satellite computer. To utilise the advantages of optical communication in space, very narrow divergence transmitted beams are used. The high-amplitude vibrations of the transmitter satellite cause a decrease in received signal power in the receiver satellite due to mispointing of the transmitted beam. In the paper, the authors derive a model of a communication system that adapts the communication system parameters to changes in received signal caused by changes in vibration amplitude. The purpose of this model is to keep the bit error rate (BER) low and constant by adapting the system bandwidth and the receiver parameters to the vibration amplitude. This model is useful for communication systems with two or more priorities of real time – for example, telephone calls and electronic mail. This means that, when the bandwidth shrinks, electronic mail messages may be delayed but the phone calls can continue. Comparison and analysis of the performance of practical standard and adaptive models of communication systems for variable vibration amplitude are presented.