Evaluation of Error Correcting Code performances of a free space optical communication system between LEO satellite and Ground Station

Abstract

The use of optical communication to transfer data between LEO satellite and optical ground station is being studied. It creates the opportunities to highly increase a transmitted data rate across a free space. The optical propagation channel has specificities that imply the potential use of error correcting code (ECC) and interleaving at physical and higher layer. The study aims to assess the performance of a combination of ECC and interleaving in presence of various channel scenarios and receiver architectures. As a result of these studies, a functional physical layer simulator is provided. The simulator emulates a signal generation and applies time series representing the propagation channel with an effect of receiver front-ends. It also features various detection methods and computes mutual information (MI) in order to approximate ECC performances. A number of receiver architectures and channel scenarios were studied. The channel scenarios combine a direct coupling of the received signal into the photo-detector (PD) and among other assume the use of pre-amplified receiver implying the signal coupling into a standard single mode fiber (SSMF) prior to the detection. Time series were generated and represent the power received at PD input depending on the chosen scenarios (without adaptive optics (AO), with tip-tilt correction, with no dynamical coupling losses or with higher order AO correction). Two modulations of OOK and DBPSK along with various detection methods were examined. The tuning of ECC parameters was studied through the computation of mutual information. Additionally two cases of physical and higher layer interleaving were implemented providing an excellent diversity to the channel seen by the codeword of ECC.