A Unified Performance Analysis of OGS-to-Satellite FSO UpLink under Turbulence and Beam Wander

Free space optical (FSO) uplink from a service provider to a Low Earth Orbit (LEO) satellite has emerged as a promising solution to transfer large amount of data to the satellite to be relayed to huge number of users over wide geographical areas. In this paper, we present a new unified model for the FSO uplink from an optical ground station (OGS) to a LEO satellite, while considering subcarrirer intensity mod-ulation/direct detection (SIM/DD) and coherent FSO detection techniques. We take into account the various channel fading effects of atmospheric turbulence, beam wander and OGS - Satellite misalignment errors. We then make use of this model to present new expressions for the outage probability and the ergodic capacity of the FSO uplink and the average symbol error rate over the FSO uplink for different digital modulation schemes in exact closed-forms. Numerical examples show that coherent FSO systems give better performance over the FSO uplink than SIM/DD FSO systems which improves more with small zenith angles and less misalignment errors.