Coherent Laser Ground-to-Satellite Communications in the Presence of Atmospheric Turbulence and Loss

Coherent Binary Phase Shift Key (BPSK) has been proposed for Low-Earth-Orbit LEO) -satellite-to-ground communications. This paper will present new models for the turbulent channel BPSK signal-to-noise ratio and average Bit Error Rate (BER). These models include equations for the linear and square-law receiver signal-to-noise ratios, turbulent channel heterodyne efficiency, turbulent carrier-to-noise and signal-to-noise ratios, signal-local oscillator beam position mismatch, and tracked beam-wander intensity variance. This paper will also show some example calculations assuming These models will be evaluated using the Round-Earth Model and the Hufnagel-Andrews-Phillips (HAP) refractive index structure parameter vertical profile model. Results show that the beam-wander intensity variance will cause high asymptotic average BERs for all receiver zenith angles and high carrier-to-noise ratios under moderate-to-strong turbulence levels. The conclusion is that additional means like forward error correction coding are needed to reduce the average BER to more desirable levels.