Statistics of Received Power Time Series for Optical LEO Satellite Uplinks

Abstract

In free-space optical satellite communications, a transmitted optical signal is perturbed by pointing inaccuracies and through the atmosphere's index-of-refraction turbulence. This leads to signal fluctuations and power fading when detected by a receiver. Knowledge of these signal instability statistics is advantageous for the design of robust ground- and space-based optical communication systems. For example, the development of optimized automatic repeat request (ARQ) and forward error correction (FEC) protocols to compensate these losses is facilitated. The channel characteristics of a ground-to-satellite (uplink) and satellite-to-ground (downlink) transmission change with the elevation angle of the link direction, and consequently, the signal fluctuations and power fading also vary. In this work, numerical time series of received power are generated for uplink scenarios to low Earth orbit (LEO) satellites for different satellite elevations. The time series are generated for two experimental scenarios, considering the effects of a gamma-gamma and lognormal-distributed atmospheric scintillation and the use of transmitter diversity. The generated series of power are compared with analytical results and measurements in terms of the run of statistical parameters, and the results are contrasted. The results can be used for link-budget design, for communications standardization, and for the analysis and design of fading mitigation techniques that prevent signal fading and data loss.