Improvement of Required SNR for Satellite-to-Ground Optical Communication Via Aperture Diversity by Using PPM

In this paper, in order to achieve sufficient bit error rate (BER) as a function of the zenith angle between satellite and ground station, SNR requirement is investigated utilizing pulse position modulation (PPM). In order to realize explicit results, many parameters included zenith angle have been considered. Results indicate that, to achieve desired BER, SNR values are in wide range while zenith angle changes from small to large values. It is shown that, instead of to establish the link with predetermined intervals of the zenith angle, aperture diversity at the receiver is utilized to communicate even large zenith angles with reasonable values of the SNR.