PROJECT TITLE :
Analysis of earth-to-satellite free-space optical link performance in the presence of turbulence, beam-wander induced pointing error and weather conditions for different intensity modulation schemes
In this study, the authors evaluate the performance of an earth-to-satellite free-area optical link in terms of bit error rate (BER) for three intensity modulation (IM) schemes [on–off keying (OOK), M-ary pulse position modulation (M-PPM) and M-ary differential PPM (M-DPPM)] and direct detection receiver. The performance is analysed in the presence of atmospheric turbulence, beam-wander induced pointing error and atmospheric condition. Turbulence with beam wander impact is modelled using gamma-gamma distribution and the weather effects are incorporated using the Beer-Lambert law. They get closed type BER expressions for the above IM schemes using combined channel state likelihood density functions. They show that for the same average power, M-PPM offers the most effective performance, followed by M-DPPM and OOK schemes. Link performance degrades for all IM schemes with increase within the worth of ground level refractive index structure parameter and bit rate. Presence of atmospheric condition like moderate, light-weight and skinny fog increase signal attenuation and this increase might be terribly high in case of thick and dense fog or clouds and can cause link failure.
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