21 August 2009 A novel spatial tracking for FSO communications through turbulent atmosphere
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Performance of quad-APD spatial tracking loop (STL) in the presence of scintillation is investigated for freespace optical (FSO) channels impaired by optical turbulence. The atmospheric turbulence is assumed to follow the weak turbulence model, described by Rytov approximation, which in turn suggests log-normal statistics for the received optical signal intensity. It is assumed that the pointing error in large part is due to atmospheric wander and that the correlation time of the beam wander is comparable to the correlation time of the amplitude variations due to amplitude scintillation. Computationally-efficient extensions of a recently proposed spatial tracking model are investigated, resulting in two alternative implementation. The proposed algorithms enable one to adjust the gain of the tracking loop, resulting in an adaptive bandwidth adjustment scenario in the presence of correlated fading. The performance of the proposed tracking loops along with that of the standard tracking loop are assessed and compared via simulation in terms of the mean square tracking error (MSTE). Simulation results reveal the effectiveness of the computationally-efficient algorithms proposed here in reducing the MSTE as compared with the standard tracking loop, while offering a realizable solution as compared to the tracking loop suggested by the previous study on the subject.
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Kamran Kiasaleh, "A novel spatial tracking for FSO communications through turbulent atmosphere", Proc. SPIE 7464, Free-Space Laser Communications IX, 74640Q (21 August 2009); doi: 10.1117/12.826626; https://doi.org/10.1117/12.826626

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