Performance Analysis of SIMO-FSO Systems With Coupled Pointing Errors and Correlated Lognormal Turbulence

초록

This paper investigates the performance of single-input multiple-output (SIMO) free space optical (FSO) systems under correlated lognormal atmospheric turbulence and coupled pointing errors caused by univariate beam displacement. In practical SIMO-FSO systems, geometric loss becomes correlated across receiver lenses due to shared pointing jitter, while atmospheric turbulence fading is also spatially correlated depending on lens spacing. By accurately accounting for these two dominant correlation sources, we derive approximate closed-form expressions for the outage probability, average bit error rate (BER), and ergodic capacity using the Fenton Wilkinson (FW) method and Gaussian-Hermite quadrature rule (GHR). Furthermore, based on the formal definition of geometric loss, we rigorously derive the exact diversity order, revealing that it is independent of the number of receiver lenses and is fundamentally limited by pointing jitter. Numerical results validate the analytical accuracy and demonstrate that increasing lens spacing effectively mitigates correlation and improves outage probability and BER in the mid-to-high signal-to-noise ratio (SNR) regime, while the associated ergodic capacity loss can be compensated by increasing the number of lenses. The proposed framework further enables the numerical determination of the optimal lens spacing that minimizes the average BER in SIMO-FSO systems.

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