Performance of Opportunistic Beam Selection for OWC System Under Foggy Channel with Pointing Error

Abstract

Performance of optical wireless communication (OWC) in outdoor environments can be significantly degraded due to the fog and pointing errors. In this letter, we consider a multi-aperture detector which employs a low complexity opportunistic beam selection (OBS) in order to improve the performance of OWC system. We analyze the OBS scheme by deriving computable bounds on the average signal-to-noise ratio (SNR), ergodic rate, and diversity order and compare its performance by deriving exact analytical expressions of a single-aperture system. The derived bounds provide insights on the system behavior depicting significant benefit for OWC systems with small link distances which are typical in foggy environments. We also demonstrate the effect of various parameters of fog and pointing error on the OWC performance and validate the derived analytical expressions using numerical and simulation analysis. A two-aperture OBS achieves an SNR gain of approximately 4 dB and improves the outage performance by more than 20 folds for a half-km OWC link comparing to the single-aperture system without acquiring the channel state information.