Over the years, free-space optical (FSO) communication has attracted considerable research interest owing to its high transmission rates via the unbounded and unlicensed bandwidths. Nevertheless, various weather conditions lead to significant deterioration of the FSO link capabilities. In this context, we report on the modelling of the channel attenuation coefficient (β) for a coastal environment and related ambient, considering the effect of coastal air temperature (T), relative humidity (RH) and dew point (TD) by employing a mobile FSO communication system capable of achieving a transmission rate of 1 Gbps at an outdoor distance of 70 m for optical beam wavelengths of 1310 nm and 1550 nm. For further validation of the proposed models, an indoor measurement over a 1.5 m distance utilizing 1310 nm, 1550 nm, and 1064 nm lasers was also performed. The first model provides a general link between T and β, while the second model provides a relation between β, RH as well as TD. By validating our attenuation coefficient model with actual outdoor and indoor experiments, we obtained a scaling parameter x and decaying parameter c values of 19.94, 40.02, 45.82 and 0.03015, 0.04096, 0.0428 for wavelengths of 1550, 1310, 1064 nm, respectively. The proposed models are well validated over the large variation of temperature and humidity over the FSO link in a coastal region and emulated indoor environment.

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This work investigates the end-to-end performance of a free space optical amplifyand-forward (AF) channel-state-information (CSI)-assisted relaying system using heterodyne detection over Malaga turbulence channels at the presence of pointing error employing rectangular quadrature amplitude modulation (R-QAM). More specifically, we present exact closed-form expressions for average bit-error rate for adaptive/non-adaptive modulation, achievable spectral efficiency, and ergodic capacity by utilizing generalized power series of Meijer's G-function. Moreover, asymptotic closed form expressions are provided to validate our work at high power regime. In addition, all the presented analytical results are illustrated using a selected set of numerical results. Moreover, we applied the bisection method to find the optimum beam width for the proposed FSO system.

In this paper, we derive the performances of optical wireless communication system utilizing adaptive subcarrier intensity modulation over the Malaga turbulent channel. More specifically, analytical closed‐form solutions and asymptotic results are derived for average bit error rate, achievable spectral efficiency, outage probability, and ergodic capacity by utilizing series expansion identity of modified Bessel function. Our asymptotic and analytical results based on series solutions with finite numbers highly matched to the numerical results. By exploiting the inherent nature of fading channel, the proposed adaptive scheme enhances the spectral efficiency without additional transmit power while satisfying the required bit error rate criterion. Copyright © 2016 John Wiley & Sons, Ltd.