Cross-layer design and analysis for FSO links using automatic repeat request and adaptive modulation/coding schemes

This paper introduces a framework for cross-layer management of data transmissions in free-space optical (FSO) systems over atmospheric turbulence channels, in which link layer automatic repeat request (ARQ) and physical layer adaptive modulation and coding (AMC) are integrated to improve the system´s spectral efficiency. The system performance is analytically studied in terms of average frame-error rate and average spectral efficiency, for which we derive closed-form expressions. In numerical results, we show how the proposed scheme outperforms a conventional one, and discuss cross-layer designs for parameters´ selection in both physical and link layers to optimise the system performance over different atmospheric turbulence conditions.