Capacity Analysis for Rayleigh/Gamma-Gamma Mixed RF/FSO Link with Fixed-Gain AF Relay

Banibrata BAG  Akinchan DAS  Aniruddha CHANDRA  Chayanika BOSE  

IEICE TRANSACTIONS on Communications   Vol.E100-B   No.10   pp.1747-1757
Publication Date: 2017/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2017OBP0001
Type of Manuscript: Special Section PAPER (Joint Special Section on Opto-electronics and Communications for Future Optical Network)
atmospheric turbulence,  gamma-gamma fading,  amplify-and-forward relay,  mixed RF/FSO system,  ergodic capacity,  

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Free-space optical (FSO) communication, which offers better data rate at a lower cost compared to radio-frequency (RF) backhauls, and is much easier to setup and maintain than optical cables, is gaining attention as an attractive substitute. Average capacity is one of the main performances metrics to understand the connectivity and data rates of a communication system but the performance analysis for mixed RF/FSO link is not straightforward as the RF link and the FSO link experiences different atmospheric perturbations. In this paper, we have investigated the ergodic capacity of a dual-hop mixed RF/FSO communication system realized with an average power scaling (APS) based amplify and forward (AF) relay. Assuming moderate to strong atmospheric turbulence, the FSO link is modeled by gamma-gamma distribution while it is assumed that the RF link experiences multipath Rayleigh fading. Simple analytical methods have been devised for obtaining concise closed-form expressions for ergodic capacity under four different rate/ power adaptation policies and are validated through extensive Monte Carlo simulations.