ABERs of LDPC-Coded Multi-Hop FSO Over Double GG Fading Channels With Pointing Error and Path Loss

The average bit error rate (ABER) performances of low-density parity-check (LDPC)-coded multi-hop free-space optical (FSO) communication system with decode-and-forward strategy over the aggregated double generalized gamma (double GG) fading channels for plane and spherical waves are investigated. In particular, on the basis of the unified closed-from expressions of the composite probability density function and cumulative distribution function in terms of the Meijer’s G function, the analytical expression of the ABER for this multi-hop FSO system is derived by generalized Gauss-Laguerre quadrature rule and verified by Monte Carlo simulation. Furthermore, LDPC codes are adopted to improve the system performance. The results show that the ABER performance over double GG distribution is mainly limited by both pointing error and path loss for these two transmission beams, whereas the fading can be significantly improved by LDPC codes, and the coding gain improvement becomes more apparent by decreasing the normalized beam-width, increasing the normalized jitter and hop numbers. This work is beneficial for the FSO system design.