On the performances of relay-aided FSO system over M distribution with pointing errors in presence of various weather conditions

Abstract

The average bit error rate (ABER) and outage performances of decode-and-forward (DF) based multi-hop parallel free-space optical (FSO) communication system with the combined effects of path loss, pointing errors (i.e., misalignment fading), and atmospheric turbulence-induced fading modeled by M distribution have been investigated in detail. Particularly, the end-to-end probability density function (PDF) and cumulative distribution function (CDF) over the aggregated fading channel are derived for the first time. Based on the binary phase-shift keying (BPSK) subcarrier intensity modulation scheme, the analytical expressions for the end-to-end ABER and outage probability are obtained, respectively. The ABER and outage performances of the present FSO system are then analyzed systematically with the effects of turbulence strengths, weather conditions, pointing errors, and structure parameters (M and N) taken into account. This study shows that the turbulent atmosphere, weather conditions and pointing errors can be mitigated by increasing the number of cooperative path (N) over M fading channels. For the fixed hop length, the FSO system performance will be degraded with the increasing hop numbers (M). But the performance will be improved with the increasing hop numbers (M) when the total distance from the source to destination is fixed. Monte Carlo simulation is also provided to verify the correctness of the proposed ABER expression.