Performance enhancement of free space optical communication system using beam-optimized serial relaying in saturated atmosphere with pointing errors

In this paper, the performance improvement of a free space optical communication system with multi-hop and beam optimization has been studied. Novel closed-form expressions for the end-to-end average bit error rate, outage probability and average capacity of multi-hop free space communication system with decode-and-forward relaying are derived. Beam optimization is done using Nelder---Mead simplex algorithm. A composite channel model using atmospheric attenuation, turbulence and pointing errors is used to model the atmospheric impairments. The saturated atmospheric conditions are modeled by negative exponential channel model, and pointing error effects are considered by normalized jitter standard deviation parameter. The performance of the free space optical communication system in terms of end-to-end average bit error rate, outage probability and average channel capacity in saturated atmospheric turbulence conditions and pointing errors is significantly enhanced by using beam-optimized serial relaying with decode-and-forward transmission. The simulation results obtained by Monte Carlo simulation are in agreement with the results obtained from the closed-form expressions.