Switching-assisted Cooperative decode-and-forward Relaying for Hybrid FSO-RF System

In this work we propose a hybrid free-space optics (FSO)/ radio-frequency (RF) system with low complexity and high performance using Time-Hysteresis (TH) assisted switching for transition between FSO and RF links. The hybrid system transmits information over FSO link when at the FSO receiver end the instantaneous signal-to-noise ratio (SNR) is greater than the predefined threshold SNR. If it drops down the predefined threshold SNR value, the system switches over RF link. To ensure the proposed model to provide better spatial diversity we considered multi-input-multi-output (MIMO) transmitter and receiver. To improve the long haul communication efficiency we included the cooperative communication using decode-and-forward (DF) relaying method and for receiver reconstruction, majority logic combining (MLC) algorithm has been utilised as very low complexity and effective detection of signals at the receiver end. The Monte-Carlo-simulation has been performed to validate the results in proposed model in different atmospheric-turbulence (AT) regimes as well as pointing errors (PE) scenarios with gereralised Malaga distribution. Key performance indices (KPI) are average symbol-error-rate (SER), bit-error-rate (BER), outage probability, secrecy rate, ergodic channel-capacity and link quality to investigate the proposed system performance. The results show that the proposed switching method for a DF hybrid system drastically enhances the performance in comparison to a single-hop (SH) scheme assisted hybrid systems as well as single RF and single FSO system. Proposed system achieves average SER of 10–6 in the lower SNR region.