Partial relay selection for combating the effects of co-channel interference in RF/FSO cooperative relaying

Abstract In this research work, mixed radio frequency (RF)/free space optical (FSO) communication systems have been investigated in the presence of multiple interferers at the relay node. The considered system incorporates partial relay selection (PRS) using the available outdated channel state information (CSI) at the relay node to combat the effect of interference. The fading on the PRS-aided RF link has been modeled using the Rayleigh distribution whereas the statistics of the co-channel interferers (CCIs) at the relay node has been modeled using Nakagami- m fading distribution. On the other hand, FSO link has been assumed to undergo α − μ distributed atmospheric turbulence with pointing errors. To this end, the model on the FSO link considers the impact of both kinds of optical demodulation schemes i.e., intensity modulation direct detection (IM/DD) and coherent demodulation. For the system under study, exact closed-form expressions for the outage probability, bit error rate (BER) and ergodic capacity have been presented. Further to this, asymptotic high signal to noise ratio (SNR) approximate expressions have been derived for outage probability, BER and ergodic capacity to extract quick insights into the results. Finally, numerical examples have been demonstrated to validate the findings of the research work.