Outage probability analysis of hard-switching based mixed FSO/IRS-aided RF communication

The performance analysis of hard-switching based mixed free-space optical (FSO)/ intelligent reflecting surface (IRS)-aided radio frequency (RF) communication system is carried out in terms of outage probability (OP). The FSO link with larger bandwidth is considered as primary link, it is active for transmission when the FSO channel condition is good enough. The RF link referred to as the back-up link is activated for transmission whenever the FSO link is poor. Further, the transmission via RF link is assisted by an IRS consisting of reflecting elements that are programmable and passive in nature. For this setup, the OP is evaluated for different numbers of reflecting elements at the IRS. In order to obtain 0:001 OP with 28 dB transmit signal-to-noise ratio (SNR) of the RF link, the required transmit SNR of the FSO link with 90 elements at the IRS in the RF link is 31 dB whereas, with 100 elements at the IRS, the required SNR is 24 dB. Thus, it has been observed that just by adding 10 extra passive IRS elements, required SNR of the FSO link can be reduced by 7 dB while keeping the OP fixed. The impact of the IRS on the OP is significant specifically when the FSO link is weak. Further, the OP performance of hardswitching scheme based mixed IRS-aided RF/FSO system has been analyzed considering both strong and moderate atmospheric turbulences, and different link distances.