Outage performance analysis of dual-hop AF relaying system with underlay spectrum sharing

In this paper, we investigate the outage performance of underlay cognitive dual-hop relaying systems under the effect of using statistical instead of instantaneous information of the interference links (from the secondary source and relay to the primary user) and the first relaying link (from the secondary source to relay) to calculate transmit power and amplifying gain for secondary network. We derive the closed-form of outage probability expression for some considered cases and validate them through simulation results. It is numerically demonstrated that using instantaneous information of the first relaying link for calculating the amplifying gain plays a vital role while using interference link statistical information does not strongly affect the system performance. Furthermore, this work shows that the fixed gain specified by averaging the individual random components of the variable gain is not applicable in underlay cognitive dual-hop relaying systems.