Outage study of cognitive relay network with multiple primary users and outdated CSI

Considering outdated channel state information (CSI) in both secondary-to-primary (S-P) links and secondary-to-secondary (S-S) links, we study outage probability (OP) of cognitive relay network (CRN) with the presence of multiple primary users (PU)s. we assume that the secondary system is deploying intermediate regenerative relay node to maintain quality of service (QoS). The relay node is selected by means of partial relay selection (PRS) technique. We derive exact expression of the OP under constraint on the maximum inflicted interference. Given to the outdated CSI, we devise a back-off power control policy to maintain interference probability (IP), resulted from outdated CSI, below a preferable value. In this regard, we propose a simple method to reduce the amount of mathematical calculations. Numerical simulations are made and results verify correctness of the analytical expressions. Findings suggest that increasing number of PUs can be useful when CSI is not acute while it degrades system performance in acute CSI.