Outage Analysis of Spectrum Sharing Cognitive DF Relay Networks Using Outdated CSI

We investigate the effect of the outdated channel state information (CSI) on the secondary relay-aided network´s performance. We carry out the analysis of the outage probability as well as the diversity order of the secondary network (SN) considering three key constraints: 1) maximum transmit power at the secondary transmitter, 2) peak interference power at the primary receiver, and 3) outdated CSI at the secondary-to-primary and secondary-to-secondary links. The performance results show that the relay cluster position, the imperfect CSI of the interference links and of the second hop are the key optimization factors. We show that the correlation coefficient of the second hop link is the key optimization parameter of the diversity order.