Performance Enhancement of Spectrum Sharing Cognitive Relay Networks With Outdated CSI

For cognitive relay networks coexisting with multiple primary transceivers, we investigate the secondary system performance using outdated channel state information (CSI). We propose a new power allocation strategy based on regression model and we derive the outage probability expression as well as the diversity order of the secondary network (SN). The performance results show that the proposed power allocation strategy allow the SN to overcome the CSI imperfectness while maintaining the transmit power and the primary network (PN) constraints. Analytical and simulation results show that the diversity order is not affected by the number of involved primary receivers.