On the performance of cognitive radio networks with DF relay assistance under primary outage constraint using SC and MRC

In this paper, we analyze the performance of a cognitive radio network (CRN) that is assisted by a single relay. In particular, the secondary user (SU) transmitter (SU-Tx) and the secondary relay (SR) utilize the licensed frequency band of the primary user (PU). To protect the PU from harmful interference, the SU-Tx and SR must regulate their transmit power to satisfy the outage probability constraint of the PU. System performance in terms of outage probability is analyzed for selection combining (SC) and maximal ratio combining (MRC). Specifically, a power allocation policy and analytical expressions for the outage probability with SC and MRC are derived. Our results show that the upper bound of the outage probability corresponding to MRC is equal to the exact expression for the outage probability for SC.