Performance analysis of cognitive relay networks with imperfect channel knowledge over Nakagami-m fading channels

In underlay cognitive radio networks, imperfect channel knowledge will have an adverse effect on the performance of both the primary users (PU) and the secondary users (SU) owing to the interference power constraint of PU. This paper investigates the performance of a cognitive relay network (CRN) with imperfect channel state information (CSI) of the interference links over Nakagami-m fading channels. Interference probability is defined to characterize the interference caused by SU to PU due to CSI imperfection. Closed-form expressions for both the interference probability of the primary user and the outage probability of the secondary system are derived and validated by simulations. It is proved that the interference probability of the primary user is always 0.5 under the condition of imperfect CSI when no power control mechanism is adopted. The effects of CSI imperfection, channel fading severity, interference probability of PU and transmit power of PU on the outage performance of the secondary system are also analyzed.