Outage Performance of Cognitive AF Relaying Networks over generalized η − μ Fading Channels

In this paper, a dual-hop cognitive amplify-and-forward (AF) relay network subject to independent nonidentically distributed (i.n.i.d.) η − μ fading channels is investigated. In the considered network, secondary users (SUs) including one secondary user source (SU-S) and one secondary user relay (SU-R) are allowed to share the same spectral resources with the primary user (PU) simultaneously under the premise that the quality of service (QoS) of PU can be guaranteed. In order to guarantee the QoS of PU, the maximum interference power limit is considered to constraint the transmit powers at SU-S and SU-R. For integer-valued fading parameters, a closedform lower bound for the outage probability (OP) of the considered networks is obtained, whereas the lower bound in integral form for the OP is derived for arbitrary-valued fading parameters. For the special case of the generalized η−μ fading channels, such as Nakagami-m fading channels, the analytical results become the previous published results. In order to obtain further insights on the OP performance, asymptotic expressions for the OP at high SNRs are derived. From the asymptotic results, we also reveal that the diversity gain of the secondary network is only determined by the fading parameters of the secondary network, whereas the primary network only affects the coding gain. Finally, simulation confirms the correctness of our analysis. Key–Words: Outage probability (OP), amplify-and-forward (AF), cognitive relaying networks (CRN), η−μ fading, spectrum sharing.