A novel adaptive spectrum access protocol in cognitive radio with primary multicast network, secondary user selection and hardware impairments

In this paper, we propose an adaptive spectrum access protocol for secondary users (SUs) be used to access licensed bands in cognitive radio networks. Specifically, if the primary network, which uses multicast communication to transmit data from one primary source to multiple primary destinations, satisfies a required system quality of service (QoS), SUs can access the licensed bands, follows an underlay spectrum sharing. Otherwise, a secondary base (SB) station must assist the primary network in obtaining the QoS so that it can find opportunities to use the bands, i.e., cooperation-based spectrum access. To enhance the performance for the secondary network, in terms of outage probability (OP), various best-user selection methods are proposed. Moreover, we take into consideration the impact of hardware impairments on the OP of both primary and secondary networks. We derive exact and asymptotic closed-form expressions of the OP over Rayleigh fading channel. From the analytical results, an optimal value of maximal interference threshold and an optimal fraction of the SBs’ transmit power to the primary data are obtained when the secondary network operates on the underlay and the cooperation-based spectrum access modes, respectively. Finally, Monte Carlo simulations are performed to verify the theoretical derivations.