Optimal Power Allocation for Multicasting in Multiple Antenna Cognitive Radio Networks
Sangeeta Bhattacharjee, Tamaghna Acharya, Uma Bhattacharya · 2018
In this paper, we consider an underlay cognitive radio (CR) multicast network where a secondary network, comprising of a cognitive base station (CBS) and multiple secondary user (SU) multicast groups, coexist with a primary user (PU) network. The CBS is equipped with multiple antennas, which transmit information to multiple multicast groups over a set of orthogonal PU channels. An exact as well as an asymptotic expression for multicast group outage probability of SUs are derived. Also, the closed form expression for outage probability of PUs, both in absence and presence of interferences from the CBS are analyzed. Furthermore, the optimal multicast group power allocation problem, to minimize the aggregate group outage probability of the CR multicast system is presented. To guarantee QoS of PUs' transmission, a probabilistic outage loss constraint is considered. In high SNR regime, the outage probability minimization problem under outage loss constraint of PUs and average transmit power constraint of the CBS, is shown to be convex in nature. Simulation results are presented to validate the proposed analytical expressions as well as the power allocation scheme. Results demonstrate that the spectral efficiency of the SUs improve significantly with the increase in antenna array size.