Power allocation for two-user cognitive multiple access channels under primary user outage constraint

This paper considers a two-user spectrum sharing cognitive radio multiple access channel (CR-MAC) coexisting with a pair of primary users (PUs). Different from the existing works in CR-MAC where the interference power constraint is applied to protect the PU transmission, a more advanced protection criterion over the interference power constraint, namely PU outage constraint, is adopted in this paper to not only protect the PU transmission but also improve the performance of the CR-MAC. Under such a constraint as well as the transmit power constraint, an iterative power allocation algorithm is proposed to maximize the ergodic sum capacity of the CR-MAC. It is shown by extensive simulations that the proposed power allocation algorithm significantly outperforms the existing algorithm based on the interference power constraint, with the same resultant PU outage probability.