On Outage Capacity of Secondary Users in Fading Cognitive Radio Networks with Primary User's Outage Constraint

This paper considers a cognitive radio network where a secondary user shares the same narrow band with a primary user for transmission. Instead of adopting the conventional interference-power/interference-temperature constraint, this paper proposes a new type of constraint for the secondary user to protect the primary transmission, which limits the maximum outage probability of the primary transmission subject to the secondary user's interference to be below a prescribed target. Under this newly proposed constraint along with the average/peak transmit power constraint, the paper derives the optimal power allocation strategies over block-fading channels for the secondary user to achieve its outage capacity. It is shown by simulations that the derived power allocation strategies achieve substantial outage capacity gains for the secondary user over the conventional power control policies based upon the interference-temperature constraint, given the same primary user's outage probability constraint.