Resource Allocation for Cognitive Radios in Dynamic Spectrum Access Environment

We investigate the dynamic spectrum sharing problem among primary and secondary users in a cognitive radio network subject to QoS constraints for secondary users and interference constraints for primary users. For a scenario where only mean channel gains from secondary users to primary receiving points, which are averaged over short-term fading, are available, we derive outage probabilities for secondary users and interference constraint violation probabilities for primary users. Based on the analysis, we develop a framework to perform joint admission control and rate/power allocation for secondary users such that statistical guarantees on the violation probabilities of both the QoS and the interference constraints are achieved. Spectrum access by the secondary users can exploit the timevarying nature of the activity of the primary users, and thereby much higher throughput can be achieved compared to the case where primary users are assumed to be active at all time. Also, via extensive numerical analysis, throughput performances of primary and secondary users are investigated considering different levels of implementation complexity due to channel estimation.