Downlink distributed binary power allocation for cognitive radio networks

We consider the downlink of a cognitive radio network consisting of multiple secondary transmitter and receiver communicating simultaneously in the presence of one primary user. The key idea within this paper is to combine multi-user diversity gains with spectral sharing techniques through inter-system coordination, in order to maximize the secondary user sum rate while maintaining a guaranteed quality of service (QoS) to a primary user. We first present a distributed power allocation algorithm that maximizes the capacity of the cognitive ratio network. The algorithm is simple to implement, since a secondary user can decide to either transmit data or stay silent over the channel coherence time depending on a specified threshold without affecting the primary users QoS. Then, we analyze performance of such an algorithm in terms of number of cognitive users able to transmit while minimizing interference to guarantee QoS for the primary user. Simulation results carried out based on a realistic network setting showed promising results.