Resource Sharing in Cognitive Radio Systems: Outage Capacity and Power Allocation under Soft Sensing

Cognitive radio technology offers tremendous potential to improve the utilization of the radio spectrum by efficiently reusing and sharing the licensed spectrum bands, as long as the interference power inflicted on the primary users of the band remains below a predefined threshold level. In this paper, we investigate the outage capacity gains offered by cognitive radio in Rayleigh fading environment where the transmit power of the secondary user can be adjusted based on soft-sensing information pertaining to the primary user. Specifically, considering joint average interference and peak transmit power constraints, we derive lower bound on the outage capacity of the secondary user's channel. We propose a power allocation policy for achieving a constant-power at the secondary's receiver and provide closed- form expressions for the outage capacity and its associated power allocation policy. Furthermore, we illustrate our analysis through numerical results and comparisons.