Spectrum Sharing in Cognitive Radio Systems: Ergodic and Outage Capacities

In this paper, we obtain the resource allocation policies pertaining to the ergodic and outage capacity notions in spectrum-sharing cognitive radio systems where the transmission parameters of the secondary users are adaptively changed based on the availability of channel state information (CSI) of the secondary user link, and soft-sensing information (SSI) about the activity of the licensed-band (primary) user as obtained from the sensing detector at the secondary user´s transmitter. Assuming availability of SSI and CSI statistics at the secondary transmitter and considering operation under constraints on average received-interference and peak transmit-power, we investigate two different capacity notions of spectrum-sharing fading channels, namely, ergodic and Outage, and obtain their corresponding optimal power allocation policies. We also sustain our theoretical results by numerical and simulation analysis.