Impact of Channel Knowledge on Cognitive Radio System Capacity

We examine the impact of channel knowledge on the secondary user (SU) in a cognitive radio system. Under a minimum signal-to-interference-and-noise ratio (SINR) constraint for the primary user (PU) receiver, we determine the SU capacity under four channel knowledge scenarios. We derive analytical expressions for the capacity cumulative distribution functions which are verified by means of simulations. We show that the lack of exact knowledge of the PU-PU channel gain by the SU-Tx either prohibits SU transmission or necessitates high interference level at the PU. We also show that the lack of exact knowledge of the SU-Tx to PU-Rx link has little or no impact on SU capacity.