Power control scheme to mitigate interference for MIMO Cognitive Radio

In this paper, the various spectrum sharing schemes between the Primary Radio (PR) link and Cognitive Radio (CR) link have been analyzed. Also the ergodic capacities of PR and CR links under Constant Power (CP) and Water filling (WF) power control policies have been analyzed. In order to mitigate the interference caused to the PR receiver from the CR transmitter, interference temperature constraint at the PR receiver in the form of either Average Interference Power (AIP) constraint or Peak Interference Power (PIP) constraint has been considered. To maximize ergodic capacity of the PR link and CR link and to mitigate the interference from CR transmitters, a novel Block Diagonalization (BD) based WF power control policy has been proposed. In this proposed scheme, secondary user can learn the null space of the other secondary users to maintain the interference constraints of the primary user using BD. Also in this proposed algorithm, optimum power levels subjected to AIP and PIP constraints have been calculated using WF power control policy. The simulation results show that the proposed BD based WF power control policy achieves higher fading channel capacities for both PR and CR links compared to CP policy and WF power policy for the predefined AIP and PIP constraints.