A robust sinr balancing technique for a multiuser MIMO cognitive radio network

We propose a robust signal to interference and noise ratio (SINR) balancing beamforming technique for a multiple input and multiple output (MIMO) based cognitive radio (CR) network. The aim is to design transmitter and receiver beamformers for multiple secondary users (SUs) while ensuring interference leakage to multiple primary users (PUs) is below a prescribed threshold. We use an iterative approach to design the receiver beamformers and transmitter beamformers so that SINRs achieved by all SUs are balanced and maximized. Due to the limited cooperation between secondary basestation (SBS) and PUs, we assume the channel state information (CSI) between the SBS and PUs is imperfect. Hence a robust beamformer design has been used to ensure the interference leakage to PU is below the specific threshold for all possible errors in the CSI.