Robust cooperative relay beamforming for cognitive radio networks

This paper considers a cognitive radio (CR) relay network which consists of a cognitive source, a cognitive destination and a number of cognitive relay nodes that share spectrum with a primary transmitter and receiver. The cognitive source is unable to communicate directly with the cognitive destination and hence uses cognitive relay nodes to create a link to the cognitive destination. Under the assumption of partial and imperfect channel state information (CSI), we propose a new robust cooperative cognitive relay beamformer that maximises the signal-to-interference-and-noise ratio (SINR) at the cognitive destination subject to a primary receiver outage probability constraint. We show that the robust beamforming problem can be stated as convex semidefinite program (SDP).