In this paper, we present a robust joint relay precoder design and transceiver power allocation for a cognitive radio network under imperfect channel state information. The secondary (or cognitive) network consists of multiple pairs of single-antenna transceiver nodes and a non-regenerative twoway relay with multiple antennas which aids the intra-pair communication process of the transceiver nodes. The secondary
nodes share the spectrum with a licensed primary user (PU) while guaranteeing that the interference to the PU receiver is maintained below a specified threshold. The proposed robust design is based on the minimization of the sum mean-square error (MSE) of the transceiver nodes under constraints on the secondary users’ transmit powers and interference to PU the receiver. Though the original problem is non-convex, we
show that the proposed design can be solved using alternating optimization of convex subproblems which have analytic or efficient numerical solutions. We illustrate the performance of the proposed designs through some selected numerical simulations.

Accepted for publication