Two-way relaying with linear processing and power control for cognitive radio systems

In this paper, we consider a cognitive radio (CR) system, where a secondary network shares spectrum with a primary network. In the secondary network, a relay station (RS) with multiple antennas performs two-way communications for multiple pairs of secondary users (SUs). In such a CR system, the main point is to provide the best system performance to SUs while protecting primary users (PUs) from excess interference introduced by the secondary network. To do this, we do linear signal processing at the RS to remove inter-pair interference for SUs and employ power control algorithm to maximize the sum rate of the secondary network while ensuring no harmful interference is introduced to PUs. The expressions of the linear processing and power control scheme are derived and the performance is simulated. Simulation results show the advantage of the proposed algorithm.