Performance improvements of interference alignment with multiuser diversity in cognitive radio networks

Interference alignment (IA) is a recent breakthrough in interference management, and has been applied to cognitive radio. However, the signal-to-noise ratio (SNR) may decrease dramatically under some channel conditions, and this will reduce the quality of service (QoS) of primary users (PUs). In this paper, a novel IA scheme exploiting multiuser diversity is proposed for spectrum sharing. In the scheme, several secondary users (SUs) wish to access the licensed spectrum, and only the ones that maximally improve the QoS of PU will be selected to share the spectrum by forming an IA network with the PU. Thus the performance of PU can be significantly improved with the help of multiuser diversity brought by SUs. To further ensure the interests of SUs, the scheme is revised and a tradeoff is made between the PU and SUs. Simulation results are presented to show the effectiveness of the proposed schemes for spectrum sharing.