Novel multiuser MIMO relay precoder design for cognitive radio systems with primary interference cancellation

Abstract

A novel multiuser MIMO cognitive radio (CR) system with enhanced interference suppression from primary system is proposed in the presence of multiple CR users and parallel streams communication. Moreover, in the overlay system with the unlicensed CR user (CU) and the licensed primary user (PU), PU performance will be degraded by interferences. Similarly, CU transmission efficiency will be reduced by PU interferences. For the traditional multiuser MIMO system, the precoding schemes are utilized to limit the CU transmission power, which can reach the no interference to PU. However, the PU signal will induce the interference to CU. For the traditional CR system, the PU interference signals are considered as white noise to study the CR performance. In this paper, we proposed a cooperative multiuser MIMO CR relay system and use the relay station to cancel the PU interference within two time slots, which can enhance the transmission quality of CR system. Note that the relay station exhibits the multiuser MIMO precoding capability to convey the negative multiple PU data for CU user to cancel PU interference. Simulation results demonstrate that the proposed CR relay system outperforms the traditional CR system and shows the linear growth of sum rate over the strong PU interference and multiple CUs and streams interference. The robust CR relay system can be extended to use in the future 5G overlay system.