A Spectrum Access Scheme for MIMO Cognitive Networks with Beamforming Design

This paper studies a spectrum access scheme to increase the spectral utilization for the multi-antenna cognitive radio (CR) network. The network comprises of one transmitter-receiver pair for primary users (PUs) and another pair for secondary users (SUs) with secondary transmitter equipped with multi-antenna. We divide the transmission time into two equal time phases, the first for PUs to transmit signals and the second for SUs to relay and transmit self-information. We aim to maximize the data rate of the secondary system through designing the beamforming vectors and power scaling factors with zero-force beamforming (ZFBF) to eliminate the co-channel interference, under the condition that PUs can achieve the target rate. The simulation results demonstrate a higher spectral utilization and a performance gain with the proposed scheme.