Spectrum Sharing Models in Cognitive Radio Networks
Nowadays, cognitive radio technique has been acknowledged as a smart and potential method to improve the spectrum utilization. In this work, we investigate a cognitive radio communication scheme, where a number of cognitive users, each with multiple antennas, can share the spectrum with the primary user. To decrease the inter-user interference, zero-forcing beamforming (ZFBF) is considered. We presented a design of three-step selection for both the cognitive users and their antennas at receiver. In the first step of the studied scheme, antennas-selection is performed to based on a certain algorithm and then user-selection is performed based on Proportional Fair algorithm. Next the active set of cognitive users is selected according to the correlation between the users in the third step. Simulation results show that at the expense of some sumrate loss, our proposed scheme can realize near fair resource allocation among the cognitive users as well as the decrease of the interference to the primary user and of the feedback.