Secondary user scheduling in cognitive radio networks with transmit beamforming for interference mitigation

Reducing interference to primary users while achieving high throughput for secondary user transmissions is a critical issue in an underlay cognitive radio network. In this paper, we explore the use of beamforming at secondary user transmitters. Two power allocation schemes, fixed transmit power allocation (FTPA) and adaptive transmit power allocation (ATPA) are investigated considering scenarios with/without beamforming. The use of beamforming is shown to significantly improve the throughput for secondary transmissions while maintaining satisfactory interference protection levels for primary users.