Optimal beamforming and power allocation for sensing-based spectrum sharing in cognitive radio networks

In this paper, the optimal beamforming and power allocation strategy for the secondary transmitter based on the sensing result on the state of the primary user in a multiantenna cognitive radio (CR) network is proposed. Unlike the existing sensing-based spectrum sharing, where the secondary transmitter employs a single antenna and adjusts only its transmit power, in the proposed scheme, the secondary transmitter employs multiple transmit antennas and adjusts the beamforming vector as well as the transmit power. An iterative algorithm that can efficiently obtain the optimal beamforming vector and power allocation is developed. Simulation results show that the proposed scheme achieves a significant rate gain over the existing sensing-based spectrum sharing schemes.