Sub-optimal joint beamforming on MISO cognitive radio

In this paper, we discuss joint beamforming schemes for the downlink of a multiple input single output coexisting radio system, where both transmitters know all the channel state information. Considering the opportunistic case where both systems have equal rights to access the spectrum, we propose sub-optimal methods for several performance criteria, including sum mean squared error, continuous sum throughout, and discrete sum throughput. Simulation results show that the proposed precoding algorithms achieve the better performance trade-offs between two radio systems and increase the spectrum efficiency at the cost of full channel state information.