Jointly optimized uncoordinated beamforming for enhancing achievable sum rate in cognitive radio network

In this paper, we propose an enhanced strategy for jointly-optimized uncoordinated beamforming over cognitive radio network. We consider a transmission of a single information stream in both primary and secondary links where both primary and secondary users are equipped with multiple antennas and transmit concurrently over the same spectrum. Specifically, the optimum weights to maximize the individual achievable rates are designed for both primary and secondary links and the achievable sum rate performance of the network under the condition that the cross interference at both receivers is totally nullified. The interference cancellation is performed at the secondary user and no coordination between the primary and secondary users is required as we considered uncoordinated beamforming in the network. The proposed design is based on singular value decomposition and iterative water-filling at the primary link while employing discrete search and gradient algorithm at the secondary link. The effect of the number of transmit and receive antennas on the proposed design is also discussed. Simulation results demonstrate that the proposed strategy improves individual user achievable rates and achievable sum rate performance as compared to the previously reported approaches.