Joint transmit beamforming and antenna selection in cognitive radio networks

This paper considers a cognitive radio network, which has a two secondary users (SU) equipped with multiple antennas, one acting as transmitter (SU TX) and the other receives the signals transmitted by SU TX (SU RX) and coexists with a primary network users, each with only one antennas. Our objective is to maximize the achievable rates or symbol error rates of the SU subject to the interference constraints on the primary users exploiting Transmit Beamforming at SU transmitter (SU TX) while reducing the costs associated with RF-chains at the radio front end. At first, the problem under consideration is formulated and then a new iterative method is proposed to find the best weight vector for beamformer in SU TX and best subset of antennas at SU RX based on convex optimization methods. Two different scenarios are considered and their advantages and disadvantages are investigated using appropriate simulations.