Power allocation based on beamforming in cooperative cognitive radio networks with arbitrary number of secondary users

Abstract

In this study, a new beamforming and power allocation method for cooperative cognitive radio (CR) networks is proposed. The proposed method can be deployed in systems with one primary user (PU) and arbitrary number of secondary users (SUs). By using transmit beamforming in both PU and SUs, multiple transmission with limited interference effect in the receivers can be attained. SUs get permission to use the licenced spectrum in the price of enhancing the data rate of the PU. The problem investigated in this study is to maximise the weighted sum rate in the multiple-input single-output (MISO) cooperative CR networks. Transmit powers and interference temperature in the receivers are the constraints that must be satisfied. By the virtue of cooperation with SUs, data rate of the PU is another constraint that must not be less than a predefined value. Transmit/receive duality in MISO and single-input multiple-output systems are used to obtain the beamforming weights in the transmit antennas. By defining a specific optimisation problem, power portion of each SU in cooperative transmission will be found in the way that constraint on the data rate of the PU is fulfilled. Simulation results show that by using the cooperative method presented in this study, data rate of the PU is enhanced.