Cognitive radio network secure communication with and without cooperative jammer

This paper investigates optimal power allocation strategies over a bank of idle independent parallel Gaussian wiretap channels where a cognitive-based transmitter and a cognitive-based receiver communicate in the presence of an eavesdropper and a friendly jammer. We initially focus on the scenario where the cognitive transceiver´s confidential message is transmitted without the assistance of a cooperative jammer (CJ) and characterize the secrecy rate maximization power allocation strategy, which indicates that only part of the sensing idle subchannels are utilized. This is a case of inefficiency in spectrum usage for cognitive radio network whose resource comes from spectrum sensing. Thus, we then extend our scenario by introducing a CJ and investigate whether we can further improve the system secrecy rate as that in non-cognitive network. In which, we focus on the joint transmitter and jammer power control and propose a suboptimal algorithm to demonstrate the benefits of introducing a CJ in our scenario.