Abstract: Cognitive Radio (CR) is an adaptive, intelligent radio technology that can automatically detects available channels in a wireless spectrum and change transmission parameters to allow more concurrent wireless communications in a given spectrum band at a location. Physical layer attack is a common attack in these networks which can degrade the performance of cognitive radio networks severely. In this attack, the attacker mimics the signals of the Primary Users (PU) to mislead the cognitive users about the existence of the primary users. Two physical layer attack approaches are studied in this paper. First, we have considered the case that the cognitive users are united against the attacker to maximize the network total throughput. Second, we have studied the case that the cognitive users are selfish but have a common attacker. In both cases, we have assumed that the cognitive network employs carrier sense multiple access with collision avoidance (CSMA/CA) to prevent collisions. We use the game theory approach to model the optimization problem and then try to solve it. Some simulations are conducted to evaluate the cognitive network performances.
