Efficient Transmission Strategy for Cognitive Radio Systems Under Primary User Emulation Attack

In energy detection-based cognitive radio (CR), the conventional transmission strategy consists in comparing the measured energy to a predefined threshold. Then, while the measured energy is less than the threshold, the secondary user (SU) is allowed to transmit over primary user's (PU) band and otherwise, no secondary transmission occurs. Here, we show that the aforementioned conventional transmission strategy is suboptimal in terms of secondary achievable data rates and probability of detection. As an alternative, we propose a different approach to CR signaling based on a spectrum access function that defines an efficient framework for the SU to access the primary spectrum. In particular, we consider the scenario of PU emulation attack (PUEA) in CR where some malicious users mimic the PU's signal, leading to a reduction of the secondary achievable data rates. By considering PUEA into account, we derive the optimal spectrum access function by maximizing the secondary transmission data rate under miss detection and false alarm constraints, which insures that the CR user does not degrade the performance of the PU. Comparative numerical results illustrate the superiority and the adequacy of the proposed transmission scheme under PUEA in terms of higher secondary achievable data rate and higher probability of detection.