Cooperative Spectrum Sensing and Decision Making Rules for Cognitive Radio

Cognitive radios are proposed to be the technology that will alleviate the problem of spectrum scarcity by using the underutilized radio frequency on non-interfering basis. So the cognitive radio user must be able detect the available spectrum opportunity reliably and efficiently. Spectrum sensing is an important functionality for cognitive users to look for spectrum holes before taking transmission in dynamic spectrum access model. In this paper we consider a realistic case where the SNR of the primary user's signal is unknown to both fusion center and cognitive radio terminals. Adaptive fuzzy system is designed to make the global spectrum sensing decision based on the observed energies from cognitive users. With the capacity of adapting system parameters, the fusion center can make a global sensing decision reliably without any requirement of channel state information, prior knowledge and prior probabilities of the primary user's signal. Simulation results prove that the sensing performance of the proposed scheme outperforms the performance of the equal gain combination based scheme, and matches the performance of the optimal soft combination scheme.