Coexistence region analysis in cognitive radio networks

We consider the coexistence between a primary user (PU) communication and cognitive users (CUs) in realistic propagation environments characterized by path loss, log-normal shadowing, and Rayleigh fading. The scenarios considered envisage two situations: the first with one CU, the second with a cognitive radio network (CRN), composed of several CUs. In the latter scenario, to account for the spatial distribution of nodes the CUs are assumed spatially distributed according to a Poisson point process. In both scenarios, we characterize the statistical distribution of the interference and, based on this, we evaluate the outage probability of the PU communication. The outage probability will then provide the required minimum radius inside which CUs communication must not be allowed, to prevent PU outage. Such minimum radius identifies a disk called exclusion region (ER), and its complement called coexistence region. The analytical framework developed, which shows the relationship between the PU outage probability, the ER, and other system parameters, is helpful for the network designer to understand interference effects and to enable coexistence.