Capacity region of Gaussian cognitive broadcast channel in low-interference-gain regime

In this paper, we consider the Gaussian cognitive broadcast channel in which the primary user communicate to the primary receivers and the cognitive user has noncausal knowledge of the primary radio´s codeword and wishes to communicate to two receivers. We characterize the largest rate region at which the cognitive user could reliably communicate under the constraints that no rate degradation is created for the primary user, and the primary receiver uses a single-user decoder just as it would be in the absence of the cognitive radio. We determine the capacity region of the Gaussian cognitive broadcast channel in the low-interference-gain regime.