Coverage Analysis of Cognitive Femtocell Networks

In heterogeneous networks, interference is one of the critical issues. In this letter, we consider a two-tier downlink network composed of macrocell base stations (MBSs) and femtocell base stations (FBSs), where the locations of MBSs and FBSs are modeled by two independent Poisson point processes (PPPs). FBSs are assumed to be cognitive and become inactive when within a certain range of active MBSs. Due to the inactivation regions, the location distribution of active FBSs no longer follows PPP, complicating the calculation of coverage probability. To circumvent this, we propose an approximation to the coverage probability for both the open access and closed access policies.