A Novel Framework for Dual-Band Femtocells Coexisting with WiFi in Unlicensed Spectrum

Exponentially growing demand for mobile data is pushing the existing mobile networks to the limit. In addition to offloading traffic onto WiFi access points (APs), dual-band femtocells (DBFs) that can simultaneously access both the licensed and unlicensed bands have been proposed for cellular networks to further exploit the unlicensed spectrum. However, the coexistence between DBFs and WiFi in the unlicensed spectrum is not without difficulty, given the potentially severe co- channel interference. In this paper, we first derive the probability of coverage overlap between DBF and WiFi APs by modelling the network nodes using a spatial bivariate Poisson point process, and then propose a novel framework for DBFs to effectively coexist with WiFi APs in the unlicensed spectrum considering various possibilities of coverage overlap between them. The performance of the proposed framework in terms of DBF channel occupancy in the unlicensed band is evaluated through both theoretical analysis and simulations.