Downlink interference minimization in cognitive LTE-femtocell networks

Minimizing the cross-tier and co-tier interference while maintaining high system throughput or spectrum efficiency is one of the major fundamental challenges within femtocell networks. Cognitive radio enabled techniques can play a key role in mitigating the interference effectively by providing more secondary spectrum access opportunities, especially in dense femtocells deployment scenarios. Supported by cognitive radio functionality, femtocell users can access and share the licensed spectra including the frequency bands of both macrocells and other licensed systems (e.g. TV White Spaces) as long as not causing harmful interference to the coexisting licensed systems. In this paper, based on cognitive sensing, we propose a joint scheme of channel assignment, power allocation and macrocell-femtocell scheduling, so as to minimize the aggregate interference from the multiple femtocells to the licensed users while taking into account each femtocell´s capacity and power budget. Moreover, we come up with the concepts of Physical Cluster (PC) and Virtual Cluster (VC) and synthetically apply the related algorithms to reduce the interference step by step. Finally, the performances of the proposed algorithms are analyzed, and numerical results have verified the viability and effectiveness of the proposed scheme in managing the femtocell interference.