Virtual clustering for resource management in cognitive femtocell networks

Femtocells are primarily used to extend high-quality radio coverage in indoor environments. Dense femtocell access point (FAP) deployment however, can lead to severe interference on femtocell user equipment (FUE) from neighbouring FAP, when they operate on the same channel. The problem is compounded as FAP are deployed in an uncoordinated manner by the end-user, which means either avoiding or minimising interference is an essential prerequisite to achieve successful femtocell operation. This paper adopts a new strategy towards radio resource distribution and management by creating virtual clusters of femtocells which are managed by a logical entity called the Virtual Cluster Controller(VCC). Each VCC is situated between the FAPs and Radio Network Controller (RNC) and has a set of sub-channels which it can allocate amongst its members. A Virtual Cluster Formation (VCF) algorithm exploits location information to assign each FAP to a VCC so that the minimum distance between a FAP and the nearest FAP allocated to the same VCC is maximised, thereby ensuring minimal inter-FAP interference. Simulation results corroborate the significant performance improvement achieved by this virtual clustering model in terms of both interference minimisation and throughput for various FAP deployment scenarios.