Cell Identifier Assignment in Two-Tier Femtocell Networks

Small cells, mainly femtocells, are believed to be a way how to deal with mobile data traffic growth in the upcoming years. To enable easy and massive femtocell deployments, a distributed method of Physical Cell Identifier (PCI) assignment should be implemented in Femtocell Access Points among other self-organizing functionalities. In this paper, we propose such a distributed algorithm enabling correct PCI assignment in a collision-free manner and resolving all confusion events based on neighbouring cells´ PCIs. The proposed algorithm is compared with the classical random algorithm by taking into account various femtocell densities, PCI ranges and sizes of neighbourhood area. Based on obtained results, the proposed algorithm leads to fewer confusion events and lower signalling network overhead even in dense femtocell environments such as office buildings or homes in city centres.