A Cell Range Expansion Framework for Closed Access Femtocell Networks

While femtocell networks represent a promising solution for extending high data-rate wireless services in indoor environments, despite their many benefits the short coverage distances involved can lead to frequent handovers being triggered resulting in overloading the macrocells. This handover problem is further exacerbated for users operating at the cell boundary. One solution is to keep the mobile station (MS) connected to the femtocell access points (FAP) by applying a handover bias to expand the femtocells coverage, though arbitrarily increasing the cell range can have a detrimental effect on system performance as the received interference will increase and may exceed tolerable levels. Many disparate factors including: FAP deployment density; resource constraints; and cell range expansion (CRE) influence the crucial interference-system performance nexus, and this was the motivation to analyse this relationship in order to facilitate successful FAP deployment. This paper critically analyses the impact of femtocell range expansion with a system-level simulation being undertaken for cooperative and non-cooperative resource allocation strategies. A new CRE framework for femtocell networks is then proposed, which takes cognisance of the interplay between key system parameters, with results confirming the cooperative model consistently outperforms the non-cooperative approach so affording enhanced system flexibility in terms of FAP range expansion.