Interference Avoidance Challenges in Densely Deployed OFDMA Hybrid Access Femto Cellular Networks

: Femtocell is a low powered small base station that operates on licensed frequency band. Femtocells are deployed by users to improve indoor coverage. Femtocells and the outer macrocell can co-exist with dedicated spectrum allocation or shared spectrum allocation strategy to avoid interference. The dedicated spectrum allocation strategy is not cost-effective as spectrum resource is limited. However the shared spectrum allocation strategy where the femtocells share the same frequency bands with the macrocell is an efficient solution, but demands specialized inter-cell interference management techniques. This paper investigates the characteristics of dense femtocells and its various access control modes and provides an overview of resource allocation, open issues and challenges for interference avoidance in dense OFDMA hybrid access femtocells.