Mobility-aware admission control with QoS guarantees in OFDMA femtocell networks

We consider the mobility- and QoS-aware admission control problem for OFDMA femtocell networks. To mitigate strong cross-tier interference in the downlink communication, we assume each macrocell is partitioned into cell center and cell edge zones where femtocells in the edge zone share the same bandwidth with the macrocell while femtocells in the center zone use different bandwidth from that allocated for the macrocell. We propose an admission control algorithm that efficiently associates low-speed and high-speed users with femto and macro BSs (FBS and MBS) to avoid large handoff overhead. In addition, calls from low-speed users that fail to connect with their nearby FBSs are allowed to overflow to the macrocell tier. Then, we develop an analytical model for performance evaluation of the proposed admission control scheme. Finally, numerical results are presented to demonstrate the impacts of different parameters (e.g., bandwidth requirements) and access design (i.e., closed versus hybrid access) on the user blocking probabilities.