QoS-Aware Admission Control for OFDMA Femtocell Networks under Fractional Frequency-Based Allocation

Fractional Frequency Reuse (FFR) is considered to provide enhancement in total throughput and an important reduction of the outage probability in two-tier macrocell-femtocell networks. However the allocation in FFR can create high cross-tier interferences to users located in the boundaries of the various zones. We propose a FFR scheme to alleviate the downlink cross-tier interference for users in these particular zones, joint with a QoS- aware analytical model to derive the blocking probabilities for different cell zones. The optimal parameters for cell channel partitioning in the proposed FFR-scheme are integrated to enhance the proposed system. Numerical results demonstrate the performance enhancement of the proposed joint FFR allocation and admission control scheme. Compared to current FFR and admission control strategies, our scheme permits to increase overall traffic by up to 40 % at cell center and 30 % at cell edge, for any given blocking probability.