Fractional Frequency Reuse to Mitigate Interference in Self-Configuring LTE-Femtocells Network

Development of femtocells is the most recent step towards increasing the network capacity of a wireless network and improving the quality of service for cellular users. However, as all the femtocells use the same radio band, it poses a serious interference issue amongst neighboring femtocells, especially when femtocells are densely deployed. In this paper, we study the problem of DL (downlink) and UL (uplink) interference amongst closed-access neighboring femtocells used in conjunction with the Long Term Evolution (LTE) technology and propose a solution to mitigate this interference using Fractional Frequency Reuse (FFR) technique. User equipments (UEs) report to their serving femto base stations (F-BSs) periodically. If the report reveals high interference level, neighboring F-BSs locally adopt FFR in a coordinated but decentralized way. FFR divides the femtocell in cell-center and cell-edge areas where the cell-edge of interfering F-BSs use distinct set of sub-carriers (SCs). The division takes place in a way such that the affected UE falls in the cell-edge area. The simulation results indicate that the proposed scheme decreases interference in the neighboring F-BSs, femto UEs (F-UEs) and macro UEs (M-UEs) and improves the overall throughput.