Interference Mitigation Based on Femtocells Grouping in Low Duty Operation

Since a large number of femtocells may coexist in one macrocell area, interference management becomes a major issue in the deployment of femtocells, and therefore has been researched actively. In the IEEE 802.16m, one way to mitigate interference is Low Duty Operation (LDO) Mode for femtocells. Femtocell in the LDO mode changes alternately between available interval and unavailable interval. During available interval, femtocell may become active on air interface by transmitting control messages, while during unavailable interval, femtocell becomes inactive on air interface. However, the operation of femtocell in the LDO mode is not efficient, since it still has available intervals even though there are no MSs will access the femtocell in anytime soon. In this case, the available intervals may not be necessary and can further cause interference to neighbor cells. In this paper, we propose an interference mitigation scheme based on the grouping of femtocells in one neighborhood area. The unnecessary available intervals in LDO can be decreased by the proposed scheme and results in decreasing interference to neighbor cells. The analysis and simulation results show that the proposed scheme has superior advantages compared to the conventional LDO scheme in IEEE 802.16m, in terms of interference reduction and energy saving aspects.