Interference mitigation based on femtocell grouping in low duty operation mode of the IEEE 802.16m standard

Abstract

Femtocell is a low power base station that would be likely deployed inside a house or office to provide more capacity to indoor users. 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 (AI), femtocell may become active on air interface by transmitting control messages, while during unavailable interval (UAI), femtocell becomes inactive on air interface. Nevertheless, the current operation of femtocell in the LDO mode is not efficient, since the femtocell still has AIs even though there are no mobile stations (MS) will access it in anytime soon. In this case, the AIs may not be necessary and can further cause interference to neighbor cells. In this thesis, we propose an interference mitigation scheme based on the grouping of femtocells in one neighborhood area. A group consists of a header and members femtocell. Using our proposed scheme, the member femtocell can have Low Duty Cycle (LDC) pattern with minimum AI. Thus, using the proposed scheme, the unnecessary AIs in LDO can be decreased which results in decreasing interference to neighbor cells. We conduct both analysis and simulation results to show the gain of proposed scheme. Both results show that the proposed scheme has superior advantages compared to the conventional LDO scheme in the IEEE 802.16m, in terms of interference mitigation and energy saving aspects.