Downlink interference mitigation for OFDMA femtocell networks

Femtocell is a very promising technology to enhance the indoor coverage and improve the network capacity. However, the cross-tier and co-tier interference are the key issues in two-tier femtocell networks. This paper treats the downlink interference problem in orthogonal frequency-division multiple-access (OFDMA) femtocell networks with partial cochannel deployment. We first propose an cross-tier interference mitigation strategy without power control among femtocell users by forcing the femto-interfering macrocell users to occupy the dedicated subcarriers. The non-interfering macrocell users, on the other hand, can use either the dedicated subcarriers, or the shared subcarriers which are also occupied by the femtocell users. Then, to mitigate the interference from macrocell base station (MBS) to femtocell users (FUs), a joint power and subcarrier allocation model based on minimizing transmit power is formulated. Furthermore, to improve the macrocell network performance, the resource allocation model based on maximizing throughput is proposed. At last, we devise a subcarrier allocation scheme to mitigate co-tier interference among femtocells. The results show that the partial cochannel scheme is the trade-off between transmit power and outage compared with cochannel and orthogonal deployment. Moreover macrocell can achieve the maximum throughput under the proposed partial cochannel deployment.