Interference mitigation depending on the number of antennas and CSI available at femtocells

Femtocells have become popular recently as a key technology to improve coverage in indoor environments. However, since femto base stations (FBSs) utilize the same spectrum as existing macro base stations (MBSs), interference between macrocells and femtocells as well as between femtocells needs to be carefully controlled. In this paper, we propose adjacent cell interference mitigation techniques exploiting transmit power control and beamforming depending on the number of antennas and channel state information (CSI) available at FBSs in the environment where closed subscriber group (CSG) FBSs are deployed densely in a macrocell. Simulation results show that the proposed techniques are effective for improving the signal-to-interference plus noise ratio (SINR) for all user equipments (UEs) including both macro and femto UEs at 5 % of the cumulative distribution function (CDF).