Interference Mitigation via CECRS Precoding in a Two-Tier Heterogeneous Network with Cooperative Femtocells

The coexistence of a macrocell and a number of femtocells often leads to a two-tier heterogeneous network, where the co-tier interference (CotIN) and cross-tier interference (CrotIN) both degrade users´ quality of service. In order to mitigate the two types of interferences, we propose a precoding scheme for the cooperative femtocells, called CotIN elimination and CrotIN suppression (CECRS) precoding. In this scheme, we first eliminate the CotINs of each user by applying the QR decomposition to channel matrix. Then, the CrotINs of MUs and FUs are suppressed by the macrocell base station (MBS) and femtocell access points (FAPs), respectively. The CECRS scheme doesn´t require much information exchange between the MBS and FAPs, and thus significantly reduce the difficulty of its implementation. Simulation results show that the CECRS effectively improves the users´ transmission rates.