Interference Alignment for Downlink Transmission of Multiple Interfering Cells

Considering line of sight channels (LOS), an achievable scheme is proposed for downlink channel in cellular networks with more than two interfering cells. The proposed scheme is based on linear precoding at the base stations (BS) and requires feedback only within each cell. For the 3-cell case, mathematical analysis is provided to show that the proposed scheme approaches to interference-free degree-of-freedom (dof) of this channel as the number of users grows. A geometric interpretation is presented to generalize the proposed scheme for more than three cells. Simulation results illustrate the dof achieved using this scheme for the 3-cell case which is important in a real cellular environment because of the three adjacent interfering cells.