  Interference alignment in the K-user MIMO interference channel with constant
channel coefficients is considered. A novel constructive method for finding the
interference alignment solution is proposed for the case where the number of
transmit antennas equals the number of receive antennas (NT = NR = N), the
number of transmitter-receiver pairs equals K = N + 1, and all interference
alignment multiplexing gains are one. The core of the method consists of
solving an eigenvalue problem that incorporates the channel matrices of all
interfering links. This procedure provides insight into the feasibility of
signal vector spaces alignment schemes in finite dimensional MIMO interference
channels.
