Beamforming in interference networks for uniform linear arrays

We consider a multiple-input single-output interference channel where each transmitter is equipped with a uniform linear array. By controlling the geometry of the array, i.e. adapting the antenna spacing, the rotation of the array, and the number of antenna elements, we investigate whether the capacity of the channel can be achieved with single user decoding capabilities at the receivers. This objective is reached when it is possible for each transmitter to perform maximum ratio transmission to its intended receiver while simultaneously nulling the interference at all unintended receivers. We provide for the two and three user case the necessary antenna spacing and rotation angle of the array in closed form. For the four user case, an integer programming problem is formulated which additionally determines the required number of antennas.