Large Aperture Antenna Array Design for Cellular LOS Massive MIMO

Massive multiple-input multiple-output (MIMO) achieves enhanced data rates with linear precoding schemes, making it an interesting PHY scheme for future mobile communications systems. The deployment of a high number of antennas facilitates reliable communication to many users in a multi-user MIMO system. However, reliable low-latency communication is only maintained, if all mobile users are served simultaneously in a multi-user MIMO fashion. In case of high inter-user correlation, for example, when two users are spatially close to each other, the user rate with linear precoding decreases. In the worst case, either of the two users is dropped by the scheduler in order to maintain a certain rate to at least one of them. We aim to improve a massive MIMO system's reliability while keeping the number of antennas constant. To decrease user correlation of closely spaced users, we design an antenna array with a large aperture. We consider designing the antenna array by array thinning, employing a genetic algorithm. This leads to a nonuniform spacing of antennas. We show that the proposed array design maintains a certain user rate more reliably for linear precoding schemes compared to a uniform linear array.