Interference Alignment Techniques for Multi-User MIMO Systems at Millimeter-Wave

The increasing bandwidth required nowadays by mobile devices forces radio technology to start looking at the 30-300 GHz spectrum, corresponding to wavelength of the order of millimeters. The large attenuation belonging to this frequency range can be effectively mitigated by the use of multiple antennas that furthermore allow interference mitigation between users accessing simultaneously the channel. In this work a review of the state-of-the-art of modern multi-user multiple-input multiple-output (MIMO) systems is given, extending various Interference alignment (IA) techniques to the millimeter wave (MMW) channel. In particular, performance achieved by IA methods over the MMW and the classical Rayleigh fading channels are compared and some considerations are given. Specifically, it is seen that IA methods at MMW are very suitable even with many users which however cannot require an excessive rate.