Cell Free Massive MIMO with Constrained Coverage

As new generations of mobile radio come into service, bandwidth is becoming more and more scarce and systems with very high spectral efficiency become vital. Having a high spectral efficiency, Massive MIMO has shown to be a promising candidate for 5G. Distributing antennas in such systems make them even more spectrally efficient. Cell free Massive MIMO distributes antennas to cover all users in an area without the need to divide the area into cells. Realization of such systems in practice requires some big challenges to be resolved first. One of them is the antenna assignment to the users, which is studied in this paper. In this paper, mathematical relations for the joint optimization problem of antenna assignment and power-weight allocation are derived. In order to make the problem solvable, it is separated into two sub-problems: antenna assignment and power-weight allocation. Results show that the proposed sub-optimum algorithms for antenna assignment and the power-weight allocation can in fact be very effective.