On the sum-rate of the uplink massive MIMO systems with multiple compact antenna arrays

The sum-rate of the uplink multiuser massive multiple-input multiple-output (MIMO) system is investigated. For the considered massive MIMO systems, the base station (BS) is equipped with a large number of antennas, which are assembled into several sub-arrays. Meanwhile, in each of the sub-arrays, antennas are densely installed. With the analysis of the sum-rate, we find that, for given total number of antennas, the sum-rate achieved by the considered systems improves, when the number of sub-arrays increases. However, the improvement of the achievable sum-rate is marginal, when the number of sub-arrays keeps on increasing. Furthermore, when the system is lightly loaded, even when all of antennas are assembled into a single compact antenna array, the achievable sum-rate is very close to that when all antennas are independent.