“…However, the problem of beamspace selection in the case of MU transmissions (MU BeamSpace Selection -MBSS) has not yet been studied enough. Existing works have only considered simplified cases when all users had the same channel conditions [19], [23], [24], [25], [26], [27], [28], [29], [30]. For example, in papers [19], [23], and [24], the authors have used data measured via real Massive MIMO testbed [31], [32], but the channel matrix for each UE has been normalized to remove the imbalance in attenuation between users, while in papers [25], [26], [27], [28], [29], and [30], channels for all UEs have been sampled from the same distribution.…”