Effect of Receive Spatial Diversity on the Degrees of Freedom Region in Multi-Cell Random Beamforming
The Random BeamForming (RBF) scheme, by exploiting multi-user diversity based scheduling, is able to achieve interference-free downlink transmissions with only partial Channel State Information (CSI) at the transmitter. The impact of receive spatial diversity on the rate performance of RBF, however, is not fully characterized even in a single-cell setup. In this paper, the authors study a multi-cell Multiple-Input Multiple-Output (MIMO) broadcast system with RBF applied at each base station and either the Minimum-Mean-Square-Error (MMSE), Matched Filter (MF), or Antenna Selection (AS) based spatial receiver at each mobile terminal. They investigate the effect of different spatial diversity receivers on the achievable sum-rate of multi-cell RBF systems subject to both the intra- and inter-cell interferences.