We focus on a two-receiver Multiple-Input-Multiple-Output (MIMO) BroadcastChannel (BC) and Interference Channel (IC) with an arbitrary number of antennasat each node. We assume an imperfect knowledge of local Channel StateInformation at the Transmitters (CSIT), whose error decays with theSignal-to-Noise-Ratio. With such configuration, we characterize the achievableDegrees-of-Freedom (DoF) regions in both BC and IC, by proposing aRate-Splitting approach, which divides each receiver's message into a commonpart and a private part. Compared to the RS scheme designed for the symmetricMIMO case, this scheme is suitable for the general asymmetric deployment withan arbitrary number of antennas at each node. In BC, the proposed block 1)employs an unequal power allocation to the private messages of the tworeceivers, 2) exploits the benefit of having an extra spatial dimension at onereceiver, and 3) is carried out with a Space-Time transmission. These featuresenable the scheme to yield a greater DoF region than trivially extending thescheme designed for the symmetric case. In IC, we modify the scheme proposedfor the BC case by applying a linear transformation to the channel matrices.Such a linear transformation allows us to identify the signal space where thetwo transmitted signals interfere with each other and propose a proper powerallocation policy. The achievable DoF regions are shown to be optimal for someantenna configurations.
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