The GDOF of 3-user MIMO Gaussian interference channel

The paper establishes the optimal generalized degrees of freedom (GDOF) of 3-user M × N multiple-input multiple-output (MIMO) Gaussian interference channel (GIC) in which each transmitter has M antennas and each receiver has N antennas. A constraint of 2M ≤ N is imposed so that random coding with message-splitting achieves the optimal GDOF. Unlike symmetric case, two cross channels to unintended receivers from each transmitter can have different strengths, and hence, well known Han-Kobayashi common-private message splitting would not achieve the optimal GDOF. Instead, splitting each user´s message into three parts is shown to achieve the optimal GDOF as well as O(1) capacity approximation.