Inner Bound on the GDOF of the K-User MIMO Gaussian Symmetric Interference Channel

Abstract

The K-user multiple input multiple output (MIMO) Gaussian symmetric interference channel where each transmitter has M antennas and each receiver has N antennas is studied from a generalized degrees of freedom (GDOF) perspective. An inner bound on the GDOF is derived using a combination of techniques such as treating interference as noise, zero forcing (ZF) at the receivers, interference alignment (IA), and extending the Han-Kobayashi (HK) scheme to K users, as a function of the number of antennas and the log INR / log SNR level. Several interesting conclusions are drawn from the derived bounds. It is shown that when K >; N/M + 1, a combination of the HK and IA schemes performs the best among the schemes considered. When N/M <; K ≤ N/M + 1, the HK-scheme outperforms other schemes and is found to be GDOF optimal in many cases. In addition, when the SNR and INR are at the same level, ZF-receiving and the HK-scheme have the same GDOF performance.