Interference, Cooperation and Connectivity - A Degrees of Freedom Perspective

TL;DR

This paper investigates the degrees of freedom in a 4-user locally-connected wireless interference network, revealing that reducing interference links can decrease capacity, using a novel entropy-based approach.

Contribution

It introduces a new outer bound on DoF for locally-connected networks using entropy sub-modularity, linking interference alignment insights to network capacity.

Findings

Bounded the DoF at 12/5 for the locally-connected network

Compared the DoF with fully connected networks, showing reduction due to link removal

Developed a novel entropy-based method for deriving DoF bounds

Abstract

We explore the interplay between interference, cooperation and connectivity in heterogeneous wireless interference networks. Specifically, we consider a 4-user locally-connected interference network with pairwise clustered decoding and show that its degrees of freedom (DoF) are bounded above by 12/5. Interestingly, when compared to the corresponding fully connected setting which is known to have 8/3 DoF, the locally connected network is only missing interference-carrying links, but still has lower DoF, i.e., eliminating these interference-carrying links reduces the DoF. The 12/5 DoF outer bound is obtained through a novel approach that translates insights from interference alignment over linear vector spaces into corresponding sub-modularity relationships between entropy functions.