The DoF of the 3-user ($p,p+1$) MIMO Interference Channel

TL;DR

This paper characterizes the degrees of freedom for a 3-user MIMO interference channel with specific antenna configurations, proving the conjectured optimal DoF using advanced signaling and interference alignment techniques.

Contribution

It proves the conjectured DoF for the (p,p+1) MIMO IC with full CSI, employing asymmetric complex signaling and interference alignment.

Findings

Optimal DoF is achieved for p=2,3 cases.

Provides explicit transmit and receive filters.

Establishes tools for proving DoF for other p values.

Abstract

The \emph{degrees of freedom} (DoF) of the 3-user multiple-input multiple-output (MIMO) interference channel (IC) with full channel state information (CSI) and constant channel coefficients are characterized when linear filters are employed and $(p,p+1)$ antennas are deployed at the transmitters and receivers, respectively. The point of departure of this paper is the work of Wang et al, which conjectured but not proved the DoF for the configuration tackled in this work. In this work we prove the optimal DoF by means of a transmission scheme based on asymmetric complex signaling (ACS) together with symbol extensions in time and interference alignment (IA) concepts. The paper deals with the $p=2,3$ cases, providing the transmit and receive filters and the tools needed for proving the achievability of the DoF for other values of $p$.