A Fixed Precoding Approach to Achieve the Degrees of Freedom in X channel

TL;DR

This paper introduces a fixed precoding scheme utilizing ergodic interference alignment to achieve the Degrees of Freedom in the X channel without full channel state information, relying only on finite-rate feedback.

Contribution

It proposes a novel fixed precoding method that achieves the DoF with limited feedback, bypassing the need for full channel knowledge at transmitters.

Findings

Finite-rate feedback suffices to achieve DoF.

Method works in Rayleigh fading environments.

Feedback rate of 2log(p)+Theta(log(log(p))) is adequate.

Abstract

This paper aims to provide a fixed precoding scheme to achieve the Degrees of Freedom DoF of the generalized ergodic X channel. This is achieved through using the notion of ergodic interference alignment technique. Accordingly, in the proposed method the transmitters do not require to know the full channel state information, while this assumption is the integral part of existing methods. Instead, a finite-rate feed-back channel is adequate to achieve the DoF. In other words, it is demonstrated that quantized versions of channel gains are adequate to achieve theDOF. To get an insight regarding the functionality of the proposed method, first we rely on finite field channel models, and then extend the terminology to more realistic cases, including dispersive fading channels in the presence of quantizer. Accordingly, in a Rayliegh fading environment, it is shown a feedback rate of 2log(p)+Theta(log(log(p))) can provide the DoF, where $p$ is the total transmit power.