Two-Hop Interference Channels: Impact of Linear Time-Varying Schemes

TL;DR

This paper investigates the two-hop interference channel with constant coefficients, demonstrating that time-varying amplify-forward relaying can achieve a sum degrees of freedom of 4/3, with a matching outer bound confirming this capacity.

Contribution

It introduces a novel analysis showing that time-varying AF relaying strategies can enhance DoF in two-hop interference channels, achieving 4/3 sum-DoF and establishing a matching outer bound.

Findings

Achieves 4/3 sum-DoF with time-varying AF relays

Develops a new outer bound matching the achievable DoF

Characterizes the sum-DoF for the two-hop interference channel

Abstract

We consider the two-hop interference channel (IC) with constant real channel coefficients, which consists of two source-destination pairs, separated by two relays. We analyze the achievable degrees of freedom (DoF) of such network when relays are restricted to perform scalar amplify-forward (AF) operations, with possibly time-varying coefficients. We show that, somewhat surprisingly, by providing the flexibility of choosing time-varying AF coefficients at the relays, it is possible to achieve 4/3 sum-DoF. We also develop a novel outer bound that matches our achievability, hence characterizing the sum-DoF of two-hop interference channels with time-varying AF relaying strategies.