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Degrees of Freedom of Cache-Aided Interference Channels Assisted by Active Intelligent Reflecting Surfaces

Abolfazl Changizi, Ali H. Abdollahi Bafghi, Masoumeh Nasiri-Kenari

TL;DR

This paper explores interference management in a cache-aided wireless network assisted by an active IRS, to enhance the achievable degrees of freedom (DoF) and jointly design the content placement, delivery phase, and phase shifts of the IRS and propose a one-shot achievable scheme.

Abstract

This paper studies cache-aided wireless networks in the presence of active intelligent reflecting surfaces (IRS) from an information-theoretic perspective. Specifically, we explore interference management in a cache-aided wireless network assisted by an active IRS, to enhance the achievable degrees of freedom (DoF). To this end, we jointly design the content placement, delivery phase, and phase shifts of the IRS and propose a one-shot achievable scheme. Our scheme exploits transmitters' cooperation, cache contents (as side information), interference alignment, and IRS capabilities, adapting to the network's parameters. We derive the achievable one-shot sum-DoF for different sizes of cache memories, network configurations, and numbers of IRS elements. Our results highlight the potential of deploying an IRS in cache-aided wireless communication systems, underscoring the enhancement of achievable DoF for various parameter regimes, particularly when the sizes of the caches (especially at the transmitters) are inadequate. Notably, we show that access to an IRS with a sufficient number of elements enables the achievement of the maximum possible DoF for various parameter regimes of interest.

Degrees of Freedom of Cache-Aided Interference Channels Assisted by Active Intelligent Reflecting Surfaces

TL;DR

This paper explores interference management in a cache-aided wireless network assisted by an active IRS, to enhance the achievable degrees of freedom (DoF) and jointly design the content placement, delivery phase, and phase shifts of the IRS and propose a one-shot achievable scheme.

Abstract

This paper studies cache-aided wireless networks in the presence of active intelligent reflecting surfaces (IRS) from an information-theoretic perspective. Specifically, we explore interference management in a cache-aided wireless network assisted by an active IRS, to enhance the achievable degrees of freedom (DoF). To this end, we jointly design the content placement, delivery phase, and phase shifts of the IRS and propose a one-shot achievable scheme. Our scheme exploits transmitters' cooperation, cache contents (as side information), interference alignment, and IRS capabilities, adapting to the network's parameters. We derive the achievable one-shot sum-DoF for different sizes of cache memories, network configurations, and numbers of IRS elements. Our results highlight the potential of deploying an IRS in cache-aided wireless communication systems, underscoring the enhancement of achievable DoF for various parameter regimes, particularly when the sizes of the caches (especially at the transmitters) are inadequate. Notably, we show that access to an IRS with a sufficient number of elements enables the achievement of the maximum possible DoF for various parameter regimes of interest.

Paper Structure

This paper contains 7 sections, 2 theorems, 33 equations, 8 figures.

Table of Contents

  1. Introduction
  2. Problem Formulation
  3. Problem Overview
  4. Detailed Problem Description
  5. Achievable Scheme
  6. Numerical Results
  7. Conclusions

Key Result

Theorem 1

Consider a cache-aided interference network with $K_T$ transmitters, $K_R$ receivers, ${\mu_T} = 1$, and ${\mu_R} \in [K_R-1]$, assisted by an IRS‌ with $Q = (L+1) L$ elements, $L \in [\min\{K_T-1, K_R-1\}]$. Then, the one-shot sum-DoF of $\mathrm{DoF_{sum}} = \operatorname{min}\{{\mu_R}+1+L, K_R\}$

Figures (8)

  • Figure 1: Illustration of a cache-aided interference channel assisted by an active IRS with $Q$ elements with $K_T$ transmitters and $K_R$ receivers, where each transmitter and receiver caches up to $M_T$ and $M_R$ files, respectively, from a library composed of $N$ files.
  • Figure 2: Achievable DoF per user versus the number of IRS elements for a cache-aided interference channel with $K_T = K_R = 26$, ${\mu_R} = 5$, and ${\mu_T} = 1$.
  • Figure 3: Achievable DoF per user versus the number of IRS elements for a cache-aided interference channel with $K_T = K_R = 26$, ${\mu_R} = 12$, and ${\mu_T} = 2$.
  • Figure 4: Achievable DoF per user versus $K_R$ for a cache-aided interference channel with $K_T = 20$, ${\mu_T} = 1$, and ${\mu_R} = 5$.
  • Figure 5: Achievable DoF per user versus $K_R$ for a cache-aided interference channel with $K_T = 20$, ${\mu_T} = 2$, ${\mu_R} = 5$.
  • ...and 3 more figures

Theorems & Definitions (11)

  • Remark 1
  • Remark 2
  • Theorem 1
  • proof
  • Definition 1: $(M, {\mu_T})$-Subset Partition
  • Example 1
  • Example 2
  • Theorem 2
  • proof
  • Example 3
  • ...and 1 more