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

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.