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

This paper studies cache-aided wireless networks in the presence of active intelligent reflecting surfaces (IRSs) from an information-theoretic perspective. Specifically, we investigate 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 IRS coefficients, and propose a one-shot achievability scheme. Our scheme exploits transmitters’ cooperation, cache contents, interference alignment, and IRS capabilities, based on the network parameters. We derive the achievable one-shot sum-DoF for different cache sizes, network configurations, and numbers of IRS elements, followed by an upper bound. Our results highlight the potential of deploying an IRS in cache-aided wireless communication systems. In particular, they underscore the enhancement of achievable DoF for various parameter regimes, especially when cache sizes 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.

💡 Research Summary

This paper investigates the degrees‑of‑freedom (DoF) performance of a K_T × K_R single‑antenna interference channel in which both transmitters and receivers are equipped with cache memories and the communication is assisted by an active intelligent reflecting surface (IRS) with Q controllable elements. The authors adopt an information‑theoretic viewpoint and focus on the high‑SNR regime, where DoF is the relevant metric.

The system model assumes a library of N files, each transmitter caching up to M_T files and each receiver up to M_R files. The direct links H_{ji}(t) and the two‑hop links (transmitter‑to‑IRS and IRS‑to‑receiver) are independent across time and users. Each IRS element applies a complex coefficient q_u(t)=ρ_u(t)·e^{jϕ_u(t)} where ρ_u(t)≥0 is an amplitude (gain) and ϕ_u(t)∈