On Storage Allocation in Cache-Enabled Interference Channels with Mixed CSIT

TL;DR

This paper analyzes the Degrees of Freedom in cache-enabled interference channels under mixed CSIT conditions, revealing that receiver storage becomes more valuable than transmitter storage when CSIT is imperfect due to training and feedback delays.

Contribution

It derives the DoF for cache-enabled interference channels with mixed CSIT, highlighting the increased importance of receiver caches under realistic CSIT acquisition scenarios.

Findings

Receiver storage is more valuable than transmitter storage with mixed CSIT.

DoF depends on cache sizes and feedback phase duration.

Transmit cooperation is limited by CSIT quality, while receiver caching remains robust.

Abstract

Recently, it has been shown that in a cache-enabled interference channel, the storage at the transmit and receive sides are of equal value in terms of Degrees of Freedom (DoF). This is derived by assuming full Channel State Information at the Transmitter (CSIT). In this paper, we consider a more practical scenario, where a training/feedback phase should exist for obtaining CSIT, during which instantaneous channel state is not known to the transmitters. This results in a combination of delayed and current CSIT availability, called mixed CSIT. In this setup, we derive DoF of a cache-enabled interference channel with mixed CSIT, which depends on the memory available at transmit and receive sides as well as the training/feedback phase duration. In contrast to the case of having full CSIT, we prove that, in our setup, the storage at the receive side is more valuable than the one at the transmit side. This is due to the fact that cooperation opportunities granted by transmitters' caches are strongly based on instantaneous CSIT availability. However, multi-casting opportunities provided by receivers' caches are robust to such imperfection.