Fundamental Storage-Latency Tradeoff in Cache-Aided MIMO Interference Networks

TL;DR

This paper investigates the fundamental tradeoff between storage capacity and latency in cache-aided MIMO interference networks, deriving optimal and near-optimal delivery times using degrees of freedom analysis.

Contribution

It introduces a new analysis of cache-aided MIMO interference networks, deriving the normalized delivery time for arbitrary parameters and caching strategies, with proven optimality in some cases.

Findings

Achieved normalized delivery time (NDT) bounds for various M, N, and cache sizes.

Demonstrated cases where NDT is optimal and others within a factor of 3 of optimal.

Extended analysis to networks with arbitrary numbers of transmitters and receivers.

Abstract

Caching is an effective technique to improve user perceived experience for content delivery in wireless networks. Wireless caching differs from traditional web caching in that it can exploit the broadcast nature of wireless medium and hence opportunistically change the network topologies. This paper studies a cache-aided MIMO interference network with 3 transmitters each equipped with M antennas and 3 receivers each with N antennas. With caching at both the transmitter and receiver sides, the network is changed to hybrid forms of MIMO broadcast channel, MIMO X channel, and MIMO multicast channels. We analyze the degrees of freedom (DoF) of these new channel models using practical interference management schemes. Based on the collective use of these DoF results, we then obtain an achievable normalized delivery time (NDT) of the network, an information-theoretic metric that evaluates the worst-case delivery time at given cache sizes. The obtained NDT is for arbitrary M, N and any feasible cache sizes. It is shown to be optimal in certain cases and within a multiplicative gap of 3 from the optimum in other cases. The extension to the network with arbitrary number of transmitters and receivers is also discussed.