Fundamental Limits of Cache-Aided Interference Management

Abstract

We consider a system, comprising a library of N files (e.g., movies) and a wireless network with KT transmitters, each equipped with a local cache of size of MT files, and KR receivers, each equipped with a local cache of size of MR files. Each receiver will ask for one of the N files in the library, which needs to be delivered. The objective is to design the cache placement (without prior knowledge of receivers' future requests) and the communication scheme to maximize the throughput of the delivery. In this setting, we show that the sum degrees-of-freedom (sum-DoF) of min, KR is achievable, and this is within a factor of 2 of the optimum, under one-shot linear schemes. This result shows that (i) the one-shot sum-DoF scales linearly with the aggregate cache size in the network (i.e., the cumulative memory available at all nodes), (ii) the transmitters' caches and receivers' caches contribute equally in the one-shot sum-DoF, and (iii) caching can offer a throughput gain that scales linearly with the size of the network.To prove the result, we propose an achievable scheme that exploits the redundancy of the content at transmitters' caches to cooperatively zero-force some outgoing interference, and availability of the unintended content at the receivers' caches to cancel (subtract) some of the incoming interference. We develop a particular pattern for cache placement that maximizes the overall gains of cache-aided transmit and receive interference cancellations. For the converse, we present an integer optimization problem which minimizes the number of communication blocks needed to deliver any set of requested files to the receivers. We then provide a lower bound on the value of this optimization problem, hence leading to an upper bound on the linear one-shot sum-DoF of the network, which is within a factor of 2 of the achievable sum-DoF.

Interference networks with caches at both ends

“…The work in [13] studies the storage-latency trade-off for cache-aided wireless interference networks consisting of K T transmitters (K T ≥ 2) and two or three receivers. Authors introduce a new coded caching technique that leverages adjustable file splitting, and using this placement phase as well as IA and ZF techniques, they caractherize the fractional delivery time, obtaining similar results to those in [7], [12]. A 3 × 3 cache-aided MIMO interference network is studied in [14], where the achievable fractional delivery time is characterized.…”

“…They propose a transmission scheme that exploits zero-forcing (ZF) and interference alignment (IA) techniques, leveraging content availability at the transmitter caches, in order to create different types of channels for delivering the remaining parts of the requested content. In [12], the authors extend this model to a K T × K R network, in which both the transmitters and receivers are equipped with cache memories. Nonetheless, in [12], the authors exploit only ZF and the receiver cache contents for interference cancellation (IC).…”

“…In [12], the authors extend this model to a K T × K R network, in which both the transmitters and receivers are equipped with cache memories. Nonetheless, in [12], the authors exploit only ZF and the receiver cache contents for interference cancellation (IC). The work in [13] studies the storage-latency trade-off for cache-aided wireless interference networks consisting of K T transmitters (K T ≥ 2) and two or three receivers.…”

“…Similarly to [12] and [19], we consider a general interference network of single antenna terminals with cache capabilities at both ends. We first propose a centralized caching and delivery scheme that uses the same placement phase as in [12], but leverages a combination of ZF, IA and IC.…”

Modeling and Analysis for Cache-Enabled Networks With Dynamic Traffic

“…[11] analyzes the benefits of caching and interference alignment at BSs in MIMO system with limited backhaul. Cache placement and interference management are elaborated in [12] cache-enabled. However, backhaul is needed for the interconnection of cache-enabled transmitters to achieve cooperative transmission in previous studies.…”