Cache-Assisted Broadcast-Relay Wireless Networks: A Delivery-Time Cache-Memory Tradeoff

03/11/2018
by   Jaber Kakar, et al.
0

An emerging trend of next generation communication systems is to provide network edges with additional capabilities such as storage resources in the form of caches to reduce file delivery latency. To investigate this aspect, we study the fundamental limits of a cache-aided broadcast-relay wireless network consisting of one central base station, M cache-equipped transceivers and K receivers from a latency-centric perspective. We use the normalized delivery time (NDT) to capture the per-bit latency for the worst-case file request pattern, normalized with respect to a reference interference-free system with unlimited transceiver cache capabilities. The objective is to design the schemes for cache placement and file delivery in order to minimize the NDT. To this end, we establish a novel converse and two types of achievability schemes applicable to both time-variant and invariant channels. The first scheme is a general one-shot scheme for any M and K that synergistically exploits both multicasting (coded) caching and distributed zero-forcing opportunities. We show that the proposed one-shot scheme (i) attains gains attributed to both individual and collective transceiver caches (ii) is NDT-optimal for various parameter settings, particularly at higher cache sizes. The second scheme, on the other hand, designs beamformers to facilitate both subspace interference alignment and zero-forcing at lower cache sizes. Exploiting both schemes, we are able to characterize for various special cases of M and K which satisfy K+M≤ 4 the optimal tradeoff between cache storage and latency. The tradeoff illustrates that the NDT is the preferred choice to capture the latency of a system rather than the commonly used sum degrees-of-freedom (DoF). In fact, our optimal tradeoff refutes the popular belief that increasing cache sizes translates to increasing the achievable sum DoF.

READ FULL TEXT

page 1

page 2

page 3

page 4

research
03/11/2018

Delivery Time Minimization in Cache-Assisted Broadcast-Relay Wireless Networks with Imperfect CSI

An emerging trend of next generation communication systems is to provide...
research
01/31/2019

Cache-aided Interference Management Using Hypercube Combinatorial Cache Designs

We consider a cache-aided interference network which consists of a libra...
research
12/16/2017

Degrees of Freedom of Interference Networks with Transmitter-Side Caches

This paper studies cache-aided interference networks with arbitrary numb...
research
12/05/2017

Broadcast Caching Networks with Two Receivers and Multiple Correlated Sources

The correlation among the content distributed across a cache-aided broad...
research
08/19/2019

Cache Subsidies for an Optimal Memory for Bandwidth Tradeoff in the Access Network

While the cost of the access network could be considerably reduced by th...
research
02/18/2020

Fundamental Limits of Wireless Caching Under Mixed Cacheable and Uncacheable Traffic

We consider cache-aided wireless communication scenarios where each user...

Please sign up or login with your details

Forgot password? Click here to reset