34 research outputs found
Wyner's Network on Caches: Combining Receiver Caching with a Flexible Backhaul
In this work, we study a large linear interference network with an equal
number of transmitters and receivers, where each transmitter is connected to
two subsequent receivers. Each transmitter has individual access to a backhaul
link (fetching the equivalent of files), while each receiver can cache
a fraction of the library. We explore the tradeoff between the
communication rate, backhaul load, and caching storage by designing algorithms
that can harness the benefits of cooperative transmission in partially
connected networks, while exploiting the advantages of multicast transmissions
attributed to user caching. We show that receiver caching and fetching content
from the backhaul are two resources that can simultaneously increase the
delivery performance in synergistic ways.
Specifically, an interesting outcome of this work is that user caching of a
fraction of the library can increase the per-user Degrees of Freedom
(puDoF) by . Further, the results reveal significant savings in the
backhaul load, even in the small cache size region. For example, the puDoF
achieved using the pair can also be achieved with the pairs and
, showing that even small caches can provide significant
savings in the backhaul load.Comment: 8 pages, 2 figures, submitted to ISIT 201
Fundamental Limits of Wireless Caching Under Mixed Cacheable and Uncacheable Traffic
We consider cache-aided wireless communication scenarios where each user
requests both a file from an a-priori generated cacheable library (referred to
as 'content'), and an uncacheable 'non-content' message generated at the start
of the wireless transmission session. This scenario is easily found in
real-world wireless networks, where the two types of traffic coexist and share
limited radio resources. We focus on single-transmitter, single-antenna
wireless networks with cache-aided receivers, where the wireless channel is
modelled by a degraded Gaussian broadcast channel (GBC). For this setting, we
study the delay-rate trade-off, which characterizes the content delivery time
and non-content communication rates that can be achieved simultaneously. We
propose a scheme based on the separation principle, which isolates the coded
caching and multicasting problem from the physical layer transmission problem.
We show that this separation-based scheme is sufficient for achieving an
information-theoretically order optimal performance, up to a multiplicative
factor of 2.01 for the content delivery time, when working in the generalized
degrees of freedom (GDoF) limit. We further show that the achievable
performance is near-optimal after relaxing the GDoF limit, up to an additional
additive factor of 2 bits per dimension for the non-content rates. A key
insight emerging from our scheme is that in some scenarios considerable amounts
of non-content traffic can be communicated while maintaining the minimum
content delivery time, achieved in the absence of non-content messages;
compliments of 'topological holes' arising from asymmetries in wireless channel
gains.Comment: Accepted for publication in the IEEE Transactions on Information
Theor