6,527 research outputs found
LAGC: Lazily Aggregated Gradient Coding for Straggler-Tolerant and Communication-Efficient Distributed Learning
Gradient-based distributed learning in Parameter Server (PS) computing
architectures is subject to random delays due to straggling worker nodes, as
well as to possible communication bottlenecks between PS and workers. Solutions
have been recently proposed to separately address these impairments based on
the ideas of gradient coding, worker grouping, and adaptive worker selection.
This paper provides a unified analysis of these techniques in terms of
wall-clock time, communication, and computation complexity measures.
Furthermore, in order to combine the benefits of gradient coding and grouping
in terms of robustness to stragglers with the communication and computation
load gains of adaptive selection, novel strategies, named Lazily Aggregated
Gradient Coding (LAGC) and Grouped-LAG (G-LAG), are introduced. Analysis and
results show that G-LAG provides the best wall-clock time and communication
performance, while maintaining a low computational cost, for two representative
distributions of the computing times of the worker nodes.Comment: Submitte
Cloud-Edge Non-Orthogonal Transmission for Fog Networks with Delayed CSI at the Cloud
In a Fog Radio Access Network (F-RAN), the cloud processor (CP) collects
channel state information (CSI) from the edge nodes (ENs) over fronthaul links.
As a result, the CSI at the cloud is generally affected by an error due to
outdating. In this work, the problem of content delivery based on fronthaul
transmission and edge caching is studied from an information-theoretic
perspective in the high signal-to-noise ratio (SNR) regime. For the set-up
under study, under the assumption of perfect CSI, prior work has shown the
(approximate or exact) optimality of a scheme in which the ENs transmit
information received from the cloud and cached contents over orthogonal
resources. In this work, it is demonstrated that a non-orthogonal transmission
scheme is able to substantially improve the latency performance in the presence
of imperfect CSI at the cloud.Comment: 5 pages, 4 figures, submitte
Fundamental Limits of Cloud and Cache-Aided Interference Management with Multi-Antenna Edge Nodes
In fog-aided cellular systems, content delivery latency can be minimized by
jointly optimizing edge caching and transmission strategies. In order to
account for the cache capacity limitations at the Edge Nodes (ENs),
transmission generally involves both fronthaul transfer from a cloud processor
with access to the content library to the ENs, as well as wireless delivery
from the ENs to the users. In this paper, the resulting problem is studied from
an information-theoretic viewpoint by making the following practically relevant
assumptions: 1) the ENs have multiple antennas; 2) only uncoded fractional
caching is allowed; 3) the fronthaul links are used to send fractions of
contents; and 4) the ENs are constrained to use one-shot linear precoding on
the wireless channel. Assuming offline proactive caching and focusing on a high
signal-to-noise ratio (SNR) latency metric, the optimal information-theoretic
performance is investigated under both serial and pipelined fronthaul-edge
transmission modes. The analysis characterizes the minimum high-SNR latency in
terms of Normalized Delivery Time (NDT) for worst-case users' demands. The
characterization is exact for a subset of system parameters, and is generally
optimal within a multiplicative factor of 3/2 for the serial case and of 2 for
the pipelined case. The results bring insights into the optimal interplay
between edge and cloud processing in fog-aided wireless networks as a function
of system resources, including the number of antennas at the ENs, the ENs'
cache capacity and the fronthaul capacity.Comment: 34 pages, 15 figures, submitte
- …