7,604 research outputs found
Age-Minimal Transmission in Energy Harvesting Two-hop Networks
We consider an energy harvesting two-hop network where a source is
communicating to a destination through a relay. During a given communication
session time, the source collects measurement updates from a physical
phenomenon and sends them to the relay, which then forwards them to the
destination. The objective is to send these updates to the destination as
timely as possible; namely, such that the total age of information is minimized
by the end of the communication session, subject to energy causality
constraints at the source and the relay, and data causality constraints at the
relay. Both the source and the relay use fixed, yet possibly different,
transmission rates. Hence, each update packet incurs fixed non-zero
transmission delays. We first solve the single-hop version of this problem, and
then show that the two-hop problem is solved by treating the source and relay
nodes as one combined node, with some parameter transformations, and solving a
single-hop problem between that combined node and the destination.Comment: Appeared in IEEE Globecom 201
Optimal Scheduling and Power Allocation for Two-Hop Energy Harvesting Communication Systems
Energy harvesting (EH) has recently emerged as a promising technique for
green communications. To realize its potential, communication protocols need to
be redesigned to combat the randomness of the harvested energy. In this paper,
we investigate how to apply relaying to improve the short-term performance of
EH communication systems. With an EH source and a non-EH half-duplex relay, we
consider two different design objectives: 1) short-term throughput
maximization; and 2) transmission completion time minimization. Both problems
are joint scheduling and power allocation problems, rendered quite challenging
by the half-duplex constraint at the relay. A key finding is that directional
water-filling (DWF), which is the optimal power allocation algorithm for the
single-hop EH system, can serve as guideline for the design of two-hop
communication systems, as it not only determines the value of the optimal
performance, but also forms the basis to derive optimal solutions for both
design problems. Based on a relaxed energy profile along with the DWF
algorithm, we derive key properties of the optimal solutions for both problems
and thereafter propose efficient algorithms. Simulation results will show that
both scheduling and power allocation optimizations are necessary in two-hop EH
communication systems.Comment: Submitted to IEEE Transaction on Wireless Communicatio
Energy Harvesting Wireless Communications: A Review of Recent Advances
This article summarizes recent contributions in the broad area of energy
harvesting wireless communications. In particular, we provide the current state
of the art for wireless networks composed of energy harvesting nodes, starting
from the information-theoretic performance limits to transmission scheduling
policies and resource allocation, medium access and networking issues. The
emerging related area of energy transfer for self-sustaining energy harvesting
wireless networks is considered in detail covering both energy cooperation
aspects and simultaneous energy and information transfer. Various potential
models with energy harvesting nodes at different network scales are reviewed as
well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications
(Special Issue: Wireless Communications Powered by Energy Harvesting and
Wireless Energy Transfer
Age Minimization in Energy Harvesting Communications: Energy-Controlled Delays
We consider an energy harvesting source that is collecting measurements from
a physical phenomenon and sending updates to a destination within a
communication session time. Updates incur transmission delays that are function
of the energy used in their transmission. The more transmission energy used per
update, the faster it reaches the destination. The goal is to transmit updates
in a timely manner, namely, such that the total age of information is minimized
by the end of the communication session, subject to energy causality
constraints. We consider two variations of this problem. In the first setting,
the source controls the number of measurement updates, their transmission
times, and the amounts of energy used in their transmission (which govern their
delays, or service times, incurred). In the second setting, measurement updates
externally arrive over time, and therefore the number of updates becomes fixed,
at the expense of adding data causality constraints to the problem. We
characterize age-minimal policies in the two settings, and discuss the
relationship of the age of information metric to other metrics used in the
energy harvesting literature.Comment: Appeared in Asilomar 201
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