116 research outputs found
Optimal Energy Allocation for Wireless Communications with Energy Harvesting Constraints
We consider the use of energy harvesters, in place of conventional batteries
with fixed energy storage, for point-to-point wireless communications. In
addition to the challenge of transmitting in a channel with time selective
fading, energy harvesters provide a perpetual but unreliable energy source. In
this paper, we consider the problem of energy allocation over a finite horizon,
taking into account channel conditions and energy sources that are time
varying, so as to maximize the throughput. Two types of side information (SI)
on the channel conditions and harvested energy are assumed to be available:
causal SI (of the past and present slots) or full SI (of the past, present and
future slots). We obtain structural results for the optimal energy allocation,
via the use of dynamic programming and convex optimization techniques. In
particular, if unlimited energy can be stored in the battery with harvested
energy and the full SI is available, we prove the optimality of a water-filling
energy allocation solution where the so-called water levels follow a staircase
function.Comment: 27 pages, 6 figures, accepted for publications at IEEE Transactions
on Signal Processin
Wireless Networks with Energy Harvesting and Power Transfer: Joint Power and Time Allocation
In this paper, we consider wireless powered communication networks which
could operate perpetually, as the base station (BS) broadcasts energy to the
multiple energy harvesting (EH) information transmitters. These employ "harvest
then transmit" mechanism, as they spend all of their energy harvested during
the previous BS energy broadcast to transmit the information towards the BS.
Assuming time division multiple access (TDMA), we propose a novel transmission
scheme for jointly optimal allocation of the BS broadcasting power and time
sharing among the wireless nodes, which maximizes the overall network
throughput, under the constraint of average transmit power and maximum transmit
power at the BS. The proposed scheme significantly outperforms "state of the
art" schemes that employ only the optimal time allocation. If a single EH
transmitter is considered, we generalize the optimal solutions for the case of
fixed circuit power consumption, which refers to a much more practical
scenario.Comment: 5 pages, 2 figures in IEEE Signal Processing Letters, vol. 23, no. 1,
January 201
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
RF Energy Harvesting Enabled Power Sharing in Relay Networks
Through simultaneous energy and information transfer, radio frequency (RF)
energy harvesting (EH) reduces the energy consumption of the wireless networks.
It also provides a new approach for the wireless devices to share each other's
energy storage, without relying on the power grid or traffic offloading. In
this paper, we study RF energy harvesting enabled power balancing within the
decode-and-forward (DF) relaying-enhanced cooperative wireless system. An
optimal power allocation policy is proposed for the scenario where both source
and relay nodes can draw power from the radio frequency signals transmitted by
each other. To maximize the overall throughput while meeting the energy
constraints imposed by the RF sources, an optimization problem is formulated
and solved. Based on different harvesting efficiency and channel condition,
closed form solutions for optimal joint source and relay power allocation are
derived.Comment: An abbreviated version will be presented at IEEE online GreenComm,
Nov., 201
Energy Harvesting Networks with General Utility Functions: Near Optimal Online Policies
We consider online scheduling policies for single-user energy harvesting
communication systems, where the goal is to characterize online policies that
maximize the long term average utility, for some general concave and
monotonically increasing utility function. In our setting, the transmitter
relies on energy harvested from nature to send its messages to the receiver,
and is equipped with a finite-sized battery to store its energy. Energy packets
are independent and identically distributed (i.i.d.) over time slots, and are
revealed causally to the transmitter. Only the average arrival rate is known a
priori. We first characterize the optimal solution for the case of Bernoulli
arrivals. Then, for general i.i.d. arrivals, we first show that fixed fraction
policies [Shaviv-Ozgur] are within a constant multiplicative gap from the
optimal solution for all energy arrivals and battery sizes. We then derive a
set of sufficient conditions on the utility function to guarantee that fixed
fraction policies are within a constant additive gap as well from the optimal
solution.Comment: To appear in the 2017 IEEE International Symposium on Information
Theory. arXiv admin note: text overlap with arXiv:1705.1030
Transmission Power Scheduling for Energy Harvesting Sensor in Remote State Estimation
We study remote estimation in a wireless sensor network. Instead of using a
conventional battery-powered sensor, a sensor equipped with an energy harvester
which can obtain energy from the external environment is utilized. We formulate
this problem into an infinite time-horizon Markov decision process and provide
the optimal sensor transmission power control strategy. In addition, a
sub-optimal strategy which is easier to implement and requires less computation
is presented. A numerical example is provided to illustrate the implementation
of the sub-optimal policy and evaluation of its estimation performance.Comment: Extended version of article to be published in the Proceedings of the
19th IFAC World Congress, 201
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