199 research outputs found
The Binary Energy Harvesting Channel with a Unit-Sized Battery
We consider a binary energy harvesting communication channel with a
finite-sized battery at the transmitter. In this model, the channel input is
constrained by the available energy at each channel use, which is driven by an
external energy harvesting process, the size of the battery, and the previous
channel inputs. We consider an abstraction where energy is harvested in binary
units and stored in a battery with the capacity of a single unit, and the
channel inputs are binary. Viewing the available energy in the battery as a
state, this is a state-dependent channel with input-dependent states, memory in
the states, and causal state information available at the transmitter only. We
find an equivalent representation for this channel based on the timings of the
symbols, and determine the capacity of the resulting equivalent timing channel
via an auxiliary random variable. We give achievable rates based on certain
selections of this auxiliary random variable which resemble lattice coding for
the timing channel. We develop upper bounds for the capacity by using a
genie-aided method, and also by quantifying the leakage of the state
information to the receiver. We show that the proposed achievable rates are
asymptotically capacity achieving for small energy harvesting rates. We extend
the results to the case of ternary channel inputs. Our achievable rates give
the capacity of the binary channel within 0.03 bits/channel use, the ternary
channel within 0.05 bits/channel use, and outperform basic Shannon strategies
that only consider instantaneous battery states, for all parameter values.Comment: Submitted to IEEE Transactions on Information Theory, August 201
Information-Theoretic Analysis of an Energy Harvesting Communication System
In energy harvesting communication systems, an exogenous recharge process
supplies energy for the data transmission and arriving energy can be buffered
in a battery before consumption. Transmission is interrupted if there is not
sufficient energy. We address communication with such random energy arrivals in
an information-theoretic setting. Based on the classical additive white
Gaussian noise (AWGN) channel model, we study the coding problem with random
energy arrivals at the transmitter. We show that the capacity of the AWGN
channel with stochastic energy arrivals is equal to the capacity with an
average power constraint equal to the average recharge rate. We provide two
different capacity achieving schemes: {\it save-and-transmit} and {\it
best-effort-transmit}. Next, we consider the case where energy arrivals have
time-varying average in a larger time scale. We derive the optimal offline
power allocation for maximum average throughput and provide an algorithm that
finds the optimal power allocation.Comment: Published in IEEE PIMRC, September 201
Communicating Using an Energy Harvesting Transmitter: Optimum Policies Under Energy Storage Losses
In this paper, short-term throughput optimal power allocation policies are
derived for an energy harvesting transmitter with energy storage losses. In
particular, the energy harvesting transmitter is equipped with a battery that
loses a fraction of its stored energy. Both single user, i.e. one
transmitter-one receiver, and the broadcast channel, i.e., one
transmitter-multiple receiver settings are considered, initially with an
infinite capacity battery. It is shown that the optimal policies for these
models are threshold policies. Specifically, storing energy when harvested
power is above an upper threshold, retrieving energy when harvested power is
below a lower threshold, and transmitting with the harvested energy in between
is shown to maximize the weighted sum-rate. It is observed that the two
thresholds are related through the storage efficiency of the battery, and are
nondecreasing during the transmission. The results are then extended to the
case with finite battery capacity, where it is shown that a similar
double-threshold structure arises but the thresholds are no longer monotonic. A
dynamic program that yields an optimal online power allocation is derived, and
is shown to have a similar double-threshold structure. A simpler online policy
is proposed and observed to perform close to the optimal policy.Comment: Submitted to IEEE Transactions on Wireless Communications, August
201
Optimal Energy Management for Energy Harvesting Transmitter and Receiver with Helper
We study energy harvesting (EH) transmitter and receiver, where the receiver
decodes data using the harvested energy from the nature and from an independent
EH node, named helper. Helper cooperates with the receiver by transferring its
harvested energy to the receiver over an orthogonal fading channel. We study an
offline optimal power management policy to maximize the reliable information
rate. The harvested energy in all three nodes are assumed to be known. We
consider four different scenarios; First, for the case that both transmitter
and the receiver have batteries, we show that the optimal policy is
transferring the helper harvested energy to the receiver, immediately. Next,
for the case of non-battery receiver and full power transmitter, we model a
virtual EH receiver with minimum energy constraint to achieve an optimal
policy. Then, we consider a non-battery EH receiver and EH transmitter with
battery. Finally, we derive optimal power management wherein neither the
transmitter nor the receiver have batteries. We propose three iterative
algorithms to compute optimal energy management policies. Numerical results are
presented to corroborate the advantage of employing the helper.Comment: It is a conference paper with 5 pages and one figure, submitted to
ISITA201
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
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