1,048 research outputs found
Throughput Maximization for the Gaussian Relay Channel with Energy Harvesting Constraints
This paper considers the use of energy harvesters, instead of conventional
time-invariant energy sources, in wireless cooperative communication. For the
purpose of exposition, we study the classic three-node Gaussian relay channel
with decode-and-forward (DF) relaying, in which the source and relay nodes
transmit with power drawn from energy-harvesting (EH) sources. Assuming a
deterministic EH model under which the energy arrival time and the harvested
amount are known prior to transmission, the throughput maximization problem
over a finite horizon of transmission blocks is investigated. In
particular, two types of data traffic with different delay constraints are
considered: delay-constrained (DC) traffic (for which only one-block decoding
delay is allowed at the destination) and no-delay-constrained (NDC) traffic
(for which arbitrary decoding delay up to blocks is allowed). For the DC
case, we show that the joint source and relay power allocation over time is
necessary to achieve the maximum throughput, and propose an efficient algorithm
to compute the optimal power profiles. For the NDC case, although the
throughput maximization problem is non-convex, we prove the optimality of a
separation principle for the source and relay power allocation problems, based
upon which a two-stage power allocation algorithm is developed to obtain the
optimal source and relay power profiles separately. Furthermore, we compare the
DC and NDC cases, and obtain the sufficient and necessary conditions under
which the NDC case performs strictly better than the DC case. It is shown that
NDC transmission is able to exploit a new form of diversity arising from the
independent source and relay energy availability over time in cooperative
communication, termed "energy diversity", even with time-invariant channels.Comment: appear in IEEE Journal on Selected Areas in Communications, special
issue on theories and methods for advanced wireless relay
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
Robust Transmissions in Wireless Powered Multi-Relay Networks with Chance Interference Constraints
In this paper, we consider a wireless powered multi-relay network in which a
multi-antenna hybrid access point underlaying a cellular system transmits
information to distant receivers. Multiple relays capable of energy harvesting
are deployed in the network to assist the information transmission. The hybrid
access point can wirelessly supply energy to the relays, achieving multi-user
gains from signal and energy cooperation. We propose a joint optimization for
signal beamforming of the hybrid access point as well as wireless energy
harvesting and collaborative beamforming strategies of the relays. The
objective is to maximize network throughput subject to probabilistic
interference constraints at the cellular user equipment. We formulate the
throughput maximization with both the time-switching and power-splitting
schemes, which impose very different couplings between the operating parameters
for wireless power and information transfer. Although the optimization problems
are inherently non-convex, they share similar structural properties that can be
leveraged for efficient algorithm design. In particular, by exploiting
monotonicity in the throughput, we maximize it iteratively via customized
polyblock approximation with reduced complexity. The numerical results show
that the proposed algorithms can achieve close to optimal performance in terms
of the energy efficiency and throughput.Comment: 14 pages, 8 figure
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
Optimal Cooperative Power Allocation for Energy Harvesting Enabled Relay Networks
In this paper, we present a new power allocation scheme for a
decode-and-forward (DF) relaying-enhanced cooperative wireless system. While
both source and relay nodes may have limited traditional brown power supply or
fixed green energy storage, the hybrid source node can also draw power from the
surrounding radio frequency (RF) signals. In particular, we assume a
deterministic RF energy harvesting (EH) model under which the signals
transmitted by the relay serve as the renewable energy source for the source
node. The amount of harvested energy is known for a given transmission power of
the forwarding signal and channel condition between the source and relay nodes.
To maximize the overall throughput while meeting the constraints imposed by the
non-sustainable energy sources and the renewable energy source, an optimization
problem is formulated and solved. Based on different harvesting efficiency and
channel condition, closed form solutions are derived to obtain the optimal
source and relay power allocation jointly. It is shown that instead of
demanding high on-grid power supply or high green energy availability, the
system can achieve compatible or higher throughput by utilizing the harvested
energy
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