1,250 research outputs found
Performance Analysis of Energy Harvesting Underlay Cooperative Cognitive Radio Relay Networks with Randomly Located Nodes
In this work, we investigate the successful data communication probability of
an energy harvesting co-operative cognitive radio network (CRN) in the presence
of Poisson field of primary users (PU). We consider the scenario where, after
harvesting energy from primary transmitters (PTs), the secondary transmitter
(ST) would transmit its symbol towards secondary destination (SD) through a
suitable secondary relay from group of randomly scattered idle nodes within a
circular region. We have considered several relay selection criteria in our
work for a better relay node selection. We have also analytically evaluated the
performance of secondary transmitter in terms of probability of successful
symbol transmission. The relationship between the performance of ST and several
network entities like density of PUs, transmit power of PTs and required
transmit power of ST have been investigated through detailed analysis. The
non-trivial trade-off between benefit of energy harvesting and interference
from PTs has been explored in this present work. Numerical results are provided
to verify the precision of derived analytical expressions
Harvest-Then-Cooperate: Wireless-Powered Cooperative Communications
In this paper, we consider a wireless-powered cooperative communication
network consisting of one hybrid access-point (AP), one source, and one relay.
In contrast to conventional cooperative networks, the source and relay in the
considered network have no embedded energy supply. They need to rely on the
energy harvested from the signals broadcasted by the AP for their cooperative
information transmission. Based on this three-node reference model, we propose
a harvest-then-cooperate (HTC) protocol, in which the source and relay harvest
energy from the AP in the downlink and work cooperatively in the uplink for the
source's information transmission. Considering a delay-limited transmission
mode, the approximate closed-form expression for the average throughput of the
proposed protocol is derived over Rayleigh fading channels. Subsequently, this
analysis is extended to the multi-relay scenario, where the approximate
throughput of the HTC protocol with two popular relay selection schemes is
derived. The asymptotic analyses for the throughput performance of the
considered schemes at high signal-to-noise radio are also provided. All
theoretical results are validated by numerical simulations. The impacts of the
system parameters, such as time allocation, relay number, and relay position,
on the throughput performance are extensively investigated.Comment: Accepted by IEEE Trans. Signal Processin
Simultaneous Information and Energy Transfer in Large-Scale Networks with/without Relaying
Energy harvesting (EH) from ambient radio-frequency (RF) electromagnetic
waves is an efficient solution for fully autonomous and sustainable
communication networks. Most of the related works presented in the literature
are based on specific (and small-scale) network structures, which although give
useful insights on the potential benefits of the RF-EH technology, cannot
characterize the performance of general networks. In this paper, we adopt a
large-scale approach of the RF-EH technology and we characterize the
performance of a network with random number of transmitter-receiver pairs by
using stochastic-geometry tools. Specifically, we analyze the outage
probability performance and the average harvested energy, when receivers employ
power splitting (PS) technique for "simultaneous" information and energy
transfer. A non-cooperative scheme, where information/energy are conveyed only
via direct links, is firstly considered and the outage performance of the
system as well as the average harvested energy are derived in closed form in
function of the power splitting. For this protocol, an interesting optimization
problem which minimizes the transmitted power under outage probability and
harvesting constraints, is formulated and solved in closed form. In addition,
we study a cooperative protocol where sources' transmissions are supported by a
random number of potential relays that are randomly distributed into the
network. In this case, information/energy can be received at each destination
via two independent and orthogonal paths (in case of relaying). We characterize
both performance metrics, when a selection combining scheme is applied at the
receivers and a single relay is randomly selected for cooperative diversity.Comment: IEEE Transactions on Communication
Wireless Information and Power Transfer for Multi-Relay Assisted Cooperative Communication
In this paper, we consider simultaneous wireless information and power
transfer (SWIPT) in multi-relay assisted two-hop relay system, where multiple
relay nodes simultaneously assist the transmission from source to destination
using the concept of distributed space-time coding. Each relay applies power
splitting protocol to coordinate the received signal energy for information
decoding and energy harvesting. The optimization problems of power splitting
ratios at the relays are formulated for both decode-and-forward (DF) and
amplify-and-forward (AF) relaying protocols. Efficient algorithms are proposed
to find the optimal solutions. Simulations verify the effectiveness of the
proposed schemes.Comment: To be published in IEEE Communications Letter
Energy Harvesting Noncoherent Cooperative Communications
This paper investigates simultaneous wireless information and power transfer
(SWIPT) in energy harvesting (EH) relay systems. Unlike existing SWIPT schemes
requiring the channel state information (CSI) for coherent information
delivery, we propose a noncoherent SWIPT framework for decode-and-forward (DF)
relay systems bypassing the need for CSI and consequently saving energy in the
network. The proposed SWIPT framework embraces power-splitting noncoherent DF
(PS-NcDF) and time-switching noncoherent DF (TS-NcDF) in a unified form, and
supports arbitrary M-ary noncoherent frequency-shift keying (FSK) and
differential phase-shift keying (DPSK). Exact (noncoherent) maximum-likelihood
detectors (MLDs) for PS-NcDF and TS-NcDF are developed in a unified form, which
involves integral evaluations yet serves as the optimum performance benchmark
for noncoherent SWIPT. To reduce the computational cost of the exact MLDs, we
also propose closed-form approximate MLDs achieving near-optimum performance,
thus serving as a practical solution for noncoherent SWIPT. Numerical results
demonstrate a performance tradeoff between the first and second hops through
the adjustment of time switching or power splitting parameters, whose optimal
values minimizing the symbol-error rate (SER) are strictly between 0 and 1. We
demonstrate that M-FSK results in a significant energy saving over M-DPSK for M
>= 8; thus M-FSK may be more suitable for EH relay systems
Distributed Power Splitting for SWIPT in Relay Interference Channels using Game Theory
In this paper, we consider simultaneous wireless information and power
transfer (SWIPT) in relay interference channels, where multiple
source-destination pairs communicate through their dedicated energy harvesting
relays. Each relay needs to split its received signal from sources into two
streams: one for information forwarding and the other for energy harvesting. We
develop a distributed power splitting framework using game theory to derive a
profile of power splitting ratios for all relays that can achieve a good
network-wide performance. Specifically, non-cooperative games are respectively
formulated for pure amplify-and-forward (AF) and decode-and-forward (DF)
networks, in which each link is modeled as a strategic player who aims to
maximize its own achievable rate. The existence and uniqueness for the Nash
equilibriums (NEs) of the formulated games are analyzed and a distributed
algorithm with provable convergence to achieve the NEs is also developed.
Subsequently, the developed framework is extended to the more general network
setting with mixed AF and DF relays. All the theoretical analyses are validated
by extensive numerical results. Simulation results show that the proposed
game-theoretical approach can achieve a near-optimal network-wide performance
on average, especially for the scenarios with relatively low and moderate
interference.Comment: Full version of a paper accepted by IEEE Trans. Wireless Commun., 14
page
Noncoherent Relaying in Energy Harvesting Communication Systems
In energy harvesting (EH) relay networks, the coherent communication requires
accurate estima- tion/tracking of the instantaneous channel state information
(CSI) which consumes extra power. As a remedy, we propose two noncoherent EH
relaying protocols based on the amplify-and-forward (AF) relaying, namely,
power splitting noncoherent AF (PS-NcAF) and time switching noncoherent AF
(TS-NcAF), which do not require any instantaneous CSI. We develop a noncoherent
framework of simultaneous wireless information and power transfer (SWIPT),
embracing PS-NcAF and TS-NcAF in a unified form. For arbitrary M-ary
noncoherent frequency-shift keying (FSK) and differential phase- shift keying
(DPSK), we derive maximum-likelihood detectors (MLDs) for PS-NcAF and TS-NcAF
in a unified form, which involves integral evaluations yet serves as the
optimum performance benchmark. To avoid expensive integral computations, we
propose a closed-form detector using the Gauss-Legendre approximation, which
achieves almost identical performance as the MLD but at substantially lower
complexity. These EH-based noncoherent detectors achieve full diversity in
Rayleigh fading. Numerical results demonstrate that our proposed PS-NcAF and
TS-NcAF may outperform the conventional grid- powered relay system under the
same total power constraint. Various insights which are useful for the design
of practical SWIPT relaying systems are obtained. Interestingly, PS-NcAF
outperforms TS-NcAF in the single-relay case, whereas TS-NcAF outperforms
PS-NcAF in the multi-relay case
Spatially Random Relay Selection for Full/Half-Duplex Cooperative NOMA Networks
This paper investigates the impact of relay selection (RS) on the performance
of cooperative non-orthogonal multiple access (NOMA), where relays are capable
of working in either full-duplex (FD) or half-duplex (HD) mode. A number of
relays (i.e., relays) are uniformly distributed within the disc. A pair of
RS schemes are considered insightfully: 1) Single-stage RS (SRS) scheme; and 2)
Two-stage RS (TRS) scheme. In order to characterize the performance of these
two RS schemes, new closed-form expressions for both exact and asymptotic
outage probabilities are derived. Based on analytical results, the diversity
orders achieved by the pair of RS schemes for FD/HD cooperative NOMA are
obtained. Our analytical results reveal that: i) The FD-based RS schemes obtain
a zero diversity order, which is due to the influence of loop interference (LI)
at the relay; and ii) The HD-based RS schemes are capable of achieving a
diversity order of , which is equal to the number of relays. Finally,
simulation results demonstrate that: 1) The FD-based RS schemes have better
outage performance than HD-based RS schemes in the low signal-to-noise radio
(SNR) region; 2) As the number of relays increases, the pair of RS schemes
considered are capable of achieving the lower outage probability; and 3) The
outage behaviors of FD/HD-based NOMA SRS/TRS schemes are superior to that of
random RS (RRS) and orthogonal multiple access (OMA) based RS schemes.Comment: 15 pages,11 figure
Truth-Telling Mechanism for Secure Two-Way Relay Communications with Energy-Harvesting Revenue
This paper brings the novel idea of paying the utility to the winning agents
in terms of some physical entity in cooperative communications. Our setting is
a secret two-way communication channel where two transmitters exchange
information in the presence of an eavesdropper. The relays are selected from a
set of interested parties such that the secrecy sum rate is maximized. In
return, the selected relay nodes' energy harvesting requirements will be
fulfilled up to a certain threshold through their own payoff so that they have
the natural incentive to be selected and involved in the communication.
However, relays may exaggerate their private information in order to improve
their chance to be selected. Our objective is to develop a mechanism for relay
selection that enforces them to reveal the truth since otherwise they may be
penalized. We also propose a joint cooperative relay beamforming and transmit
power optimization scheme based on an alternating optimization approach. Note
that the problem is highly non-convex since the objective function appears as a
product of three correlated Rayleigh quotients. While a common practice in the
existing literature is to optimize the relay beamforming vector for given
transmit power via rank relaxation, we propose a second-order cone programming
(SOCP)-based approach in this paper which requires a significantly lower
computational task. The performance of the incentive control mechanism and the
optimization algorithm has been evaluated through numerical simulations.Comment: Accepted in IEEE Transactions on Wireless Communication
Distributed Multi-Relay Selection in Accumulate-then-Forward Energy Harvesting Relay Networks
This paper investigates a wireless-powered cooperative network (WPCN)
consisting of one source-destination pair and multiple decode-and-forward (DF)
relays. We develop an energy threshold based multi-relay selection (ETMRS)
scheme for the considered WPCN. The proposed ETMRS scheme can be implemented in
a fully distributed manner as the relays only need local information to switch
between energy harvesting and information forwarding modes. By modeling the
charging/discharging behaviours of the finite-capacity battery at each relay as
a finite-state Markov Chain (MC), we derive an analytical expression for the
system outage probability of the proposed ETMRS scheme over mixed Nakagami-
and Rayleigh fading channels. Based on the derived expression, the optimal
energy thresholds for all the relays corresponding to the minimum system outage
probability can be obtained via an exhaustive search. However, this approach
becomes computationally prohibitive when the number of relays and the
associated number of battery energy levels is large. To resolve this issue, we
propose a heuristic approach to optimize the energy threshold for each relay.
To gain some useful insights for practical relay design, we also derive the
upper bound for system outage probability corresponding to the case that all
relays are equipped with infinite-capacity batteries. Numerical results
validate our theoretical analysis. It is shown that the proposed heuristic
approach can achieve a near-optimal system performance and our ETMRS scheme
outperforms the existing single-relay selection scheme and common energy
threshold scheme.Comment: Accepted to appear in IEEE Transactions on Green Communications and
Networkin
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