1,016 research outputs found
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
Joint Resource Optimization for Multicell Networks with Wireless Energy Harvesting Relays
This paper first considers a multicell network deployment where the base
station (BS) of each cell communicates with its cell-edge user with the
assistance of an amplify-and-forward (AF) relay node. Equipped with a power
splitter and a wireless energy harvester, the self-sustaining relay scavenges
radio frequency (RF) energy from the received signals to process and forward
the information. Our aim is to develop a resource allocation scheme that
jointly optimizes (i) BS transmit powers, (ii) received power splitting factors
for energy harvesting and information processing at the relays, and (iii) relay
transmit powers. In the face of strong intercell interference and limited radio
resources, we formulate three highly-nonconvex problems with the objectives of
sum-rate maximization, max-min throughput fairness and sum-power minimization.
To solve such challenging problems, we propose to apply the successive convex
approximation (SCA) approach and devise iterative algorithms based on geometric
programming and difference-of-convex-functions programming. The proposed
algorithms transform the nonconvex problems into a sequence of convex problems,
each of which is solved very efficiently by the interior-point method. We prove
that our algorithms converge to the locally optimal solutions that satisfy the
Karush-Kuhn-Tucker conditions of the original nonconvex problems. We then
extend our results to the case of decode-and-forward (DF) relaying with
variable timeslot durations. We show that our resource allocation solutions in
this case offer better throughput than that of the AF counterpart with equal
timeslot durations, albeit at a higher computational complexity. Numerical
results confirm that the proposed joint optimization solutions substantially
improve the network performance, compared with cases where the radio resource
parameters are individually optimized
Secure Two-Way Transmission via Wireless-Powered Untrusted Relay and External Jammer
In this paper, we propose a two-way secure communication scheme where two
transceivers exchange confidential messages via a wireless powered untrusted
amplify-and-forward (AF) relay in the presence of an external jammer. We take
into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ)
scenarios. Based on the time switching (TS) architecture at the relay, the data
transmission is done in three phases. In the first phase, both the
energy-starved nodes, the untrustworthy relay and the jammer, are charged by
non-information radio frequency (RF) signals from the sources. In the second
phase, the two sources send their information signals and concurrently, the
jammer transmits artificial noise to confuse the curious relay. Finally, the
third phase is dedicated to forward a scaled version of the received signal
from the relay to the sources. For the proposed secure transmission schemes, we
derive new closed-form lower-bound expressions for the ergodic secrecy sum rate
(ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the
asymptotic ESSR to determine the key parameters; the high SNR slope and the
high SNR power offset of the jamming based scenarios. To highlight the
performance advantage of the proposed FJ, we also examine the scenario of
without jamming (WoJ). Finally, numerical examples and discussions are provided
to acquire some engineering insights, and to demonstrate the impacts of
different system parameters on the secrecy performance of the considered
communication scenarios. The numerical results illustrate that the proposed FJ
significantly outperforms the traditional one-way communication and the
Constellation rotation approach, as well as our proposed benchmarks, the
two-way WoJ and GNJ scenarios.Comment: 14 pages, 6 figures, Submitted to IEEE Transactions on Vehicular
Technolog
Simultaneous Wireless Information and Power Transfer for Decode-and-Forward Multi-Hop Relay Systems in Energy-Constrained IoT Networks
This paper studies a multi-hop decode-and-forward (DF) simultaneous wireless
information and power transfer (SWIPT) system where a source sends data to a
destination with the aid of multi-hop relays which do not depend on an external
energy source. To this end, we apply power splitting (PS) based SWIPT relaying
protocol so that the relays can harvest energy from the received signals from
the previous hop to reliably forward the information of the source to the
destination. We aim to solve two optimization problems relevant to our system
model. First, we minimize the transmit power at the source under the individual
quality-of-service (QoS) threshold constraints of the relays and the
destination nodes by optimizing PS ratios at the relays. The second is to
maximize the minimum system achievable rate by optimizing the PS ratio at each
relay. Based on convex optimization techniques, the globally optimal PS ratio
solution is obtained in closed-form for both problems. By setting the QoS
threshold constraint the same for each node for the source transmit power
problem, we discovered that either the minimum source transmit power or the
maximum system throughput can be found using the same approach. Numerical
results demonstrate the superiority of the proposed optimal SWIPT PS design
over conventional fixed PS ratio schemes.Comment: 14 pages, 14 figures, Accepted for Publication in IEEE Internet of
Things Journa
Power Management Strategies in Energy-Harvesting Wireless Sensor Networks
Power management strategies are extremely important in Wireless Sensor Networks (WSNs). The objective is to make the nodes operate as long as possible. In the same context, in this article, our aim is to provide the optimal transmission power to maximize the network lifetime using the Orthogonal Multiple Access Channel (OMAC) in Harvesting System (HS). We consider that the nodes have direct communication with a Fusion Center (FC) with causal Channel Side Information (CSI) at the sender and receiver.We begin the analysis by considering a single transmitter node powered by a rechargeable battery with limited capacity energy. Afterward, we generalize the analysis with M transmitter nodes. In both cases, the transmitters are able to harvest energy from nature.Eventually, we show the viability of our approach in simulations results
Relaying in the Internet of Things (IoT): A Survey
The deployment of relays between Internet of Things (IoT) end devices and gateways can improve link quality. In cellular-based IoT, relays have the potential to reduce base station overload. The energy expended in single-hop long-range communication can be reduced if relays listen to transmissions of end devices and forward these observations to gateways. However, incorporating relays into IoT networks faces some challenges. IoT end devices are designed primarily for uplink communication of small-sized observations toward the network; hence, opportunistically using end devices as relays needs a redesign of both the medium access control (MAC) layer protocol of such end devices and possible addition of new communication interfaces. Additionally, the wake-up time of IoT end devices needs to be synchronized with that of the relays. For cellular-based IoT, the possibility of using infrastructure relays exists, and noncellular IoT networks can leverage the presence of mobile devices for relaying, for example, in remote healthcare. However, the latter presents problems of incentivizing relay participation and managing the mobility of relays. Furthermore, although relays can increase the lifetime of IoT networks, deploying relays implies the need for additional batteries to power them. This can erode the energy efficiency gain that relays offer. Therefore, designing relay-assisted IoT networks that provide acceptable trade-offs is key, and this goes beyond adding an extra transmit RF chain to a relay-enabled IoT end device. There has been increasing research interest in IoT relaying, as demonstrated in the available literature. Works that consider these issues are surveyed in this paper to provide insight into the state of the art, provide design insights for network designers and motivate future research directions
Applications of Repeated Games in Wireless Networks: A Survey
A repeated game is an effective tool to model interactions and conflicts for
players aiming to achieve their objectives in a long-term basis. Contrary to
static noncooperative games that model an interaction among players in only one
period, in repeated games, interactions of players repeat for multiple periods;
and thus the players become aware of other players' past behaviors and their
future benefits, and will adapt their behavior accordingly. In wireless
networks, conflicts among wireless nodes can lead to selfish behaviors,
resulting in poor network performances and detrimental individual payoffs. In
this paper, we survey the applications of repeated games in different wireless
networks. The main goal is to demonstrate the use of repeated games to
encourage wireless nodes to cooperate, thereby improving network performances
and avoiding network disruption due to selfish behaviors. Furthermore, various
problems in wireless networks and variations of repeated game models together
with the corresponding solutions are discussed in this survey. Finally, we
outline some open issues and future research directions.Comment: 32 pages, 15 figures, 5 tables, 168 reference
- …