1,242 research outputs found
Effective Capacity in Wireless Networks: A Comprehensive Survey
Low latency applications, such as multimedia communications, autonomous
vehicles, and Tactile Internet are the emerging applications for
next-generation wireless networks, such as 5th generation (5G) mobile networks.
Existing physical-layer channel models, however, do not explicitly consider
quality-of-service (QoS) aware related parameters under specific delay
constraints. To investigate the performance of low-latency applications in
future networks, a new mathematical framework is needed. Effective capacity
(EC), which is a link-layer channel model with QoS-awareness, can be used to
investigate the performance of wireless networks under certain statistical
delay constraints. In this paper, we provide a comprehensive survey on existing
works, that use the EC model in various wireless networks. We summarize the
work related to EC for different networks such as cognitive radio networks
(CRNs), cellular networks, relay networks, adhoc networks, and mesh networks.
We explore five case studies encompassing EC operation with different design
and architectural requirements. We survey various delay-sensitive applications
such as voice and video with their EC analysis under certain delay constraints.
We finally present the future research directions with open issues covering EC
maximization
Cognitive Wireless Powered Network: Spectrum Sharing Models and Throughput Maximization
The recent advance in radio-frequency (RF) wireless energy transfer (WET) has
motivated the study of wireless powered communication network (WPCN), in which
distributed wireless devices are powered via dedicated WET by the hybrid
access-point (H-AP) in the downlink (DL) for uplink (UL) wireless information
transmission (WIT). In this paper, by exploiting the cognitive radio (CR)
technique, we study a new type of CR enabled secondary WPCN, called cognitive
WPCN, under spectrum sharing with the primary wireless communication system. In
particular, we consider a cognitive WPCN, consisting of one single H-AP with
constant power supply and distributed users, shares the same spectrum for its
DL WET and UL WIT with an existing primary communication link, where the WPCN's
WET/WIT and the primary link's WIT may interfere with each other. Under this
new setup, we propose two coexisting models for spectrum sharing of the two
systems, namely underlay and overlay based cognitive WPCNs, depending on
different types of knowledge on the primary user transmission available at the
cognitive WPCN. For each model, we maximize the sum-throughput of the cognitive
WPCN by optimizing its transmission under different constraints applied to
protect the primary user transmission. Analysis and simulation results are
provided to compare the sum-throughput of the cognitive WPCN versus the
achievable rate of the primary user in two coexisting models. It is shown that
the overlay based cognitive WPCN outperforms the underlay based counterpart,
thanks to its fully cooperative WET/WIT design with the primary WIT, while it
also requires higher complexity for implementation.Comment: This is the longer version of a paper to appear in IEEE Transactions
on Cognitive Communications and Networkin
Fundamental Green Tradeoffs: Progresses, Challenges, and Impacts on 5G Networks
With years of tremendous traffic and energy consumption growth, green radio
has been valued not only for theoretical research interests but also for the
operational expenditure reduction and the sustainable development of wireless
communications. Fundamental green tradeoffs, served as an important framework
for analysis, include four basic relationships: spectrum efficiency (SE) versus
energy efficiency (EE), deployment efficiency (DE) versus energy efficiency
(EE), delay (DL) versus power (PW), and bandwidth (BW) versus power (PW). In
this paper, we first provide a comprehensive overview on the extensive on-going
research efforts and categorize them based on the fundamental green tradeoffs.
We will then focus on research progresses of 4G and 5G communications, such as
orthogonal frequency division multiplexing (OFDM) and non-orthogonal
aggregation (NOA), multiple input multiple output (MIMO), and heterogeneous
networks (HetNets). We will also discuss potential challenges and impacts of
fundamental green tradeoffs, to shed some light on the energy efficient
research and design for future wireless networks.Comment: revised from IEEE Communications Surveys & Tutorial
Optimization of Energy-Constrained Wireless Powered Communication Networks with Heterogeneous Nodes
In this paper, we study wireless networks where nodes have two energy
sources, namely a battery and radio frequency (RF) energy harvesting circuitry.
We formulate two optimization problems with different objective functions,
namely maximizing the sum throughput and maximizing the minimum throughput, for
enhanced fairness. Furthermore, we show the generality of the proposed system
model through characterizing the conditions under which the two formulated
optimization problems can be reduced to the corresponding problems of different
known wireless networks, namely, conventional wireless networks
(battery-powered) and wireless powered communications networks (WPCNs) with
only RF energy harvesting nodes. In addition, we introduce WPCNs with two types
of nodes, with and without RF energy harvesting capability, in which the nodes
without RF energy harvesting are utilized to enhance the sum throughput, even
beyond WPCNs with all energy harvesting nodes. We establish the convexity of
all formulated problems which opens room for efficient solution using standard
techniques. Our numerical results show that the two types of wireless networks,
namely WPCNs with only RF energy harvesting nodes and conventional wireless
networks, are considered, respectively, as lower and upper bounds on the
performance of the generalized problem setting in terms of the maximum sum
throughput and the maxmin throughput. Moreover, the results reveal new insights
and throughput-fairness trade-offs unique to our new problem setting.Comment: Accepted for publication in Wireless Networks, 201
End-to-end Throughput Maximization for Underlay Multi-hop Cognitive Radio Networks with RF Energy Harvesting
This paper studies a green paradigm for the underlay coexistence of primary
users (PUs) and secondary users (SUs) in energy harvesting cognitive radio
networks (EH-CRNs), wherein battery-free SUs capture both the spectrum and the
energy of PUs to enhance spectrum efficiency and green energy utilization. To
lower the transmit powers of SUs, we employ multi-hop transmission with time
division multiple access, by which SUs first harvest energy from the RF signals
of PUs and then transmit data in the allocated time concurrently with PUs, all
in the licensed spectrum. In this way, the available transmit energy of each SU
mainly depends on the harvested energy before the turn to transmit, namely
energy causality. Meanwhile, the transmit powers of SUs must be strictly
controlled to protect PUs from harmful interference. Thus, subject to the
energy causality constraint and the interference power constraint, we study the
end-to-end throughput maximization problem for optimal time and power
allocation. To solve this nonconvex problem, we first equivalently transform it
into a convex optimization problem and then propose the joint optimal time and
power allocation (JOTPA) algorithm that iteratively solves a series of
feasibility problems until convergence. Extensive simulations evaluate the
performance of EH-CRNs with JOTPA in three typical deployment scenarios and
validate the superiority of JOTPA by making comparisons with two other resource
allocation algorithms
Power Control and Relay Selection in Full-Duplex Cognitive Relay Networks: Coherent versus Non-coherent Scenarios
This paper investigates power control and relay selection in Full Duplex
Cognitive Relay Networks (FDCRNs), where the secondary-user (SU) relays can
simultaneously receive and forward the signal from the SU source. We study both
non-coherent and coherent scenarios. In the non-coherent case, the SU relay
forwards the signal from the SU source without regulating the phase, while in
the coherent scenario, the SU relay regulates the phase when forwarding the
signal to minimize the interference at the primary-user (PU) receiver. We
consider the problem of maximizing the transmission rate from the SU source to
the SU destination subject to the interference constraint at the PU receiver
and power constraints at both the SU source and SU relay. We develop
low-complexity and high-performance joint power control and relay selection
algorithms. The superior performance of the proposed algorithms are confirmed
using extensive numerical evaluation. In particular, we demonstrate the
significant gain of phase regulation at the SU relay (i.e., the gain of the
coherent mechanism over the noncoherent mechanism).Comment: The 51st Annual Conference on Information Systems and Sciences 2017
(IEEE CISS 2017
Resource Allocation for Secure Communications in Cooperative Cognitive Wireless Powered Communication Networks
We consider a cognitive wireless powered communication network (CWPCN)
sharing the spectrum with a primary network who faces security threats from
eavesdroppers (EAVs). We propose a new cooperative protocol for the wireless
powered secondary users (SU) to cooperate with the primary user (PU). In the
protocol, the SUs first harvest energy from the power signals transmitted by
the cognitive hybrid access point during the wireless power transfer (WPT)
phase, and then use the harvested energy to interfere with the EAVs and gain
transmission opportunities at the same time during the wireless information
transfer (WIT) phase. Taking the maximization of the SU ergodic rate as the
design objective, resource allocation algorithms based on the dual optimization
method and the block coordinate descent method are proposed for the cases of
perfect channel state information (CSI) and collusive/non-collusive EAVs under
the PU secrecy constraint. More PU favorable greedy algorithms aimed at
minimizing the PU secrecy outage probability are also proposed. We furthermore
consider the unknown EAVs' CSI case and propose an efficient algorithm to
improve the PU security performance. Extensive simulations show that our
proposed protocol and corresponding resource allocation algorithms can not only
let the SU gain transmission opportunities but also improve the PU security
performance even with unknown EAVs' CSI.Comment: Submitted to IEEE Systems Journal for possible publicatio
Relay Control for Full-Duplex Relaying with Wireless Information and Energy Transfer
This study investigates wireless information and energy transfer for dual-hop
amplify-and-forward full-duplex relaying systems. By forming energy efficiency
(EE) maximization problem into a concave fractional program of transmission
power, three relay control schemes are separately designed to enable energy
harvesting and full-duplex information relaying. With Rician fading modeled
residual self-interference channel, analytical expressions of outage
probability and ergodic capacity are presented for the maximum relay,
signal-to-interference-plus-noise-ratio (SINR) relay, and target relay. It has
shown that EE maximization problem of the maximum relay is concave for time
switching factor, so that bisection method has been applied to obtain the
optimized value. By incorporating instantaneous channel information, the SINR
relay with collateral time switching factor achieves an improved EE over the
maximum relay in delay-limited and delay-tolerant transmissions. Without
requiring channel information for the second-hop, the target relay ensures a
competitive performance for outage probability, ergodic capacity, and EE.
Comparing to the direct source-destination transmission, numerical results show
that the proposed relaying scheme is beneficial in achieving a comparable EE
for low-rate delay-limited transmission.Comment: 16 pages, 12 figure
Full-Duplex Non-Orthogonal Multiple Access for Modern Wireless Networks
Non-orthogonal multiple access (NOMA) is an interesting concept to provide
higher capacity for future wireless communications. In this article, we
consider the feasibility and benefits of combining full-duplex operation with
NOMA for modern communication systems. Specifically, we provide a comprehensive
overview on application of full-duplex NOMA in cellular networks, cooperative
and cognitive radio networks, and characterize gains possible due to
full-duplex operation. Accordingly, we discuss challenges, particularly the
self-interference and inter-user interference and provide potential solutions
to interference mitigation and quality-of-service provision based on
beamforming, power control, and link scheduling. We further discuss future
research challenges and interesting directions to pursue to bring full-duplex
NOMA into maturity and use in practice.Comment: Revised, IEEE Wireless Communication Magazin
Full-Duplex Wireless-Powered Communication Network with Energy Causality
In this paper, we consider a wireless communication network with a
full-duplex hybrid access point (HAP) and a set of wireless users with energy
harvesting capabilities. The HAP implements the full-duplex through two
antennas: one for broadcasting wireless energy to users in the downlink and one
for receiving independent information from users via
time-division-multiple-access (TDMA) in the uplink at the same time. All users
can continuously harvest wireless power from the HAP until its transmission
slot, i.e., the energy causality constraint is modeled by assuming that energy
harvested in the future cannot be used for tranmission. Hence, latter users'
energy harvesting time is coupled with the transmission time of previous users.
Under this setup, we investigate the sum-throughput maximization (STM) problem
and the total-time minimization (TTM) problem for the proposed multi-user
full-duplex wireless-powered network. The STM problem is proved to be a convex
optimization problem. The optimal solution strategy is then obtained in
closed-form expression, which can be computed with linear complexity. It is
also shown that the sum throughput is non-decreasing with increasing of the
number of users. For the TTM problem, by exploiting the properties of the
coupling constraints, we propose a two-step algorithm to obtain an optimal
solution. Then, for each problem, two suboptimal solutions are proposed and
investigated. Finally, the effect of user scheduling on STM and TTM are
investigated through simulations. It is also shown that different user
scheduling strategies should be used for STM and TTM.Comment: Energy Harvesting, Wireless Power Transfer, Full-Duplex, Optimal
Resource Allocation, Optimizatio
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