21,304 research outputs found
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
On Green Energy Powered Cognitive Radio Networks
Green energy powered cognitive radio (CR) network is capable of liberating
the wireless access networks from spectral and energy constraints. The
limitation of the spectrum is alleviated by exploiting cognitive networking in
which wireless nodes sense and utilize the spare spectrum for data
communications, while dependence on the traditional unsustainable energy is
assuaged by adopting energy harvesting (EH) through which green energy can be
harnessed to power wireless networks. Green energy powered CR increases the
network availability and thus extends emerging network applications. Designing
green CR networks is challenging. It requires not only the optimization of
dynamic spectrum access but also the optimal utilization of green energy. This
paper surveys the energy efficient cognitive radio techniques and the
optimization of green energy powered wireless networks. Existing works on
energy aware spectrum sensing, management, and sharing are investigated in
detail. The state of the art of the energy efficient CR based wireless access
network is discussed in various aspects such as relay and cooperative radio and
small cells. Envisioning green energy as an important energy resource in the
future, network performance highly depends on the dynamics of the available
spectrum and green energy. As compared with the traditional energy source, the
arrival rate of green energy, which highly depends on the environment of the
energy harvesters, is rather random and intermittent. To optimize and adapt the
usage of green energy according to the opportunistic spectrum availability, we
discuss research challenges in designing cognitive radio networks which are
powered by energy harvesters
Energy-Efficient User Association with Open Loop Power Control for Uplink Heterogeneous Cellular Networks
Energy reduction for wireless systems becomes more and more important due to
its impact on the operation cost and global carbon footprint. In this paper, we
investigate three kinds of energy-efficient association schemes under open loop
power control for uplink heterogeneous cellular networks, which are formulated
as a whole energy efficiency maximization problem, a sum energy efficiency
maximization problem and a utility maximization problem respectively. The third
case takes account of load balancing level and user's fairness in the
energy-efficient association. Considering that the first problem is in a
fractional mixed-integer form, we introduce an energy efficiency parameter to
convert it into a parametric subtractive form, and then design an effective
iterative algorithm to achieve the optimal solutions. As for the third problem,
we first introduce a dual variable to decouple the constraint and then develop
a distributed algorithm using dual decomposition. In addition, we also give the
convergence proof for the proposed algorithms. In order to confirm the
effectiveness of energy-efficient user association algorithms, we introduce
other association rules for comparison, and investigate the influences of
different parameters on the association performance of these association rules
A Survey on Mobile Edge Networks: Convergence of Computing, Caching and Communications
As the explosive growth of smart devices and the advent of many new
applications, traffic volume has been growing exponentially. The traditional
centralized network architecture cannot accommodate such user demands due to
heavy burden on the backhaul links and long latency. Therefore, new
architectures which bring network functions and contents to the network edge
are proposed, i.e., mobile edge computing and caching. Mobile edge networks
provide cloud computing and caching capabilities at the edge of cellular
networks. In this survey, we make an exhaustive review on the state-of-the-art
research efforts on mobile edge networks. We first give an overview of mobile
edge networks including definition, architecture and advantages. Next, a
comprehensive survey of issues on computing, caching and communication
techniques at the network edge is presented respectively. The applications and
use cases of mobile edge networks are discussed. Subsequently, the key enablers
of mobile edge networks such as cloud technology, SDN/NFV and smart devices are
discussed. Finally, open research challenges and future directions are
presented as well
Mobile Converged Networks: Framework, Optimization and Challenges
In this paper, a new framework of mobile converged networks is proposed for
flexible resource optimization over multi-tier wireless heterogeneous networks.
Design principles and advantages of this new framework of mobile converged
networks are discussed. Moreover, mobile converged network models based on
interference coordination and energy efficiency are presented and the
corresponding optimization algorithms are developed. Furthermore, future
challenges of mobile converged networks are identified to promote the study in
modeling and performance analysis of mobile converged networks.Comment: 17 pages, 6 figure
Applications of Economic and Pricing Models for Resource Management in 5G Wireless Networks: A Survey
This paper presents a comprehensive literature review on applications of
economic and pricing theory for resource management in the evolving fifth
generation (5G) wireless networks. The 5G wireless networks are envisioned to
overcome existing limitations of cellular networks in terms of data rate,
capacity, latency, energy efficiency, spectrum efficiency, coverage,
reliability, and cost per information transfer. To achieve the goals, the 5G
systems will adopt emerging technologies such as massive Multiple-Input
Multiple-Output (MIMO), mmWave communications, and dense Heterogeneous Networks
(HetNets). However, 5G involves multiple entities and stakeholders that may
have different objectives, e.g., high data rate, low latency, utility
maximization, and revenue/profit maximization. This poses a number of
challenges to resource management designs of 5G. While the traditional
solutions may neither efficient nor applicable, economic and pricing models
have been recently developed and adopted as useful tools to achieve the
objectives. In this paper, we review economic and pricing approaches proposed
to address resource management issues in the 5G wireless networks including
user association, spectrum allocation, and interference and power management.
Furthermore, we present applications of economic and pricing models for
wireless caching and mobile data offloading. Finally, we highlight important
challenges, open issues and future research directions of applying economic and
pricing models to the 5G wireless networks
Joint User Association and Power Control for Load Balancing in Downlink Heterogeneous Cellular Networks
Instead of achievable rate in the conventional association, we utilize the
effective rate to design two association schemes for load balancing in
heterogeneous cellular networks (HCNs), which are both formulated as such
problems with maximizing the sum of effective rates. In these two schemes, the
one just considers user association, but the other introduces power control to
mitigate interference and reduce energy consumption while performing user
association. Since the effective rate is closely related to the load of some BS
and the achievable rate of some user, it can be used as a key factor of
association schemes for load balancing in HCNs. To solve the association
problem without power control, we design a one-layer iterative algorithm, which
converts the sum-of-ratio form of original optimization problem into a
parameterized polynomial form. By combining this algorithm with power control
algorithm, we propose a two-layer iterative algorithm for the association
problem with power control. Specially, the outer layer performs user
association using the algorithm of problem without power control, and the inner
layer updates the transmit power of each BS using a power update function
(PUF). At last, we give some convergence and complexity analyses for the
proposed algorithms. As shown in simulation results, the proposed schemes have
superior performance than the conventional association, and the scheme with
joint user association and power control achieves a higher load balancing gain
and energy efficiency than conventional scheme and other offloading scheme.Comment: 10 page
Recent Advances in Cloud Radio Access Networks: System Architectures, Key Techniques, and Open Issues
As a promising paradigm to reduce both capital and operating expenditures,
the cloud radio access network (C-RAN) has been shown to provide high spectral
efficiency and energy efficiency. Motivated by its significant theoretical
performance gains and potential advantages, C-RANs have been advocated by both
the industry and research community. This paper comprehensively surveys the
recent advances of C-RANs, including system architectures, key techniques, and
open issues. The system architectures with different functional splits and the
corresponding characteristics are comprehensively summarized and discussed. The
state-of-the-art key techniques in C-RANs are classified as: the fronthaul
compression, large-scale collaborative processing, and channel estimation in
the physical layer; and the radio resource allocation and optimization in the
upper layer. Additionally, given the extensiveness of the research area, open
issues and challenges are presented to spur future investigations, in which the
involvement of edge cache, big data mining, social-aware device-to-device,
cognitive radio, software defined network, and physical layer security for
C-RANs are discussed, and the progress of testbed development and trial test
are introduced as well.Comment: 27 pages, 11 figure
A Survey on High-Speed Railway Communications: A Radio Resource Management Perspective
High-speed railway (HSR) communications will become a key feature supported
by intelligent transportation communication systems. The increasing demand for
HSR communications leads to significant attention on the study of radio
resource management (RRM), which enables efficient resource utilization and
improved system performance. RRM design is a challenging problem due to
heterogenous quality of service (QoS) requirements and dynamic characteristics
of HSR wireless communications. The objective of this paper is to provide an
overview on the key issues that arise in the RRM design for HSR wireless
communications. A detailed description of HSR communication systems is first
presented, followed by an introduction on HSR channel models and
characteristics, which are vital to the cross-layer RRM design. Then we provide
a literature survey on state-of-the-art RRM schemes for HSR wireless
communications, with an in-depth discussion on various RRM aspects including
admission control, mobility management, power control and resource allocation.
Finally, this paper outlines the current challenges and open issues in the area
of RRM design for HSR wireless communications.Comment: 40 pages, 10 figures. Submitted to Computer Communication
A Survey on QoE-oriented Wireless Resources Scheduling
Future wireless systems are expected to provide a wide range of services to
more and more users. Advanced scheduling strategies thus arise not only to
perform efficient radio resource management, but also to provide fairness among
the users. On the other hand, the users' perceived quality, i.e., Quality of
Experience (QoE), is becoming one of the main drivers within the schedulers
design. In this context, this paper starts by providing a comprehension of what
is QoE and an overview of the evolution of wireless scheduling techniques.
Afterwards, a survey on the most recent QoE-based scheduling strategies for
wireless systems is presented, highlighting the application/service of the
different approaches reported in the literature, as well as the parameters that
were taken into account for QoE optimization. Therefore, this paper aims at
helping readers interested in learning the basic concepts of QoE-oriented
wireless resources scheduling, as well as getting in touch with its current
research frontier.Comment: Revised version: updated according to the most recent related
literature; added references; corrected typo
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