5,812 research outputs found
Energy Efficiency of Opportunistic Device-to-Device Relaying Under Lognormal Shadowing
Energy consumption is a major limitation of low power and mobile devices.
Efficient transmission protocols are required to minimize an energy consumption
of the mobile devices for ubiquitous connectivity in the next generation
wireless networks. Opportunistic schemes select a single relay using the
criteria of the best channel and achieve a near-optimal diversity performance
in a cooperative wireless system. In this paper, we study the energy efficiency
of the opportunistic schemes for device-to-device communication. In the
opportunistic approach, an energy consumed by devices is minimized by selecting
a single neighboring device as a relay using the criteria of minimum consumed
energy in each transmission in the uplink of a wireless network. We derive
analytical bounds and scaling laws on the expected energy consumption when the
devices experience log-normal shadowing with respect to a base station
considering both the transmission as well as circuit energy consumptions. We
show that the protocol improves the energy efficiency of the network comparing
to the direct transmission even if only a few devices are considered for
relaying. We also demonstrate the effectiveness of the protocol by means of
simulations in realistic scenarios of the wireless network.Comment: 30 pages, 8 figure
A Survey on Device-to-Device Communication in Cellular Networks
Device-to-Device (D2D) communication was initially proposed in cellular
networks as a new paradigm to enhance network performance. The emergence of new
applications such as content distribution and location-aware advertisement
introduced new use-cases for D2D communications in cellular networks. The
initial studies showed that D2D communication has advantages such as increased
spectral efficiency and reduced communication delay. However, this
communication mode introduces complications in terms of interference control
overhead and protocols that are still open research problems. The feasibility
of D2D communications in LTE-A is being studied by academia, industry, and the
standardization bodies. To date, there are more than 100 papers available on
D2D communications in cellular networks and, there is no survey on this field.
In this article, we provide a taxonomy based on the D2D communicating spectrum
and review the available literature extensively under the proposed taxonomy.
Moreover, we provide new insights to the over-explored and under-explored areas
which lead us to identify open research problems of D2D communication in
cellular networks.Comment: 18 pages; 8 figures; Accepted for publication in IEEE Communications
Surveys and Tutorial
TeamPhone: Networking Smartphones for Disaster Recovery
In this paper, we investigate how to network smartphones for providing
communications in disaster recovery. By bridging the gaps among different kinds
of wireless networks, we have designed and implemented a system called
TeamPhone, which provides smartphones the capabilities of communications in
disaster recovery. Specifically, TeamPhone consists of two components: a
messaging system and a self-rescue system. The messaging system integrates
cellular networking, ad-hoc networking and opportunistic networking seamlessly,
and enables communications among rescue workers. The self-rescue system groups,
schedules and positions the smartphones of trapped survivors. Such a group of
smartphones can cooperatively wake up and send out emergency messages in an
energy-efficient manner with their location and position information so as to
assist rescue operations. We have implemented TeamPhone as a prototype
application on the Android platform and deployed it on off-the-shelf
smartphones. Experimental results demonstrate that TeamPhone can properly
fulfill communication requirements and greatly facilitate rescue operations in
disaster recovery
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
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
Low-Rate Machine-Type Communication via Wireless Device-to-Device (D2D) Links
Wireless cellular networks feature two emerging technological trends. The
first is the direct Device-to-Device (D2D) communications, which enables direct
links between the wireless devices that reutilize the cellular spectrum and
radio interface. The second is that of Machine-Type Communications (MTC), where
the objective is to attach a large number of low-rate low-power devices, termed
Machine-Type Devices (MTDs) to the cellular network. MTDs pose new challenges
to the cellular network, one if which is that the low transmission power can
lead to outage problems for the cell-edge devices. Another issue imminent to
MTC is the \emph{massive access} that can lead to overload of the radio
interface. In this paper we explore the opportunity opened by D2D links for
supporting MTDs, since it can be desirable to carry the MTC traffic not through
direct links to a Base Station, but through a nearby relay. MTC is modeled as a
fixed-rate traffic with an outage requirement. We propose two network-assisted
D2D schemes that enable the cooperation between MTDs and standard cellular
devices, thereby meeting the MTC outage requirements while maximizing the rate
of the broadband services for the other devices. The proposed schemes apply the
principles Opportunistic Interference Cancellation and the Cognitive Radio's
underlaying. We show through analysis and numerical results the gains of the
proposed schemes.Comment: 12 Pages, 9 Figures, Submitted to JSAC "Device-to-Device
Communications in Cellular Networks" on the 20th of May 201
Intelligent Wireless Communications Enabled by Cognitive Radio and Machine Learning
The ability to intelligently utilize resources to meet the need of growing
diversity in services and user behavior marks the future of wireless
communication systems. Intelligent wireless communications aims at enabling the
system to perceive and assess the available resources, to autonomously learn to
adapt to the perceived wireless environment, and to reconfigure its operating
mode to maximize the utility of the available resources. The perception
capability and reconfigurability are the essential features of cognitive radio
while modern machine learning techniques project great potential in system
adaptation. In this paper, we discuss the development of the cognitive radio
technology and machine learning techniques and emphasize their roles in
improving spectrum and energy utility of wireless communication systems. We
describe the state-of-the-art of relevant techniques, covering spectrum sensing
and access approaches and powerful machine learning algorithms that enable
spectrum- and energy-efficient communications in dynamic wireless environments.
We also present practical applications of these techniques and identify further
research challenges in cognitive radio and machine learning as applied to the
existing and future wireless communication systems
Network Slicing in Fog Radio Access Networks: Issues and Challenges
Network slicing has been advocated by both academia and industry as a
cost-efficient way to enable operators to provide networks on an as-a-service
basis and meet the wide range of use cases that the fifth generation wireless
network will serve. The existing works on network slicing are mainly targeted
at the partition of the core network, and the prospect of network slicing in
radio access networks should be jointly exploited. To solve this challenge, an
enhanced network slicing in fog radio access networks (F-RANs), termed as
access slicing, is proposed. This article comprehensively presents a novel
architecture and related key techniques for access slicing in F-RANs. The
proposed hierarchical architecture of access slicing consists of centralized
orchestration layer and slice instance layer, which makes the access slicing
adaptively implement in an convenient way. Meanwhile, key techniques and their
corresponding solutions, including the radio and cache resource management, as
well as the social-aware slicing, are presented. Open issues in terms of
standardization developments and field trials are identified
Compressive Rate Estimation with Applications to Device-to-Device Communications
We develop a framework that we call compressive rate estimation. We assume
that the composite channel gain matrix (i.e. the matrix of all channel gains
between all network nodes) is compressible which means it can be approximated
by a sparse or low rank representation. We develop and study a novel sensing
and reconstruction protocol for the estimation of achievable rates. We develop
a sensing protocol that exploits the superposition principle of the wireless
channel and enables the receiving nodes to obtain non-adaptive random
measurements of columns of the composite channel matrix. The random
measurements are fed back to a central controller that decodes the composite
channel gain matrix (or parts of it) and estimates individual user rates. We
analyze the rate loss for a linear and a non-linear decoder and find the
scaling laws according to the number of non-adaptive measurements. In
particular if we consider a system with nodes and assume that each column
of the composite channel matrix is sparse, our findings can be summarized
as follows. For a certain class of non-linear decoders we show that if the
number of pilot signals scales like , then the rate
loss compared to perfect channel state information remains bounded. For a
certain class of linear decoders we show that the rate loss compared to perfect
channel state information scales like
A Survey of Protocols and Standards for Internet of Things
The rapid growth in technology and internet connected devices has enabled
Internet of Things (IoT) to be one of the important fields in computing.
Standards, technologies and platforms targeting IoT ecosystem are being
developed at a very fast pace. IoT enables things to communicate and coordinate
decisions for many different types of applications including healthcare, home
automation, disaster recovery, and industry automation. It is expected to
expand to even more applications in the future. This paper surveys several
standards by IEEE, IETF and ITU that enable technologies enabling the rapid
growth of IoT. These standards include communications, routing, network and
session layer protocols that are being developed to meet IoT requirements. The
discussion also includes management and security protocols in addition to the
current challenges in IoT which gives insights into the current research to
solve such challenges.Comment: E-preprin
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