44,716 research outputs found
A Study Of Cooperative Spectrum Sharing Schemes For Internet Of Things Systems
The Internet of Things (IoT) has gained much attention in recent years with the massive increase in the number of connected devices. Cognitive Machine-to-Machine (CM2M) communications is a hot research topic in which a cognitive dimension allows M2M networks to overcome the challenges of spectrum scarcity, interference, and green requirements. In this paper, we propose a Generalized Cooperative Spectrum Sharing (GCSS) scheme for M2M communication. Cooperation extends the coverage of wireless networks as well as increasing their throughput while reducing the energy consumption of the connected low power devices. We study the outage performance of the proposed GCSS scheme for M2M system and derive exact expressions for the outage probability. We also analyze the effect of varying transmission powers on the performance of the system
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
Joint Energy and Spectrum Cooperation for Cellular Communication Systems
Powered by renewable energy sources, cellular communication systems usually
have different wireless traffic loads and available resources over time. To
match their traffics, it is beneficial for two neighboring systems to cooperate
in resource sharing when one is excessive in one resource (e.g., spectrum),
while the other is sufficient in another (e.g., energy). In this paper, we
propose a joint energy and spectrum cooperation scheme between different
cellular systems to reduce their operational costs. When the two systems are
fully cooperative in nature (e.g., belonging to the same entity), we formulate
the cooperation problem as a convex optimization problem to minimize their
weighted sum cost and obtain the optimal solution in closed form. We also study
another partially cooperative scenario where the two systems have their own
interests. We show that the two systems seek for partial cooperation as long as
they find inter-system complementarity between the energy and spectrum
resources. Under the partial cooperation conditions, we propose a distributed
algorithm for the two systems to gradually and simultaneously reduce their
costs from the non-cooperative benchmark to the Pareto optimum. This
distributed algorithm also has proportional fair cost reduction by reducing
each system's cost proportionally over iterations. Finally, we provide
numerical results to validate the convergence of the distributed algorithm to
the Pareto optimality and compare the centralized and distributed cost
reduction approaches for fully and partially cooperative scenarios.Comment: This is the longer version of a paper to appear in IEEE Transactions
on Communication
Green Cellular Networks: A Survey, Some Research Issues and Challenges
Energy efficiency in cellular networks is a growing concern for cellular
operators to not only maintain profitability, but also to reduce the overall
environment effects. This emerging trend of achieving energy efficiency in
cellular networks is motivating the standardization authorities and network
operators to continuously explore future technologies in order to bring
improvements in the entire network infrastructure. In this article, we present
a brief survey of methods to improve the power efficiency of cellular networks,
explore some research issues and challenges and suggest some techniques to
enable an energy efficient or "green" cellular network. Since base stations
consume a maximum portion of the total energy used in a cellular system, we
will first provide a comprehensive survey on techniques to obtain energy
savings in base stations. Next, we discuss how heterogeneous network deployment
based on micro, pico and femto-cells can be used to achieve this goal. Since
cognitive radio and cooperative relaying are undisputed future technologies in
this regard, we propose a research vision to make these technologies more
energy efficient. Lastly, we explore some broader perspectives in realizing a
"green" cellular network technologyComment: 16 pages, 5 figures, 2 table
Cooperation in 5G HetNets: Advanced Spectrum Access and D2D Assisted Communications
The evolution of conventional wireless communication networks to the fifth
generation (5G) is driven by an explosive increase in the number of wireless
mobile devices and services, as well as their demand for all-time and
everywhere connectivity, high data rates, low latency, high energy-efficiency
and improved quality of service. To address these challenges, 5G relies on key
technologies, such as full duplex (FD), device-to-device (D2D) communications,
and network densification. In this article, a heterogeneous networking
architecture is envisioned, where cells of different sizes and radio access
technologies coexist. Specifically, collaboration for spectrum access is
explored for both FD- and cognitive-based approaches, and cooperation among
devices is discussed in the context of the state-of-the-art D2D assisted
communication paradigm. The presented cooperative framework is expected to
advance the understandings of the critical technical issues towards dynamic
spectrum management for 5G heterogeneous networks.Comment: to appear in IEEE Wireless Communication
Outage Analysis of Spectrum Sharing Energy Harvesting Cognitive Relays in Nakagami- Channels
Energy harvesting (EH) cognitive relays are an exciting solution to the
problem of inefficient use of spectrum while achieving green communications and
spatial diversity. In a spectrum sharing scenario, we investigate the
performance of a cognitive relay network, where a secondary source communicates
with its destination over Nakagami- channels via decode-and-forward EH
relays while maintaining the outage probability of the primary user below a
predefined threshold. Specifically, we derive a closed-form expression for the
secondary outage probability and show that it is a function of the probability
of an EH relay having sufficient energy for relaying, which in turn, depends on
the energy harvesting and consumption rates of the EH relay and the primary
outage probability threshold. We also show that relaxing the primary outage
constraint may not always benefit the cognitive EH relay network due to the
limitations imposed on the relay's transmit power by the energy constraint.Comment: To be presented at IEEE GLOBECOM 201
Dynamic Sleep Control in Green Relay-Assisted Networks for Energy Saving and QoS Improving
We study the relay station (RS) sleep control mechanism targeting on reducing
energy consumption while improving users' quality of service (QoS) in green
relay-assisted cellular networks, where the base station (BS) is powered by
grid power and the RSs are powered by renewable energy. By adopting green RSs,
the grid power consumption of the BS is greatly reduced. But due to the
uncertainty and stochastic characteristics of the renewable energy, power
supply for RSs is not always sufficient. Thus the harvested energy needs to be
scheduled appropriately to cater to the dynamic traffic so as to minimize the
energy saving in the long term. An optimization problem is formulated to find
the optimal sleep ratio of RSs to match the time variation of energy harvesting
and traffic arrival. To fully use the renewable energy, green-RS-first
principle is adopted in the user association process. The optimal RS sleeping
policy is obtained through dynamic programming (DP) approach, which divides the
original optimization problem into per-stage subproblems. A reduced DP
algorithm and a greedy algorithm are further proposed to greatly reduce the
computation complexity. By simulations, the reduced DP algorithm outperforms
the greedy algorithm in achieving satisfactory energy saving and QoS
performance.Comment: 7 papers, 4 figure
D2D User Selection For Simultaneous Spectrum Sharing And Energy Harvesting
This paper presents a device-to-device (D2D) user selection protocol wherein
multiple D2D pairs coexist with a cellular network. In the developed framework,
certain D2D users harvest energy and share the spectrum of the cellular users
by adopting a hybrid time switching and power splitting protocol. The D2D user
which harvests the maximum energy and achieves the desired target rate for the
cellular communication is selected to serve as a decode-and-forward (DF) relay
for the cellular user. The proposed work analyzes the impact of increase in the
number of D2D users on the performance of cellular user as well as derives an
upper bound on the time duration of energy harvesting within which best
possible rate for cellular user can be obtained. The performance of the
proposed protocol has been quantified by obtaining the closed form expressions
of outage probability
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
Aqua Computing: Coupling Computing and Communications
The authors introduce a new vision for providing computing services for
connected devices. It is based on the key concept that future computing
resources will be coupled with communication resources, for enhancing user
experience of the connected users, and also for optimising resources in the
providers' infrastructures. Such coupling is achieved by Joint/Cooperative
resource allocation algorithms, by integrating computing and communication
services and by integrating hardware in networks. Such type of computing, by
which computing services are not delivered independently but dependent of
networking services, is named Aqua Computing. The authors see Aqua Computing as
a novel approach for delivering computing resources to end devices, where
computing power of the devices are enhanced automatically once they are
connected to an Aqua Computing enabled network. The process of resource
coupling is named computation dissolving. Then, an Aqua Computing architecture
is proposed for mobile edge networks, in which computing and wireless
networking resources are allocated jointly or cooperatively by a Mobile Cloud
Controller, for the benefit of the end-users and/or for the benefit of the
service providers. Finally, a working prototype of the system is shown and the
gathered results show the performance of the Aqua Computing prototype.Comment: A shorter version of this paper will be submitted to an IEEE magazin
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