1,406 research outputs found
Session-Based Cooperation in Cognitive Radio Networks: A Network-Level Approach
In cognitive radio networks (CRNs), secondary users (SUs) can proactively
obtain spectrum access opportunities by helping with primary users' (PUs') data
transmissions. Currently, such kind of spectrum access is implemented via a
cooperative communications based link-level frame-based cooperative (LLC)
approach where individual SUs independently serve as relays for PUs in order to
gain spectrum access opportunities. Unfortunately, this LLC approach cannot
fully exploit spectrum access opportunities to enhance the throughput of CRNs
and fails to motivate PUs to join the spectrum sharing processes. To address
these challenges, we propose a network-level session-based cooperative (NLC)
approach where SUs are grouped together to cooperate with PUs session by
session, instead of frame by frame as what has been done in existing works, for
spectrum access opportunities of the corresponding group. Thanks to our
group-based session-by-session cooperating strategy, our NLC approach is able
to address all those challenges in the LLC approach. To articulate our NLC
approach, we further develop an NLC scheme under a cognitive capacity
harvesting network (CCHN) architecture. We formulate the cooperative mechanism
design as a cross-layer optimization problem with constraints on primary
session selection, flow routing and link scheduling. To search for solutions to
the optimization problem, we propose an augmented scheduling index ordering
based (SIO-based) algorithm to identify maximal independent sets. Through
extensive simulations, we demonstrate the effectiveness of the proposed NLC
approach and the superiority of the augmented SIO-based algorithm over the
traditional method
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
Aeronautical Ad Hoc Networking for the Internet-Above-The-Clouds
The engineering vision of relying on the ``smart sky" for supporting air
traffic and the ``Internet above the clouds" for in-flight entertainment has
become imperative for the future aircraft industry. Aeronautical ad hoc
Networking (AANET) constitutes a compelling concept for providing broadband
communications above clouds by extending the coverage of Air-to-Ground (A2G)
networks to oceanic and remote airspace via autonomous and self-configured
wireless networking amongst commercial passenger airplanes. The AANET concept
may be viewed as a new member of the family of Mobile ad hoc Networks (MANETs)
in action above the clouds. However, AANETs have more dynamic topologies,
larger and more variable geographical network size, stricter security
requirements and more hostile transmission conditions. These specific
characteristics lead to more grave challenges in aircraft mobility modeling,
aeronautical channel modeling and interference mitigation as well as in network
scheduling and routing. This paper provides an overview of AANET solutions by
characterizing the associated scenarios, requirements and challenges.
Explicitly, the research addressing the key techniques of AANETs, such as their
mobility models, network scheduling and routing, security and interference are
reviewed. Furthermore, we also identify the remaining challenges associated
with developing AANETs and present their prospective solutions as well as open
issues. The design framework of AANETs and the key technical issues are
investigated along with some recent research results. Furthermore, a range of
performance metrics optimized in designing AANETs and a number of
representative multi-objective optimization algorithms are outlined
Computational Intelligence Inspired Data Delivery for Vehicle-to-Roadside Communications
We propose a vehicle-to-roadside communication protocol based on distributed clustering where a coalitional game approach is used to stimulate the vehicles to join a cluster, and a fuzzy logic algorithm is employed to generate stable clusters by considering multiple metrics of vehicle velocity, moving pattern, and signal qualities between vehicles. A reinforcement learning algorithm with game theory based reward allocation is employed to guide each vehicle to select the route that can maximize the whole network performance. The protocol is integrated with a multi-hop data delivery virtualization scheme that works on the top of the transport layer and provides high performance for multi-hop end-to-end data transmissions. We conduct realistic computer simulations to show the performance advantage of the protocol over other approaches
Reconfigurable Wireless Networks
Driven by the advent of sophisticated and ubiquitous applications, and the
ever-growing need for information, wireless networks are without a doubt
steadily evolving into profoundly more complex and dynamic systems. The user
demands are progressively rampant, while application requirements continue to
expand in both range and diversity. Future wireless networks, therefore, must
be equipped with the ability to handle numerous, albeit challenging
requirements. Network reconfiguration, considered as a prominent network
paradigm, is envisioned to play a key role in leveraging future network
performance and considerably advancing current user experiences. This paper
presents a comprehensive overview of reconfigurable wireless networks and an
in-depth analysis of reconfiguration at all layers of the protocol stack. Such
networks characteristically possess the ability to reconfigure and adapt their
hardware and software components and architectures, thus enabling flexible
delivery of broad services, as well as sustaining robust operation under highly
dynamic conditions. The paper offers a unifying framework for research in
reconfigurable wireless networks. This should provide the reader with a
holistic view of concepts, methods, and strategies in reconfigurable wireless
networks. Focus is given to reconfigurable systems in relatively new and
emerging research areas such as cognitive radio networks, cross-layer
reconfiguration and software-defined networks. In addition, modern networks
have to be intelligent and capable of self-organization. Thus, this paper
discusses the concept of network intelligence as a means to enable
reconfiguration in highly complex and dynamic networks. Finally, the paper is
supported with several examples and case studies showing the tremendous impact
of reconfiguration on wireless networks.Comment: 28 pages, 26 figures; Submitted to the Proceedings of the IEEE (a
special issue on Reconfigurable Systems
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
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Cloned Access Point Detection and Point Detection and Prevention Mechanism in IEEE 802.11 Wireless Mesh Networks
IEEE 802.11 Wireless Mesh Network (WMN) is an
emerging low cost, decentralized community-based broadband technology, which is based on self-healing and multi-hop deployment of Access Points (APs), so that to increase the coverage area with maximum freedom to end-users to join or leave the
network from anywhere anytime having low deployment and maintenance cost. Such kind of decentralized structure and multihop architecture increases its security vulnerabilities especially
against the APs. One of such possible security attack is the placement of cloned AP to create serious performance degradation in IEEE 802.11 WMN. In this paper, we discuss the different
security vulnerabilities of AP in IEEE 802.11 WMN along with possible research directions. We also propose a mutual cooperation mechanism between the multi-hop APs and serving gateway so that
to detect and prevent the possibility of cloned AP. In this way the large scale exploitation of IEEE 802.11 WMN can be eliminated
Statistical Routing for Multihop Wireless Cognitive Networks
To account for the randomness of propagation channels and interference levels
in hierarchical spectrum sharing, a novel approach to multihop routing is
introduced for cognitive random access networks, whereby packets are randomly
routed according to outage probabilities. Leveraging channel and interference
level statistics, the resultant cross-layer optimization framework provides
optimal routes, transmission probabilities, and transmit-powers, thus enabling
cognizant adaptation of routing, medium access, and physical layer parameters
to the propagation environment. The associated optimization problem is
non-convex, and hence hard to solve in general. Nevertheless, a successive
convex approximation approach is adopted to efficiently find a
Karush-Kuhn-Tucker solution. Augmented Lagrangian and primal decomposition
methods are employed to develop a distributed algorithm, which also lends
itself to online implementation. Enticingly, the fresh look advocated here
permeates benefits also to conventional multihop wireless networks in the
presence of channel uncertainty.Comment: Accepted for publication on the IEEE Journal on Selected Areas in
Communications - Cognitive Radio Series (Nov 2012 Issue
System Power Minimization to Access Non-Contiguous Spectrum in Cognitive Radio Networks
Wireless transmission using non-contiguous chunks of spectrum is becoming
increasingly important due to a variety of scenarios such as: secondary users
avoiding incumbent users in TV white space; anticipated spectrum sharing
between commercial and military systems; and spectrum sharing among
uncoordinated interferers in unlicensed bands. Multi-Channel Multi-Radio (MCMR)
platforms and Non-Contiguous Orthogonal Frequency Division Multiple Access
(NC-OFDMA) technology are the two commercially viable transmission choices to
access these non-contiguous spectrum chunks. Fixed MC-MRs do not scale with
increasing number of non-contiguous spectrum chunks due to their fixed set of
supporting radio front ends. NC-OFDMA allows nodes to access these
non-contiguous spectrum chunks and put null sub-carriers in the remaining
chunks. However, nulling sub-carriers increases the sampling rate (spectrum
span) which, in turn, increases the power consumption of radio front ends. Our
work characterizes this trade-off from a cross-layer perspective, specifically
by showing how the slope of ADC/DAC power consumption versus sampling rate
curve influences scheduling decisions in a multi-hop network. Specifically, we
provide a branch and bound algorithm based mixed integer linear programming
solution that performs joint power control, spectrum span selection, scheduling
and routing in order to minimize the system power of multi-hop NC-OFDMA
networks. We also provide a low complexity (O(E^2 M^2)) greedy algorithm where
M and E denote the number of channels and links respectively. Numerical
simulations suggest that our approach reduces system power by 30% over
classical transmit power minimization based cross-layer algorithms.Comment: Submitted to IEEE Transactions on Cognitive Communications and
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