1,525 research outputs found
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
Techniques for Cooperative Cognitive Radio Networks
The frequency spectrum is an essential resource for wireless communication.
Special sections of the spectrum are used for military purposes, governments
sell some frequency bands to broadcasting and mobile communications companies
for commercial use, others such as ISM (Industrial, Science and Medical) bands
are available for the public free of charge. As the spectrum becomes
overcrowded, there seem to be two possible solutions: pushing the frequency
limits higher to frequencies of 60 GHz and above, or reaggregating the densely
used licensed frequency bands. The new Cognitive Radio (CR) approach comes with
the feasible solution to spectrum scarcity. Secondary utilization of a licensed
spectrum band can enhance the spectrum usage and introduce a reliable solution
to its dearth. In such a cognitive radio network, secondary users can access
the spectrum under the constraint that a minimum quality of service is
guaranteed for the licensed primary users. In this thesis, we focus on spectrum
sharing techniques in cognitive radio network where there is a number of
secondary users sharing unoccupied spectrum holes. More specifically, we
introduce two collaborative cognitive radio networks in which the secondary
user cooperate with the primary user to deliver the data of the primary user.Comment: Master's thesi
A Distributed MAC Protocol for Cooperation in Random Access Networks
WLAN is one of the most successful applications of wireless communications in
daily life because of low cost and ease of deployment. The enabling technique
for this success is the use of random access schemes for the wireless channel.
Random access requires minimal coordination between the nodes, which
considerably reduces the cost of the infrastructure. Recently, cooperative
communication in wireless networks has been of increasing interest because it
promises higher rates and reliability. An additional MAC overhead is necessary
to coordinate the nodes to allow cooperation and this overhead can possibly
cancel out the cooperative benefits. In this work, a completely distributed
protocol is proposed that allows nodes in the network to cooperate via Two-Hop
and Decode-and-Forward for transmitting their data to a common gateway node. It
is shown that high throughput gains are obtained in terms of the individual
throughput that can be guaranteed to any node in the network. These results are
validated by Monte Carlo simulations.Comment: 5 pages, improved presentation compared to previous version v
Optimal Resource Allocation and Relay Selection in Bandwidth Exchange Based Cooperative Forwarding
In this paper, we investigate joint optimal relay selection and resource
allocation under bandwidth exchange (BE) enabled incentivized cooperative
forwarding in wireless networks. We consider an autonomous network where N
nodes transmit data in the uplink to an access point (AP) / base station (BS).
We consider the scenario where each node gets an initial amount (equal, optimal
based on direct path or arbitrary) of bandwidth, and uses this bandwidth as a
flexible incentive for two hop relaying. We focus on alpha-fair network utility
maximization (NUM) and outage reduction in this environment. Our contribution
is two-fold. First, we propose an incentivized forwarding based resource
allocation algorithm which maximizes the global utility while preserving the
initial utility of each cooperative node. Second, defining the link weight of
each relay pair as the utility gain due to cooperation (over noncooperation),
we show that the optimal relay selection in alpha-fair NUM reduces to the
maximum weighted matching (MWM) problem in a non-bipartite graph. Numerical
results show that the proposed algorithms provide 20- 25% gain in spectral
efficiency and 90-98% reduction in outage probability.Comment: 8 pages, 7 figure
Resource Allocation in Wireless Networks with RF Energy Harvesting and Transfer
Radio frequency (RF) energy harvesting and transfer techniques have recently
become alternative methods to power the next generation of wireless networks.
As this emerging technology enables proactive replenishment of wireless
devices, it is advantageous in supporting applications with quality-of-service
(QoS) requirement. This article focuses on the resource allocation issues in
wireless networks with RF energy harvesting capability, referred to as RF
energy harvesting networks (RF-EHNs). First, we present an overview of the
RF-EHNs, followed by a review of a variety of issues regarding resource
allocation. Then, we present a case study of designing in the receiver
operation policy, which is of paramount importance in the RF-EHNs. We focus on
QoS support and service differentiation, which have not been addressed by
previous literatures. Furthermore, we outline some open research directions.Comment: To appear in IEEE Networ
Incentive Schemes for Mobile Peer-to-Peer Systems and Free Riding Problem: A Survey
Mobile peer-to-peer networks are quite prevalent and popular now days due to
advent of business scenarios where all the services are going mobile like
whether it's to find good restaurants, healthy diet books making friends,
job-hunting, real state info or cab-sharing etc. As the mobile users are
increasing day by day, peer-to-peer networks getting bigger and complex. In
contrast to client server system in peer-to-peer network resource sharing is
done on the basis of mutual consent and agreed policies with no central
authority and controlling entity. Incentive schemes for P2P networks are
devised to encourage the participation and to adhere the policies agreed. P2P
services based only on altruistic behaviour of users are facing serious
challenges like Free riding or The tragedy of commons. Free riders are the
users who consume the bandwidth of the system (perform downloading) but don't
show altruistic behaviour (deny uploading) and act as a parasite for the P2P
network. To counter the free riding issue many Incentive schemes are suggested
by the researchers. In this paper we will survey the different incentive
schemes, their architectures keeping eye on how they handle the challenges of
modern P2P network.Comment: 29 pages, 10 figures, scholarly repor
Resource Allocation and Fairness in Wireless Powered Cooperative Cognitive Radio Networks
We integrate a wireless powered communication network with a cooperative
cognitive radio network, where multiple secondary users (SUs) powered
wirelessly by a hybrid access point (HAP) help a primary user relay the data.
As a reward for the cooperation, the secondary network gains the spectrum
access where SUs transmit to HAP using time division multiple access. To
maximize the sum-throughput of SUs, we present a secondary sum-throughput
optimal resource allocation (STORA) scheme. Under the constraint of meeting
target primary rate, the STORA scheme chooses the optimal set of relaying SUs
and jointly performs the time and energy allocation for SUs. Specifically, by
exploiting the structure of the optimal solution, we find the order in which
SUs are prioritized to relay primary data. Since the STORA scheme focuses on
the sum-throughput, it becomes inconsiderate towards individual SU throughput,
resulting in low fairness. To enhance fairness, we investigate three resource
allocation schemes, which are (i) equal time allocation, (ii) minimum
throughput maximization, and (iii) proportional time allocation. Simulation
results reveal the trade-off between sum-throughput and fairness. The minimum
throughput maximization scheme is the fairest one as each SU gets the same
throughput, but yields the least SU sum-throughput.Comment: Accepted in IEEE Transactions on Communication
General Auction-Theoretic Strategies for Distributed Partner Selection in Cooperative Wireless Networks
It is unrealistic to assume that all nodes in an ad hoc wireless network
would be willing to participate in cooperative communication, especially if
their desired Quality-of- Service (QoS) is achievable via direct transmission.
An incentivebased auction mechanism is presented to induce cooperative behavior
in wireless networks with emphasis on users with asymmetrical channel fading
conditions. A single-object secondprice auction is studied for cooperative
partner selection in singlecarrier networks. In addition, a multiple-object
bundled auction is analyzed for the selection of multiple simultaneous partners
in a cooperative orthogonal frequency-division multiplexing (OFDM) setting. For
both cases, we characterize equilibrium outage probability performance, seller
revenue, and feedback bounds. The auction-based partner selection allows
winning bidders to achieve their desired QoS while compensating the seller who
assists them. At the local level sellers aim for revenue maximization, while
connections are drawn to min-max fairness at the network level. The proposed
strategies for partner selection in self-configuring cooperative wireless
networks are shown to be robust under conditions of uncertainty in the number
of users requesting cooperation, as well as minimal topology and channel link
information available to individual users.Comment: 13 pages, to appear, IEEE Transactions on Communication
Delay-Limited Cooperative Communication with Reliability Constraints in Wireless Networks
We investigate optimal resource allocation for delay-limited cooperative
communication in time varying wireless networks. Motivated by real-time
applications that have stringent delay constraints, we develop a dynamic
cooperation strategy that makes optimal use of network resources to achieve a
target outage probability (reliability) for each user subject to average power
constraints. Using the technique of Lyapunov optimization, we first present a
general framework to solve this problem and then derive quasi-closed form
solutions for several cooperative protocols proposed in the literature. Unlike
earlier works, our scheme does not require prior knowledge of the statistical
description of the packet arrival, channel state and node mobility processes
and can be implemented in an online fashion.Comment: 13 pages, 4 figure
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