9,730 research outputs found
An Energy Efficient Decoding Scheme for Wireless Body Area Sensor Networks
One of the major challenges in Wireless Body Area Networks (WBANs) is to
prolong the lifetime of network. Traditional research work focuses on
minimizing transmit power; however, in the case of short range communication
the consumption power in decoding is significantly larger than transmit power.
This paper investigates the minimization of total power consumption by reducing
the decoding power consumption. For achieving a desired Bit Error Rate (BER),
we introduce some fundamental results on the basis of iterative message-passing
algorithms for Low Density Parity Check Code (LDPC). To reduce energy
dissipation in decoder, LDPC based coded communications between sensors are
considered. Moreover, we evaluate the performance of LDPC at different code
rates and introduce Adaptive Iterative Decoding (AID) by exploiting threshold
on the number of iterations for a certain BER (0.0004). In iterative LDPC
decoding, the total energy consumption of network is reduced by 20 to 25%.Comment: Journal of Basic and Applied Scientific Research. 2013. arXiv admin
note: substantial text overlap with arXiv:1309.075
Ambient Backscatter Communications: A Contemporary Survey
Recently, ambient backscatter communications has been introduced as a
cutting-edge technology which enables smart devices to communicate by utilizing
ambient radio frequency (RF) signals without requiring active RF transmission.
This technology is especially effective in addressing communication and energy
efficiency problems for low-power communications systems such as sensor
networks. It is expected to realize numerous Internet-of-Things (IoT)
applications. Therefore, this paper aims to provide a contemporary and
comprehensive literature review on fundamentals, applications, challenges, and
research efforts/progress of ambient backscatter communications. In particular,
we first present fundamentals of backscatter communications and briefly review
bistatic backscatter communications systems. Then, the general architecture,
advantages, and solutions to address existing issues and limitations of ambient
backscatter communications systems are discussed. Additionally, emerging
applications of ambient backscatter communications are highlighted. Finally, we
outline some open issues and future research directions.Comment: 32 pages, 18 figures, journa
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
Underwater Optical Wireless Communications, Networking, and Localization: A Survey
Underwater wireless communications can be carried out through acoustic, radio
frequency (RF), and optical waves. Compared to its bandwidth limited acoustic
and RF counterparts, underwater optical wireless communications (UOWCs) can
support higher data rates at low latency levels. However, severe aquatic
channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great
challenges for UOWCs and significantly reduce the attainable communication
ranges, which necessitates efficient networking and localization solutions.
Therefore, we provide a comprehensive survey on the challenges, advances, and
prospects of underwater optical wireless networks (UOWNs) from a layer by layer
perspective which includes: 1) Potential network architectures; 2) Physical
layer issues including propagation characteristics, channel modeling, and
modulation techniques 3) Data link layer problems covering link configurations,
link budgets, performance metrics, and multiple access schemes; 4) Network
layer topics containing relaying techniques and potential routing algorithms;
5) Transport layer subjects such as connectivity, reliability, flow and
congestion control; 6) Application layer goals and state-of-the-art UOWN
applications, and 7) Localization and its impacts on UOWN layers. Finally, we
outline the open research challenges and point out the future directions for
underwater optical wireless communications, networking, and localization
research.Comment: This manuscript is submitted to IEEE Communication Surveys and
Tutorials for possible publicatio
A Journey from Improper Gaussian Signaling to Asymmetric Signaling
The deviation of continuous and discrete complex random variables from the
traditional proper and symmetric assumption to a generalized improper and
asymmetric characterization (accounting correlation between a random entity and
its complex conjugate), respectively, introduces new design freedom and various
potential merits. As such, the theory of impropriety has vast applications in
medicine, geology, acoustics, optics, image and pattern recognition, computer
vision, and other numerous research fields with our main focus on the
communication systems. The journey begins from the design of improper Gaussian
signaling in the interference-limited communications and leads to a more
elaborate and practically feasible asymmetric discrete modulation design. Such
asymmetric shaping bridges the gap between theoretically and practically
achievable limits with sophisticated transceiver and detection schemes in both
coded/uncoded wireless/optical communication systems. Interestingly,
introducing asymmetry and adjusting the transmission parameters according to
some design criterion render optimal performance without affecting the
bandwidth or power requirements of the systems. This dual-flavored article
initially presents the tutorial base content covering the interplay of
reality/complexity, propriety/impropriety and circularity/noncircularity and
then surveys majority of the contributions in this enormous journey.Comment: IEEE COMST (Early Access
Energy-Throughput Trade-offs in a Wireless Sensor Network with Mobile Relay
In this paper we analyze the trade-offs between energy and throughput for
links in a wireless sensor network. Our application of interest is one in which
a number of low-powered sensors need to wirelessly communicate their
measurements to a communications sink, or destination node, for communication
to a central processor. We focus on one particular sensor source, and consider
the case where the distance to the destination is beyond the peak power of the
source. A relay node is required. Transmission energy of the sensor and the
relay can be adjusted to minimize the total energy for a given throughput of
the connection from sensor source to destination. We introduce a bounded random
walk model for movement of the relay between the sensor and destination nodes,
and characterize the total transmission energy and throughput performance using
Markov steady state analysis. Based on the trade-offs between total energy and
throughput we propose a new time-sharing protocol to exploit the movement of
the relay to reduce the total energy. We demonstrate the effectiveness of
time-sharing for minimizing the total energy consumption while achieving the
throughput requirement. We then show that the time-sharing scheme is more
energy efficient than the popular sleep mode scheme
Survey of Important Issues in UAV Communication Networks
Unmanned Aerial Vehicles (UAVs) have enormous potential in the public and
civil domains. These are particularly useful in applications where human lives
would otherwise be endangered. Multi-UAV systems can collaboratively complete
missions more efficiently and economically as compared to single UAV systems.
However, there are many issues to be resolved before effective use of UAVs can
be made to provide stable and reliable context-specific networks. Much of the
work carried out in the areas of Mobile Ad Hoc Networks (MANETs), and Vehicular
Ad Hoc Networks (VANETs) does not address the unique characteristics of the UAV
networks. UAV networks may vary from slow dynamic to dynamic; have intermittent
links and fluid topology. While it is believed that ad hoc mesh network would
be most suitable for UAV networks yet the architecture of multi-UAV networks
has been an understudied area. Software Defined Networking (SDN) could
facilitate flexible deployment and management of new services and help reduce
cost, increase security and availability in networks. Routing demands of UAV
networks go beyond the needs of MANETS and VANETS. Protocols are required that
would adapt to high mobility, dynamic topology, intermittent links, power
constraints and changing link quality. UAVs may fail and the network may get
partitioned making delay and disruption tolerance an important design
consideration. Limited life of the node and dynamicity of the network leads to
the requirement of seamless handovers where researchers are looking at the work
done in the areas of MANETs and VANETs, but the jury is still out. As energy
supply on UAVs is limited, protocols in various layers should contribute
towards greening of the network. This article surveys the work done towards all
of these outstanding issues, relating to this new class of networks, so as to
spur further research in these areas.Comment: arXiv admin note: substantial text overlap with arXiv:1304.3904 by
other author
Free Space Optical Communication: Challenges and Mitigation Techniques
In recent years, free space optical (FSO) communication has gained
significant importance owing to its unique features: large bandwidth, license
free spectrum, high data rate, easy and quick deployability, less power and low
mass requirement. FSO communication uses optical carrier in the near infrared
(IR) and visible band to establish either terrestrial links within the Earths
atmosphere or inter-satellite or deep space links or ground to satellite or
satellite to ground links. However, despite of great potential of FSO
communication, its performance is limited by the adverse effects (viz.,
absorption, scattering and turbulence) of the atmospheric channel. Out of these
three effects, the atmospheric turbulence is a major challenge that may lead to
serious degradation in the bit error rate (BER) performance of the system and
make the communication link infeasible. This paper presents a comprehensive
survey on various challenges faced by FSO communication system for both
terrestrial and space links. It will provide details of various performance
mitigation techniques in order to have high link availability and reliability
of FSO system. The first part of the paper will focus on various types of
impairments that poses a serious challenge to the performance of FSO system for
both terrestrial and space links. The latter part of the paper will provide the
reader with an exhaustive review of various techniques used in FSO system both
at physical layer as well as at the upper layers (transport, network or link
layer) to combat the adverse effects of the atmosphere. Further, this survey
uniquely offers the current literature on FSO coding and modulation schemes
using various channel models and detection techniques. It also presents a
recently developed technique in FSO system using orbital angular momentum to
combat the effect of atmospheric turbulence.Comment: 28 pages, 13 figures and 8 table
Distributed Topology Design for Network Coding Deployed Large-scale Sensor Networks
In this paper, we propose a solution to the distributed topology formation
problem for large-scale sensor networks with multi-source multicast flows. The
proposed solution is based on game-theoretic approaches in conjunction with
network coding. The proposed algorithm requires significantly low computational
complexity, while it is known as NP-hard to find an optimal topology for
network coding deployed multi-source multicast flows. In particular, we
formulate the problem of distributed network topology formation as a network
formation game by considering the nodes in the network as players that can take
actions for making outgoing links. The proposed solution decomposes the
original game that consists of multiple players and multicast flows into
independent link formation games played by only two players with a unicast
flow. We also show that the proposed algorithm is guaranteed to determine at
least one stable topology. Our simulation results confirm that the
computational complexity of the proposed solution is low enough for practical
deployment in large-scale networks
Opportunistic Spectrum Sharing in Dynamic Access Networks: Deployment Challenges, Optimizations, Solutions, and Open Issues
In this paper, we investigate the issue of spectrum assignment in CRNs and
examine various opportunistic spectrum access approaches proposed in the
literature. We provide insight into the efficiency of such approaches and their
ability to attain their design objectives. We discuss the factors that impact
the selection of the appropriate operating channel(s), including the important
interaction between the cognitive linkquality conditions and the time-varying
nature of PRNs. Protocols that consider such interaction are described. We
argue that using best quality channels does not achieve the maximum possible
throughput in CRNs (does not provide the best spectrum utilization). The impact
of guard bands on the design of opportunistic spectrum access protocols is also
investigated. Various complementary techniques and optimization methods are
underlined and discussed, including the utilization of variablewidth spectrum
assignment, resource virtualization, full-duplex capability, cross-layer
design, beamforming and MIMO technology, cooperative communication, network
coding, discontinuousOFDM technology, and software defined radios. Finally, we
highlight several directions for future research in this field
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