1,678 research outputs found
Error Rate Analysis of GF(q) Network Coded Detect-and-Forward Wireless Relay Networks Using Equivalent Relay Channel Models
This paper investigates simple means of analyzing the error rate performance
of a general q-ary Galois Field network coded detect-and-forward cooperative
relay network with known relay error statistics at the destination. Equivalent
relay channels are used in obtaining an approximate error rate of the relay
network, from which the diversity order is found. Error rate analyses using
equivalent relay channel models are shown to be closely matched with simulation
results. Using the equivalent relay channels, low complexity receivers are
developed whose performances are close to that of the optimal maximum
likelihood receiver.Comment: 28 pages, 10 figures. This work has been submitted to the IEEE for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
CoopGeo: A Beaconless Geographic Cross-Layer Protocol for Cooperative Wireless Ad Hoc Networks
Cooperative relaying has been proposed as a promising transmission technique
that effectively creates spatial diversity through the cooperation among
spatially distributed nodes. However, to achieve efficient communications while
gaining full benefits from cooperation, more interactions at higher protocol
layers, particularly the MAC (Medium Access Control) and network layers, are
vitally required. This is ignored in most existing articles that mainly focus
on physical (PHY)-layer relaying techniques. In this paper, we propose a novel
cross-layer framework involving two levels of joint design---a MAC-network
cross-layer design for forwarder selection (or termed routing) and a MAC-PHY
for relay selection---over symbol-wise varying channels. Based on location
knowledge and contention processes, the proposed cross-layer protocol, CoopGeo,
aims at providing an efficient, distributed approach to select next hops and
optimal relays along a communication path. Simulation results demonstrate that
CoopGeo not only operates properly with varying densities of nodes, but
performs significantly better than the existing protocol BOSS in terms of
packet error rate, transmission error probability, and saturated throughput
Near-Optimal Modulo-and-Forward Scheme for the Untrusted Relay Channel
This paper studies an untrusted relay channel, in which the destination sends
artificial noise simultaneously with the source sending a message to the relay,
in order to protect the source's confidential message. The traditional
amplify-and-forward (AF) scheme shows poor performance in this situation
because of the interference power dilemma: providing better security by using
stronger artificial noise will decrease the confidential message power from the
relay to the destination. To solve this problem, a modulo-and-forward (MF)
operation at the relay with nested lattice encoding at the source is proposed.
For this system with full channel state information at the transmitter (CSIT),
theoretical analysis shows that the proposed MF scheme approaches the secrecy
capacity within 1/2 bit for any channel realization, and hence achieves full
generalized security degrees of freedom (G-SDoF). In contrast, the AF scheme
can only achieve a small fraction of the G-SDoF. For this system without any
CSIT, the total outage event, defined as either connection outage or secrecy
outage, is introduced. Based on this total outage definition, analysis shows
that the proposed MF scheme achieves the full generalized secure diversity gain
(G-SDG) of order one. On the other hand, the AF scheme can only achieve a G-SDG
of 1/2 at most
Higher Order Statistics in Switched Diversity Systems
We analyze the level crossing rate (LCR) and the average fade duration of the
output signal-to-noise-ratio (SNR) in generalized switched diversity systems.
By using a common approach, we study these higher order statistics for two
different kinds of configurations: (1) Colocated diversity, i.e. receiver
equipped with multiple antennas, and (2) Distributed diversity, i.e. relaying
link with multiple single-antenna threshold-based decode-and-forward (DF)
relays. In both cases, we consider the switched diversity combining strategies
Selection Combining and Switch \& Stay Combining (SSC). Whenever using
threshold-based techniques such as DF or SSC, the output SNR is a discontinuous
random process and hence classic Rice approach to calculate the LCR is not
applicable. Thus, we use an alternative formulation in terms of the one and
two-dimensional cumulative distribution functions of the output SNR. Our
results are general, and hold for any arbitrary distribution of fading at the
different diversity branches. Moreover, we develop a general asymptotic
framework to calculate these higher order statistics in high mean SNR
environments which only needs of the univariate probability density function
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
Anonymous Networking amidst Eavesdroppers
The problem of security against timing based traffic analysis in wireless
networks is considered in this work. An analytical measure of anonymity in
eavesdropped networks is proposed using the information theoretic concept of
equivocation. For a physical layer with orthogonal transmitter directed
signaling, scheduling and relaying techniques are designed to maximize
achievable network performance for any given level of anonymity. The network
performance is measured by the achievable relay rates from the sources to
destinations under latency and medium access constraints. In particular,
analytical results are presented for two scenarios:
For a two-hop network with maximum anonymity, achievable rate regions for a
general m x 1 relay are characterized when nodes generate independent Poisson
transmission schedules. The rate regions are presented for both strict and
average delay constraints on traffic flow through the relay.
For a multihop network with an arbitrary anonymity requirement, the problem
of maximizing the sum-rate of flows (network throughput) is considered. A
selective independent scheduling strategy is designed for this purpose, and
using the analytical results for the two-hop network, the achievable throughput
is characterized as a function of the anonymity level. The throughput-anonymity
relation for the proposed strategy is shown to be equivalent to an information
theoretic rate-distortion function
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
Diffusion Based Molecular Communication: Principle, Key Technologies, and Challenges
Molecular communication (MC) is a kind of communication technology based on
biochemical molecules for internet of bio-nano things, in which the biochemical
molecule is used as the information carrier for the interconnection of
nano-devices. In this paper, the basic principle of diffusion based MC and the
corresponding key technologies are comprehensively surveyed. In particular, the
state-of-the-art achievements relative to the diffusion based MC are discussed
and compared, including the system model, the system performance analysis with
key influencing factors, the information coding and modulation techniques.
Meanwhile, the multi-hop nano-network based on the diffusion MC is presented as
well. Additionally, given the extensiveness of the research area, open issues
and challenges are presented to spur future investigations, in which the
involvement of channel model, information theory, self-organizing nano-network,
and biochemical applications are put forward
Socially-Aware Networking: A Survey
The widespread proliferation of handheld devices enables mobile carriers to
be connected at anytime and anywhere. Meanwhile, the mobility patterns of
mobile devices strongly depend on the users' movements, which are closely
related to their social relationships and behaviors. Consequently, today's
mobile networks are becoming increasingly human centric. This leads to the
emergence of a new field which we call socially-aware networking (SAN). One of
the major features of SAN is that social awareness becomes indispensable
information for the design of networking solutions. This emerging paradigm is
applicable to various types of networks (e.g. opportunistic networks, mobile
social networks, delay tolerant networks, ad hoc networks, etc) where the users
have social relationships and interactions. By exploiting social properties of
nodes, SAN can provide better networking support to innovative applications and
services. In addition, it facilitates the convergence of human society and
cyber physical systems. In this paper, for the first time, to the best of our
knowledge, we present a survey of this emerging field. Basic concepts of SAN
are introduced. We intend to generalize the widely-used social properties in
this regard. The state-of-the-art research on SAN is reviewed with focus on
three aspects: routing and forwarding, incentive mechanisms and data
dissemination. Some important open issues with respect to mobile social sensing
and learning, privacy, node selfishness and scalability are discussed.Comment: accepted. IEEE Systems Journal, 201
Markov Decision Processes with Applications in Wireless Sensor Networks: A Survey
Wireless sensor networks (WSNs) consist of autonomous and resource-limited
devices. The devices cooperate to monitor one or more physical phenomena within
an area of interest. WSNs operate as stochastic systems because of randomness
in the monitored environments. For long service time and low maintenance cost,
WSNs require adaptive and robust methods to address data exchange, topology
formulation, resource and power optimization, sensing coverage and object
detection, and security challenges. In these problems, sensor nodes are to make
optimized decisions from a set of accessible strategies to achieve design
goals. This survey reviews numerous applications of the Markov decision process
(MDP) framework, a powerful decision-making tool to develop adaptive algorithms
and protocols for WSNs. Furthermore, various solution methods are discussed and
compared to serve as a guide for using MDPs in WSNs
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