1,542 research outputs found
Alternating Optimization Techniques for Power Allocation and Receiver Design in Multihop Wireless Sensor Networks
In this paper, we consider a multihop wireless sensor network with multiple
relay nodes for each hop where the amplify-and-forward scheme is employed. We
present algorithmic strategies to jointly design linear receivers and the power
allocation parameters via an alternating optimization approach subject to
different power constraints which include global, local and individual ones.
Two design criteria are considered: the first one minimizes the mean-square
error and the second one maximizes the sum-rate of the wireless sensor network.
We derive constrained minimum mean-square error and constrained maximum
sum-rate expressions for the linear receivers and the power allocation
parameters that contain the optimal complex amplification coefficients for each
relay node. An analysis of the computational complexity and the convergence of
the algorithms is also presented. Computer simulations show good performance of
our proposed methods in terms of bit error rate and sum-rate compared to the
method with equal power allocation and an existing power allocation scheme.Comment: 10 figures, 13 pages. IEEE Transactions on Vehicular Technology,
2014. arXiv admin note: text overlap with arXiv:1303.384
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
Wireless Network Design for Control Systems: A Survey
Wireless networked control systems (WNCS) are composed of spatially
distributed sensors, actuators, and con- trollers communicating through
wireless networks instead of conventional point-to-point wired connections. Due
to their main benefits in the reduction of deployment and maintenance costs,
large flexibility and possible enhancement of safety, WNCS are becoming a
fundamental infrastructure technology for critical control systems in
automotive electrical systems, avionics control systems, building management
systems, and industrial automation systems. The main challenge in WNCS is to
jointly design the communication and control systems considering their tight
interaction to improve the control performance and the network lifetime. In
this survey, we make an exhaustive review of the literature on wireless network
design and optimization for WNCS. First, we discuss what we call the critical
interactive variables including sampling period, message delay, message
dropout, and network energy consumption. The mutual effects of these
communication and control variables motivate their joint tuning. We discuss the
effect of controllable wireless network parameters at all layers of the
communication protocols on the probability distribution of these interactive
variables. We also review the current wireless network standardization for WNCS
and their corresponding methodology for adapting the network parameters.
Moreover, we discuss the analysis and design of control systems taking into
account the effect of the interactive variables on the control system
performance. Finally, we present the state-of-the-art wireless network design
and optimization for WNCS, while highlighting the tradeoff between the
achievable performance and complexity of various approaches. We conclude the
survey by highlighting major research issues and identifying future research
directions.Comment: 37 pages, 17 figures, 4 table
End-to-End Performance Analysis of Underwater Optical Wireless Relaying and Routing Techniques Under Location Uncertainty
On the contrary of low speed and high delay acoustic systems, underwater
optical wireless communication (UOWC) can deliver a high speed and low latency
service at the expense of short communication ranges. Therefore, multihop
communication is of utmost importance to improve degree of connectivity and
overall performance of underwater optical wireless networks (UOWNs). In this
regard, this paper investigates relaying and routing techniques and provides
their end-to-end (E2E) performance analysis under the location uncertainty. To
achieve robust and reliable links, we first consider adaptive beamwidths and
derive the divergence angles under the absence and presence of a
pointing-acquisitioning-and-tracking (PAT) mechanism. Thereafter, important E2E
performance metrics (e.g., data rate, bit error rate, transmission power,
amplifier gain, etc.) are obtained for two potential relaying techniques;
decode & forward (DF) and optical amplify & forward (AF). We develop
centralized routing schemes for both relaying techniques to optimize E2E rate,
bit error rate, and power consumption. Alternatively, a distributed routing
protocol, namely Light Path Routing (LiPaR), is proposed by leveraging the
range-beamwidth tradeoff of UOWCs. LiPaR is especially shown to be favorable
when there is no PAT mechanism and available network information. In order to
show the benefits of multihop communications, extensive simulations are
conducted to compare different routing and relaying schemes under different
network parameters and underwater environments
Opportunism in Multiuser Relay Channels: Scheduling, Routing and Spectrum Reuse
In order to understand the key merits of multiuser diversity techniques in
relay-assisted cellular multihop networks, this paper analyzes the spectral
efficiency of opportunistic (i.e., channel-aware) scheduling algorithms over a
fading multiuser relay channel with users in the asymptotic regime of large
(but finite) number of users. Using tools from extreme-value theory, we
characterize the limiting distribution of spectral efficiency focusing on Type
I convergence and utilize it in investigating the large system behavior of the
multiuser relay channel as a function of the number of users and physical
channel signal-to-noise ratios (SNRs). Our analysis results in very accurate
formulas in the large (but finite) regime, provides insights on the
potential performance enhancements from multihop routing and spectrum reuse
policies in the presence of multiuser diversity gains from opportunistic
scheduling and helps to identify the regimes and conditions in which
relay-assisted multiuser communication provides a clear advantage over direct
multiuser communication.Comment: 5 page
Joint Maximum Sum-Rate Receiver Design and Power Adjustment for Multihop Wireless Sensor Networks
In this paper, we consider a multihop wireless sensor network (WSN) with
multiple relay nodes for each hop where the amplify-and-forward (AF) scheme is
employed. We present a strategy to jointly design the linear receiver and the
power allocation parameters via an alternating optimization approach that
maximizes the sum rate of the WSN. We derive constrained maximum sum-rate (MSR)
expressions along with an algorithm to compute the linear receiver and the
power allocation parameters with the optimal complex amplification coefficients
for each relay node. Computer simulations show good performance of our proposed
methods in terms of sum rate compared to the method with equal power
allocation.Comment: 3 figure
Interference Suppression and Group-Based Power Adjustment via Alternating Optimization for DS-CDMA Networks with Multihop Relaying
This work presents joint interference suppression and power allocation
algorithms for DS-CDMA networks with multiple hops and decode-and-forward (DF)
protocols. A scheme for joint allocation of power levels across the relays
subject to group-based power constraints and the design of linear receivers for
interference suppression is proposed. A constrained minimum mean-squared error
(MMSE) design for the receive filters and the power allocation vectors is
devised along with an MMSE channel estimator. In order to solve the proposed
optimization efficiently, a method to form an effective group of users and an
alternating optimization strategy are devised with recursive alternating least
squares (RALS) algorithms for estimating the parameters of the receiver, the
power allocation and the channels. Simulations show that the proposed
algorithms obtain significant gains in capacity and performance over existing
schemes.Comment: 2 figures. arXiv admin note: substantial text overlap with
arXiv:1301.5912, arXiv:1301.009
Full-Duplex Relay Selection in Cognitive Underlay Networks
In this work, we analyze the performance of full-duplex relay selection
(FDRS) in spectrum-sharing networks. Contrary to half-duplex relaying,
full-duplex relaying (FDR) enables simultaneous listening/forwarding at the
secondary relay(s), thereby allowing for a higher spectral efficiency. However,
since the source and relay simultaneously transmit in FDR, their superimposed
signal at the primary receiver should now satisfy the existing interference
constraint, which can considerably limit the secondary network throughput. In
this regard, relay selection can offer an adequate solution to boost the
secondary throughput while satisfying the imposed interference limit. We first
analyze the performance of opportunistic FDRS with residual self-interference
(RSI) by deriving the exact cumulative distribution function of its end-to-end
signal-to-interference-plus-noise ratio under Nakagami-m fading. We also
evaluate the offered diversity gain of relay selection for different
full-duplex cooperation schemes in the presence/absence of a direct
source-destination link. When the adopted RSI link gain model is sublinear in
the relay power, which agrees with recent research findings, we show that
remarkable diversity gain can be recovered even in the presence of an
interfering direct link. Second, we evaluate the end-to-end performance of FDRS
with interference constraints due to the presence of a primary receiver.
Finally, the presented exact theoretical findings are verified by numerical
simulations
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
Joint Iterative Power Allocation and Linear Interference Suppression Algorithms in Cooperative DS-CDMA Networks
This work presents joint iterative power allocation and interference
suppression algorithms for spread spectrum networks which employ multiple hops
and the amplify-and-forward cooperation strategy for both the uplink and the
downlink. We propose a joint constrained optimization framework that considers
the allocation of power levels across the relays subject to individual and
global power constraints and the design of linear receivers for interference
suppression. We derive constrained linear minimum mean-squared error (MMSE)
expressions for the parameter vectors that determine the optimal power levels
across the relays and the linear receivers. In order to solve the proposed
optimization problems, we develop cost-effective algorithms for adaptive joint
power allocation, and estimation of the parameters of the receiver and the
channels. An analysis of the optimization problem is carried out and shows that
the problem can have its convexity enforced by an appropriate choice of the
power constraint parameter, which allows the algorithms to avoid problems with
local minima. A study of the complexity and the requirements for feedback
channels of the proposed algorithms is also included for completeness.
Simulation results show that the proposed algorithms obtain significant gains
in performance and capacity over existing non-cooperative and cooperative
schemes.Comment: 9 figures; IET Communications, 201
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