4,945 research outputs found
Base Station Cooperation for Confidential Broadcasting in Multi-Cell Networks
We design linear precoders that perform confidential
broadcasting in multi-cell networks for two different forms
of base station (BS) cooperation, namely, multi-cell processing
(MCP) and coordinated beamforming (CBf). We consider a twocell
network where each cell consists of an N-antenna BS and
K single-antenna users. For such a network, we design a linear
precoder based on the regularized channel inversion (RCI) for
the MCP and a linear precoder based on the generalized RCI
for the CBf. For each form of BS cooperation, we derive new
channel-independent expressions to approximate the secrecy sum
rate achieved by the precoder in the large system regime where
K, N → ∞ with a fixed ratio β = K/N. Using these results, we
determine the optimal regularization parameters of the RCI and
the generalized RCI precoders that maximize the secrecy sum
rate for the MCP and the CBf, respectively. We further propose
power-reduction strategies that significantly increase the secrecy
sum rate at high transmit signal-to-noise ratios when the network
load is high. Our numerical results substantiate the derived
expressions, verify the optimality of the determined optimal
regularization parameters, and demonstrate the performance
improvement offered by the proposed power-reduction strategies.ARC Discovery Projects Grant DP15010390
Regularized Channel Inversion for Simultaneous Confidential Broadcasting and Power Transfer: A Large System Analysis
We propose for the first time new transmission
schemes based on linear precoding to enable simultaneous confidential
broadcasting and power transfer (SCBPT) in a multiuser
multi-input single-output (MISO) network, where a BS with N
antennas simultaneously transmits power and confidential messages
to K single-antenna users. We first design two transmission
schemes based on the rules of regularized channel inversion
(RCI) for both power splitting (PS) and time switching (TS)
receiver architectures, namely, RCI-PS and RCI-TS schemes.
For each scheme, we derive channel-independent expressions to
approximate the secrecy sum rate and the harvested power in
the large-system regime where K, N → ∞ with a fixed ratio
β = K/N. Based on the large-system results, we jointly optimize
the regularization parameter of the RCI and the PS ratio or the
TS ratio such that the secrecy sum rate is maximized subject
to an energy-harvesting constraint. We then present the tradeoff
between the secrecy sum rate and the harvested power achieved
by each scheme, and find that neither scheme always outperforms
the other one. Motivated by this fact, we design an RCI-hybrid
scheme based on the RCI and a newly proposed hybrid receiver
architecture. The hybrid receiver architecture takes advantages
of both the PS and TS receiver architectures. We show that the
RCI-hybrid scheme outperforms both the RCI-PS and RCI-TS
schemes.ARC Discovery Projects Grant DP15010390
Confidential broadcasting via coordinated beamforming in two-cell networks
We design a linear precoder based on the principles
of the generalized regularized channel inversion (RCI)
precoder that achieves confidential broadcasting in a two-cell
network. In each cell of the network, an N-antenna base station
(BS) communicates with K single-antenna users. We consider
coordinated beamforming where the BSs in the two cells do
not share messages but the users in the two cells feed back
their channel state information to both BSs. In the precoder
design, we determine the optimal regularization parameter that
maximizes the secrecy sum rate. To this end, we derive new
channel-independent expressions for the secrecy sum rate in the
large-system regime, where K and N approach infinity with a
fixed ratio µ = K/N. Moreover, we propose a power-reduction
strategy that significantly improves the secrecy sum rate at high
transmit signal-to-noise ratios when µ is higher than 0.5
Wireless Physical Layer Security: Towards Practical Assumptions and Requirements
The current research on physical layer security is far from
implementations in practical networks, arguably due to
impractical assumptions in the literature and the limited
applicability of physical layer security. Aiming to reduce the
gap between theory and practice, this thesis focuses on wireless
physical layer security towards practical assumptions and
requirements.
In the first half of the thesis, we reduce the dependence of
physical layer security on impractical assumptions. The secrecy
enhancements and analysis based on impractical assumptions cannot
lead to any true guarantee of secrecy in practical networks. The
current study of physical layer security was often based on the
idealized assumption of perfect channel knowledge on both
legitimate users and eavesdroppers. We study the impact of
channel estimation errors on secure transmission designs. We
investigate the practical scenarios where both the transmitter
and the receiver have imperfect channel state information (CSI).
Our results show how the optimal transmission design and the
achievable throughput vary with the amount of knowledge on the
eavesdropper's channel. Apart from the assumption of perfect CSI,
the analysis of physical layer security often ideally assumed the
number of eavesdropper antennas to be known. We develop an
innovative approach to study secure communication systems without
knowing the number of eavesdropper antennas by introducing the
concept of spatial constraint into physical layer security. That
is, the eavesdropper is assumed to have a limited spatial region
to place (possibly an infinite number of) antennas. We show that
a non-zero secrecy rate is achievable with the help of a friendly
jammer, even if the eavesdropper places an infinite number of
antennas in its spatial region.
In the second half of the thesis, we improve the applicability of
physical layer security. The current physical layer security
techniques to achieve confidential broadcasting were limited to
application in single-cell systems. The primary challenge to
achieve confidential broadcasting in the multi-cell network is to
deal with not only the inter-cell but also the intra-cell
information leakage and interference. To tackle this challenge,
we design linear precoders performing confidential broadcasting
in multi-cell networks. We optimize the precoder designs to
maximize the secrecy sum rate with based on the large-system
analysis. Finally, we improve the applicability of physical layer
security from a fundamental aspect. The analysis of physical
layer security based on the existing secrecy metric was often not
applicable in practical networks. We propose new metrics for
evaluating the secrecy of transmissions over fading channels to
address the practical limitations of using existing secrecy
metrics for such evaluations. The first metric establishes a link
between the concept of secrecy outage and the eavesdropper's
ability to decode confidential messages. The second metric
provides an error-probability-based secrecy metric which is often
used for the practical implementation of secure wireless systems.
The third metric characterizes how much or how fast the
confidential information is leaked to the eavesdropper. We show
that the proposed secrecy metrics enable one to appropriately
design secure communication systems with different views on how
secrecy is measured
A New Look at Physical Layer Security, Caching, and Wireless Energy Harvesting for Heterogeneous Ultra-dense Networks
Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low
latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small
cells with different antenna configurations. Existing work has widely studied
spectral and energy efficiency in such networks and shown that high spectral
and energy efficiency can be achieved. This article investigates the benefits
of heterogeneous ultra-dense network architecture from the perspectives of
three promising technologies, i.e., physical layer security, caching, and
wireless energy harvesting, and provides enthusiastic outlook towards
application of these technologies in heterogeneous ultra-dense networks. Based
on the rationale of each technology, opportunities and challenges are
identified to advance the research in this emerging network.Comment: Accepted to appear in IEEE Communications Magazin
A Survey of Access Control Models in Wireless Sensor Networks
Copyright 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/)Wireless sensor networks (WSNs) have attracted considerable interest in the research community, because of their wide range of applications. However, due to the distributed nature of WSNs and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. Resource constraints in sensor nodes mean that security mechanisms with a large overhead of computation and communication are impractical to use in WSNs; security in sensor networks is, therefore, a challenge. Access control is a critical security service that offers the appropriate access privileges to legitimate users and prevents illegitimate users from unauthorized access. However, access control has not received much attention in the context of WSNs. This paper provides an overview of security threats and attacks, outlines the security requirements and presents a state-of-the-art survey on access control models, including a comparison and evaluation based on their characteristics in WSNs. Potential challenging issues for access control schemes in WSNs are also discussed.Peer reviewe
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