13,295 research outputs found
Secure Communication over Parallel Relay Channel
We investigate the problem of secure communication over parallel relay
channel in the presence of a passive eavesdropper. We consider a four terminal
relay-eavesdropper channel which consists of multiple relay-eavesdropper
channels as subchannels. For the discrete memoryless model, we establish outer
and inner bounds on the rate-equivocation region. The inner bound allows mode
selection at the relay. For each subchannel, secure transmission is obtained
through one of two coding schemes at the relay: decoding-and-forwarding the
source message or confusing the eavesdropper through noise injection. For the
Gaussian memoryless channel, we establish lower and upper bounds on the perfect
secrecy rate. Furthermore, we study a special case in which the relay does not
hear the source and show that under certain conditions the lower and upper
bounds coincide. The results established for the parallel Gaussian
relay-eavesdropper channel are then applied to study the fading
relay-eavesdropper channel. Analytical results are illustrated through some
numerical examples.Comment: To Appear in IEEE Transactions on Information Forensics and Securit
Achieving secrecy without knowing the number of eavesdropper antennas
The existing research on physical layer security commonly assumes the number
of eavesdropper antennas to be known. Although this assumption allows one to
easily compute the achievable secrecy rate, it can hardly be realized in
practice. In this paper, we provide 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.
Specifically, the eavesdropper is assumed to have a limited spatial region to
place (possibly an infinite number of) antennas. From a practical point of
view, knowing the spatial constraint of the eavesdropper is much easier than
knowing the number of eavesdropper antennas. We derive the achievable secrecy
rates of the spatially-constrained system with and without friendly jamming. 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. Furthermore, we find that the achievable secrecy rate does not
monotonically increase with the jamming power, and hence, we obtain the
closed-form solution of the optimal jamming power that maximizes the secrecy
rate.Comment: IEEE transactions on wireless communications, accepted to appea
Directional Modulation via Symbol-Level Precoding: A Way to Enhance Security
Wireless communication provides a wide coverage at the cost of exposing
information to unintended users. As an information-theoretic paradigm, secrecy
rate derives bounds for secure transmission when the channel to the
eavesdropper is known. However, such bounds are shown to be restrictive in
practice and may require exploitation of specialized coding schemes. In this
paper, we employ the concept of directional modulation and follow a signal
processing approach to enhance the security of multi-user MIMO communication
systems when a multi-antenna eavesdropper is present. Enhancing the security is
accomplished by increasing the symbol error rate at the eavesdropper. Unlike
the information-theoretic secrecy rate paradigm, we assume that the legitimate
transmitter is not aware of its channel to the eavesdropper, which is a more
realistic assumption. We examine the applicability of MIMO receiving algorithms
at the eavesdropper. Using the channel knowledge and the intended symbols for
the users, we design security enhancing symbol-level precoders for different
transmitter and eavesdropper antenna configurations. We transform each design
problem to a linearly constrained quadratic program and propose two solutions,
namely the iterative algorithm and one based on non-negative least squares, at
each scenario for a computationally-efficient modulation. Simulation results
verify the analysis and show that the designed precoders outperform the
benchmark scheme in terms of both power efficiency and security enhancement.Comment: This manuscript is submitted to IEEE Journal of Selected Topics in
Signal Processin
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