3,289 research outputs found
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
Secure Beamforming for MIMO Two-Way Communications with an Untrusted Relay
This paper studies the secure beamforming design in a multiple-antenna
three-node system where two source nodes exchange messages with the help of an
untrusted relay node. The relay acts as both an essential signal forwarder and
a potential eavesdropper. Both two-phase and three-phase two-way relay
strategies are considered. Our goal is to jointly optimize the source and relay
beamformers for maximizing the secrecy sum rate of the two-way communications.
We first derive the optimal relay beamformer structures. Then, iterative
algorithms are proposed to find source and relay beamformers jointly based on
alternating optimization. Furthermore, we conduct asymptotic analysis on the
maximum secrecy sum-rate. Our analysis shows that when all transmit powers
approach infinity, the two-phase two-way relay scheme achieves the maximum
secrecy sum rate if the source beamformers are designed such that the received
signals at the relay align in the same direction. This reveals an important
advantage of signal alignment technique in against eavesdropping. It is also
shown that if the source powers approach zero the three-phase scheme performs
the best while the two-phase scheme is even worse than direct transmission.
Simulation results have verified the efficiency of the secure beamforming
algorithms as well as the analytical findings.Comment: 10 figures, Submitted to IEEE Transactions on Signal Processin
Joint Source and Relay Precoding Designs for MIMO Two-Way Relaying Based on MSE Criterion
Properly designed precoders can significantly improve the spectral efficiency
of multiple-input multiple-output (MIMO) relay systems. In this paper, we
investigate joint source and relay precoding design based on the
mean-square-error (MSE) criterion in MIMO two-way relay systems, where two
multi-antenna source nodes exchange information via a multi-antenna
amplify-and-forward relay node. This problem is non-convex and its optimal
solution remains unsolved. Aiming to find an efficient way to solve the
problem, we first decouple the primal problem into three tractable
sub-problems, and then propose an iterative precoding design algorithm based on
alternating optimization. The solution to each sub-problem is optimal and
unique, thus the convergence of the iterative algorithm is guaranteed.
Secondly, we propose a structured precoding design to lower the computational
complexity. The proposed precoding structure is able to parallelize the
channels in the multiple access (MAC) phase and broadcast (BC) phase. It thus
reduces the precoding design to a simple power allocation problem. Lastly, for
the special case where only a single data stream is transmitted from each
source node, we present a source-antenna-selection (SAS) based precoding design
algorithm. This algorithm selects only one antenna for transmission from each
source and thus requires lower signalling overhead. Comprehensive simulation is
conducted to evaluate the effectiveness of all the proposed precoding designs.Comment: 32 pages, 10 figure
Grassmannian Beamforming for MIMO Amplify-and-Forward Relaying
In this paper, we derive the optimal transmitter/ receiver beamforming
vectors and relay weighting matrix for the multiple-input multiple-output
amplify-and-forward relay channel. The analysis is accomplished in two steps.
In the first step, the direct link between the transmitter (Tx) and receiver
(Rx) is ignored and we show that the transmitter and the relay should map their
signals to the strongest right singular vectors of the Tx-relay and relay-Rx
channels. Based on the distributions of these vectors for independent
identically distributed (i.i.d.) Rayleigh channels, the Grassmannian codebooks
are used for quantizing and sending back the channel information to the
transmitter and the relay. The simulation results show that even a few number
of bits can considerably increase the link reliability in terms of bit error
rate. For the second step, the direct link is considered in the problem model
and we derive the optimization problem that identifies the optimal Tx
beamforming vector. For the i.i.d Rayleigh channels, we show that the solution
to this problem is uniformly distributed on the unit sphere and we justify the
appropriateness of the Grassmannian codebook (for determining the optimal
beamforming vector), both analytically and by simulation. Finally, a modified
quantizing scheme is presented which introduces a negligible degradation in the
system performance but significantly reduces the required number of feedback
bits.Comment: Submitted to IEEE Journal of Selected Areas in Communications,
Special Issue on Exploiting Limited Feedback in Tomorrows Wireless
Communication Network
Nonregenerative MIMO Relaying with Optimal Transmit Antenna Selection
We derive optimal SNR-based transmit antenna selection rules at the source
and relay for the nonregenerative half duplex MIMO relay channel. While antenna
selection is a suboptimal form of beamforming, it has the advantage that the
optimization is tractable and can be implemented with only a few bits of
feedback from the destination to the source and relay. We compare the bit error
rate of optimal antenna selection at both the source and relay to other
proposed beamforming techniques and propose methods for performing the
necessary limited feedback
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