377 research outputs found
Secure Transmission in Amplify-and-Forward Diamond Networks with a Single Eavesdropper
Unicast communication over a network of -parallel relays in the presence
of an eavesdropper is considered. The relay nodes, operating under individual
power constraints, amplify and forward the signals received at their inputs.
The problem of the maximum secrecy rate achievable with AF relaying is
addressed. Previous work on this problem provides iterative algorithms based on
semidefinite relaxation. However, those algorithms result in suboptimal
performance without any performance and convergence guarantees. We address this
problem for three specific network models, with real-valued channel gains. We
propose a novel transformation that leads to convex optimization problems. Our
analysis leads to (i)a polynomial-time algorithm to compute the optimal secure
AF rate for two of the models and (ii) a closed-form expression for the optimal
secure rate for the other.Comment: 12pt font, 18 pages, 1 figure, conferenc
Joint Relay Selection and Power Allocation in Large-Scale MIMO Systems with Untrusted Relays and Passive Eavesdroppers
In this paper, a joint relay selection and power allocation (JRP) scheme is
proposed to enhance the physical layer security of a cooperative network, where
a multiple antennas source communicates with a single-antenna destination in
presence of untrusted relays and passive eavesdroppers (Eves). The objective is
to protect the data confidentially while concurrently relying on the untrusted
relays as potential Eves to improve both the security and reliability of the
network. To realize this objective, we consider cooperative jamming performed
by the destination while JRP scheme is implemented. With the aim of maximizing
the instantaneous secrecy rate, we derive a new closed-form solution for the
optimal power allocation and propose a simple relay selection criterion under
two scenarios of non-colluding Eves (NCE) and colluding Eves (CE). For the
proposed scheme, a new closed-form expression is derived for the ergodic
secrecy rate (ESR) and the secrecy outage probability as security metrics, and
a new closed-form expression is presented for the average symbol error rate
(SER) as a reliability measure over Rayleigh fading channels. We further
explicitly characterize the high signal-to-noise ratio slope and power offset
of the ESR to highlight the impacts of system parameters on the ESR. In
addition, we examine the diversity order of the proposed scheme to reveal the
achievable secrecy performance advantage. Finally, the secrecy and reliability
diversity-multiplexing tradeoff of the optimized network are provided.
Numerical results highlight that the ESR performance of the proposed JRP scheme
for NCE and CE cases is increased with respect to the number of untrustworthy
relays.Comment: 18 pages, 10 figures, IEEE Transactions on Information Forensics and
Security (In press
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
- …