117 research outputs found
Artificial-Noise-Aided Secure Multi-Antenna Transmission with Limited Feedback
We present an optimized secure multi-antenna transmission approach based on
artificial-noise-aided beamforming, with limited feedback from a desired
single-antenna receiver. To deal with beamformer quantization errors as well as
unknown eavesdropper channel characteristics, our approach is aimed at
maximizing throughput under dual performance constraints - a connection outage
constraint on the desired communication channel and a secrecy outage constraint
to guard against eavesdropping. We propose an adaptive transmission strategy
that judiciously selects the wiretap coding parameters, as well as the power
allocation between the artificial noise and the information signal. This
optimized solution reveals several important differences with respect to
solutions designed previously under the assumption of perfect feedback. We also
investigate the problem of how to most efficiently utilize the feedback bits.
The simulation results indicate that a good design strategy is to use
approximately 20% of these bits to quantize the channel gain information, with
the remainder to quantize the channel direction, and this allocation is largely
insensitive to the secrecy outage constraint imposed. In addition, we find that
8 feedback bits per transmit antenna is sufficient to achieve approximately 90%
of the throughput attainable with perfect feedback.Comment: to appear in IEEE Transactions on Wireless Communication
Fronthaul Quantization as Artificial Noise for Enhanced Secret Communication in C-RAN
This work considers the downlink of a cloud radio access network (C-RAN), in
which a control unit (CU) encodes confidential messages, each of which is
intended for a user equipment (UE) and is to be kept secret from all the other
UEs. As per the C-RAN architecture, the encoded baseband signals are quantized
and compressed prior to the transfer to distributed radio units (RUs) that are
connected to the CU via finite-capacity fronthaul links. This work argues that
the quantization noise introduced by fronthaul quantization can be leveraged to
act as "artificial" noise in order to enhance the rates achievable under
secrecy constraints. To this end, it is proposed to control the statistics of
the quantization noise by applying multivariate, or joint, fronthaul
quantization/compression at the CU across all outgoing fronthaul links.
Assuming wiretap coding, the problem of jointly optimizing the precoding and
multivariate compression strategies, along with the covariance matrices of
artificial noise signals generated by RUs, is formulated with the goal of
maximizing the weighted sum of achievable secrecy rates while satisfying per-RU
fronthaul capacity and power constraints. After showing that the artificial
noise covariance matrices can be set to zero without loss of optimaliy, an
iterative optimization algorithm is derived based on the concave convex
procedure (CCCP), and some numerical results are provided to highlight the
advantages of leveraging quantization noise as artificial noise.Comment: to appear in Proc. IEEE SPAWC 201
Secure Massive MIMO Communication with Low-resolution DACs
In this paper, we investigate secure transmission in a massive multiple-input
multiple-output (MIMO) system adopting low-resolution digital-to-analog
converters (DACs). Artificial noise (AN) is deliberately transmitted
simultaneously with the confidential signals to degrade the eavesdropper's
channel quality. By applying the Bussgang theorem, a DAC quantization model is
developed which facilitates the analysis of the asymptotic achievable secrecy
rate. Interestingly, for a fixed power allocation factor , low-resolution
DACs typically result in a secrecy rate loss, but in certain cases they provide
superior performance, e.g., at low signal-to-noise ratio (SNR). Specifically,
we derive a closed-form SNR threshold which determines whether low-resolution
or high-resolution DACs are preferable for improving the secrecy rate.
Furthermore, a closed-form expression for the optimal is derived. With
AN generated in the null-space of the user channel and the optimal ,
low-resolution DACs inevitably cause secrecy rate loss. On the other hand, for
random AN with the optimal , the secrecy rate is hardly affected by the
DAC resolution because the negative impact of the quantization noise can be
compensated for by reducing the AN power. All the derived analytical results
are verified by numerical simulations.Comment: 14 pages, 10 figure
On the Design of Artificial-Noise-Aided Secure Multi-Antenna Transmission in Slow Fading Channels
In this paper, we investigate the design of artificial-noise-aided secure
multi-antenna transmission in slow fading channels. The primary design concerns
include the transmit power allocation and the rate parameters of the wiretap
code. We consider two scenarios with different complexity levels: i) the design
parameters are chosen to be fixed for all transmissions, ii) they are
adaptively adjusted based on the instantaneous channel feedback from the
intended receiver. In both scenarios, we provide explicit design solutions for
achieving the maximal throughput subject to a secrecy constraint, given by a
maximum allowable secrecy outage probability. We then derive accurate
approximations for the maximal throughput in both scenarios in the high
signal-to-noise ratio region, and give new insights into the additional power
cost for achieving a higher security level, whilst maintaining a specified
target throughput. In the end, the throughput gain of adaptive transmission
over non-adaptive transmission is also quantified and analyzed.Comment: to appear in IEEE Transactions on Vehicular Technolog
Secure beamforming transmission with limited training and feedback
We consider the secure beamforming transmission over a quasi-static block fading channel from a multi-antenna transmitter to a desired single-antenna receiver, in the presence of a passive single-antenna eavesdropper. We focus on a practical scenario where the transmitter can only acquire the statistical channel knowledge of the eavesdropper and the partial channel knowledge of the legitimate receiver through a finite amount of signaling overhead. To keep control of the outage events caused by the limited channel knowledge, We firstly propose a strategy to determine the wiretap code parameters under the outage constraints, based on which we establish a necessary transmission condition to guarantee a positive secrecy rate. Aided by this transmission condition, we propose an on-off-based transmission scheme and characterize the secrecy throughput performance of the system. Our designed transmission scheme is beneficial for the deployment of physical layer security in practical frequency division duplex (FDD) systems with limited training and feedback.ARC Discovery Projects Grant DP15010390
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