49 research outputs found
Learning End-to-End Codes for the BPSK-constrained Gaussian Wiretap Channel
Finite-length codes are learned for the Gaussian wiretap channel in an
end-to-end manner assuming that the communication parties are equipped with
deep neural networks (DNNs), and communicate through binary phase-shift keying
(BPSK) modulation scheme. The goal is to find codes via DNNs which allow a pair
of transmitter and receiver to communicate reliably and securely in the
presence of an adversary aiming at decoding the secret messages. Following the
information-theoretic secrecy principles, the security is evaluated in terms of
mutual information utilizing a deep learning tool called MINE (mutual
information neural estimation). System performance is evaluated for different
DNN architectures, designed based on the existing secure coding schemes, at the
transmitter. Numerical results demonstrate that the legitimate parties can
indeed establish a secure transmission in this setting as the learned codes
achieve points on almost the boundary of the equivocation region
An Overview of Physical Layer Security with Finite-Alphabet Signaling
Providing secure communications over the physical layer with the objective of
achieving perfect secrecy without requiring a secret key has been receiving
growing attention within the past decade. The vast majority of the existing
studies in the area of physical layer security focus exclusively on the
scenarios where the channel inputs are Gaussian distributed. However, in
practice, the signals employed for transmission are drawn from discrete signal
constellations such as phase shift keying and quadrature amplitude modulation.
Hence, understanding the impact of the finite-alphabet input constraints and
designing secure transmission schemes under this assumption is a mandatory step
towards a practical implementation of physical layer security. With this
motivation, this article reviews recent developments on physical layer security
with finite-alphabet inputs. We explore transmit signal design algorithms for
single-antenna as well as multi-antenna wiretap channels under different
assumptions on the channel state information at the transmitter. Moreover, we
present a review of the recent results on secure transmission with discrete
signaling for various scenarios including multi-carrier transmission systems,
broadcast channels with confidential messages, cognitive multiple access and
relay networks. Throughout the article, we stress the important behavioral
differences of discrete versus Gaussian inputs in the context of the physical
layer security. We also present an overview of practical code construction over
Gaussian and fading wiretap channels, and we discuss some open problems and
directions for future research.Comment: Submitted to IEEE Communications Surveys & Tutorials (1st Revision
Randomized Convolutional Codes for the Wiretap Channel
We study application of convolutional codes to the randomized encoding scheme introduced by Wyner as a way of confusing the eavesdropper over a wiretap channel. We describe optimal and practical sub-optimal decoders for the main and the eavesdropper's channels, and estimate the security gap, which is used as the main metric. The sub-optimal decoder works based on the trellis of the code generated by a convolutional code and its dual, where one encodes the data bits and the other encodes the random bits. By developing a code design metric, we describe how these two generators should be selected for optimal performance over a Gaussian wiretap channel. We also propose application of serially concatenated convolutional codes to this setup so as to reduce the resulting security gaps. Furthermore, we provide an analytical characterization of the system performance by extending existing lower and upper bounds for coded systems to the current randomized convolutional coding scenario. We illustrate our findings via extensive simulations and numerical examples, which show that the newly proposed coding scheme can outperform the other existing methods in the literature in terms of security gap. © 1972-2012 IEEE
Developing a relationship between static Young’s modulus and seismic parameters
Mechanical properties of petroleum reservoirs can be determined via static techniques based on laboratory triaxial tests
under reservoir conditions. Dynamic approaches represent an alternative in cases where such static laboratory data are
unavailable. Dynamic elastic properties are calculated using ultrasonic wave measurements in the laboratory or in situ well
logging. Different relationships have been proposed to estimate static properties from dynamic ones based on the available
data from a particular reservoir. However, these relationships are often reservoir-specific, making them inadequate for general
seismic inversion purposes. This research proposes a method for developing relationships between seismic parameters
and static Young’s modulus in carbonate reservoirs by integrating ultrasonic measurements, well logging data, and rock
mechanic tests. A multistage triaxial test simulating the reservoir conditions was used to fully control the stress and strain
during the geomechanical experiments. Static Young’s modulus was cross-correlated with a broad spectrum of seismic
parameters that can be extracted from seismic inversion (e.g., acoustic impedance, shear impedance, Lambda–rho, and
mu–rho). Separate analytic relationships were proposed to convert dynamic Young’s modulus and seismic parameters into
static Young’s modulus. Analysis of variance was used to evaluate the results and study the applicability and reliability of
the obtained relationships. Furthermore, the reliability of the obtained relationships was successfully confirmed by well
logging data and blind well analysis. The proposed methodology can be used to predict rock behavior for geomechanical
and structural modeling
Effect of brine-CO2 fracture flow on velocity and electrical resistivity of naturally fractured tight sandstones
Fracture networks inside geological CO2 storage reservoirs can serve as primary fluid flow conduit, particularly in low-permeability formations. While some experiments focused on the geophysical properties of brine- and CO2-saturated rocks during matrix flow, geophysical monitoring of fracture flow when CO2 displaces brine inside the fracture seems to be overlooked. We have conducted laboratory geophysical monitoring of fluid flow in a naturally fractured tight sandstone during brine and liquid CO2 injection. For the experiment, the low-porosity, low-permeability naturally fractured core sample from the Triassic De Geerdalen Formation was acquired from the Longyearbyen CO2 storage pilot at Svalbard, Norway. Stress-dependence, hysteresis and the influence of fluid-rock interactions on fracture permeability were investigated. The results suggest that in addition to stress level and pore pressure, mobility and fluid type can affect fracture permeability during loading and unloading cycles. Moreover, the fluid-rock interaction may impact volumetric strain and consequently fracture permeability through swelling and dry out during water and CO2 injection, respectively. Acoustic velocity and electrical resistivity were measured continuously in the axial direction and three radial levels. Geophysical monitoring of fracture flow revealed that the axial P-wave velocity and axial electrical resistivity are more sensitive to saturation change than the axial S-wave, radial P-wave, and radial resistivity measurements when CO2 was displacing brine, and the matrix flow was negligible. The marginal decreases of acoustic velocity (maximum 1.6% for axial Vp) compared to 11% increase in axial electrical resistivity suggest that in the case of dominant fracture flow within the fractured tight reservoirs, the use of electrical resistivity methods have a clear advantage compared to seismic methods to monitor CO2 plume. The knowledge learned from such experiments can be useful for monitoring geological CO2 storage where the primary fluid flow conduit is fracture network.acceptedVersio
Programming Wireless Security through Learning-Aided Spatiotemporal Digital Coding Metamaterial Antenna
The advancement of future large-scale wireless networks necessitates the
development of cost-effective and scalable security solutions. Conventional
cryptographic methods, due to their computational and key management
complexity, are unable to fulfill the low-latency and scalability requirements
of these networks. Physical layer (PHY) security has been put forth as a
cost-effective alternative to cryptographic mechanisms that can circumvent the
need for explicit key exchange between communication devices, owing to the fact
that PHY security relies on the physics of the signal transmission for
providing security. In this work, a space-time-modulated digitally-coded
metamaterial (MTM) leaky wave antenna (LWA) is proposed that can enable PHY
security by achieving the functionalities of directional modulation (DM) using
a machine learning-aided branch and bound (B&B) optimized coding sequence. From
the theoretical perspective, it is first shown that the proposed space-time MTM
antenna architecture can achieve DM through both the spatial and spectral
manipulation of the orthogonal frequency division multiplexing (OFDM) signal
received by a user equipment. Simulation results are then provided as
proof-of-principle, demonstrating the applicability of our approach for
achieving DM in various communication settings. To further validate our
simulation results, a prototype of the proposed architecture controlled by a
field-programmable gate array (FPGA) is realized, which achieves DM via an
optimized coding sequence carried out by the learning-aided branch-and-bound
algorithm corresponding to the states of the MTM LWA's unit cells. Experimental
results confirm the theory behind the space-time-modulated MTM LWA in achieving
DM, which is observed via both the spectral harmonic patterns and bit error
rate (BER) measurements
An Overview of Physical Layer Security with Finite Alphabet Signaling
Providing secure communications over the physical layer with the objective of achieving secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step towards a practical implementation of physical layer security. With this motivation, this article reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and discuss some open problems and directions for future research