Passive Fingerprinting of Same-Model Electrical Devices by Current Consumption.

One possible device authentication method is based on device fingerprints, such as software- or hardware-based unique characteristics. In this paper, we propose a fingerprinting technique based on passive externally measured information, i.e., current consumption from the electrical network. The key insight is that small hardware discrepancies naturally exist even between same-electrical-circuit devices, making it feasible to identify slight variations in the consumed current under steady-state conditions. An experimental database of current consumption signals of two similar groups containing 20 same-model computer displays was collected. The resulting signals were classified using various state-of-the-art time-series classification (TSC) methods. We successfully identified 40 similar (same-model) electrical devices with about 94% precision, while most errors were concentrated in confusion between a small number of devices. A simplified empirical wavelet transform (EWT) paired with a linear discriminant analysis (LDA) classifier was shown to be the recommended classification method.

Coherence Time Evaluation in Indoor Optical Wireless Communication Channels.

The coherence time is the time over which the channel-gain-values correlation coefficient drops below a predefined threshold. The coherence time is typically used to quantify the pace of appreciable channel changes and is important, for example, for determining handoff and resource allocation time constraints. The goal of this work is to experimentally measure the coherence time of indoor optical wireless communication (OWC) channels under various mobile scenarios. The amount of movement was quantified by mobile sensor measurements. The experiments show that it is reasonable to assume that the channel varies slowly for a time period of ~100 milliseconds for most mobile scenarios.

Recording device identification by ENF harmonics power analysis.

Two important aspects of digital audio forensics are integrity validation of the recorded contents and identification of the acquisition device that produced the recording. One of the effective methods for integrity validation is based on induced electrical network frequency (ENF) signal analysis. The goal of this paper is to extend the usage of the ENF signal for the identification of the acquisition device. The proposed identification method is based on the harmonic amplitude coefficients of ENF signals that are effectively applied as feature vectors. The evaluation results demonstrate the efficacy of the proposed approach.

Symbol error rate of soft-decision multiple pulse position modulation over turbulent channels.

Soft-decision multiple-pulse-position modulation (MPPM) is one of the favored free-space optical communication modulations. This paper derives theoretical expressions for the symbol error rate of both fast and slow fading conditions applied for soft-decision MPPM without channel state information at the receiver as a particular case of nonmemoryless channel conditions. The theoretical expressions for lognormal and gamma-gamma modeled turbulence were successfully verified by simulation.

Coherence distance in indoor optical wireless communication channels.

The coherence distance (CD) is the spatial distance over which the channel does not change appreciably. It is a common and important wireless communication channel parameter. While adoption of this parameter in the realm of radio-frequency is well established, it is a less familiar concept in the realm of optical wireless communication (OWC), where it can be beneficial as a measure for spatial optical channel changes. In this Letter, the average CD is proposed as a metric to characterize indoor OWC channels and a method for its evaluation is outlined.

Free-space optical channel simulator for weak-turbulence conditions.

Free-space optical (FSO) communication may be severely influenced by the inevitable turbulence effect that results in channel gain fluctuations and fading. The objective of this paper is to provide a simple and effective simulator of the weak-turbulence FSO channel that emulates the influence of the temporal covariance effect. Specifically, the proposed model is based on lognormal distributed samples with a corresponding correlation time. The simulator is based on the solution of the first-order stochastic differential equation (SDE). The results of the provided SDE analysis reveal its efficacy for turbulent channel modeling.

Evaluation of the estimation accuracy of polarization-based roll angle measurement.

The orientation of remote objects can be easily measured optically and very accurately using optical technologies. In this paper, we address the accuracy of a roll angle estimation technique that is based on the estimation of the polarization of a retroreflected beam and is applied in a long-range measurement task. Over long transmission ranges, the optical power decreases significantly leading to severe SNR deterioration. As a result, the measurement accuracy decreases. In this study, the estimation is carried out using a maximum-likelihood estimator and its performance is evaluated using the analytical Cramer-Rao bound.