Video frame deletion detection based on time–frequency analysis

With the emergence of diverse multimedia editing software, a great number of edited or tampered video resources appear on the Internet, some of which can mix with the genuine ones. Digital video authenticity is an important step to make the best use of these video resources. As a common video forgery operation, frame tampering can change the video content and confuse viewers by removing or inserting some specific frames. In this paper, we explore the traces created by compression process and propose a new method to detect frame tampering based on the high-frequency features of reconstructed DCT coefficients in the tampered sequences. Experimental results demonstrate that our proposed method can effectively detect frame tampering operation, and accurately locate the breakpoint of frame tampering in the streams.     

Hardware realization of the robust time–frequency distributions

A hardware realization of the L-estimate forms of robust time–frequency distributions is proposed. This hardware realization can be used for instantaneous frequency estimation for signals corrupted by a mixture of impulse and Gaussian noise. The most complex part in the hardware implementation is the block that performs sorting operation. In addition to the continuous realization, a recursive realization of the Bitonic sort network is proposed as well. The recursive approach also provides a fast sorting operation with a significantly reduced number of components. In order to verify the results, the FPGA implementations of the proposed systems were designed.     

Steady-state analysis of the carrier synchronizer for QPSK signals†

In this paper, the steady-state analysis of the carrier synchronizer consisting of the cascade of a bandpass filter (BPF), and non-linearity (NL) and a phase-locked loop (PLL) for a quadrature phase shift keyed (QPSK) signal corrupted by white gaussian noise is presented. The analysis is based on the transform method and the harmonic representation of cyclostationary processes. Some of the conclusions are similar to those obtained from the non-return to zero (NRZ) pulse amplitude modulated (PAM) synchronizer. Among these include: (1) the odd symmetry NL cannot be adopted to restore the carrier; (2) there is an optimum bandwidth of the BPF to minimize the phase jitter of the synchronizer output signal; and (3) conventional design theory still applies for the PLL in the QPSK carrier synchronizer. In addition to these results, we also conclude that: (1) we have to choose a harmonic with order of at least 4; and (2) the PLL output phase variance is more sensitive to the synchronizer input signal-to-noise ratio (S/N) than the NRZ synchronizer. A significant improvement of the QPSK synchronizer performance over that of the NRZ case is possible when the S/N is large.     

A technique to improve the linearization of frequency–voltage characteristic of LC-VCO

This paper presents a very low-power linearization technique to improve the linearity of frequency-voltage characteristic of LC-VCO (voltage controlled oscillator) using MOS varactor. This reduces the VCO gain (K _VCO) variation and its required value over the tuning voltage range. Low K _VCO improves noise and reference spur performances at the output of phase lock loop/frequency synthesizer (FS). Low K _VCO variation reduces FS loop stability problem. Using this VCO circuit, a fully on-chip integer-N frequency synthesizer has been fabricated in 0.18 μm epi-digital CMOS technology for 2.45 GHz ZigBee application. The measured VCO phase noise is ?115.76 and ?125.23 dBc/Hz at 1 and 3 MHz offset frequencies, respectively from 2.445 GHz carrier and the reference spur of the frequency synthesizer is ?68.62 dBc. The used supply voltage is 1.5 V.     

A new approach to the design and analysis of peer‐to‐peer mobile networks

This paper introduces a new model and methodological approach for dealing with the probabilistic nature of mobile networks based on the theory of random graphs. Probabilistic dependence between the random links prevents the direct application of the theory of random graphs to communication networks. The new model, termed Random Network Model, generalizes conventional random graph models to allow for the inclusion of link dependencies in a mobile network. The new Random Network Model is obtained through the superposition of Kolmogorov complexity and random graph theory, making in this way random graph theory applicable to mobile networks. To the best of the authors' knowledge, it is the first application of random graphs to the field of mobile networks and a first general modeling framework for dealing with adhoc network mobility. The application of this methodology makes it possible to derive results with proven properties. The theory is demonstrated by addressing the issue of the establishment of a connected virtual backbone among mobile clusterheads in a peertopeer mobile wireless network. Using the Random Network Model, we show that it is possible to construct a randomized distributed algorithm which provides connectivity with high probability, requiring exponentially fewer connections (peertopeer logical links) per clusterhead than the number of connections needed for an algorithm with a worst case deterministic guarantee.     

2D space–time wave-digital multi-fan filter banks for signals consisting of multiple plane waves

Two dimensional space–time fan filters may be used for the highly-selective enhancement of spatio-temporal plane-waves on the basis of their directions of arrival. Unlike uniform bandwidth beam filters, ideal fan filters transmit passband signals over a range of directions of arrival that is independent of their 1D temporal spectrum. In this work, closed-form 2D wave-digital filter design equations and corresponding hardware architectures are proposed for realizing M independent fan-shaped passbands having independently steerable directionality and selectivity. A design method based on LCR ladder networks is proposed and implemented using a 2D time-multiplexed raster-scanned architecture that is suitable for low frequency applications such as audio, multimedia, seismic and ultrasonic beamforming. The architectures are designed, simulated, physically realized and tested on FPGA-based prototypes. Examples of 2D IIR M-fan filterbanks with FPGA implementations, together with measured results from on-chip hardware verifications, show the successful design and hardware realization. The filterbanks and hardware architectures are shown to be suitable for real-time sensor-array beamforming applications using custom VLSI circuits.     

On the diversity analysis of symbol remapping in cooperative BICM–OFDM scheme for frequency selective Rayleigh fading channels

In this paper, diversity analysis of a symbol remapping scheme in cooperative systems is considered. We employ Bit Interleaved Coded Modulation and Orthogonal Frequency Division Multiplexing, which are widely used at wireless networks. In this paper, at the cooperative scheme, relays operate in DF mode and the effect of their erroneous detection will be considered. We present a closed form of the asymptotic worst-case pairwise error probability at the destination for our proposed scheme. It will be shown that this scheme exploits full spatial and frequency diversities. After that, we work on designing a new precoder matrix. Moreover, we propose two new subcarrier allocations for the proposed scheme. All new methods have been suggested to achieve the available diversities with a better performance than current state of the art. Finally, the simulation results reveal the analytical derivations and confirm the obtained diversity gain of the proposed systems.     

Protocol for the application of cooperative MIMO based on clustering in sparse wireless sensor networks

Wireless sensor networks (WSN) using cooperative multiple-input multiple-output (MIMO) communication are effective tools to collect data in several environments. However, how to apply cooperative MIMO in WSN remains a critical challenge, especially in sparse WSN. In this article, a novel clustering scheme is proposed for the application of cooperative MIMO in sparse WSN by extending the traditional low-energy adaptive clustering hierarchy (LEACH) protocol. This clustering scheme solves the problem that the cluster heads (CH) cannot find enough secondary cluster heads (SCH), which are used to cooperate and inform multiple-antenna transmitters with CHs. On the basis of this protocol, the overall energy consumption of the networks model is developed, and the optimal number of CHs is obtained. The simulation results show that this protocol is feasible for the sparse WSN. The simulation results also illustrate that this protocol provides significant energy efficiencies, even after allowing for additional overheads.     

Signal-to-noise enhancement in TSSI–GC–IMS: Development of two dimensional sensor for detection of chemicals

Over the years, Ion Mobility Spectrometry (IMS) which refers to the techniques and cutting-edge instruments for characterizing of analytes by their gas phase mobility has been gaining popularity and validity among scientific researchers for detecting chemicals. This novel gas sensor with its high analytical speed, low detection limits, ease of use and ruggedness during transport has also become the dominant commercial technology in different industries. In spite of these paramount advantages, this detector has difficulty identifying matrix compounds. To overcome this problem a Gas Chromatograph (GC) can be used to introduce individual components of mixture into an IMS. The output signal of the hyphenated GC–IMS method is an extraordinary small, time-dependent current produced by mobile ions in atmospheric pressure. To exploit the qualitative and quantitative information hidden in this sensitive noisy signal, various signal processing methods have been nominated for spectrum filtration and improving signal-to-noise ratio (SNR). In the present paper an attempt is made to design and construct a GC–IMS instrument coupled with a Thermal Solid Sample Introduction (TSSI) module for injection of solid samples to capillary GC column. Moreover, various spectrum filtration methods for removing noise from GC–IMS signal would be investigated. The GC–IMS instrument used in this research was designed and constructed in Institute of Materials and Energy, Isfahan, Detector group and can be used as a chemical sensor for rapid detection of a broad range of chemical mixtures in many operational environments including on-board Volatile Organic Analyzer Sensor (VOAS) in space missions. The capability of constructed sensor for detection of complex mixtures has been proved by analyzing a mixture of three pesticides as test materials. Our proposed method for removing noise from the real-time TSSI–GC–IMS signal will be presented and its efficacy will be proved by offering real experiments.     

Application of the inner–outer flexible GMRES-FFT method to the analysis of scattering and radiation by cavity-backed patch antennas and arrays

The finite element-boundary integral (FE-BI) method is applied for the analysis of scattering and radiation by cavity-backed patch antenna and arrays. In this investigation, the FE-BI formulations have been implemented using brick element volumes and it allows for a particular use of the efficient FFT-based iterative solver. The inner–outer flexible GMRES algorithm is applied to solve the equation with a higher convergence speed when compared with the standard GMRES algorithm.     

Thermal–mechanical behavior of the bonding wire for a power module subjected to the power cycling test

Two analytical methods were proposed in this research, coupled electro-thermal finite element (FE) analysis and thermal–mechanical FE analysis, to analyze the mechanical behavior of bonding wire of power module under cyclic power loads, and the International Electrotechnical Commission standard is adopted in conducting a power cycling test. The exterior temperature distribution was measured by an infrared thermometer. Moreover, the junction temperature is calculated from the given thermal impedance of the semiconductor chip, chip power loss, and case temperature. Subsequently, the simulated temperature distribution via electro-thermal FE analysis is compared with experimental results to validate the methodology used in the aforementioned analysis. The analysis shows compressive stress at the wire/chip interface due to CTE mismatch between the aluminum and the chip. Moreover, the major driving force contributing to the shear stress at the interface is the self-expansion of the wire bump.     

On the validity of unintentional doping densities extracted using Mott–Schottky analysis for thin film organic devices

The organic electronic devices are often understood invoking the concept of ‘unintentional doping’. However, the applicability and usefulness of this controversial concept is not very clear and is under much recent debate. In this work, we revaluate the validity of this concept through careful experiments and detailed numerical simulations. Specifically, we use the Capacitance Voltage (CV) measurement of pentacene devices as a testbed to unravel the role of injecting electrodes and unintentional doping (if any). Indeed, our results indicate that the CV of pentacene capacitors can be solely understood in terms of properties of the contact electrodes. The unintentional doping, if present, has an inconsequential role in device performance. Our conclusions indicate that, often, an incorrect interpretation of CV results would lead to unphysical values of unintentional doping and have obvious implications towards the fundamental understanding of organic semiconductor device physics, modeling, and characterization; thus resolving many ambiguities in literature by providing a consistent interpretation through a coherent conceptual framework.     

Correction to: Attack Resilient and Efficient Protocol Based on Greedy Perimeter Coordinator Routing—Mobility Awareness for Preventing the Attack in the VANET

Wireless Personal Communications -     

320 × 240 CMOS array for the spectral range of 3–5 μm based on PtSi photodiodes

The results of research and development of a 320 × 240 platinum silicide focal plane array (FPA) for the spectral range of 3–5 μm are presented. The development is based entirely on CMOS technology. It is shown that the FPA makes it possible to adjust the photosignal accumulation time at a fixed frame rate and subtract the background constant component in the output device.     

Assessment of the potential risk for humans exposed to millimeter‐wave wireless LANs: the power absorbed in the eye

This paper deals with the interaction between a millimeterwavelength plane wave and the human eye. The study has been conducted utilizing the finite difference time domain (FDTD) numerical technique, and an accurate eye model obtained through photographic images of the human head. A partly automatic procedure has been developed to obtain the FDTDcompatible eye model. The dielectric properties of the human tissues at millimeter wavelengths have been extrapolated from experimental data available at lower frequencies and by using Debyes dispersion equation. The power distribution in the exposed eye has been calculated in both conditions of closed and open eye, and the results have been compared with the limits settled by some of the most recognized safety standards for human exposure.     

Effective Hamiltonians for heterostructures based on direct-gap III–V semiconductors. The kp perturbation theory and the method of invariants

A sequential procedure for obtaining effective kp Hamiltonians for arbitrary heterostructures based on direct-gap semiconductors with identical lattice parameters is suggested. The heterostructure potential is described with the help of characteristic functions f _l (a), which indicate atom substitution in sublattice l of the reference crystal in unit cell a. The kp perturbation theory for heterostructures, which takes into account the scattering effects of charge carriers on the additional local potential that emerges due to atom substitution, is developed. A method of constructing the corresponding effective kp Hamiltonians by the method of invariants, which takes into account the microscopic symmetry of interfaces, is suggested. Along with the band parameters, the obtained Hamiltonians contain additional parameters, which have no analogs in bulk materials. The derivation of the effective Hamiltonians of bands Γ₁, Γ₆, Γ₁₅, and Γ₈ in heterostructures based on cubic III–V semiconductors with atom substitution in one sublattice is given as an example.     

A strategy to enhance both VOC and JSC of A–D–A type small molecules based on diketopyrrolopyrrole for high efficient organic solar cells

Four different diketopyrrolopyrrole (DPP)-based small molecules (SMs) with A–D–A type structure were synthesized, where electron-donating unit (D) was systematically varied with different electron-donating power (thiophene vs. phenylene; thienothiophene vs. naphthalene) and different molecular planarity (bithiophene vs. thienothiophene; and biphenylene vs. naphthalene). The small molecules with weak donating unit (phenylene or naphthalene) have deeper HOMO energy levels than those with strong donating unit (thiophene or thienothiophene), and thus exhibit higher V_OC. When the fused aromatic ring (thienothiophene or naphthalene) with planar molecular structure is introduced in SMs, the SMs exhibit high hole mobility and thus afford high J_SC. As a result, the introduction of naphthalene (weak donating power and planar structure) enhances both V_OC and J_SC, resulting in a promising power conversion efficiency of 4.4%. This result provides a valuable guideline for rational design of conjugated small molecules for high performance organic solar cells.     

Parent–Daughter Confusion Component: A New Approach for the Construction of Nonlinear Confusion Component

The nonlinear confusion component is one of an integral part of any modern block cipher. This nonlinear confusion component is used to hides the relationship between the ciphertext and the key. The primary objective of this article is to formulate a new mechanism for the construction this confusion component. Usually substitution box (S-box) is used to achieve this kind of characteristics in block ciphers. We have utilized deoxyribonucleic acid (DNA) sequences for the construction of new S-boxes with optimized cryptographic characteristics. The projected technique fundamentally optimized the DNA sequences along with traditional confusion component to generate a completely new S-box. The obtained S-boxes have the same cryptographic strength as a parent S-box have.

     

Light emitting diodes for the spectral range of λ=3.3–4.3 μm fabricated from the InGaAs-and InAsSbP-based solid solutions: Electroluminescence in the temperature range of 20–180°C

Light emitting diodes (LEDs) with λ_max=3.4 and 4.3 µm (t=20°C) were studied at elevated temperatures. It is demonstrated that LEDs operating in the temperature range t=20–180°C can be described using the classical concepts of injection radiation sources and the processes of charge carrier recombination. The temperature dependences of reverse currents in the saturation regions of current-voltage characteristics are consistent with the increase in the intrinsic-carrier concentration according to the Shockley theory. The emission spectra are described on the assumption of the direct band-to-band transitions, spherically symmetric bands, and thermalized charge carriers. The current-power characteristics are proportional to I ^3/2 suggesting that the contribution of the nonradiative Auger recombination is dominant. The radiation power decreases exponentially with the temperature which is characteristic of the CHSH and CHCC processes.     

High-speed photodiodes for the mid-infrared spectral region 1.2–2.4 μm based on GaSb/GaInAsSb/GaAlAsSb heterostructures with a transmission band of 2–5 GHz

High-speed p-i-n photodiodes for the spectral range of 1.2–2.4 μm are fabricated for the first time based on a GaAs/GaInAsSb/GaAlAsSb heterostructure with separated sensitive-(50 μm in diameter) and contact mesas, which are connected by a bridge front contact. The use of an unconventional design for the contact mesa with a Si₃N₄ insulating sublayer 0.3 μm thick under the metal contact made it possible to lower both the intrinsic photodiode capacitance and the reverse dark currents. The photodiodes have a low intrinsic capacitance of 3–5 pF at zero bias and 0.8–1.5 pF at a reverse bias of 3.0 V. The photodiode operating speed, which is determined by the time of increasing the photoresponse pulse to a level of 0.1–0.9, is 50–100 ps. The transmission band of the photodiodes reaches 2–5 GHz. The photodiodes are characterized by low reverse dark currents I _d = 200–1500 nA with a reverse bias of U = ?(0.5–3.0) V, a high current monochromatic sensitivity of R _i = 1.10–1.15 A/W, and a detectability of D*(λ_max, 1000, 1) = 0.9 × 10¹¹ W^?1 cm Hz^1/2 at wavelengths of 2.0–2.2 μm.