Speech signals protection via logo watermarking based on the time–frequency analysis

A procedure for logo watermarking of speech signals is proposed. In order to take full advantage of both time and frequency domains, we have used joint time–frequency representation of speech signal, which provides a more comprehensive information compared to each domain individually. Time–frequency-based selection of the discrete Fourier transform coefficients is used for logo embedding. The proposed coefficients selection provides both the imperceptibility and robustness requirements. The binary logo is embedded by using the concept of bit-plane modification. The logo extraction procedure is provided as well. The robustness of the proposed procedure is tested under various attacks such as compression, noise addition, filtering, re-sampling, re-quantization, time stretch, pitch scaling, etc.     

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.     

Beam-forming of broadband QFM signals using generalized time–frequency transform

ABSTRACT

Detection and localisation of contacts using sensor array play a significant role in the area of array signal processing. In this paper, a new beam-forming analysis for broad-banded quadratic frequency modulated (QFM) signals using generalised time–frequency transform (GTFT) is presented by extending the conventional fractional Fourier transform (FrFT). As FrFT is constrained to the analysis of linear chirps, detection using GTFT is found to be the appropriate selection for higher-order chirps with the suitable choice of the kernel. The parameters of the QFM signal is extracted using the polynomial chirplet transform time–frequency distribution method. Subsequently, the direction of arrival (DoA) estimation algorithms viz. conventional beam-former (CBF), minimum variance distortionless response (MVDR), multiple signal classification (MUSIC) and minimum norm (MN) are re-cast using the quadratic steering vector derived for QFM chirps and hence renamed as GTFT-CBF, GTFT-MVDR, GTFT-MUSIC and GTFT-MN, respectively. The efficacy of the algorithm is validated through various signals including practical sonar array data. It is seen from the theoretical analysis as well as simulations that GTFT-MUSIC excels other DoA (bearing) estimation techniques. The GTFT analysis on back propagated signals using sonar array aided in effective underwater channel modelling.     

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.     

Single channel source separation using time–frequency non-negative matrix factorization and sigmoid base normalization deep neural networks

Multidimensional Systems and Signal Processing - Conventional single channel speech separation has two long-standing issues. The first issue, over-smoothing, is addressed, and estimated signals are...     

Spectral efficiency analysis of digital signals for 3.1–10.6 GHz ultra-wideband radio systems

Spectral efficiency analysis of widely used types of digital signals in the 3.1–10.6 GHz frequency band is presented. Peculiarities of energy accumulation in the specified frequency band are demonstrated for video signals and modulated signals. Optimal durations, which provide maximum value of spectral efficiency, of the considered video signals are determined. Practical recommendations on using the considered digital signals in the 3.1–10.6 GHz ultra-wideband radio systems are concluded.     

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.     

Correction to: Fishbone Diagram: Application to Identify the Root Causes of Student–Staff Problems in Technical Education

Wireless Personal Communications - There were spelling errors in the second author’s name in the initial online publication. The original article has been corrected.     

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.     

Time-domain analysis of lossy multiconductor transmission lines based on the Lax–Wendroff technique

Taking advantage of the hyperbolic characteristics of the telegrapher equations, this paper applies the Lax–Wendroff technique, usually used in fluid dynamics, to transmission line analysis. A second-order-accurate Lax–Wendroff difference scheme for the telegrapher equations for both uniform and nonuniform transmission lines is derived. Based on this scheme, a new method for analyzing lossy multiconductor transmission lines which do not need to be decoupled is presented by combining with matrix operations. Using numerical experiments, the proposed method is compared with the characteristic method, the fast Fourier transform (FFT) approach, and the Lax–Friedrichs technique. With the presented method, a circuit including lossy multiconductor transmission lines is analyzed and the results are consistent with those of PSPICE. The nonlinear circuit including nonuniform lossy multiconductor transmission lines is also computed and the results are verified by HSPICE. The proposed method can be conveniently applied to either linear or nonlinear circuits which include general transmission lines, and is proved to be efficient.     

Autonomous allocation of wireless body-sensor networks to frequency channels: modeling with repeated “balls-in-bins” experiments

Wireless Networks - In this paper we model a situation where several wireless body sensor networks (WBSN) compete for occupation of a number of frequency channels. Each channel can host at most one...     

Application of the Crank–Nicolson FDTD method for analysis of a wideband multi-section hybrid coupler

In this paper the Crank–Nicolson (CN) finite-difference time-domain (FDTD) method is applied for the analysis of a planar wideband hybrid coupler. The proposed method is applied for analysis of transmission lines. Stability issue is investigated for different cases, including lossless and lossy transmission lines. Sufficient conditions for unconditional stability are derived. As a practical problem, a wideband compact hybrid coupler working on 1–6 GHz frequency band is analyzed using the CN-FDTD method. Measurement results show that the proposed coupler provides coupling of 3 ± 0.8 dB with 90° ± 0.85° phase shift and demonstrate the return loss and isolation better than 16 dB over 1–6 GHz. To validate the accuracy of the method, the results of this scheme are compared with measurements and the conditional stable leap-frog (LF) FDTD method. It is observed that using the CN-FDTD, the temporal step-size can be increased up to 1500 time compared with the LF-FDTD method with still good agreement with the measured results.     

A method for the amplitude–phase synthesis of antenna array based on control of the set of nonidentical partial beams

An iterative method for the amplitude–phase synthesis of antenna arrays based on control of the set of partial beams is proposed. In this method, two additional partial beams are added to the radiation pattern at each step. The shape of each beam is optimized with consideration for the difference between the synthesized and specified radiation patterns. Parameters specifying the shape of additional partial beams are chosen with the help of the genetic algorithm. The results of numerical studies allowing comparison of the proposed synthesis method to the least-squares method and the method based on control of the set of identical partial beams are presented.     

A performance analysis of polling schemes for IEEE 802.11 MAC over the Gilbert–Elliot channel

An IEEE 802.11 wireless local area network (WLAN) provides the centralized polling-based medium access control (MAC) to support Quality of Service (QoS) requirements. In this letter, we present a performance analysis of popular polling MAC schemes over the Gilbert–Elliot channel model. We describe our validation through simulations under various channel conditions and discuss performance characteristics of the polling schemes.