Showing papers in "Aeu-international Journal of Electronics and Communications in 2012"

A cluster-based routing protocol for wireless sensor networks with nonuniform node distribution

Abstract: Due to the nonuniform node distribution, the energy consumption among nodes are more imbalanced in cluster-based wireless sensor networks. Based on this problem, in this paper, a cluster-based routing protocol for wireless sensor networks with nonuniform node distribution is proposed, which includes an energy-aware clustering algorithm EADC and a cluster-based routing algorithm. EADC uses competition range to construct clusters of even sizes. At the same time, the routing algorithm increases forwarding tasks of the nodes in scarcely covered areas by forcing cluster heads to choose nodes with higher energy and fewer member nodes as their next hops, and finally, achieves load balance among cluster heads. Theoretical analysis and simulation results show that our protocol can balance the energy consumption among nodes and increase the network lifetime significantly.

A hybrid genetic algorithm and chaotic function model for image encryption

Abstract: The security of digital images has attracted much attention recently. In this study, a new method based on a hybrid model is proposed for image encryption. The hybrid model is composed of a genetic algorithm and a chaotic function. In the first stage of the proposed method, a number of encrypted images are constructed using the original image and the chaotic function. In the next stage, these encrypted images are used as the initial population for the genetic algorithm. In each stage of the genetic algorithm, the answer obtained from the previous iteration is optimized to produce the best-encrypted image. The best-encrypted image is defined as the image with the highest entropy and the lowest correlation coefficient among adjacent pixels. The use of genetic algorithms in image encryption has been attempted for the first time in this paper. Analyzing the results from the performed experiments, a high level of resistance of the proposed method against brute-force and statistical invasions is obviously illustrated. The obtained entropy and correlation coefficients of the method are approximately 7.9978 and −0.0009, respectively.

Analog circuit sizing via swarm intelligence

Abstract: Together with the increase in electronic circuit complexity, the design and optimization processes have to be automated with high accuracy. Predicting and improving the design quality in terms of performance, robustness and cost is the central concern of electronic design automation. Generally, optimization is a very difficult and time consuming task including many conflicting criteria and a wide range of design parameters. Particle swarm optimization (PSO) was introduced as an efficient method for exploring the search space and handling constrained optimization problems. In this work, PSO has been utilized for accommodating required functionalities and performance specifications considering optimal sizing of analog integrated circuits with high optimization ability in short computational time. PSO based design results are verified with SPICE simulations and compared to previous studies.

Neural network applications in smart antenna arrays: A review

Abstract: Techniques employed in the synthesis of antenna arrays vary from complex analytical methods to iterative numerical methods based on optimisation algorithms. The drawback of these techniques is that they usually consider the array factor but not the interaction between array elements and real-time problems. This omission induces an error in the resultant radiation pattern; therefore, the physical relations between the array feeding details and the corresponding radiation patterns are taken into account to improve the accuracy. The behaviour of an antenna array is nonlinear in nature, resulting in an extremely high complexity using this approach, and it is usually disregarded. A neural-network-based solution can avoid complexity by establishing a relation between the desired radiation patterns and feeding details such as voltage and spacing in the real antenna array and can help convert the real array into a smart array. Several neural network applications in smart antenna array synthesis are reviewed in this paper.

0.5V bulk-driven analog building blocks

Abstract: Basic analog building blocks, such as voltage follower (VF), second generation Current Conveyor (CCII), and Current Feedback Operational Amplifier (CFOA), capable for operating under 0.5 V supply voltage, are introduced in this paper. The input stage of the proposed blocks is based on bulk-driven pMOS devices, and simultaneously offers the advantages of almost rail-to-rail input/output voltage swing and capability for operation under the extremely low supply voltage. Their performances have been evaluated and compared through simulation results using a standard 0.18 μm n-well process. The bandwidth of the voltage and current followers for both CCII and CFOA is 11 MHz and 10 MHz, respectively. The power consumption of CCII and CFOA is 30 μW and 50 μW, respectively.

Resistor-less current-mode four-phase quadrature oscillator using CCCDTAs and grounded capacitors

Abstract: A current-mode four-phase quadrature oscillator (FPQO) using 2 current controlled current differencing transconductance amplifiers (CCCDTAs) and 2 grounded capacitors is presented. The proposed oscillator can provide 4 sinusoidal output currents with 90 phase difference. The oscillation condition and oscillation frequency can be controlled independently and electronically by adjusting the bias currents of the CCCDTA. Both the oscillation condition and oscillation frequency tuning laws are non-interactive and dual-current controlled. High output impedances of the configuration enable the circuit to be cascaded without additional current buffers. The use of only grounded capacitors is ideal for integration. The circuit performances are depicted through PSPICE simulations, they show good agreement to theoretical anticipation.

A series of new circuits based on CFTAs

Abstract: The paper presents a series of basic circuits based on CFTAs (current follower transconductance amplifier), which contain amplifier, lossless integrator, first-order universal current-mode filter, simulation resistor, negative resistance converter, gyrator, capacitor multiplier, and frequency-dependent negative resistance circuit. Having used canonic number of grounded capacitors and resistors, the circuits are easy to be integrated and the parameters of the circuits can be adjusted electronically by tuning bias currents of the CFTAs. It is noted that the results of circuit simulations are in agreement with theory.

Single CDTA-based current-mode quadrature oscillator

Abstract: This letter presents a single CDTA (Current Differencing Transconductance Amplifier)-based current-mode quadrature oscillator (QO). The proposed circuit structure is very simple, which only consists of one CDTA, one resistor and two capacitors, and it is easy for monolithic integration. The oscillation frequency of the QO can be electronically controlled by the bias current of the CDTA. Moreover, the oscillator can provide two quadrature current outputs. PSPICE simulation results are provided to verify all the theoretical analysis.

Strictly passive FIR filtering for state-space models with external disturbance

Abstract: This paper proposes a new strictly passive filter with a finite impulse response (FIR) structure for linear state-space signal models with external disturbance. This filter is called a strictly passive FIR filter (SPFF). We apply the strict passivity concept to derive a new linear filter with FIR structure and quasi-deadbeat property. The gain matrix of the proposed SPFF in this paper can be determined by resorting to the solution to a linear matrix inequality (LMI) feasibility problem. An illustrative example is presented to show the validity of the SPFF.

Image segmentation with complicated background by using seeded region growing

Abstract: This study proposes a novel seeded region growing based image segmentation method for complicated background in both color and gray level images. The proposed fuzzy edge detection method, that only detects the connected edge, is used with fuzzy image pixel similarity to automatically select the initial seeds not in the detail and complicated background. The fuzzy distance is used to determine the difference between the pixel and region in the consequent region growing and the difference between two regions in the region merging. The conventional region growing is modified in this study to ensure that the pixel on the edge is processed later than other pixels. Finally, the simulations in study prove that the proposed method is better than other existing segmentation methods.

Tunable versatile current-mode universal filter based on plus-type DVCCs

Abstract: This paper presents a new tunable versatile current-mode universal filter with four inputs and three outputs. The proposed configuration employs three plus-type differential voltage current conveyors, two grounded capacitors and three grounded resistors. Its high impedance outputs enable easy cascading in current-mode operation. The circuit can be used as either a single-input and three-output or four-input and two-output. In the operation of single-input and three-output circuit, the bandpass, highpass and bandreject filtering responses can be realized simultaneously. In the operation of four-input and two-output circuit, both inverting and non-inverting type lowpass, bandpass, highpass, bandreject and allpass filtering responses can be simultaneously realized by selecting different four input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency by adjusting the grounded passive components. No component matching condition is required for realizing all the filter responses, and all the passive and active sensitivities are low. HSPICE simulation results based on using TSMC 0.18 μm 1P6M CMOS process technology and supply voltages ±0.9 V to verify the theoretical analysis.

A new single MCCCDTA based Wien-bridge oscillator with AGC

Abstract: This paper presents a new current-mode Wien-bridge oscillator with automatic amplitude control. The oscillator only employs single MCCCDTA as the active element and provides two current outputs with small distortion from high output impedances. Its oscillation condition and frequency can be tuned electronically, linearly and independently through tuning bias currents of MCCCDTA. The circuit simulation results are in agreement with theory.

A compact low-profile dual-band antenna for WLAN and WAVE applications

Abstract: A compact and low-profile patch antenna with a simple structure is presented for the wireless local-area network (WLAN) and the wireless access in the vehicular environment (WAVE) applications. The proposed antenna with an overall size of only 23 mm × 25 mm is fed by a coplanar waveguide (CPW), and yields 10-dB impedance bandwidths of about 250 MHz centered at 2.44 GHz and of about 22% ranging from 5.13 to 6.38 GHz suitable for the WLAN 2.4/5.2/5.8 GHz and the WAVE 5.9 GHz (IEEE 802.11p) applications. Also, good dipole-like patterns and high average antenna gain of ≥2.3 dBi over the operating bands have been obtained. In this design, resonance can be effectively controlled by simply tuning the shaped slots on the patch. Mechanism of mode excitations and effect of the added slot's length on resonance for the proposed antenna are examined and discussed in detail. The experimental results have validated the proposed design as useful for modern mobile communication.

A robust spread spectrum based image watermarking in ridgelet domain

Abstract: A new robust method of spread spectrum based image watermarking is proposed in this article. Spread spectrum technique and scrambling are used for increasing robustness and invisibility of the algorithm. Our suggested method is carried out using ridgelet transform as an efficient transform for representing images with line singularities. In embedding part, the host image is partitioned into non-overlapping blocks and ridgelet transform is applied to each single block. In this way, a curved edge is divided into some straight edges so that ridgelet transform shows optimal performance even for complicated images with curve edges. To embed the watermark bits, the best directions of ridgelet coefficients are selected with respect to their variance intensity. In extraction part, a computationally efficient detection method is used for detecting watermark logo blindly from distorted watermarked image. To achieve more robust algorithm firstly, we find the best place to insert the watermark bits and secondly, we encode the scrambled watermark bits by pseudo random sequences with an authentication key. Robustness of our proposed method is tested against different kinds of attacks. According to the experimental results, proposed method shows much improved performance in comparison to other published works.

Improved vowel onset point detection using epoch intervals

Abstract: Vowel onset point (VOP) is the instant at which the onset of vowel takes place in the speech signal. Accurate detection of VOP is useful for applications such as consonant–vowel (CV) unit recognition and speech rate modification. Existing VOP detection methods determine VOPs within 40 ms deviation, which may not be suitable for the applications mentioned above. In this paper, a two level approach using multiple sources of evidence is proposed for the accurate detection of VOP. In the proposed method, at the first level, VOPs are identified by combining the complementary evidence from excitation source, spectral peaks and modulation spectrum. At the second level, hypothesized VOPs are verified (genuine or spurious), and their positions are corrected using the uniform epoch intervals present in vowel region. Zero frequency filter method is used to determine the epoch locations in speech. Performance of the proposed method is analyzed using TIMIT database, and compared with the recent method which uses the combination of evidence from excitation source, spectral peaks and modulation spectrum. Using the proposed method about 85% of VOPs are detected within 10 ms deviation.

A novel current-mode four-quadrant CMOS analog multiplier/divider

Abstract: This paper presents, a new current mode four-quadrant CMOS analog multiplier/divider based on dual translinear loops. Compared with the previous works this circuit has a simpler structure resulting in lower power consumption and higher frequency response. Simulation results, performed using HSPICE with 0.25 μm technology, confirm performance of the proposed circuit.

A compact CPW fed slot antenna for ultra wide band applications

Abstract: A printed compact coplanar waveguide fed triangular slot antenna for ultra wide band (UWB) communication systems is presented. The antenna comprises of a triangular slot loaded ground plane with a T shaped strip radiator to enhance the bandwidth and radiation. This compact antenna has a dimension of 26 mm × 26 mm when printed on a substrate of dielectric constant 4.4 and thickness 1.6 mm. Design equations are implemented and validated for different substrates. The pulse distortion is insignificant and is verified by the measured antenna performance with high signal fidelity and virtually steady group delay. The simulation and experiment reveal that the proposed antenna exhibits good impedance match, stable radiation patterns and constant gain and group delay over the entire operating band.

On the design of inscribed triangle circular fractal antenna for UWB applications

Abstract: In this article, an ultrawide band inscribed triangle circular fractal antenna is presented. The antenna has been designed on FR4 substrate dielectric constant ɛ r = 4.3 and thickness of substrate 1.53 mm with initial dimension of 30 mm diameter. The experimental result of fractal antenna exhibits the excellent ultra bandwidth from 2.25 GHz to 15 GHz corresponds to 147.83% impedance bandwidth at VSWR 2:1. This ultrawide band characteristcs of antenna has been achieved by using the CPW-fed and fractal concept. The measured radiation pattern of fractal antenna is nealy omnidirectional in azimuth plane and bidirectional in elevation plane. The measured group delay of proposed antenna is almost constant throughout the band. Such type of antenna is very useful for UWB communication system.

Improved harmonic balance implementation of Floquet analysis for nonlinear circuit simulation

Abstract: We present a novel algorithm for the efficient numerical computation of the Floquet quantities (eigenvalues, direct and adjoint eigenvectors) relevant to the assessment of the stability and noise properties of nonlinear forced and autonomous circuits. The approach is entirely developed in the frequency domain by means of the application of the Harmonic Balance technique, thus avoiding lengthy time–frequency transformations which might also impair the accuracy of the calculated quantities. An improvement in the computation time around one order of magnitude is observed.

A note on the criterion for the elimination of overflow oscillations in fixed-point digital filters with saturation arithmetic and external disturbance

Abstract: A recently reported criterion for the exponential stability and H ∞ performance of fixed-point digital filters with saturation arithmetic and external disturbance is reviewed. It is shown that there is a technical error in this criterion. A corrected version of the criterion is presented. Finally, a relaxed version of the criterion is made available.

Low-complexity PAPR reduction technique for OFDM systems using modified widely linear SLM scheme

Abstract: In this paper, a modified widely linear selective mapping (MWL-SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) of the orthogonal frequency-division multiplexing (OFDM) systems. In the proposed MWL-SLM scheme, through partition one complex signals into two real signals and combining the linear properties of the Fourier Transform, at most 4 M 2 candidate signals can be obtained but only require M inverse fast Fourier transform (IFFT) operations. As a result, the proposed SLM scheme has the ability to generate more candidates when compared with conventional SLM (C-SLM) and widely linear SLM (WL-SLM). Therefore, MWL-SLM outperforms C-SLM and WL-SLM for the same computational cost of IFFT operations. Alternatively, for a given number of candidates, MWL-SLM has slightly inferior PAPR reduction performance to C-SLM and WL-SLM but requires less IFFT operations to be implemented, thus resulting in a lower computational complexity. Simulation results demonstrate the effectiveness of the proposed scheme.

Three-input single-output second-order filters using current-feedback amplifiers

Abstract: In this study, a novel second order universal filter using current-feedback amplifier, commercially available active component, is presented. The signal-flow graph method is used to synthesize the filter. The proposed filter has three high impedance input and one output, (multiple input single output (MISO) configuration). It can generate all biquadratic filtering functions namely: low-pass (LP), band-pass (BP), high-pass (HP), band-reject (BR) and all-pass (AP) at the output terminal by selecting different input signal combinations. The validity of the proposed circuits is demonstrated by simulations.

A real-time dual watermarking algorithm of H.264/AVC video stream for Video-on-Demand service

Abstract: a b s t r a c t A real-time dual watermarking algorithm of H.264/AVC compressed video is proposed for Video-onDemand (VOD) service. The copyright information and user information are modulated by CDMA spreading strategies as watermark. At the encoder side, copyright information is embedded into the first non-zero coefficient of Intra 4 × 4 coded blocks in the luminance components of I frames. An effective error compensation mechanism is simultaneously introduced into the embedding process, which strictly restricts the distortion caused by quantization and watermark embedding within a step size of quantization. At the server side, a XOR based mapping rule is utilized for watermark embedding because the number of non-zero coefficients after quantization is quite less in P frames. Every two bits of the private user information is mapped to three non-zero coefficients of P frames. Experimental results on test sequences demonstrate that the proposed approach has just slight influence on bit rate and PSNR with real-time performance for VOD services, and achieves the dual purposes of copyright protection and pirate tracking.

Reversible data hiding scheme using reference pixel and multi-layer embedding

Abstract: This paper presents a lossless data hiding scheme. The proposed scheme is based on the pixel difference histogram shifting to spare space for data hiding. Pixel differences are generated between a reference pixel and its neighbors in a pre-assigned block. After the difference histogram shifting, a large number of data can be embedded into the cover image, and multi-layer embedding is used to improve the hiding capacity. Different from previous works based on histogram shifting the proposed scheme can extract the hidden data and recover the exact original cover image with no extra information except the length of hidden data and the stego-image itself. Experimental results show that the average pure payload among eight commonly used grayscale images is up to 1.08 bits per pixel (bpp) while keeping low distortion.

A publicly verifiable lossless watermarking scheme for copyright protection and ownership assertion

Abstract: In this paper, a discrete cosine transform based copyright protection scheme that does not require the original image for logo verification is proposed. Features of logistic map and discrete cosine transform are used to generate the verification map. Digital signature and timestamp are used to make copyright proving publicly verifiable. We have combined cryptographic tools and digital watermarking, in order to enhance the security and reliability of copyright protection. In addition, chaotic map is used to generate a chaotic pattern image, which can be used as secret key to improve the security of proposed algorithm. Experiments are conducted to show the robustness and effectiveness of the proposed algorithm. Experimental results show that our scheme outperforms related works in most of the cases.

Path loss model and prediction of range, power and throughput for 802.11n in large conference rooms

Abstract: In this paper, a path loss (PL) model for IEEE 802.11n in large conference rooms is proposed. The PL can be described accurately by a one-slope model with PL exponents varying from 1.2 to 1.7. The influence of humans (during a meeting) on the PL model is investigated. It was found that the PL exponent increases towards 2 in the presence of humans. Further, the effect of frequency (2.4/5 GHz), antenna configuration (SISO vs. MIMO 2×2), bandwidth (20 vs. 40 MHz) and transmit power on the required number of access points for wireless conferencing, total radiated power consumption and maximum throughput is investigated. This is done by link budget calculation, based on our proposed PL model as well as the IEEE 802.11 TGn channel model. In this evaluation, it was found that the two PL models predict some essentially different effects concerning throughput and radiated power.

Goos–Hänchen shift as a probe in evanescent slab waveguide sensors

Abstract: The present paper deals with three-layer planar waveguide optical sensor. Different from the conventional slab waveguide sensors in which the effective refractive index of the propagating mode is taken to be the probe for detection changes in the analyte refractive index, we adopt Goos–Hanchen (GH) shift as the sensing probe for the proposed sensor. We show that the GH shift is strongly dependent on the refractive index of the cladding, thus it is a good candidate for detection changes in the analyte refractive index. We present and study the sensitivity of the GH shift at the cladding–film and substrate–film interfaces. It is found that GH shift has a high sensitivity and can be used for versatile optical slab waveguide sensors.

Compact dual-band patch antenna using spiral shaped electromagnetic bandgap structures for high speed wireless networks

Abstract: This paper presents a compact dual-band slot antenna for 1.8/2.4 GHz WLAN applications using electromagnetic bandgap (EBG) structures. The slotted rectangular radiating element is surrounded by a spiral-like EBG. The antenna size is very compact (60 mm × 60 mm × 3.27 mm), and can be integrated easily with other RF front-end circuits. The working frequency of the patch antenna falls inside the EBG which will lead to the suppression of the surface waves. It is demonstrated that the proposed antenna can completely cover the required bandwidths of IEEE 802.11b/g and IEEE 802.11a with satisfactory radiation characteristics. The simulation is carried out using the finite integration time domain method (FITD) analysis technique. The EM simulated return loss, gain, directivity, radiation pattern, antenna efficiency and VSWR are presented for proposed antenna array. Good agreement is achieved between the simulated and measured results.

A high speed, fully digital IC random number generator

Abstract: System-on-a-chip solutions require hardware based integrated circuit random number generators for trustworthy transmission of information. This paper presents, a fully digital, high speed ASIC random number generator based on ring oscillators. Prototypes have been designed and fabricated in HHNEC's 0.25 μm eFlash process with a supply voltage of 2.5 V. The circuit occupies 0.052 mm 2 and dissipates 0.095 W of power. IC design level experiences, measurements, analysis of measurements and statistical test results are also demonstrated. Instead of resilient function, employed in the previous ring oscillators based design, which decreases the throughput by a factor of 16, we propose to use only a simple Von Neumann corrector which improves this result by a factor of 4. We achieved fulfilled test results from NIST 800-22 test suit after Von Neumann corrector with a sampling frequency of 74 MHz. Since, Von Neumann corrector is used as a post-processor, the throughput becomes 18.5 Mbps. Furthermore, we propose to use doubled ring oscillators structure, thus, a 125 Mbps throughput, which is the highest data rate to date with fulfilled test results, is attained without any postprocessing. The results were repeatable numerous times.

Study of shadowing effect by aircraft maneuvering for air-to-ground communication

Abstract: This paper investigates the shadowing effect induced by an aircraft during maneuvering for air-to-ground communication at C band. Narrowband measurements with a linear flight route and a circular flight route have been conducted and the results are compared in this paper. It is found that, the communication link can easily be shadowed by the aircraft body. Due to this shadowing, the transmitted signal undergoes significant attenuation of up to 28 dB at 5.7 GHz. Results also show that spatial diversity at the ground station is unable to eliminate this shadowing effect caused by the aircraft during maneuvering.