On the performance of energy detection-based CR with SC diversity over IG channel

Cognitive radio (CR) is a viable 5G technology to address the scarcity of the spectrum. Energy detection-based sensing is known to be the simplest method as far as hardware complexity is concerned. In this paper, the performance of spectrum sensing-based energy detection technique in CR networks over inverse Gaussian channel for selection combining diversity technique is analysed. More specifically, accurate analytical expressions for the average detection probability under different detection scenarios such as single channel (no diversity) and with diversity reception are derived and evaluated. Further, the detection threshold parameter is optimised by minimising the probability of error over several diversity branches. The results clearly show the significant improvement in the probability of detection when optimised threshold parameter is applied. The impact of shadowing parameters on the performance of energy detector is studied in terms of complimentary receiver operating characteristic curve. To verify the correctness of our analysis, the derived analytical expressions are corroborated via exact result and Monte Carlo simulations.     

Design simplifications for bi notch filters

A methodology for designing FIR bi notch filters (NF) derived from second order prototype IIR NFs is suggested. Rejection bandwidth for the designed filter can be controlled by suitable choice of ‘r’, the pole radius of the IIR prototype NFs. The suggested bi-NF can also be adapted to eliminate second, third and fourth order harmonics of periodic noise besides the fundamental noise frequency component. Such filters find application in switched mode power regulators meant to supply ripple free dc for sensitive electronic gadgets and also in host of communication circuits. A special case when two notch frequencies ω₁ and ω₂ are such that [(cos ω₁)(cos ω₂) = −1/2] has also been discussed. The IIR bi-NF design for this special case results reduction in the number of multipliers without affecting the response of the desired NF. For the afore, referred condition, the required design weights of FIR bi-NF reduce to almost half in number resulting in reduced computations. The number of zero weights further reduces with increase in ‘r’ value. Also, the frequency response becomes better, with reduced ripples in the pass bands, when ‘r’ is increased and the length ‘L’ of the FIR NF is chosen appropriately.     

An APWM resonant inverter topology for high frequency AC power distribution systems

In this paper, an asymmetrical pulse-width-modulated (APWM) resonant inverter topology is presented for high frequency AC power distribution systems. The inverter system is comprised of simple power and control circuitry. The detailed analysis shows that the proposed inverter has very low total harmonic distortion, near-zero switching losses, and fast transient response. A design procedure is illustrated as well. Simulation and experimental results are presented to prove the performance of the proposed inverter.     

Experimental validation of mechanical stress models by micro-Raman spectroscopy

It is shown that micro-Raman spectroscopy offers a unique tool for the validation of stress models for microelectronics devices. Starting from an analytical or numerical model that describes the variation of local stress in a device, the corresponding Raman shift is calculated and compared with the data. In this way feed-back is given to the model. This technique is demonstrated for stripes (Si₃N₄, COSi₂, W) on a Si substrate, but can be applied to any device where Raman data can be obtained.     

Phase equilibria of the Si-Ge-Ti system relevant to the reactions between SiGe alloys and Ti

The semiconductor-rich region of the Si-Ge-Ti ternary isotherm at 900°C was determined by metallography, x-ray diffraction, and electron microprobe analysis. The sample alloys were prepared by arc-melting. These alloys were brought to equilibrium by annealing at 900°C for 400 h. It was confirmed that at 900°C, TiSi₂ and TiGe₂ form a continuous solid solution Ti(Si_1−yGe_y)₂ with the C54 crystal structure. It was also shown that, other than Ti(Si_1−yGe_y)₂ and Si_1−xGe_x, there is not any binary or ternary phase within the Si-Ge-TiGe₂-TiSi₂ trapezoid region. Between the Ti(Si_1−yGe_y)₂ and Si_1−xGe_x single-phase fields is the Ti(Si_1−yGe_y)₂-Si_1−xGe_x two-phase region. The tie-lines for this two-phase region were determined. The tie-lines tilt slightly toward the TiSi₂ and Ge corners. In other words, at equilibrium, the silicon to germanium atomic ratio is larger in Ti(Si_1−yGe_y)₂ than in Si_1−xGe_x (x>y). This tendency for tie-lines to tilt toward the TiSi₂ and Ge corners had been proposed in the literature as the reason for the interesting microstructure evolution during the reactions between SiGe alloys and Ti. In addition, the possible diffusion paths for the reactions between SiGe alloys and Ti were discussed based on the obtained isotherm. Recognizing Si and Ge have higher mobilities in Ti(Si_1−yGe_y)₂, it is predicted that for SiGe the extent of concentration change is large but occurs over a shorter distance, and for TiSi₂ the extent of concentration change is small but occurs over a longer distance.     

Semiconductor optical amplifiers in WDM tree-net

In this paper, effectiveness of semiconductor optical amplifiers (SOAs) in tree-net in terms of increase in the number of users has been investigated. In the analysis, SOAs with (i) unsaturated gain, (ii) average gain saturation, and (iii) average gain saturation with gain fluctuations have been considered. Further, the results for the tree-net are compared with those for the star network. It is observed that tree-net supports more number of users than star for a given number of SOAs     

Electrical impedance tomography of complex conductivitydistributions with noncircular boundary

Electrical impedance tomography (EIT) uses low-frequency current and voltage measurements made on the boundary of a body to compute the conductivity distribution within the body. Since the permittivity distribution inside the body also contributes significantly to the measured voltages, the present reconstruction algorithm images complex conductivity distributions. A finite element model (FEM) is used to solve the forward problem, using a 6017-node mesh for a piecewise-linear potential distribution. The finite element solution using this mesh is compared with the analytical solution for a homogeneous field and a maximum error of 0.05% is observed in the voltage distribution. The boundary element method (BEM) is also used to generate the voltage data for inhomogeneous conductivity distributions inside regions with noncircular boundaries. An iterative reconstruction algorithm is described for approximating both the conductivity and permittivity distributions from this data. The results for an off-centered inhomogeneity showed a 35% improvement in contrast from that seen with only one iteration, for both the conductivity and the permittivity values. It is also shown that a significant improvement in images results from accurately modeling a noncircular boundary. Both static and difference images are distorted by assuming a circular boundary and the amount of distortion increases significantly as the boundary shape becomes more elliptical. For a homogeneous field in an elliptical body with axis ratio of 0.73, an image reconstructed assuming the boundary to be circular has an artifact at the center of the image with an error of 20%. This error increased to 37% when the axis ratio was 0.64. A reconstruction algorithm which used a mesh with the same axis ratio as the elliptical boundary reduced the error in the conductivity values to within 0.5% of the actual values     

Performance Comparison Between Different Tunneling Techniques Using Different Routing Protocols

Wireless Personal Communications - Migration to IPv6 becomes a priority with the draining of IPv4 addresses. But both IPv4 and IPv6 have different structures, and directly bringing IPv6 into the...     

Image denoising by supervised adaptive fusion of decomposed images restored using wave atom,curvelet and wavelet transform

This paper presents an efficient image denoising method that adaptively combines the features of wavelets, wave atoms and curvelets. Wavelet shrinkage is used to denoise the smooth regions in the image while wave atoms are employed to denoise the textures, and the edges will take advantage of curvelet denoising. The received noisy image is firstly decomposed into a homogenous (smooth/cartoon) part and a textural part. The cartoon part of the noisy image is denoised using wavelet transform, and the texture part of the noisy image is denoised using wave atoms. The two denoised images are then fused adaptively. For adaptive fusion, different weights are chosen from the variance map of the denoised texture image. Further improvement in denoising results is achieved by denoising the edges through curvelet transform. The information about edge location is gathered from the variance map of denoised cartoon image. The denoised image results in perfect presentation of the smooth regions and efficient preservation of textures and edges in the image.