Clustering and scheduling methods based on SLNR in downlink CoMP system简

In downlink coordinated multi-point（CoMP） system, full cooperation is always not applicable in real world because of its high request in the backhaul. To deal with this problem, clustering decision is made to process transmission. In this paper clustering methods based on the metric signal-to-leakage-plus-noise（SLNR） is proposed. In addition, user scheduling schemes based on SLNR is also put up to make the scheduling set as large as possible. Simulation results show that the proposed clustering methods not only reduce the data sharing among the cooperating base stations（BSs）, but also improve the system throughput compared with the traditional clustering methods based on channel strength.     

Research and design of wap service system based on MISC platform

1 Introduction With the introduction of high mobile handsets with increasingly powerful functions and the applications of WAP2.0 with considerably novel technologies, a series of diverse hot WAP services have come into being and have been successfully lau…     

Design and implementation of high-speed real-time data acquisition system based on FPGA

1 Introduction Electromagnetic radiation will be generated when an electric device, especially video display unit, works, and can give rise to electromagnetic leakage. When the electromagnetic leakage is recognized, the available information can be recove…     

Classification of linear and non-linear modulations using the Baum–Welch algorithm and MCMC methods

Satellite transmissions classically use constant amplitude linear modulation schemes, such as M-state phase shift keying (M-PSK), because of their high robustness to amplifier non-linearities. However, other modulation formats are interesting in a satellite transmission context. For instance, non-linear modulations such as Gaussian minimum shift keying (GMSK) present a higher spectral efficiency and appear in new standards for telemetry/telecommand satellite links. Another example is offset-QPSK (OQPSK) modulation that allows one to decrease the out-of-band interference due to band limiting and the non-linearity of the amplifier. To get a compromise between the robustness to amplifier non-linearities provided by MPSK modulation and the spectral efficiency given by QAM modulation, the recent broadcasting satellite standard (DVB-S2) proposes new modulation schemes called APSK. Obviously, all satellite systems that use various modulation schemes will have to co-exist. In this context, modulation recognition using the received communication signal is essential. In that context, this paper studies two Bayesian classifiers to recognize linear and non-linear modulations. These classifiers estimate the posterior probabilities of the received signal, given each possible modulation, and plug them into the optimal Bayes decision rule. Two algorithms are used for that purpose. The first one generates samples distributed according to the posterior distributions of the possible modulations using Markov chain Monte Carlo (MCMC) methods. The second algorithm estimates the posterior distribution of the possible modulations using the Baum–Welch (BW) algorithm. The performance of the resulting classifiers is assessed through several simulation results.     

Design of band–notched UWB antenna using a hybrid optimization based on ABC and DE algorithms

In this study, a novel UWB antenna with dual band–rejection is designed by using a new hybrid optimization algorithm based artificial bee colony algorithm (ABC) and differential evolution (DE). The hybrid performance of ABC and DE (H–ABCDE) is tested on well–known benchmark functions. To show its performance on a design problem, an optimization interface (OI) which simultaneously communicates with H–ABCDE and an electromagnetic simulation tool is developed. Hence OI integrating H–ABCDE and HyperLynx® 3D EM is used to design and optimize an antenna. A low profile UWB monopole antenna operating over the frequency range of 2.9–13.0 GHz is then designed through OI. In order to achieve band–rejection operation, various slits and strips have been loaded on the antenna. It thus rejects the dual–band of 3.3–3.6 GHz and 5.15–5.825 GHz corresponds to the operation bands of WLAN and WiMAX. Furthermore, the optimized antenna is prototyped to investigate the measurement performance and it is compared with several designs in the literature. Therefore, H–ABCDE can successfully adapt to the extended electromagnetic problem as well as engineering optimization tasks.     

Retrieval of head–neck medical images using Gabor filter based on power-law transformation method and rank BHMT

This research aims to work on the specific medical domain. In this work, retrieval of the head–neck medical images from a database is discussed. Content-based medical image retrieval system (CBMIR) is used for retrieving the head–neck images. CBMIR is automatic and more efficient compared with the text-based approach. Shape and texture features are used for constructing feature vector. Texture feature is extracted using a modified Gabor filter based on power-law transformation method. Shape feature is extracted using rank BHMT (rank-order blur hit or miss transformation) method. Shape and texture features are combined to form a single feature vector. Threshold value very near to zero is used to retrieve images from the database. The proposed method is compared with log-Gabor filters and rank BHMT method. Combinations of modified Gabor filter with rank BHMT gave better performance than other methods.     

Improvement of oxide thickness determination on MOS structures using capacitance–voltage measurements at high frequencies

It is well known that capacitance–voltage (C–V) measurements provide a simple determination of oxide thickness, but with the scaling down of components the classical method is not appropriated any more. We have observed that for two devices with the same oxide thickness and different surfaces, the classical method is accurate for large area but it is not adapted for the small one. We present a new procedure to make an accurate electrical determination of the oxide thickness on metal-oxide-semiconductor (MOS) structures of low dimensions in U.L.S.I. technology. Our method does not require a measurement in strong accumulation. It is based on C–V measurements at frequencies higher than 1 MHz associated to a non-linear optimisation of the experimental and theoretical band bending versus bias voltage curve (Ψ_S=f(V_g)), in the depletion mode. By this way, a corrective factor is estimated with precision in order to make an accurate determination of the oxide thickness value. We show that the frequency associated to the non-linear optimisation of Ψ_S=f(V_g) is function of the MOS device dimensions and is increased when the surface decreases. The experimental results obtained on low-dimension MOS structures and different oxide thickness are precise and in total agreement with those measured by ellipsometry. By using our new procedure the accuracy of oxide thickness determination is improved.     

Photoelectric and optical properties of Schottky-barrier photodiodes based on IrSi–Si

The basic properties in the Schottky-barrier photodiodes (SBPDs) can be reduced to photon absorption in the silicide layer and internal photoemission of charge carriers from a metal to a semiconductor. Therefore, the quantum efficiency and photoresponse of these photodiodes (PDs) are primarily determined by electronic and optical processes in the metal silicide rather than in the semiconductor. This implies that, to a first approximation, the SBPD photoresponse is independent of semiconductor parameters such as the doping level, degree of compensation of impurities, and minority-carrier lifetime. The main reasons for photoresponse nonuniformity in multielement detector arrays are thereby ruled out.     

Dark satellite image enhancement using knee transfer function and gamma correction based on DWT–SVD

In this paper, an improved and simple approach for enhancement of dark and low contrast satellite image based on knee function and gamma correction using discrete wavelet transform with singular value decomposition (DWT–SVD) has been proposed for quality enhancement of feature. In addition, this method can also process the high resolution dark or very low contrast images, and offers best enhanced result using tuning parameter of Gamma. The technique decomposes the input image into four frequency subbands by using DWT and estimates the singular value matrix of the low–low subband image, and then compute the knee transfer function using gamma correction for further improvement of the LL component. Afterward, processed LL band image undergoes IDWT together with the unprocessed LH, HL, and HH subbands to generate an appropriate enhanced image. Although, various histogram equalization approaches has been proposed in the literature, they tend to degrade the overall image quality by exhibiting saturation artifacts in both low- and high-intensity regions. The proposed algorithm overcomes this problem using knee function and gamma correction. The experimental results show that the proposed algorithm enhances the overall contrast and visibility of local details better than the existing techniques.     

Mitigation of channel estimation error in TR–UWB system based on a novel MMSE equalizer

The time reversal (TR) technique combined with the ultra-wideband (UWB) system offers a new potential for decreasing the cost and complexity of the UWB receivers. In spite of TR–UWB's good performance in perfect channel state information (CSI), it is very sensitive to the channel estimation error. The effect of channel imperfection on the TR–UWB system is considered in this paper. At first, based on a minimum mean square error (MMSE) equalizer receiver, a prefilter is calculated in closed form to improve the performance of the TR–UWB system in an imperfect CSI scenario. Furthermore, for comparison purposes, a similar calculation for prefilter is carried out based on a simple matched filter (MF) receiver. Then, in order to improve the MF receiver performance, a two-stage iteration-based algorithm is developed. The initial value for this iteration-based improved algorithm is considered to be a prefilter which is calculated in the TR–UWB system with MMSE equalizer. This optimized algorithm causes the channel estimation error in the TR–UWB system to become zero in some steps. Finally, exhaustive simulations are done to demonstrate the performance advantage attained by the improved algorithm.     

Investigations about the effect of annealing temperatures in the presence of oxygen flow on optical and electronic properties of titanium nano-layers by using Kramers–Kronig and DFT methods

Nano-layers of titanium were deposited on glass substrates by resistive evaporation at room temperature. Thickness of the layers was measured 66.8 nm, by a quartz crystal method. Deposition conditions such as deposition rate, vacuum pressure, incidence of angle and substrate temperature were the same for all layers. After producing pure Ti layers a post-annealing method was used in the presence of a uniform oxygen flow of 6 cm³/s and different 100 °C, 200 °C and 300 °C annealing temperatures. Optical reflectance and transmittance of the layers were measured in the wave length of 200–4100 nm by a spectrophotometer. Kramers–Kronig relations were used to calculate the optical constants. The influence of annealing temperature and oxygen flow on optical properties is investigated. Also to make the obtained optical results clearer, a full-potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) has been used. Comparison results confirm that in higher annealing temperatures the obtained structure is more similar to anatase crystalline one. According to AFM images, by increasing annealing temperature in the presence of oxygen flow, configuration of layers change and due to high annealing temperature and surface diffusion effect, void fraction increases. With increase in annealing temperature to 300 °C, anatase phase structure (A(004)) gets clearer and sharper also other phase structures are about to grow.     

Calculation of the Schottky barrier and current–voltage characteristics of metal–alloy structures based on silicon carbide

A simple but nonlinear model of the defect density at a metal–semiconductor interface, when a Schottky barrier is formed by surface defects states localized at the interface, is developed. It is shown that taking the nonlinear dependence of the Fermi level on the defect density into account leads to a Schottky barrier increase by 15–25%. The calculated barrier heights are used to analyze the current–voltage characteristics of n-M/p-(SiC)_1–x(AlN)_x structures. The results of calculations are compared to experimental data.     

Side chain effect on photovoltaic properties of D–A copolymers based on benzodithiophene and thiophene-substituted bithiazole

Two donor–acceptor (D−A) copolymers, PEHBDT-BTz and PODBDT-BTz, containing the same backbone of benzodithiophene (BDT) and bithiazole (BTz) units but different side chains were designed and synthesized. Effects of the side chains of BDT and BTz units on solubility, absorption spectra, energy levels, film morphology, and photovoltaic properties of the polymers were investigated. Results showed that the more branched side chains could increase the molecular weight and the introduction of alkylthienyl groups into BTz unit benefits to broaden the absorption and lower the bandgaps as well as deepen HOMO levels, which are propitious to improve the short-circuit current density (J_sc) and open-circuit voltage (V_oc) of photovoltaic cells. Polymer solar cells (PSCs) were prepared with the polymers as electron donors and PCBM as an acceptor. The device fabrication conditions, including the additive, the different acceptor and blend ratio of the polymer donor and acceptor, have been optimized. PCE of PSCs based on the copolymers varied from 2.92% for PODBDT-BTz to 3.71% for PEHBDT-BTz, depending on the type and topology of the side chains on the BDT moiety. The results indicate that an appropriate choice of side chains on the backbone is an effective way to improve photovoltaic performance of the related PSCs.     

Design and experimental analysis of fiber grating vibration demodulation system based on the 3 × 3 coupler

A novel fiber grating vibration demodulation system, based on 2×2 and 3×3 couplers, is designed. Based on the phase unwrapping algorithm, the three-way asymmetrical output of the 3×3 coupler and demodulation state characteristics of the system when the vibration signal includes high harmonic waves are analyzed in simulations. The result shows that when the three-way output is asymmetrical, the maximum deviation of demodulation signal is 1.625%, and when the vibration signal includes high harmonic waves, the maximum deviation of demodulation signal is 0.9%. The corresponding experiment is conducted. The experimental result shows that the dynamic resolution of the system is 25.22 nɛ / $ \sqrt {Hz} $ \sqrt {Hz} when the vibration pitch is 5.5 Hz.     

Fabrication and performance evaluation of symmetrical supercapacitor based on manganese oxide nanorods–PANI composite

Manganese oxide nanorods distributed over polyaniline (PANI) network was prepared by one step facile synthesis condition. pH of the reactant solution was tuned using sulfuric acid. Effect of pH on the morphology, chemical composition, structure and electrochemical performance of the prepared materials were studied. Thermal investigation reveals the decomposition of PANI at temperatures below 600 °C. Structural details and chemical composition of the compound was obtained from XRD, FTIR and XPS studies. α type MnO₂ was found to be crystallized in the prepared MnO₂–PANI composite. Single crystal manganese oxide nanorods distributed over the PANI network was cognizant from the FESEM and HRTEM investigations. Nanorods of average diameter 82 nm and length 482 nm were obtained without deploying any surfactants or templates. Electrochemical techniques like Cyclic Voltammetry (CV), Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS) were utilized. Study results indicate that the composites prepared shows excellent electrochemical performance. Among the prepared materials, MnP-46 exhibits a maximum specific capacitance of 687 Fg⁻¹ at 5 mV s⁻¹ scan rate and a capacitance retention of 95% over 2000 cycling. Promising performance of MnP-46 was further tested in a symmetrical two cell configuration. The cell was operative upto 1 V potential window. MnP-46 in a symmetrical arrangement demonstrates 179 Fg⁻¹ at 5 mV/s scan rate. High conductivity of the electrode material was confirmed from the Nyquist plot.     

Electrical and photoelectrical characterization of an organic–inorganic heterojunction based on quinoline yellow dye

An organic–inorganic contact was fabricated by forming a thin film of quinoline yellow dye (QY) on a p-Si wafer and evaporating Al metal on the film. The current–voltage (I–V) and capacitance–voltage (C–V) measurements of Al/QY/p-Si heterostructure were applied in dark and room temperature to calculate the characteristic parameters of diode like ideality factor, barrier height and series resistance. Ideality factor and barrier height values were found as 1.23 and 0.87 eV from I–V data, respectively. The series resistance value of the device was determined as 1.8 kΩ by using modified Norde function. The C–V measurements were carried out at different frequencies and it was seen that capacitance value decreased with increasing frequency. Interface state density distribution was calculated by means of I–V measurement. In addition the optical absorption of thin QY film on glass was measured and optical band gap of the film was found as 2.73 eV. Furthermore, I–V measurements of Al/QY/p-Si/Al were taken under illumination between 40 and 100 mW/cm². It was observed that reverse bias current of the device increased with light intensity. Thus, the heterojunction had a strong response to the light and it can be suitable for electrical and optoelectronic applications like a photodiode.     

Performance analysis of mode division multiplexing based free space optics system incorporating on–off keying and polarization shift keying under dynamic environmental conditions

In this paper, we propose a novel mode division multiplexing (MDM) based FSO transmission system incorporating polarization shift keying (PolSK) to enhance the information carrying capacity of the system. Using numerical simulations, we report the transmission of two independent 40 Gbps information signals using distinct Laguerre Gaussian modes up to an FSO transmission reach of 90 km under the influence of clear environmental conditions using the proposed system. Further, the influence of different environmental conditions such as rain, haze, and fog on the performance of the proposed link using bit error rate as performance metrics has also been investigated in this paper. Also, we report a comparative analysis of PolSK and on–off keying modulation formats in the proposed MDM-FSO link under the same environmental conditions. The simulation results show that under different weather conditions, PolSK based MDM-FSO transmission system demonstrates better performance.

     

Robust control of the DC–DC boost converter based on the uncertainty and disturbance estimator

In this paper, a robust non-linear controller based on the uncertainty and disturbance estimator (UDE) scheme is successfully developed and implemented for the output voltage regulation of the DC–DC boost converter. System uncertainties, external disturbances and unknown non-linear dynamics are lumped as a signal that is accurately estimated using a low-pass filter and their effects are cancelled by the controller. This methodology forms the basis of the UDE-based controller. A simple procedure is also developed that systematically determines the parameters of the controller to meet certain specifications. Using simulation, the effectiveness of the proposed controller is compared against the sliding-mode control (SMC). Experimental tests also show that the proposed controller is robust to system uncertainties, large input and load perturbations.     

On the fractal nature of light-emitting structures based on III–N nanomaterials and related phenomena

It is shown that a three-dimensional fractal–percolation system is formed in nanomaterials of light-emitting InGaN/GaN and AlGaN/GaN structures in the presence of conducting extended defects and local inhomogeneities of the composition of the solid solutions; this system determines the electrophysical properties of light-emitting diodes fabricated on the basis of these structures. The geometry and properties of this system depend nonlinearly on the degree of disorder in the nanomaterial of the structures, on the value of the injection current, and on the rate of alloy growth.